AD AD9887

a
FEATURES
Analog Interface
140 MSPS Maximum Conversion Rate
330 MHz Analog Bandwidth
0.5 V to 1.0 V Analog Input Range
500 ps p-p PLL Clock Jitter at 140 MSPS
3.3 V Power Supply
Full Sync Processing
Midscale Clamp
4:2:2 Output Format Mode
Digital (DVI 1.0 Compatible) Interface
112 MHz Operation (1 Pixel/Clock Mode)
High Skew Tolerance of One Full Input Clock
Sync Detect for “Hot Plugging”
APPLICATIONS
RGB Graphics Processing
LCD Monitors and Projectors
Plasma Display Panels
Scan Converters
Micro Displays
Digital TV
Dual Interface for
Flat Panel Displays
AD9887
FUNCTIONAL BLOCK DIAGRAM
ANALOG
INTERFACE
REF
REFIN
RAIN
CLAMP
GAIN
CLAMP
A/D
BAIN
CLAMP
A/D
8
8
ROUTB
8
GOUTA
8
GOUTB
8
BOUTA
8
BOUTB
8
A/D
8
8
DATACK
2
HSYNC
VSYNC
COAST
CLAMP
CKINV
CKEXT
FILT
REFOUT
ROUTA
HSOUT
SYNC
PROCESSING
AND CLOCK
GENERATION
VSOUT
8
SOGOUT
8
SCDT
8
M
U
X
E
S
SCL
SERIAL REGISTER
AND
POWER MANAGEMENT
SDA
GENERAL DESCRIPTION
The AD9887 offers designers the flexibility of a dual analog and
digital interface for flat panel displays (FPDs) on a single chip.
Both interfaces are optimized for excellent image quality supporting
display resolutions up to SXGA (1280 × 1024 at 75 Hz). Either the
analog or the digital interface can be selected by the user.
Analog Interface
For ease of design and to minimize cost, the AD9887 is a fully
integrated interface solution for FPDs. The AD9887 includes an
analog interface with a 140 MHz triple ADC with internal 1.25 V
reference, PLL to generate a pixel clock from HSYNC, programmable gain, offset, and clamp control. The user provides only a
3.3 V power supply, analog input, and HSYNC. Three-state
CMOS outputs may be powered from 2.5 V to 3.3 V.
The AD9887’s on-chip PLL generates a pixel clock from HSYNC.
Pixel clock output frequencies range from 12 MHz to 140 MHz.
PLL clock jitter is 500 ps p-p typical at 140 MSPS. When a
COAST signal is presented, the PLL maintains its output frequency in the absence of HSYNC. A sampling phase adjustment is
provided. Data, HSYNC and Clock output phase relationships are
maintained. The PLL can be disabled and an external clock input
provided as the pixel clock. The AD9887 also offers full sync processing for composite sync and sync-on-green applications.
A clamp signal is generated internally or may be provided by
the user through the CLAMP input pin. The analog interface
is fully programmable via a 2-wire serial interface.
A1
8
8
8
ROUTA
ROUTB
GOUTA
GOUTB
BOUTA
BOUTB
2
A0
DATACK
HSOUT
DIGITAL
INTERFACE
8
ROUTA
VSOUT
8
ROUTB
SOGOUT
8
GOUTA
8
GOUTB
8
BOUTA
8
Rx0+
DE
Rx0–
8
Rx1+
Rx1–
Rx2+
DVI
RECEIVER
8
8
Rx2–
RxC+
2
BOUTB
DATACK
DE
RxC–
HSYNC
RTERM
VSYNC
AD9887
Digital Interface
The AD9887 contains a Digital Video Interface (DVI 1.0) compatible receiver. This receiver supports displays ranging from VGA
to SXGA (25 MHz to 112 MHz). The receiver operates with
true color (24-bit) panels in 1 or 2 pixel(s)/clock mode, and also
features an intrapair skew tolerance up to one full clock cycle.
Fabricated in an advanced CMOS process, the AD9887 is provided in a 160-lead MQFP surface mount plastic package and is
speciﬁed over the 0°C to 70°C temperature range.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2001
AD9887–SPECIFICATIONS
ANALOG INTERFACE (V
D
Parameter
= 3.3 V, VDD = 3.3 V, ADC Clock = Maximum Conversion Rate, unless otherwise noted.)
Temp
Test
Level
Min
RESOLUTION
DC ACCURACY
Differential Nonlinearity
Integral Nonlinearity
No Missing Codes
ANALOG INPUT
Input Voltage Range
Minimum
Maximum
Gain Tempco
Input Bias Current
Input Offset Voltage
Input Full-Scale Matching
Offset Adjustment Range
25°C
Full
25°C
Full
Full
I
VI
I
VI
VI
Full
Full
25°C
25°C
Full
Full
Full
Full
VI
VI
V
IV
IV
VI
VI
VI
44
1.20
AD9887KS-140
Typ
Max
8
Bits
± 0.5
± 0.5
LSB
LSB
LSB
LSB
+1.25/–1.0
+1.25/–1.0
± 0.5
± 1.4
± 2.5
Guaranteed
0.5
0.5
1.0
135
Full
VI
V
Sampling Phase Tempco
Full
Full
Full
Full
Full
Full
Full
Full
Full
Full
Full
Full
Full
Full
25°C
Full
Full
VI
IV
IV
VI
VI
VI
VI
VI
VI
VI
VI
IV
VI
IV
IV
IV
IV
DIGITAL INPUTS
Input Voltage, High (VIH)
Input Voltage, Low (VIL)
Input Current, High (VIH)
Input Current, Low (V IL)
Input Capacitance
Full
Full
Full
Full
25°C
VI
VI
IV
IV
V
2.6
Full
Full
VI
VI
2.4
Full
IV
45
150
50
1
1
50
8.0
56
44
1.25
1.30
1.20
7
Full
Unit
8
1.0
Temperature Coefﬁcient
DIGITAL OUTPUTS
Output Voltage, High (VOH)
Output Voltage, Low (V OL)
Duty Cycle
DATACK, DATACK
Output Coding
Min
+1.15/–1.0
+1.15/–1.0
± 0.5
± 1.40
± 1.75
Guaranteed
REFERENCE OUTPUT
Output Voltage
SWITCHING PERFORMANCE 1
Maximum Conversion Rate
Minimum Conversion Rate
Clock to Data Skew, tSKEW
tBUFF
tSTAH
tDHO
tDAL
tDAH
tDSU
tSTASU
tSTOSU
HSYNC Input Frequency
Maximum PLL Clock Rate
Minimum PLL Clock Rate
PLL Jitter
AD9887KS-100
Typ
Max
50
1
1
50
8.0
56
1.25
1.30
7
± 50
± 50
100
–0.5
4.7
4.0
0
4.7
4.0
250
4.7
4.0
15
100
110
400
10
+2.0
–0.5
4.7
4.0
0
4.7
4.0
250
4.7
4.0
15
140
12
7002
10002
110
400
15
12
7003
10003
15
0.8
–1.0
1.0
3
3
2.4
0.4
50
Binary
–2–
55
45
50
Binary
MSPS
MSPS
ns
µs
µs
µs
µs
µs
ns
µs
µs
kHz
MHz
MHz
ps p-p
ps p-p
ps/°C
2.6
0.8
–1.0
1.0
V
ppm/°C
140
10
+2.0
V p-p
V p-p
ppm/°C
µA
µA
mV
% FS
% FS
V
V
µA
µA
pF
0.4
V
V
55
%
REV. 0
AD9887
Parameter
Temp
Test
Level
POWER SUPPLY
VD Supply Voltage
VDD Supply Voltage
PVD Supply Voltage
ID Supply Current (V D)
IDD Supply Current (V DD)4
IPVD Supply Current (PVD)
Total Supply Current4
Power-Down Supply Current
Full
Full
Full
25°C
25°C
25°C
Full
Full
IV
IV
IV
V
V
V
VI
VI
25°C
25°C
25°C
25°C
Full
V
V
V
V
V
330
2
1.5
46
45
330
2
1.5
46
45
MHz
ns
ns
dB
dB
Full
V
60
60
dBc
V
30
30
°C/W
DYNAMIC PERFORMANCE
Analog Bandwidth, Full Power
Transient Response
Overvoltage Recovery Time
Signal-to-Noise Ratio (SNR)5
(Without Harmonics)
fIN = 40.7 MHz
Crosstalk
THERMAL CHARACTERISTICS
θJA Junction-to-Ambient6
Thermal Resistance
Min
3.0
2.2
3.0
AD9887KS-100
Typ
Max
3.3
3.3
3.3
140
34
15
170
18
NOTES
1
Drive Strength = 11.
2
VCO Range = 01, Charge Pump Current = 001, PLL Divider = 1693.
3
VCO Range = 10, Charge Pump Current = 110, PLL Divider = 1600.
4
DEMUX = 1, DATACK and DATACK Load = 10 pF, Data Load = 5 pF.
5
Using external pixel clock.
6
Simulated typical performance with package mounted to a 4-layer board.
Speciﬁcations subject to change without notice.
REV. 0
–3–
3.6
3.6
3.6
258
25
Min
3.0
2.2
3.0
AD9887KS-140
Typ
Max
3.3
3.3
3.3
155
48
16
215
18
3.6
3.6
3.6
258
25
Unit
V
V
V
mA
mA
mA
mA
mA
AD9887–SPECIFICATIONS
DIGITAL INTERFACE (V
D
= 3.3 V, VDD = 3 V, Clock = Maximum)
Parameter
Conditions
Test
Level
Min
RESOLUTION
DC DIGITAL I/O SPECIFICATIONS
High-Level Input Voltage, (VIH)
Low-Level Input Voltage, (VIL)
High-Level Output Voltage, (VOH)
Low-Level Output Voltage, (VOL)
Input Clamp Voltage, (VCINL)
Input Clamp Voltage, (VCIPL)
Output Clamp Voltage, (VCONL)
Output Clamp Voltage, (VCOPL)
Output Leakage Current, (IOL)
DC SPECIFICATIONS
Output High Drive
(IOHD) (VOUT = VOH)
(ICL = –18 mA)
(ICL = +18 mA)
(ICL = –18 mA)
(ICL = +18 mA)
(High Impedance)
PVD Supply Voltage
VD Supply Current (Typical Pattern)1
VDD Supply Current (Typical Pattern)1, 4
IV
IV
V
V
2.2
3.0
PVD Supply Current (Typical Pattern)1
Total Supply Current (Typical Pattern)1, 4
VD Supply Current (Worst-Case Pattern)2
VDD Supply Current (Worst-Case Pattern)2, 4
PVD Supply Current (Worst-Case Pattern)2
Total Supply Current (Worst-Case Pattern)2, 4
Power-Down Supply Current (IPD)
V
VI
V
V
V
VI
VI
POWER SUPPLY
VD Supply Voltage
VDD Supply Voltage
Minimum Value for 2 Pixels per
Clock Mode
AC SPECIFICATIONS
Intrapair (+ to –) Differential Input Skew (TDPS)
Channel-to-Channel Differential Input Skew (TCCS)
Low-to-High Transition Time for Data and
Controls (DLHT)
Low-to-High Transition Time for DATACK (DLHT)
High-to-Low Transition Time for Data and
Controls (DHLT)
Output Drive = High; CL = 10 pF
Output Drive = Med; CL = 7 pF
Output Drive = Low; CL = 5 pF
Output Drive = High; CL = 10 pF
Output Drive = Med; CL = 7 pF
Output Drive = Low; CL = 5 pF
Output Drive = High; CL = 10 pF
Output Drive = Med; CL = 7 pF
Output Drive = Low; CL = 5 pF
–4–
V
V
V
0.4
V
GND – 0.8 V
VDD + 0.8 V
GND – 0.8 V
VDD + 0.8 V
+10
µA
–10
3.0
Differential Input Voltage Single-Ended Amplitude
Bits
2.4
IV
DATACK Low Drive
(VOLC) (VOUT = VOL)
8
0.8
75
(VOHC) (VOUT = VOH)
Unit
2.6
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
(IOLD) (VOUT = VOL)
Output Drive = High
Output Drive = Med
Output Drive = Low
Output Drive = High
Output Drive = Med
Output Drive = Low
Output Drive = High
Output Drive = Med
Output Drive = Low
Output Drive = High
Output Drive = Med
Output Drive = Low
VI
VI
VI
VI
IV
IV
IV
IV
IV
AD9887KS
Typ
Max
13
8
5
–9
–7
–5
25
12
8
–25
–19
–8
800
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mV
3.3
3.6
V
3.3
3.3
274
38
3.6
3.6
V
V
mA
mA
21
362
280
75
21
400
13
25
IV
IV
360
1.0
IV
IV
IV
IV
IV
IV
IV
IV
IV
2.0
3.0
3.4
1.3
1.9
2.5
2.7
3.0
3.3
mA
mA
mA
mA
mA
mA
mA
ps
Clock
Period
ns
ns
ns
ns
ns
ns
ns
ns
ns
REV. 0
AD9887
Parameter
Test
Level
Conditions
AC SPECIFICATIONS (continued)
High-to-Low Transition Time for DATACK (DHLT)
Output Drive = High; CL =10 pF
Output Drive = Med; CL = 7 pF
Output Drive = Low; CL = 5 pF
AD9887KS
Min
Typ
Max
Clock to Data Skew, tSKEW
Duty Cycle, tDCYCLE
IV
IV
IV
IV
IV
–0.5
45
1.4
1.7
2.1
+2.0
55
DATACK Frequency (FCIP) (1 Pixel/Clock)
DATACK Frequency (FCIP) (2 Pixels/Clock)
VI
IV
20
10
112
56
Unit
ns
ns
ns
ns
% of
Period
High
MHz
MHz
NOTES
1
The typical pattern contains a gray scale area, Output Drive = High.
2
The worst-case pattern contains a black and white checkerboard pattern, Output Drive = High.
3
The setup and hold times with respect to the DATACK rising edge are the same as the falling edge.
4
1 Pixel/clock mode, DATACK and DATACK Load = 10 pF, Data Load = 5 pF.
ABSOLUTE MAXIMUM RATINGS *
EXPLANATION OF TEST LEVELS
VD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 V
VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 V
Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . VD to 0.0 V
VREF IN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VD to 0.0 V
Digital Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 V to 0.0 V
Digital Output Current . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
Operating Temperature . . . . . . . . . . . . . . . . . –25°C to +85°C
Storage Temperature . . . . . . . . . . . . . . . . . . –65°C to +150°C
Maximum Junction Temperature . . . . . . . . . . . . . . . . 150°C
Maximum Case Temperature . . . . . . . . . . . . . . . . . . . 150°C
Test Level
Explanation
I
II
100% production tested.
100% production tested at 25°C and sample
tested at speciﬁed temperatures.
Sample tested only.
Parameter is guaranteed by design and characterization testing.
Parameter is a typical value only.
100% production tested at 25°C; guaranteed
by design and characterization testing.
III
IV
V
VI
*Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions outside of those indicated in the operation
sections of this speciﬁcation is not implied. Exposure to absolute maximum ratings
for extended periods may affect device reliability.
ORDERING GUIDE
Model
Temperature
Range
Package
Description
Package
Option
AD9887KS-140
AD9887KS-100
AD9887/PCB
0°C to 70°C
0°C to 70°C
25°C
Plastic Quad Flatpack
Plastic Quad Flatpack
Evaluation Board
S-160
S-160
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the AD9887 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
REV. 0
–5–
WARNING!
ESD SENSITIVE DEVICE
AD9887
121
122
123
125
124
126
128
127
129
130
131
132
133
134
135
136
137
139
138
140
141
142
143
144
145
146
148
149
147
150
151
152
153
154
155
156
157
1
120 RMIDSCV
119 RAIN
PIN 1
IDENTIFIER
2
3
4
118 RCLAMPV
117 VD
116 GND
5
6
115 VD
114 V
D
113 GND
7
8
9
112 GND
111 GMIDSCV
110 GAIN
10
11
12
13
109 GCLAMPV
108 SOGIN
14
107 VD
106 GND
15
16
105 VD
104 VD
103 GND
17
18
19
20
102 GND
101 BMIDSCV
AD9887
21
22
100 BAIN
99 BCLAMPV
TOP VIEW
(Not to Scale)
23
98 VD
97 GND
24
25
96 VD
95 GND
26
27
28
94 CKINV
93 CLAMP
29
30
92 SDA
91 SCL
31
90 A0
32
89 A1
88 PVD
33
34
35
87 PVD
86 GND
36
85 GND
37
84 COAST
38
83 CKEXT
82 HSYNC
39
40
80
79
78
77
76
75
74
73
72
71
70
69
68
67
65
66
64
63
61
62
60
59
58
57
56
55
54
53
52
51
50
49
47
48
46
45
44
43
GND
GND
VDD
GND
SCANOUT
CTL0
CTL1
CTL2
CTL3
SCANCLK
VD
GND
RTERM
VD
VD
Rx2+
Rx2–
GND
Rx1+
Rx1–
GND
Rx0+
Rx0–
GND
RxC+
RxC–
VD
VD
GND
VD
NC
NC
NC
GND
PVD
GND
PVD
FILT
PVD
GND
42
81 VSYNC
41
VDD
GND
GREEN A<7>
GREEN A<6>
GREEN A<5>
GREEN A<4>
GREEN A<3>
GREEN A<2>
GREEN A<1>
GREEN A<0>
VDD
GND
GREEN B<7>
GREEN B<6>
GREEN B<5>
GREEN B<4>
GREEN B<3>
GREEN B<2>
GREEN B<1>
GREEN B<0>
VDD
GND
BLUE A<7>
BLUE A<6>
BLUE A<5>
BLUE A<4>
BLUE A<3>
BLUE A<2>
BLUE A<1>
BLUE A<0>
VDD
GND
BLUE B<7>
BLUE B<6>
BLUE B<5>
BLUE B<4>
BLUE B<3>
BLUE B<2>
BLUE B<1>
BLUE B<0>
158
160
159
RED B<0>
RED B<1>
RED B<2>
RED B<3>
RED B<4>
RED B<5>
RED B<6>
RED B<7>
GND
VDD
RED A<0>
RED A<1>
RED A<2>
RED A<3>
RED A<4>
RED A<5>
RED A<6>
RED A<7>
GND
VDD
SOGOUT
HSOUT
VSOUT
DE
SCDT
DATACK
DATACK
GND
VDD
GND
GND
SCANIN
GND
VD
REFOUT
REFIN
VD
VD
GND
GND
PIN CONFIGURATION
NC = NO CONNECT
–6–
REV. 0
AD9887
Table I. Complete Pinout List
Pin
Pin
Name
Function
Value
Pin
Number
Interface
Analog Video
Inputs
RAIN
GAIN
BAIN
Analog Input for Converter R
Analog Input for Converter G
Analog Input for Converter B
0.0 V to 1.0 V
0.0 V to 1.0 V
0.0 V to 1.0 V
119
110
100
Analog
Analog
Analog
External
Sync/Clock
Inputs
HSYNC
VSYNC
SOGIN
CLAMP
COAST
CKEXT
CKINV
Horizontal SYNC Input
Vertical SYNC Input
Input for Sync-on-Green
Clamp Input (External CLAMP Signal)
PLL COAST Signal Input
External Pixel Clock Input (to Bypass the PLL) to VDD or Ground
ADC Sampling Clock Invert
3.3 V CMOS
3.3 V CMOS
0.0 V to 1.0 V
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
82
81
108
93
84
83
94
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Sync Outputs
HSOUT
VSOUT
SOGOUT
HSYNC Output Clock (Phase-Aligned with DATACK)
VSYNC Output Clock (Phase-Aligned with DATACK)
Sync on Green Slicer Output
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
139
138
140
Both
Both
Analog
Voltage
Reference
REFOUT
REFIN
Internal Reference Output (Bypass with 0.1 µF to Ground)
Reference Input (1.25 V ± 10%)
1.25 V
1.25 V ± 10%
126
125
Analog
Analog
Clamp Voltages
RMIDSCV
RCLAMPV
GMIDSCV
GCLAMPV
BMIDSCV
BCLAMPV
Red Channel Midscale Clamp Voltage Output
Red Channel Midscale Clamp Voltage Input
Green Channel Midscale Clamp Voltage Output
Green Channel Midscale Clamp Voltage Input
Blue Channel Midscale Clamp Voltage Output
Blue Channel Midscale Clamp Voltage Input
120
118
111
109
101
99
Analog
Analog
Analog
Analog
Analog
Analog
PLL Filter
FILT
Connection for External Filter Components for Internal PLL
Power Supply
VD
VDD
PVD
GND
Analog Power Supply
Output Power Supply
PLL Power Supply
Ground
3.3 V ± 10%
3.3 V ± 10%
3.3 V ± 10%
0V
Serial Port
(2-Wire
Serial Interface)
SDA
SCL
A0
A1
Serial Port Data I/O
Serial Port Data Clock (100 kHz Max)
Serial Port Address Input 1
Serial Port Address Input 2
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
92
91
90
89
Both
Both
Both
Both
Data Outputs
Red B[7:0]
Green B[7:0]
Blue B[7:0]
Red A[7:0]
Green A[7:0]
Blue A[7:0]
Port B/Odd Outputs of Converter “Red,” Bit 7 Is the MSB
Port B/Odd Outputs of Converter “Green,” Bit 7 Is the MSB
Port B/Odd Outputs of Converter “Blue,” Bit 7 Is the MSB
Port A/Even Outputs of Converter “Red,” Bit 7 Is the MSB
Port A/Even Outputs of Converter “Green,” Bit 7 Is the MSB
Port A/Even Outputs of Converter “Blue,” Bit 7 Is the MSB
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
153–160
13–20
33–40
143–150
3–10
23–30
Both
Both
Both
Both
Both
Both
Data Clock
Outputs
DATACK
DATACK
Data Output Clock for the Analog and Digital Interface
Data Output Clock Complement for the Analog Interface Only
3.3 V CMOS
3.3 V CMOS
134
135
Both
Both
Type
0.0 V to 0.75 V
0.0 V to 0.75 V
0.0 V to 0.75 V
78
Analog
Both
Both
Both
Both
Sync Detect
SCDT
Sync Detect Output
3.3 V CMOS
136
Both
Scan Function
SCANIN
SCANOUT
SCANCLK
Input for SCAN Function
Output for SCAN Function
Clock for SCAN Function
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
129
45
50
Both
Both
Both
No Connect
NC
These Pins Should be Left Unconnected
71–73
Both
Digital Video
Data Inputs
Rx0+
Rx0–
Rx1+
Rx1–
Rx2+
Rx2–
Digital Input Channel 0 True
Digital Input Channel 0 Complement
Digital Input Channel 1 True
Digital Input Channel 1 Complement
Digital Input Channel 2 True
Digital Input Channel 2 Complement
62
63
59
60
56
57
Digital
Digital
Digital
Digital
Digital
Digital
Digital Video
Clock Inputs
Rxc+
Rxc–
Digital Data Clock True
Digital Data Clock Complement
65
66
Digital
Digital
Data Enable
DE
Data Enable
3.3 V CMOS
137
Digital
Control Bits
CTL[0:3]
Decoded Control Bits
3.3 V CMOS
46–49
Digital
RTERM
RTERM
Sets Internal Termination Resistance
53
Digital
REV. 0
–7–
AD9887
DESCRIPTIONS OF PINS SHARED BETWEEN ANALOG
AND DIGITAL INTERFACES
HSOUT
VSOUT
Data Clock Outputs
DATACK
DATACK
Horizontal Sync Output
A reconstructed and phase-aligned version of
the video HSYNC. The polarity of this output
can be controlled via a serial bus bit. In analog
interface mode the placement and duration
are variable. In digital interface mode the
placement and duration are set by the graphics
transmitter.
Just like the data outputs, the data clock outputs are shared between the two interfaces.
They also behave differently depending on
which interface is active. Refer to the sections
on the two interfaces to determine how these
pins behave.
Various
Vertical Sync Output
The separated VSYNC from a composite
signal or a direct pass through of the VSYNC
input. The polarity of this output can be controlled via a serial bus bit. The placement and
duration in all modes is set by the graphics
transmitter.
SCDT
Serial Port Data I/O
Serial Port Data Clock
Serial Port Address Input 1
Serial Port Address Input 2
For a full description of the 2-wire serial register and how it works, refer to the Control
Register section.
SCAN Function
SCANIN
Data Input for SCAN Function
Data can be loaded serially into the 48-bit
SCAN register through this pin, clocking it in
with the SCANCLK pin. It then comes out of
the 48 data outputs in parallel. This function
is useful for loading known data into a graphics controller chip for testing purposes.
Data Outputs
RED A
RED B
GREEN A
GREEN B
BLUE A
BLUE B
Chip Active/Inactive Detect Output
The logic for the SCDT pin is [analog interface
HSYNC detection] OR [digital interface DE
detection]. So, the SCDT pin will switch to
logic LOW under two conditions, when neither interface is active or when the chip is in
full chip power-down mode. The data outputs
are automatically three-stated when SCDT is
LOW. This pin can be read by a controller in
order to determine periods of inactivity.
Serial Port (2-Wire)
SDA
SCL
A0
A1
Data Output Clock
Data Output Clock Complement
Data Output, Red Channel, Port A/Even
Data Output, Red Channel, Port B/Odd
Data Output, Green Channel, Port A/Even
Data Output, Green Channel, Port B/Odd
Data Output, Blue Channel, Port A/Even
Data Output, Blue Channel, Port B/Odd
SCANOUT
Data Output for SCAN Function
The data in the 48-bit SCAN register can be
read through this pin. Data is read on a FIFO
basis and is clocked via the SCANCLK pin.
SCANCLK
The main data outputs. Bit 7 is the MSB.
These outputs are shared between the two
interfaces and behave according to which
interface is active. Refer to the sections on the
two interfaces for more information on how
these outputs behave.
Data Clock for SCAN Function
This pin clocks the data through the SCAN
register. It controls both data input and data
output.
–8–
REV. 0
AD9887
Table II. Analog Interface Pin List
Pin Type
Pin Name
Function
Value
Pin No.
Analog Video Inputs
RAIN
GAIN
BAIN
HSYNC
VSYNC
SOGIN
CLAMP
COAST
CKEXT
Analog Input for Converter R
Analog Input for Converter G
Analog Input for Converter B
Horizontal SYNC Input
Vertical SYNC Input
Sync-on-Green Input
Clamp Input (External CLAMP Signal)
PLL COAST Signal Input
External Pixel Clock Input (to Bypass Internal PLL)
or 10 kΩ to VDD
ADC Sampling Clock Invert
HSYNC Output (Phase-Aligned with DATACK and DATACK)
VSYNC Output (Asynchronous)
Sync-on-Green Slicer Output or Raw HSYNC Output
Internal Reference Output (bypass with 0.1 µF to ground)
Reference Input (1.25 V ± 10%)
Voltage output equal to the RED converter midscale voltage.
During midscale clamping, the RED Input is clamped to this pin.
Voltage output equal to the GREEN converter midscale voltage.
During midscale clamping, the GREEN Input is clamped to this pin.
Voltage output equal to the BLUE converter midscale voltage.
During midscale clamping, the BLUE Input is clamped to this pin.
Connection for External Filter Components for Internal PLL
Main Power Supply
PLL Power Supply (Nominally 3.3 V)
Output Power Supply
Ground
0.0 V to 1.0 V
0.0 V to 1.0 V
0.0 V to 1.0 V
3.3 V CMOS
3.3 V CMOS
0.0 V to 1.0 V
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
119
110
100
82
81
108
93
84
83
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
1.25 V
1.25 V ± 10%
0.5 V ± 50%
0.0 V to 0.75 V
0.5 V ± 50%
0.0 V to 0.75 V
0.5 V ± 50%
0.0 V to 0.75 V
94
139
138
140
126
125
120
118
111
109
101
99
78
External
Sync/Clock
Inputs
Sync Outputs
Voltage Reference
Clamp Voltages
PLL Filter
Power Supply
CKINV
HSOUT
VSOUT
SOGOUT
REFOUT
REFIN
RMIDSCV
RCLAMPV
GMIDSCV
GCLAMPV
BMIDSCV
BCLAMPV
FILT
VD
PVD
VDD
GND
PIN FUNCTION DETAILS (ANALOG INTERFACE)
Inputs
RAIN
Analog Input for RED Channel
GAIN
Analog Input for GREEN Channel
BAIN
Analog Input for BLUE Channel
High-impedance inputs that accept the RED,
GREEN, and BLUE channel graphics signals,
respectively. For RGB, the three channels are
identical and can be used for any colors, but
colors are assigned for convenient reference.
For proper 4:2:2 formatting in a YUV application, the Y channel must be connected to
the GAIN input, U must be connected to the
BAIN input, and V must be connected to the
RAIN input.
Polarity = 0, the falling edge of HSYNC is
used. When HSYNC Polarity = 1, the rising
edge is active.
The input includes a Schmitt trigger for noise
immunity, with a nominal input threshold
of 1.5 V.
Electrostatic Discharge (ESD) protection
diodes will conduct heavily if this pin is driven
more than 0.5 V above the maximum tolerance voltage (3.3 V), or more than 0.5 V
below ground.
VSYNC
SOGIN
Sync-on-Green Input
This input is provided to assist with processing
signals with embedded sync, typically on the
GREEN channel. The pin is connected to a
high-speed comparator with an internally
generated threshold, which is set to 0.15 V
above the negative peak of the input signal.
Horizontal Sync Input
This input receives a logic signal that establishes the horizontal timing reference and
provides the frequency reference for pixel
clock generation.
When connected to an ac-coupled graphics
signal with embedded sync, it will produce a
noninverting digital output on SOGOUT.
When not used, this input should be left
unconnected. For more details on this function and how it should be conﬁgured, refer to
the Sync-on-Green section.
The logic sense of this pin is controlled by
serial register 0Fh Bit 7 (HSYNC Polarity).
Only the leading edge of HSYNC is active,
the trailing edge is ignored. When HSYNC
REV. 0
Vertical Sync Input
This is the input for vertical sync.
They accommodate input signals ranging
from 0.5 V to 1.0 V full scale. Signals should
be ac-coupled to these pins to support clamp
operation.
HSYNC
3.3 V ± 5%
3.3 V ± 5%
3.3 V or 2.5 V ± 5%
0V
–9–
AD9887
CLAMP
This logic input may be used to deﬁne the
time during which the input signal is clamped
to the reference dc level, (ground for RGB or
midscale for YUV). It should be exercised
when the reference dc level is known to be
present on the analog input channels, typically
during the back porch of the graphics signal.
The CLAMP pin is enabled by setting control
bit EXTCLMP to 1, (the default power-up is 0).
When disabled, this pin is ignored and the
clamp timing is determined internally by
counting a delay and duration from the trailing
edge of the HSYNC input. The logic sense of
this pin is controlled by CLAMPOL. When
not used, this pin must be grounded and
EXTCLMP programmed to 0.
COAST
This pin should be exercised only during blanking
intervals (typically vertical blanking) as it may
produce several samples of corrupted data during
the phase shift.
External Clamp Input (Optional)
CKINV should be grounded when not used.
Outputs
DRA7-0
Data Output, Red Channel, Port A
DRB7-0
Data Output, Red Channel, Port B
DGA7-0
Data Output, Green Channel, Port A
DGB7-0
Data Output, Green Channel, Port B
DBA7-0
Data Output, Blue Channel, Port A
DBB7-0
Data Output, Blue Channel, Port B
These are the main data outputs. Bit 7 is the MSB.
Each channel has two ports. When the part is
operated in single-channel mode (DEMUX = 0),
all data are presented to Port A, and Port B is
placed in a high-impedance state.
Clock Generator Coast Input (Optional)
This input may be used to cause the pixel clock
generator to stop synchronizing with HSYNC
and continue producing a clock at its current
frequency and phase. This is useful when
processing signals from sources that fail to
produce horizontal sync pulses when in the
vertical interval. The COAST signal is generally
not required for PC-generated signals. Applications requiring COAST can do so through
the internal COAST found in the SYNC
processing engine.
Programming DEMUX to 1 established dualchannel mode, wherein alternate pixels are
presented to Port A and Port B of each channel. These will appear simultaneously, two
pixels presented at the time of every second
input pixel, when PAR is set to 1 (parallel
mode). When PAR = 0, pixel data appear
alternately on the two ports, one new sample
with each incoming pixel (interleaved mode).
In dual channel mode, the ﬁrst pixel after
HSYNC is routed to Port A. The second pixel
goes to Port B, the third to A, etc.
The logic sense of this pin is controlled by
COAST Polarity.
When not used, this pin may be grounded and
COAST Polarity programmed to 1, or tied
HIGH and COAST Polarity programmed to 0.
COAST Polarity defaults to 1 at power-up.
CKEXT
The delay from pixel sampling time to output is
ﬁxed. When the sampling time is changed by
adjusting the PHASE register, the output timing is
shifted as well. The DATACK, DATACK, and
HSOUT outputs are also moved, so the timing
relationship among the signals is maintained.
External Clock Input (Optional)
This pin may be used to provide an external
clock to the AD9887, in place of the clock
internally generated from HSYNC.
DATACK
Data Output Clock
DATACK
Data Output Clock Complement
It is enabled by programming EXTCLK to 1.
When an external clock is used, all other internal
functions operate normally. When unused, this
pin should be tied to VDD or to GROUND, and
EXTCLK programmed to 0. The clock phase
adjustment still operates when an external clock
source is used.
CKINV
Differential data clock output signals to be
used to strobe the output data and HSOUT
into external logic.
They are produced by the internal clock generator and are synchronous with the internal
pixel sampling clock.
When the AD9887 is operated in single-channel mode, the output frequency is equal to the
pixel sampling frequency. When operating in
dual channel mode, the clock frequency is onehalf the pixel frequency.
Sampling Clock Inversion (Optional)
This pin may be used to invert the pixel
sampling clock, which has the effect of
shifting the sampling phase 180°. This is in
support of Alternate Pixel Sampling mode,
wherein higher-frequency input signals (up
to 280 Mpps) may be captured by ﬁrst sampling the odd pixels, then capturing the even
pixels on the subsequent frame.
When the sampling time is changed by adjusting
the PHASE register, the output timing is shifted
as well. The Data, DATACK, DATACK, and
HSOUT outputs are all moved, so the timing
relationship among the signals is maintained.
–10–
REV. 0
AD9887
Either or both signals may be used, depending on the timing mode and interface design
employed.
HSOUT
Power Supply
VD
These pins supply power to the main elements
of the circuit. It should be ﬁltered to be as
quiet as possible.
Horizontal Sync Output
A reconstructed and phase-aligned version of
the Hsync input. Both the polarity and duration of this output can be programmed via
serial bus registers.
VDD
If the AD9887 is interfacing with lowervoltage logic, VDD may be connected to a
lower supply voltage (as low as 2.2 V) for
compatibility.
Sync-On-Green Slicer Output
This pin can be programmed to output
either the output from the Sync-On-Green
slicer comparator or an unprocessed but
delayed version of the HSYNC input. See
the Sync Block Diagram to view how this
pin is connected.
(Note: The output from this pin is the sliced
SOG, without additional processing from the
AD9887.)
PVD
GND
The absolute accuracy of this output is ± 4%,
and the temperature coefﬁcient is ± 50 ppm,
which is adequate for most AD9887 applications. If higher accuracy is required, an
external reference may be employed instead.
If an external reference is used, connect this
pin to ground through a 0.1 µF capacitor.
REFIN
Reference Input
The reference input accepts the master reference voltage for all AD9887 internal circuitry
(1.25 V ± 10%). It may be driven directly by
the REFOUT pin. Its high impedance presents a very light load to the reference source.
This pin should always be bypassed to Ground
with a 0.1 µF capacitor.
FILT
External Filter Connection
For proper operation, the pixel clock generator PLL requires an external ﬁlter. Connect
the ﬁlter shown Figure 7 to this pin. For
optimal performance, minimize noise and
parasitics on this node.
REV. 0
Ground
The ground return for all circuitry on chip.
It is recommended that the application circuit
board have a single, solid ground plane.
Internal Reference Output
Output from the internal 1.25 V bandgap reference. This output is intended to drive relatively
light loads. It can drive the AD9887 Reference
Input directly, but should be externally buffered if it is used to drive other loads as well.
Clock Generator Power Supply
The most sensitive portion of the AD9887 is
the clock generation circuitry. These pins
provide power to the clock PLL and help the
user design for optimal performance. The
designer should provide noise-free power to
these pins.
Analog Interface
REFOUT
Digital Output Power Supply
These supply pins are identiﬁed separately
from the VD pins so special care can be taken
to minimize output noise transferred into the
sensitive analog circuitry.
By maintaining alignment with DATACK,
DATACK, and Data, data timing with
respect to horizontal sync can always be
determined.
SOGOUT
Main Power Supply
THEORY OF OPERATION (INTERFACE DETECTION)
Active Interface Detection and Selection
The AD9887 includes circuitry to detect whether or not an
interface is active.
For detecting the analog interface, the circuitry monitors the
presence of HSYNC, VSYNC, and Sync-on-Green. The result of
the detection circuitry can be read from the 2-wire serial interface bus at address 11H Bits 7, 6, and 5 respectively. If one of
these sync signals disappears, the maximum time it takes for the
circuitry to detect it is 100 ms.
There are two stages for detecting the digital interface. The ﬁrst
stage searches for the presence of the digital interface clock.
The circuitry for detecting the digital interface clock is active
even when the digital interface is powered down. The result of
this detection stage can be read from the 2-wire serial interface
bus at address 11H Bit 4. If the clock disappears, the maximum
time it takes for the circuitry to detect it is 100 ms. The second
stage attempts to detect DE on the digital interface. Detection is
accomplished when 32 DEs have been counted. DE can only be
detected when the digital interface is powered up, so it is not
always active. The DE detection circuitry is one of the logic
inputs used to set the SyncDT output pin (Pin 136). The logic
for the SyncDT pin is [DE detect] OR [HSYNC detect].
There is an override for the automatic interface selection. It is
the AIO bit (Active Interface Override). When the AIO bit is set
to Logic 0, the automatic circuitry will be used. When the AIO
bit is set to Logic 1, the AIS bit will be used to determine the
active interface rather than the automatic circuitry.
–11–
AD9887
and the power-down bit to determine the correct power state.
In a given power mode not all circuitry in the inactive interface
is powered down completely. When the digital interface is
active, the bandgap reference and HSYNC detect circuitry is not
powered down. When the analog interface is active, the digital
interface clock detect circuit is not powered down. Table IV
summarizes how the AD9887 determines which power mode to
be in and what circuitry is powered on/off in each of these
modes. The power-down command has priority, followed by the
active interface override, and then the automatic circuitry.
Power Management
The AD9887 is a dual interface device with shared outputs.
Only one interface can be used at a time. For this reason, the
chip automatically powers down the unused interface. When
the analog interface is being used, most of the digital interface
circuitry is powered down and vice-versa. This helps to minimize
the AD9887 total power dissipation. In addition, if neither interface has activity on it, the chip powers down both interfaces.
The AD9887 uses the activity detect circuits, the active interface bits in the serial registers, the active interface override bits,
Table III. Interface Selection Controls
AIO
Analog
Interface Detect
Digital
Interface Detect
AIS
Active
Interface
1
X
X
0
0
1
X
Analog
Digital
None
0
0
0
1
X
Digital
1
0
X
Analog
1
0
X
Analog
1
Digital
Description
Force the analog interface active.
Force the digital interface active.
Neither interface was detected. Both interfaces are
powered down and the SyncDT pin gets set to Logic 0.
The digital interface was detected. Power down the
analog interface.
The analog interface was detected. Power down the
digital interface.
Both interfaces were detected. The analog interface has
priority.
Both interfaces were detected. The digital interface has
priority.
Table IV. Power-Down Mode Descriptions
Mode
PowerDown1
Inputs
Analog
Digital
Interface Interface
Detect2
Detect3
Active
Active
Interface Interface
Override Select
Soft Power-Down (Seek Mode)
1
0
0
0
X
Digital Interface On
1
0
1
0
X
Analog Interface On
1
1
0
0
X
Serial Bus Arbitrated Interface
Serial Bus Arbitrated Interface
Override to Analog Interface
Override to Digital Interface
Absolute Power-Down
1
1
1
1
0
1
1
X
X
X
1
1
X
X
X
0
0
1
1
X
0
1
0
1
X
Powered On or Comments
Serial Bus, Digital Interface Clock Detect,
Analog Interface Activity Detect, SOG,
Bandgap Reference
Serial Bus, Digital Interface, Analog Interface
Activity Detect, SOG, Outputs, Bandgap
Reference
Serial Bus, Analog Interface, Digital Interface
Clock Detect, SOG, Outputs, Bandgap
Reference
Same as Analog Interface On Mode
Same as Digital Interface On Mode
Same as Analog Interface On Mode
Same as Digital Interface On Mode
Serial Bus
NOTES
1
Power-down is controlled via bit 0 in serial bus Register 12h.
2
Analog Interface Detect is determined by OR-ing Bits 7, 6, and 5 in serial bus Register 11h.
3
Digital Interface Detect is determined by Bit 4 in serial bus Register 11h.
–12–
REV. 0
AD9887
THEORY OF OPERATION AND DESIGN GUIDE
(ANALOG INTERFACE)
General Description
The AD9887 is a fully integrated solution for capturing analog
RGB signals and digitizing them for display on flat panel monitors
or projectors. The device is ideal for implementing a computer
interface in HDTV monitors or as the front end to highperformance video scan converters.
Implemented in a high-performance CMOS process, the interface can capture signals with pixel rates of up to 140 MHz and,
with an Alternate Pixel Sampling mode, up to 280 MHz.
The AD9887 includes all necessary input buffering, signal dc
restoration (clamping), offset and gain (brightness and contrast)
adjustment, pixel clock generation, sampling phase control,
and output data formatting. All controls are programmable via
a 2-wire serial interface. Full integration of these sensitive analog
functions makes system design straightforward and less sensitive to the physical and electrical environment.
HSYNC, VSYNC Inputs
The AD9887 receives a horizontal sync signal and uses it to
generate the pixel clock and clamp timing. It is possible to operate
the AD9887 without applying HSYNC (using an external clock,
external clamp) but a number of features of the chip will be
unavailable, so it is recommended that HSYNC be provided.
This can be either a sync signal directly from the graphics
source, or a preprocessed TTL or CMOS level signal.
The HSYNC input includes a Schmitt trigger buffer and is capable
of handling signals with long rise times, with superior noise
immunity. In typical PC-based graphic systems, the sync signals
are simply TTL-level drivers feeding unshielded wires in the
monitor cable. As such, no termination is required or desired.
When the VSYNC input is selected as the source for VSYNC, it is
used for COAST generation and is passed through to the
VSOUT pin.
Serial Control Port
With a typical power dissipation of less than 725 mW and an
operating temperature range of 0°C to 70°C, the device requires
no special environmental considerations.
The serial control port is designed for 3.3 V logic. If there are
5 V drivers on the bus, these pins should be protected with
150 Ω series resistors placed between the pull-up resistors and
the input pins.
Input Signal Handling
Output Signal Handling
The AD9887 has three high-impedance analog input pins for
the Red, Green, and Blue channels. They will accommodate
signals ranging from 0.5 V to 1.0 V p-p.
The digital outputs are designed and speciﬁed to operate from a
3.3 V power supply (VDD). They can also work with a VDD as
low as 2.5 V for compatibility with other 2.5 V logic.
Signals are typically brought onto the interface board via a
DVI-I connector, a 15-lead D connector, or BNC connectors.
The AD9887 should be located as close as practical to the
input connector. Signals should be routed via matched-impedance
traces (normally 75 Ω) to the IC input pins.
Clamping
RGB Clamping
At that point the signal should be resistively terminated (75 Ω
to the signal ground return) and capacitively coupled to the
AD9887 inputs through 47 nF capacitors. These capacitors
form part of the dc restoration circuit.
Most graphics systems produce RGB signals with black at
ground and white at approximately 0.75 V. However, if sync
signals are embedded in the graphics, the sync tip is often at
ground and black is at 300 mV. The white level will then be
approximately 1.0 V. Some common RGB line ampliﬁer boxes
use emitter-follower buffers to split signals and increase drive
capability. This introduces a 700 mV dc offset to the signal, which
is removed by clamping for proper capture by the AD9887.
In an ideal world of perfectly matched impedances, the best performance can be obtained with the widest possible signal bandwidth.
The wide bandwidth inputs of the AD9887 (330 MHz) can
track the input signal continuously as it moves from one pixel
level to the next, and digitize the pixel during a long, flat pixel
time. In many systems, however, there are mismatches, reflections, and noise, which can result in excessive ringing and
distortion of the input waveform. This makes it more difﬁcult
to establish a sampling phase that provides good image quality.
It has been shown that a small inductor in series with the input
is effective in rolling off the input bandwidth slightly, and providing a high quality signal over a wider range of conditions.
Using a Fair-Rite #2508051217Z0 High-Speed Signal Chip
Bead inductor in the circuit of Figure 1 gives good results in
most applications.
47nF
RGB
INPUT
RAIN
GAIN
BAIN
To digitize the incoming signal properly, the dc offset of the
input must be adjusted to ﬁt the range of the on-board A/D
converters.
The key to clamping is to identify a portion (time) of the signal
when the graphic system is known to be producing black. Originating
from CRT displays, the electron beam is “blanked” by sending a
black level during horizontal retrace to prevent disturbing the
image. Most graphics systems maintain this format of sending a
black level between active video lines.
An offset is then introduced which results in the A/D converters
producing a black output (code 00h) when the known black
input is present. The offset then remains in place when other
signal levels are processed, and the entire signal is shifted to
eliminate offset errors.
In systems with embedded sync, a blacker-than-black signal
(HSYNC) is produced briefly to signal the CRT that it is time
to begin a retrace. For obvious reasons, it is important to avoid
75⍀
Figure 1. Analog Input Interface Circuit
REV. 0
–13–
AD9887
clamping on the tip of HSYNC. Fortunately, there is virtually
always a period following HSYNC called the back porch where
a good black reference is provided. This is the time when clamping should be done.
RMIDSCV
RCLAMPV
0.1␮F
GMIDSCV
The clamp timing can be established by exercising the CLAMP
pin at the appropriate time (with EXTCLMP = 1). The polarity
of this signal is set by the Clamp Polarity bit.
The value of the external input coupling capacitor affects the performance of the clamp. If the value is too small, there can be an
amplitude change during a horizontal line time (between clamping
intervals). If the capacitor is too large, it will take excessively long for
the clamp to recover from a large change in incoming signal offset.
The recommended value (47 nF) results in recovery from a step error
of 100 mV to within 1/2 LSB in 10 lines using a clamp duration of
20 pixel periods on a 60 Hz SXGA signal.
YUV Clamping
YUV signals are slightly different from RGB signals in that the
dc reference level (black level in RGB signals) will be at the
midpoint of the U and V video signal. For these signals it can
be necessary to clamp to the midscale range of the A/D converter range (80h) rather than bottom of the A/D converter
range (00h).
Clamping to midscale rather than ground can be accomplished
by setting the clamp select bits in the serial bus register. Each of
the three converters has its own selection bit so that they can be
clamped to either midscale or ground independently. These bits
are located in Register 0Fh and are Bits 0–2.
BMIDSCV
BCLAMPV
0.1␮F
Figure 2. Typical Clamp Conﬁguration for RBG/YUV
Applications
Gain and Offset Control
The AD9887 can accommodate input signals with inputs ranging from 0.5 V to 1.0 V full scale. The full-scale range is set in
three 8-bit registers (Red Gain, Green Gain, and Blue Gain).
A code of 0 establishes a minimum input range of 0.5 V; 255
corresponds with the maximum range of 1.0 V. Note that
increasing the gain setting results in an image with less contrast.
The offset control shifts the entire input range, resulting in a
change in image brightness. Three 7-bit registers (Red Offset,
Green Offset, Blue Offset) provide independent settings for
each channel.
The offset controls provide a ± 63 LSB adjustment range. This
range is connected with the full-scale range, so if the input range
is doubled (from 0.5 V to 1.0 V) then the offset step size is also
doubled (from 2 mV per step to 4 mV per step).
Figure 3 illustrates the interaction of gain and offset controls.
The magnitude of an LSB in offset adjustment is proportional
to the full-scale range, so changing the full-scale range also
changes the offset. The change is minimal if the offset setting is
near midscale. When changing the offset, the full-scale range is
not affected, but the full-scale level is shifted by the same amount
as the zero-scale level.
The midscale reference voltage that each A/D converter clamps
to is provided independently on the RMIDSCV, GMIDSCV, and
BMIDSCV pins. Each converter must have its own midscale reference because both offset adjustment and gain adjustment for
each converter will affect the dc level of midscale.
During clamping, the Y and V converters are clamped to their
respective midscale reference input. These inputs are pins
BCLAMPV, and RCLAMPV for the U and V converters respectively.
The typical connections for both RGB and YUV clamping are
shown below in Figure 2. Note: if midscale clamping is not
required, all of the midscale voltage outputs should still be connected to ground through a 0.1 µF capacitor.
–14–
OFFSET = 7Fh
OFFSET = 3Fh
1.0
INPUT RANGE – V
An easier method of clamp timing employs the AD9887 internal
clamp timing generator. The Clamp Placement register is programmed with the number of pixel clocks that should pass after
the trailing edge of HSYNC before clamping starts. A second
register (Clamp Duration) sets the duration of the clamp.
These are both 8-bit values, providing considerable flexibility in
clamp generation. The clamp timing is referenced to the trailing
edge of HSYNC, the back porch (black reference) always follows
HSYNC. A good starting point for establishing clamping is to
set the clamp placement to 08h (providing eight pixel periods
for the graphics signal to stabilize after sync) and set the clamp
duration to 14h (giving the clamp 20 pixel periods to reestablish
the black reference).
GCLAMPV
0.1␮F
OFFSET = 00h
0.5
OFFSET = 7Fh
OFFSET = 3Fh
0.0
OFFSET = 00h
00h
FFh
GAIN
Figure 3. Gain and Offset Control
REV. 0
AD9887
PIXEL CLOCK
Sync-on-Green
INVALID SAMPLE TIMES
The Sync-on-Green input operates in two steps. First, it sets a
baseline clamp level from the incoming video signal with a
negative peak detector. Second, it sets the Sync trigger level
(nominally 150 mV above the negative peak). The exact trigger
level is variable and can be programmed via register 11H. The
Sync-on-Green input must be ac-coupled to the green analog
input through its own capacitor as shown in Figure 4. The value
of the capacitor must be 1 nF ± 20%. If Sync-on-Green is not
used, this connection is not required and SOGIN should be left
unconnected. (Note: The Sync-on-Green signal is always negative polarity.) Please refer to the Sync Processing section for more
information.
Figure 5. Pixel Sampling Times
47nF
Any jitter in the clock reduces the precision with which the
sampling time can be determined, and must also be subtracted
from the stable pixel time.
RAIN
47nF
BAIN
47nF
GAIN
SOGIN
1nF
Figure 4. Typical Clamp Conﬁguration for RGB/YUV
Applications
Clock Generation
A Phase Locked Loop (PLL) is employed to generate the pixel
clock. The HSYNC input provides a reference frequency for the
PLL. A Voltage Controlled Oscillator (VCO) generates a much
higher pixel clock frequency. This pixel clock is divided by the
PLL divide value (Registers 01H and 02H) and phase compared
with the Hsync input. Any error is used to shift the VCO frequency and maintain lock between the two signals.
The stability of this clock is a very important element in providing the clearest and most stable image. During each pixel time,
there is a period when the signal is slewing from the old pixel
amplitude and settling at its new value. Then there is a time
when the input voltage is stable, before the signal must slew to a
new value (see Figure 5). The ratio of the slewing time to the
stable time is a function of the bandwidth of the graphics DAC
and the bandwidth of the transmission system (cable and termination). It is also a function of the overall pixel rate. Clearly, if the
dynamic characteristics of the system remain ﬁxed, the slewing
and settling times are likewise ﬁxed. This time must be subtracted from the total pixel period, leaving the stable period. At
higher pixel frequencies, the total cycle time is shorter, and the
stable pixel time becomes shorter as well.
14
The PLL characteristics are determined by the loop ﬁlter
design, by the PLL charge pump current and by the VCO range
setting. The loop ﬁlter design is illustrated in Figure 7. Recommended settings of VCO range and charge pump current for
VESA standard display modes are listed in Table VII.
PVD
10
8
6
RZ 3.3k⍀
FILT
Figure 7. PLL Loop Filter Detail
Four programmable registers are provided to optimize the performance of the PLL. These registers are:
1. The 12-Bit Divisor Register. The input Hsync frequencies
range from 15 kHz to 110 kHz. The PLL multiplies the
frequency of the Hsync signal, producing pixel clock frequencies in the range of 12 MHz to 140 MHz. The Divisor
Register controls the exact multiplication factor. This register
may be set to any value between 221 and 4095. (The divide
ratio that is actually used is the programmed divide ratio
plus one.)
4
135.0
94.5
108.0
85.5
78.8
75.0
65.0
50.0
56.3
40.0
36.0
31.5
0
25.2
2
0
PIXEL CLOCK – MHz
Figure 6. Pixel Clock Jitter vs. Frequency
REV. 0
CZ 0.039␮F
CP 0.0039␮F
2. The 2-Bit VCO Range Register. To lower the sensitivity of
the output frequency to noise on the control signal, the VCO
operating frequency range is divided into four overlapping
regions. The VCO Range register sets this operating range.
Because there are only four possible regions, only the two
least-signiﬁcant bits of the VCO Range register are used.
The frequency ranges for the lowest and highest regions
are shown in Table V.
12
JITTER (p-p) – %
Considerable care has been taken in the design of the AD9887’s
clock generation circuit to minimize jitter. As indicated in Figure 6, the clock jitter of the AD9887 is less than 6% of the total
pixel time in all operating modes, making the reduction in the
valid sampling time due to jitter negligible.
–15–
AD9887
3. The 3-Bit Charge Pump Current Register. This register
allows the current that drives the low pass loop ﬁlter to be
varied. The possible current values are listed in Table VI.
provides 32 phase-shift steps of 11.25° each. The Hsync
signal with an identical phase shift is available through the
HSOUT pin. Phase adjustment is still available if the pixel
clock is being provided externally.
Table V. VCO Frequency Ranges
PV1
PV0
Pixel Clock
Range (MHz)
KVCO Gain
(MHz/V)
0
0
1
1
0
1
0
1
12–35
35–70
70–110
110–140
150
150
150
180
4. The 5-Bit Phase Adjust Register. The phase of the generated
sampling clock may be shifted to locate an optimum sampling point within a clock cycle. The Phase Adjust register
Table VI. Charge Pump Current/Control Bits
Ip2
Ip1
Ip0
Current (␮A)
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
50
100
150
250
350
500
750
1500
The COAST allows the PLL to continue to run at the same
frequency, in the absence of the incoming Hsync signal. This
may be used during the vertical sync period, or any other
time that the Hsync signal is unavailable. The polarity of
the COAST signal may be set through the Coast Polarity Bit.
Also, the polarity of the Hsync signal may be set through the
HSYNC polarity Bit. If not using automatic polarity
detection, the HSYNC and COAST polarity bits should
be set to match the Polarity of their respective signals.
Table VII. Recommended VCO Range and Charge Pump Current Settings for Standard Display Formats
Refresh
Rate (Hz)
Horizontal
Frequency
(kHz)
Pixel Rate
(MHz)
VCORNGE
CURRENT
Standard
Resolution
VGA
640 × 480
60
72
75
85
31.5
37.7
37.5
43.3
25.175
31.500
31.500
36.000
00
00
00
00
101
101
110
110
SVGA
800 × 600
56
60
72
75
85
35.1
37.9
48.1
46.9
53.7
36.000
40.000
50.000
49.500
56.250
00
01
01
01
01
101
101
101
101
110
XGA
1024 × 768
60
70
75
80
85
48.4
56.5
60.0
64.0
68.3
65.000
75.000
78.750
85.500
94.500
01
10
10
10
10
110
101
101
101
101
SXGA
1280 × 1024
60
75
85
64.0
80.0
91.1
108.000
135.000
157.500*
10
11
10
110
110
110
UXGA
1600 × 1200
60
65
70
75
85
75.0
81.3
87.5
93.8
106.3
162.000*
175.500*
189.000*
202.500*
229.500*
10
10
10
10
11
110
110
110
110
110
*Graphics sampled at one-half the incoming pixel rate using Alternate Pixel Sampling mode.
–16–
REV. 0
AD9887
OFFSET
7
GAIN
8
DAC
DAC
SCANCLK
REF
SCANIN
IN
CLAMP
tSU = 3ns
8
ADC
x1.2
t HOLD = 0ns
Figure 11. SCAN Setup and Hold
VOFF
Alternate Pixel Sampling Mode
A Logic 1 input on Clock Invert (CKINV, Pin 94) inverts the
nominal ADC clock. CKINV can be switched between frames
to implement the alternate pixel sampling mode. This allows
higher effective image resolution to be achieved at lower pixel
rates but with lower frame rates.
Figure 8. ADC Block Diagram (Single Channel Output)
OFFSET
RANGE
INPUT RANGE
VOFF
(128 CODES)
VOFF
(128 CODES)
0V
On one frame, only even pixels are digitized. On the subsequent
frame, odd pixels are sampled. By reconstructing the entire
frame in the graphics controller, a complete image can be reconstructed. This is very similar to the interlacing process that is
employed in broadcast television systems, but the interlacing is
vertical instead of horizontal. The frame data is still presented to
the display at the full desired refresh rate (usually 60 Hz) so no
flicker artifacts are added.
INPUT RANGE
0.5V
OFFSET RANGE
1V
0V
Figure 9. Relationship of Offset Range to Input Range
SCAN Function
The SCAN function is intended as a pseudo JTAG function for
manufacturing test of the board. The ordinary operation of the
AD9887 is disabled during SCAN.
To enable the SCAN function, set register 14h, bit 2 to 1. To
SCAN in data to all 48 digital outputs, apply 48 serial bits of
data and 48 clocks (typically 5 MHz, max of 20 MHz) to the
SCANIN and SCANCLK pins respectively. The data is shifted
in on the rising edge of SCANCLK. The first serial bit shifted
in will appear at the RED A<7> output after one clock cycle.
After 48 clocks, the first bit is shifted all the way to the BLU
B<0>. The 48th bit will now be at the RED A<7> output. If
SCANCLK continues after 48 cycles, the data will continue to be
shifted from RED A<7> to BLU B<0> and will come out of the
SCANOUT pin as serial data on the falling edge of SCANCLK.
This is illustrated in Figure 10. A setup time (tSU) of 3 ns
should be plenty and no hold time (tHOLD) is required (≥ 0 ns).
This is illustrated in Figure 11.
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
O
E
Figure 12. Odd and Even Pixels in a Frame
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
O1
Figure 13. Odd Pixels from Frame 1
SCANCLK
SCANIN
BIT 1
RED A<7>
BLUE B<0>
SCANOUT
X
BIT 2
BIT 47
BIT 3
BIT 48
BIT 1
BIT 2
BIT 3
BIT 46
BIT 47
BIT 48
X
X
X
X
X
X
BIT 1
BIT 2
X
X
X
Figure 10. SCAN Timing
REV. 0
X
–17–
X
BIT 1
BIT 2
AD9887
PXLCLK
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
E2
ANY OUTPUT
SIGNAL
DATA OUT
DATACK
(OUTPUT)
tSKEW
tDCYCLE
tPER
Figure 17. Analog Output Timing
Hsync Timing
Figure 14. Even Pixels from Frame 2
Horizontal sync is processed in the AD9887 to eliminate
ambiguity in the timing of the leading edge with respect to the
phase-delayed pixel clock and data.
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
The Hsync input is used as a reference to generate the pixel
sampling clock. The sampling phase can be adjusted, with respect
to Hsync, through a full 360° in 32 steps via the Phase Adjust
register (to optimize the pixel sampling time). Display systems use
Hsync to align memory and display write cycles, so it is important
to have a stable timing relationship between Hsync output
(HSOUT) and data clock (DATACK).
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
O1E2O1E2O1E2O1E2O1E2O1E2
Figure 15. Combine Frame Output from Graphics Controller
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
O3E2O3E2O3E2O3E2O3E2O3E2
Figure 16. Subsequent Frame from Controller
Timing (Analog Interface)
The following timing diagrams show the operation of the
AD9887 analog interface in all clock modes. The part establishes timing by having the sample that corresponds to the pixel
digitized when the leading edge of HSYNC occurs sent to the
“A” data port. In Dual Channel Mode, the next sample is sent
to the “B” port. Future samples are alternated between the “A”
and “B” data ports. In Single Channel Mode, data is only sent
to the “A” data port, and the “B” port is placed in a high
impedance state.
The Output Data Clock signal is created so that its rising edge
always occurs between “A” data transitions, and can be used to
latch the output data externally.
Three things happen to Horizontal Sync in the AD9887. First,
the polarity of Hsync input is determined and will thus have a
known output polarity. The known output polarity can be programmed either active high or active low (Register 04H, Bit 4).
Second, HSOUT is aligned with DATACK and data outputs.
Third, the duration of HSOUT (in pixel clocks) is set via Register 07H. HSOUT is the sync signal that should be used to drive
the rest of the display system.
Coast Timing
In most computer systems, the Hsync signal is provided continuously on a dedicated wire. In these systems, the COAST
input and function are unnecessary, and should not be used.
In some systems, however, Hsync is disturbed during the Vertical Sync period (Vsync). In some cases, Hsync pulses disappear.
In other systems, such as those that employ Composite Sync
(Csync) signals or embed Sync-On-Green (SOG), Hsync includes
equalization pulses or other distortions during Vsync. To avoid
upsetting the clock generator during Vsync, it is important to
ignore these distortions. If the pixel clock PLL sees extraneous
pulses, it will attempt to lock to this new frequency, and will
have changed frequency by the end of the Vsync period. It will
then take a few lines of correct Hsync timing to recover at the
beginning of a new frame, resulting in a “tearing” of the image
at the top of the display.
The COAST input is provided to eliminate this problem. It is
an asynchronous input that disables the PLL input and allows
the clock to free-run at its then-current frequency. The PLL can
free-run for several lines without signiﬁcant frequency drift.
Coast can be provided by the graphics controller or it can be
internally generated by the AD9887 Sync processing engine.
–18–
REV. 0
AD9887
RGBIN
P0
P1
P2
P3
P4
P5
P6
P7
HSYNC
PxCK
HS
5-PIPE DELAY
ADCCK
DATACK
D0
DOUTA
D1
D2
D3
D4
D5
D6
D7
HSOUT
Figure 18. Single Channel Mode (Analog Interface)
RGBIN
P0 P1 P2 P3 P4 P5 P6 P7
HSYNC
PxCK
HS
5-PIPE DELAY
ADCCK
DATACK
DOUTA
D0
D2
D4
D6
HSOUT
Figure 19. Single Channel Mode, 2 Pixels/Clock (Even Pixels) (Analog Interface)
RGBIN
P0 P1 P2 P3 P4 P5 P6 P7
HSYNC
PxCK
HS
5.5-PIPE DELAY
ADCCK
DATACK
DOUTA
D1
D3
D5
D7
HSOUT
Figure 20. Single Channel Mode, 2 Pixels/Clock (Odd Pixels) (Analog Interface)
REV. 0
–19–
AD9887
RGBIN
P0
P1
P2
P3
P4
P5
P6
P7
HSYNC
PxCK
HS
3-PIPE DELAY
ADCCK
DATACK
DOUTA
D0
DOUTB
D2
D1
D4
D3
D6
D7
D5
HSOUT
Figure 21. Dual Channel Mode, Interleaved Outputs (Analog Interface), Outphase = 1
RGBIN
P0
P1
P2
P3
P4
P5
P6
P7
HSYNC
PxCK
HS
7-PIPE DELAY
ADCCK
DATACK
DOUTA
D2
D0
DOUTB
D1
D4
D3
D6
D5
D7
HSOUT
Figure 22. Dual Channel Mode, Parallel Outputs (Analog Interface), Outphase = 1
RGBIN
P0 P1 P2 P3 P4 P5 P6 P7
HSYNC
PxCK
HS
3-PIPE DELAY
ADCCK
DATACK
DOUTA
DOUTB
D4
D0
D2
D6
HSOUT
Figure 23. Dual Channel Mode, Interleaved Outputs, 2 Pixels/Clock (Even Pixels) (Analog Interface), Outphase = 1
–20–
REV. 0
AD9887
RGBIN
P0 P1 P2 P3 P4 P5 P6 P7
HSYNC
PxCK
HS
5-PIPE DELAY
ADCCK
DATACK
DOUTA
D1
DOUTB
D5
D3
D7
HSOUT
Figure 24. Dual Channel Mode, Interleaved Outputs, 2 Pixels/Clock (Odd Pixels) (Analog Interface), Outphase = 1
RGBIN
P0 P1 P2 P3 P4 P5 P6 P7
HSYNC
PxCK
HS
7-PIPE DELAY
ADCCK
DATACK
DOUTA
D0
D4
DOUTB
D2
D6
HSOUT
Figure 25. Dual Channel Mode, Parallel Outputs, 2 Pixels/Clock (Even Pixels) (Analog Interface), Outphase = 1
RGBIN
P0 P1 P2 P3 P4 P5 P6 P7
HSYNC
PxCK
HS
7.5-PIPE DELAY
ADCCK
DATACK
DOUTA
D1
D5
DOUTB
D3
D7
HSOUT
Figure 26. Dual Channel Mode, Parallel Outputs, 2 Pixels/Clock (Odd Pixels) (Analog Interface), Outphase = 1
REV. 0
–21–
AD9887
RGBIN
P0
P1
P2
P3
P4
P5
P6
P7
HSYNC
PXCK
HS
6-PIPE DELAY
ADCCK
DATACK
GOUTA
Y0
Y1
Y2
Y3
Y4
Y5
Y6
ROUTA
U0
V0
U2
V2
U4
V4
U6
V6
HSOUT
Figure 27. 4:2:2 Output Mode
Table VIII. Digital Interface Pin List
Pin Type
Pin Name
Digital Video Data Inputs
Rx0+
Rx0–
Rx1+
Rx1–
Rx2+
Rx2–
RxC+
RxC–
RTERM
Digital Video Clock Inputs
Termination Control
Outputs
Power Supply
Function
Value
Digital Input Channel 0 True
Digital Input Channel 0 Complement
Digital Input Channel 1 True
Digital Input Channel 1 Complement
Digital Input Channel 2 True
Digital Input Channel Two’s Complement
Digital Data Clock True
Digital Data Clock Complement
Control Pin for Setting the Internal
Termination Resistance
DE
Data Enable
HSYNC
HSYNC Output
VSYNC
VSYNC Output
CTL0, CTL1, Decoded Control Bit Outputs
CTL2, CTL3
Main Power Supply
VD
PLL Power Supply
PVD
VDD
Output Power Supply
GND
Ground Supply
GND
Ground Supply
–22–
Pin No.
62
63
59
60
56
57
65
66
53
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
3.3 V CMOS
137
139
138
46–49
3.3 V ± 5%
3.3 V ± 5%
3.3 V or 2.5 V ± 5%
0V
0V
REV. 0
AD9887
DIGITAL INTERFACE PIN DESCRIPTIONS
Digital Video Data Inputs
THEORY OF OPERATION (DIGITAL INTERFACE)
Capturing of the Encoded Data
Rx0+
Rx0–
Rx1+
Rx1–
Rx2+
Rx2–
The ﬁrst step in recovering the encoded data is to capture the
raw data. To accomplish this, the AD9887 employs a high-speed
Phase Locked Loop (PLL), to generate clocks capable of
oversampling the data at the correct frequencies. The data
capture circuitry continuously monitors the incoming data during
horizontal and vertical blanking times (when DE is low), and
independently selects the best sampling phase for each data
channel. The phase information is stored and used until the next
blanking period (one video line).
Positive Differential Input Video Data (Channel 0)
Negative Differential Input Video Data (Channel 0)
Positive Differential Input Video Data (Channel 1)
Negative Differential Input Video Data (Channel 1)
Positive Differential Input Video Data (Channel 2)
Negative Differential Input Video Data (Channel 2)
These six pins receive three pairs of differential,
low voltage swing input pixel data from a digital
graphics transmitter.
Digital Video Clock Inputs
RxC+
RxC–
Positive Differential Input Video Clock
Negative Differential Input Video Clock
These two pins receive the differential, low voltage
swing input pixel clock from a digital graphics
transmitter.
Termination Control
RTERM
Internal Termination Set Pin
This pin is used to set the termination resistance
for all of the digital interface high-speed inputs. To
set, place a resistor of value equal to 10× the desired
input termination resistance between this pin (Pin
53) and ground supply. Typically, the value of this
resistor should be 500 Ω.
The digital interface data is captured in groups of 10 bits each,
called a data frame. During the active data period, each frame is
made up the nine encoded video data bits and one dc balancing
bit. The data capture block receives this data serially, but outputs each frame in parallel 10-bit words.
Special Characters
During periods of horizontal or vertical blanking time (when
DE is low), the digital transmitter will transmit special characters.
The AD9887 will receive these characters and use them to set the
video frame boundaries and the phase recovery loop for each
channel. There are four special characters that can be received.
They are used to identify the top, bottom, left side, and right side
of each video frame. The data receiver can differentiate these
special characters from active data because the special characters
have a different number of transitions per data frame.
Channel Resynchronization
Outputs
DE
Data Frames
Data Enable Output
This pin outputs the state of data enable, (DE).
The AD9887 decodes DE from the incoming
stream of data. The DE signal will be HIGH during active video and will be LOW while there is no
active video.
Power Supply
VD
Main Power Supply
It should be as quiet and as ﬁltered as possible.
PVD
PLL Power Supply
The purpose of the channel resynchronization block is to resynchronize the three data channels to a single internal data clock.
Coming into this block, all three data channels can be on different phases of the three times oversampling PLL clock (0°, 120°,
and 240°). This block can resynchronize the channels from a
worst-case skew of one full input period (8.93 ns at 112 MHz).
Data Decoder
The data decoder receives frames of data and sync signals from
the data capture block (in 10-bit parallel words), and decodes
them into groups of eight RGB/YUV bits, two control bits, and
a data enable bit (DE).
It should be as quiet and as ﬁltered as possible.
VDD
Outputs Power Supply
The power for the data and clock outputs. It can
run at 3.3 V or 2.5 V.
REV. 0
–23–
AD9887
GENERAL TIMING DIAGRAMS (DIGITAL INTERFACE)
TIMING MODE DIAGRAMS (DIGITAL INTERFACE)
80%
80%
INTERNAL
ODCLK
TST
20%
20%
DLHT
DATACK
DLHT
DE
Figure 28. Digital Output Rise and Fall Time
QE[23:0]
FIRST
PIXEL
SECOND
PIXEL
THIRD
PIXEL
FOURTH
PIXEL
TCIP, RCIP
QO[23:0]
TCIH, RCIH
Figure 32. 1 Pixel per Clock (DATACK Inverted)
TCIL, RCIL
INTERNAL
ODCLK
Figure 29. Clock Cycle/High/Low Times
TST
DATACK
DE
RX0
VDIFF = 0V
QE[23:0]
FIRST
PIXEL
SECOND
PIXEL
THIRD
PIXEL
FOURTH
PIXEL
RX1
TCCS
QO[23:0]
VDIFF = 0V
Figure 33. 1 Pixels per Clock (DATACK Inverted)
RX2
Figure 30. Channel-to-Channel Skew Timing
INTERNAL
ODCLK
TST
DATACK
(INTERNAL)
DATACK
DATA OUT
DE
DATACK
(PIN)
tSKEW
Figure 31. DVI Output Timing
QE[23:0]
FIRST PIXEL
THIRD PIXEL
QO[23:0]
SECOND PIXEL
FOURTH PIXEL
Figure 34. 2 Pixel per Clock
INTERNAL
ODCLK
TST
DATACK
DE
QE[23:0]
QO[23:0]
FIRST PIXEL
THIRD PIXEL
SECOND PIXEL
FOURTH PIXEL
Figure 35. 2 Pixels per Clock (DATACK Inverted)
–24–
REV. 0
AD9887
2-Wire Serial Register Map
The AD9887 is initialized and controlled by a set of registers, which determine the operating modes. An external controller is
employed to write and read the Control Registers through the 2-line serial interface port.
Table IX. Control Register Map
Hex
Address
Read and
Write or
Read Only
Bits
00H
RO
7:0
01H
R/W
7:0
01101001
PLL Div MSB This register is for Bits [11:4] of the PLL divider. Larger values mean
the PLL operates at a faster rate. This register should be loaded ﬁrst
whenever a change is needed. (This will give the PLL more time to
lock.) See Note 1.
02H
R/W
7:4
1101****
PLL Div LSB
Bits [7:4] LSBs of the PLL divider word. See Note 1.
03H
R/W
7:2
1*******
*01*****
VCO/CPMP
Bit 7—Must be set to 1 for proper device operation.
Bits [6:5] VCO Range. Selects VCO frequency range. (See PLL
description.)
Bits [4:2] Charge Pump Current. Varies the current that drives the
low-pass ﬁlter. (See PLL description.)
Default
Value
Register
Name
Chip Revision
***001**
Function
Bits 7 through 4 represent functional revisions to the analog interface.
Bits 3 through 0 represent nonfunctional related revisions.
Revision 0 = 0000 0000
04H
R/W
7:3
10000***
Phase Adjust
ADC Clock phase adjustment. Larger values mean more delay.
(1 LSB = T/32)
05H
R/W
7:0
10000000
Clamp
Placement
Places the Clamp signal an integer number of clock periods after the trailing edge of the Hsync signal.
06H
R/W
7:0
10000000
Clamp
Duration
Number of clock periods that the Clamp signal is actively clamping.
07H
R/W
7:0
00100000
Hsync Output
Pulsewidth
Sets the number of pixel clocks that HSOUT will remain active.
08H
R/W
7:0
10000000
Red Gain
Controls ADC input range (Contrast) of each respective channel.
Bigger values give less contrast.
09H
R/W
7:0
10000000
Green Gain
0AH
R/W
7:0
10000000
Blue Gain
0BH
R/W
7:1
1000000*
Red Offset
0CH
R/W
7:1
1000000*
Green Offset
0DH
R/W
7:1
1000000*
Blue Offset
0EH
R/W
7:3
1*******
Mode
Control 1
*1******
**0*****
***0****
****0***
REV. 0
Controls dc offset (Brightness) of each respective channel. Bigger
values decrease brightness.
Bit 7—Channel Mode. Determines Single Channel or Dual Channel
Output Mode. (Logic 0 = Single Channel Mode, Logic 1 = Dual
Channel Mode.)
Bit 6—Output Mode. Determine Interleaved or Parallel Output Mode.
(Logic 0 = Interleaved Mode, Logic 1 = Parallel Mode.)
Bit 5—OUTPHASE. Determines which port outputs the ﬁrst data byte
after Hsync. (Logic 0 = B Port, Logic 1 = A Port.)
Bit 4—Hsync Output polarity. (Logic 0 = Logic High Sync, Logic 1 =
Logic Low Sync.)
Bit 3—Vsync Output Invert. (Logic 0 = Invert, Logic 1 = No Invert.)
–25–
AD9887
Table IX. Control Register Map (continued)
Hex
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name
0FH
R/W
7:0
1*******
PLL and
Clamp Control
Bit 7—HSYNC Polarity. Indicates the polarity of incoming HSYNC
signal to the PLL. (Logic 0 = Active Low, Logic 1 = Active High.)
Bit 6—Coast Polarity. Changes polarity of external COAST signal.
(Logic 0 = Active Low, Logic 1 = Active High.)
Bit 5—Clamp Function. Chooses between HSYNC for Clamp signal
or another external signal to be used for clamping. (Logic 0 = HSYNC,
Logic 1 = Clamp.)
Bit 4—Clamp Polarity. Valid only with external CLAMP signal. (Logic 0 =
Active Low, Logic 1 selects Active High.)
Bit 3—EXTCLK. Shuts down the PLL and allows the use of an external
clock to drive the part. (Logic 0 = use internal PLL, Logic 1 = bypassing of the internal PLL.)
Bit 2—Red Clamp Select—Logic 0 selects clamp to ground. Logic 1
selects clamp to midscale (voltage at Pin 120).
Bit 1—Green Clamp Select—Logic 0 selects clamp to ground. Logic 1
selects clamp to midscale (voltage at Pin 111).
Bit 0—Blue Clamp Select—Logic 0 selects clamp to ground. Logic 1
selects clamp to midscale (voltage at Pin 101).
Mode
Control 2
Bit 7—Clk Inv: Data clock output invert. (Logic 0 = Not Inverted,
Logic 1 = Inverted.) (Digital Interface Only.)
Bit 6—Pix Select: Selects either 1 or 2 pixels per clock mode.
(Logic 0 = 1 pixel/clock, Logic 1 = 2 pixels/clock.) (Digital Interface
Only.)
Bit 5, 4—Output Drive: Selects between high, medium, and low
output drive strength. (Logic 11 or 10 = High, 01 = Medium, and
00 = Low.)
Bit 3—P DO: High Impedance Outputs. (Logic 0 = Normal, Logic
1 = High Impedance.)
Bit 2—Sync Detect (SyncDT) Polarity. This bit sets the polarity
for the SyncDT output pin. (Logic 1 = Active High, Logic 0 =
Active Low.)
Sync Detect/
Active
Interface
Bit 7—Analog Interface Hsync Detect. It is set to Logic 1 if Hsync
is present on the analog interface; otherwise it is set to Logic 0.
Bit 6—Analog Interface Sync-on-Green Detect. It is set to Logic 1
if sync is present on the green video input; otherwise it is set to 0.
Bit 5—Analog Interface Vsync Detect. It is set to Logic 1 if Vsync
is present on the analog interface; otherwise it is set to Logic 0.
Bit 4—Digital Interface Clock Detect. It is set to Logic 1 if the
clock is present on the digital interface; otherwise it is set to Logic 0.
Bit 3—AI: Active Interface. This bit indicates which interface is
active. (Logic 0 = Analog Interface, Logic 1 = Digital Interface.)
Bit 2—AHS: Active Hsync. This bit indicates which analog HSYNC
is being used. (Logic 0 = HSYNC Input Pin, Logic 1 = HSYNC
from Sync-on-Green.)
Bit 1—AVS: Active Vsync. This bit indicates which analog VSYNC
is being used. (Logic 0 = VSYNC input pin, Logic 1 = VSYNC from
sync separator.)
*1******
**0*****
***1****
****0***
*****0**
******0*
*******0
10H
R/W
7:2
0*******
*0******
**11****
****0***
*****1**
11H
RO
7:1
Function
–26–
REV. 0
AD9887
Table IX. Control Register Map (continued)
Hex
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name
12H
R/W
7:0
0*******
Active
Interface
Bit 7—AIO: Active Interface Override. If set to Logic 1, the user
can select the active interface via Bit 6. If set to Logic 0, the active
interface is selected via Bit 3 in Register 11H.
Bit 6—AIS: Active Interface Select. Logic 0 selects the analog interface as active. Logic 1 selects the digital interface as active. Note:
The indicated interface will be active only if Bit 7 is set to Logic 1
or if both interfaces are active (Bits 6 or 7 and 4 = Logic 1 in
Register 11H.)
Bit 5—Active Hsync Override. If set to Logic 1, the user can select
the Hsync to be used via Bit 4. If set to Logic 0, the active interface
is selected via Bit 2 in Register 11H.
Bit 4—Active Hsync Select. Logic 0 selects Hsync as the active
sync. Logic 1 selects Sync-on-Green as the active sync. Note: The
indicated Hsync will be used only if Bit 5 is set to Logic 1 or if
both syncs are active (Bits 6, 7 = Logic 1 in Register 11H.)
Bit 3—Active Vsync Override. If set to Logic 1, the user can select
the Vsync to be used via Bit 2. If set to Logic 0, the active interface
is selected via Bit 1 in Register 11H.
Bit 2—Active Vsync Select. Logic 0 selects Raw Vsync as the
output Vsync. Logic 1 selects Sync Separated Vsync as the output
Vsync. Note: The indicated Vsync will be used only if Bit 3 is set
to Logic 1.
Bit 1—Coast Select. Logic 0 selects the coast input pin to be used for
the PLL coast. Logic 1 selects Vsync to be used for the PLL coast.
Bit 0—PWRDN. Full Chip Power-Down, active low. (Logic 0 =
Full Chip Power-Down, Logic 1 = Normal.)
*0******
**0*****
***0****
****0***
*****0**
******0*
*******1
Function
13H
R/W
7:0
00100000
Sync
Separator
Threshold
Sync Separator Threshold—Sets the number of clocks the sync
separator will count to before toggling high or low. This should be
set to some number greater than the maximum Hsync or equalization pulsewidth.
14H
R/W
7:0
***1****
****0***
*****0**
******0*
Control Bits
Bit 4—Must be set to 1 for proper operation.
Bit 3—Must be set to 0 for proper operation.
Bit 2—Scan Enable. (Logic 0 = Not Enabled, Logic 1 = Enabled.)
Bit 1—Coast Polarity Override. (Logic 0 = Polarity determined by
chip, Logic 1 = Polarity set by Bit 6 in Register 0Fh.)
Bit 0—Hsync Polarity Override. (Logic 0 = Polarity determined by
chip, Logic 1 = Polarity set by Bit 7 in Register 0Fh.)
Polarity Status
Bit 7—Hsync Input Polarity Status. (Logic 1 = Active High,
Logic 0 = Active Low.)
Bit 6—Vsync Output Polarity Status. (Logic 0 = Active High,
Logic 1 = Active Low.)
Bit 5—Coast Input Polarity Status. (Logic 1 = Active High,
Logic 0 = Active Low.)
*******0
15H
RO
7:5
16H
R/W
7:2
10111***
******1*
Control Bits 2
Bits [7:3]—Sync-On-Green Slicer Threshold
Bit 1—Must be set to 0 for proper operation.
17H
R/W
7:0
00000000
Pre-Coast
Sets the number of Hsyncs that coast goes active prior to Vsync.
18H
R/W
7:0
00000000
Post-Coast
Sets the number of Hsyncs that coast goes active following Vsync.
19H
R/W
7:0
00000000
Test Register
Must be set to default for proper operation.
1AH
R/W
7:0
11111111
Test Register
Must be set to 01000001 for proper operation.
REV. 0
–27–
AD9887
Table IX. Control Register Map (continued)
Hex
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name
Function
1BH
R/W
7:0
00000000
Test Register
Must be set to 00010000 for proper operation.
1CH
R/W
7:0
000001**
******1*
4:2:2 Control
Bits [7:2]—Must be set to 011011** for proper operation.
Bit 1—Must be set to default for proper operation.
*******1
Bit 0—Output Format Mode Select
Logic 1 = 4:4:4 mode
Logic 0 = 4:2:2 mode
1DH
RO
7:0
Test Register
Reserved for future use.
1EH
RO
7:0
Test Register
Reserved for future use.
1FH
RO
7:0
Test Register
Reserved for future use.
NOTE
1
The AD9887 only updates the PLL divide ratio when the LSBs are written to (Register 02h).
–28–
REV. 0
AD9887
The PLL gives the best jitter performance at high frequencies. For this reason, in order to output low pixel
rates and still get good jitter performance, the PLL actually operates at a higher frequency but then divides down
the clock rate afterwards. Table X shows the pixel rates
for each VCO range setting. The PLL output divisor is
automatically selected with the VCO range setting.
2-WIRE SERIAL CONTROL REGISTER DETAIL
CHIP IDENTIFICATION
00
7–0 Chip Revision
Bits 7 through 4 represent functional revisions to the
analog interface. Changes in these bits will generally
indicate that software and/or hardware changes will be
required for the chip to work properly. Bits 3 through 0
represent nonfunctional related revisions and are reset to
0000 whenever the MSBs are changed. Changes in these
bits are considered transparent to the user.
Table X. VCO Ranges
PLL DIVIDER CONTROL
01
7–0 PLL Divide Ratio MSBs
The eight most signiﬁcant bits of the 12-bit PLL divide ratio
PLLDIV. (The operational divide ratio is PLLDIV + 1.)
The PLL derives a pixel clock from the incoming Hsync
signal. The pixel clock frequency is then divided by an
integer value, such that the output is phase-locked to
Hsync. This PLLDIV value determines the number of
pixel times (pixels plus horizontal blanking overhead) per
line. This is typically 20% to 30% more than the number
of active pixels in the display.
CURRENT
Current (␮A)
000
001
010
011
100
101
110
111
50
100
150
250
350
500
750
1500
The power-up default value is CURRENT = 001.
04
7–3 Clock Phase Adjust
A ﬁve-bit value that adjusts the sampling phase in 32 steps
across one pixel time. Each step represents an 11.25° shift
in sampling phase.
The power-up default value is 16.
CLAMP TIMING
05
7–0 Clamp Placement
An eight-bit register that sets the position of the internally
generated clamp.
7–4 PLL Divide Ratio LSBs
When EXTCLMP = 0, a clamp signal is generated internally, at a position established by the clamp placement and
for a duration set by the clamp duration. Clamping is
started (Clamp Placement) pixel periods after the trailing
edge of Hsync. The clamp placement may be programmed
to any value between 1 and 255. A value of 0 is not
supported.
The power-up default value of PLLDIV is 1693
(PLLDIVM = 69h, PLLDIVL = Dxh).
The AD9887 updates the full divide ratio only when this
register is written.
CLOCK GENERATOR CONTROL
03
7 TEST Set to One
The clamp should be placed during a time that the input
signal presents a stable black-level reference, usually the
back porch period between Hsync and the image.
6–5 VCO Range Select
Two bits that establish the operating range of the clock
generator.
When EXTCLMP = 1, this register is ignored.
VCORNGE must be set to correspond with the desired
operating frequency (incoming pixel rate).
REV. 0
4–2 CURRENT Charge Pump Current
See Table VII for the recommended CURRENT settings.
The four least signiﬁcant bits of the 12-bit PLL divide ratio
PLLDIV. The operational divide ratio is PLLDIV + 1.
03
12–35
35–70
70–110
110–140
Table XI. Charge Pump Currents
The power-up default value of PLLDIV is 1693
(PLLDIVM = 69h, PLLDIVL = Dxh).
02
00
01
10
11
Three bits that establish the current driving the loop ﬁlter
in the clock generator.
VESA has established some standard timing speciﬁcations,
which will assist in determining the value for PLLDIV as
a function of horizontal and vertical display resolution
and frame rate (Table VII).
The AD9887 updates the full divide ratio only when the
LSBs are changed. Writing to this register by itself will not
trigger an update.
Pixel Rate Range
The power-up default value is = 01.
03
The 12-bit value of the PLL divider supports divide ratios
from 221 to 4095. The higher the value loaded in this
register, the higher the resulting clock frequency with
respect to a ﬁxed Hsync frequency.
However, many computer systems do not conform precisely to the recommendations, and these numbers should
be used only as a guide. The display system manufacturer
should provide automatic or manual means for optimizing
PLLDIV. An incorrectly set PLLDIV will usually produce
one or more vertical noise bars on the display. The greater
the error, the greater the number of bars produced.
VCORNGE
–29–
AD9887
06
7–0 Clamp Duration
0C
An 8-bit register that sets the duration of the internally
generated clamp.
A 7-bit offset binary word that sets the dc offset of the
GREEN channel. See REDOFST (0B).
When EXTCLMP = 0, a clamp signal is generated internally, at a position established by the clamp placement
and for a duration set by the clamp duration. Clamping is
started (clamp placement) pixel periods after the trailing
edge of Hsync, and continues for (clamp duration) pixel
periods. The clamp duration may be programmed to any
value between 1 and 255. A value of 0 is not supported.
0D
MODE CONTROL 1
0E 7 Channel Mode
A bit that determines whether all pixels are presented to a
single port (A), or alternating pixels are demultiplexed to
Ports A and B.
Table XII. Channel Mode Settings
When EXTCLMP = 1, this register is ignored.
Hsync Pulsewidth
07
7–0 Hsync Output Pulsewidth
DEMUX
Function
0
1
All Data Goes to Port A
Alternate Pixels Go to Port A and Port B
When DEMUX = 0, Port B outputs are in a high-impedance
state. The maximum data rate for single port mode is
100 MHz. The timing diagrams show the effects of this option.
An 8-bit register that sets the duration of the Hsync
output pulse.
The leading edge of the Hsync output is triggered by the
internally generated, phase-adjusted PLL feedback clock.
The AD9887 then counts a number of pixel clocks equal
to the value in this register. This triggers the trailing edge
of the Hsync output, which is also phase-adjusted.
The power-up default value is 1.
0E
6 Output Mode
A bit that determines whether all pixels are presented to
Port A and Port B simultaneously on every second
DATACK rising edge, or alternately on port A and Port B
on successive DATACK rising edges.
INPUT GAIN
08
7–0 Red Channel Gain Adjust
Table XIII. Output Mode Settings
An 8-bit word that sets the gain of the RED channel.
The AD9887 can accommodate input signals with a
full-scale range of between 0.5 V and 1.5 V p-p. Setting
REDGAIN to 255 corresponds to an input range of 1.0 V.
A REDGAIN of 0 establishes an input range of 0.5 V.
Note that INCREASING REDGAIN results in the picture
having LESS CONTRAST (the input signal uses fewer
of the available converter codes). See Figure 3.
PARALLEL
Function
0
1
Data Is Interleaved
Data Is Simultaneous On Every Other
Data Clock
When in single port mode (DEMUX = 0), this bit is ignored. The timing diagrams show the effects of this option.
7–0 Green Channel Gain Adjust
The power-up default value is PARALLEL = 1.
An 8-bit word that sets the gain of the GREEN channel.
See REDGAIN (08).
0A
7–1 Blue Channel Offset Adjust
A 7-bit offset binary word that sets the dc offset of the
GREEN channel. See REDOFST (0B).
For the best results, the clamp duration should be set to
include the majority of the black reference signal time that
follows the Hsync signal trailing edge. Insufﬁcient clamping time can produce brightness changes at the top of the
screen, and a slow recovery from large changes in the
Average Picture Level (APL), or brightness.
09
7–1 Green Channel Offset Adjust
0E
5 Output Port Phase
One bit that determines whether even pixels or odd pixels
go to Port A.
7–0 Blue Channel Gain Adjust
An 8-bit word that sets the gain of the BLUE channel.
See REDGAIN (08).
Table XIV. Output Port Phase Settings
INPUT OFFSET
0B 7–1 Red Channel Offset Adjust
A 7-bit offset binary word that sets the dc offset of the RED
channel. One LSB of offset adjustment equals approximately
one LSB change in the ADC offset. Therefore, the absolute
magnitude of the offset adjustment scales as the gain of the
channel is changed. A nominal setting of 63 results in the
channel nominally clamping the back porch (during the
clamping interval) to Code 00. An offset setting of 127
results in the channel clamping to Code 63 of the ADC. An
offset setting of 0 clamps to code –63 (off the bottom of
the range). Increasing the value of Red Offset DECREASES
the brightness of the channel.
–30–
OUTPHASE
First Pixel After Hsync
0
1
Port B
Port A
In normal operation (OUTPHASE = 1), when operating
in dual-port output mode (DEMUX = 1), the ﬁrst sample
after the Hsync leading edge is presented at Port A. Every
subsequent ODD sample appears at Port A. All EVEN
samples go to Port B.
When OUTPHASE = 0, these ports are reversed and the
ﬁrst sample goes to Port B.
REV. 0
AD9887
When DEMUX = 0, this bit is ignored as data always
comes out of only Port A.
0E
4 HSYNC Output Polarity
Active LOW means that the clock generator will ignore Hsync
inputs when COAST is LOW, and continue operating at the
same nominal frequency until COAST goes HIGH.
One bit that determines the polarity of the HSYNC output and the SOG output. Table XV shows the effect of
this option. SYNC indicates the logic state of the sync pulse.
Active HIGH means that the clock generator will ignore
Hsync inputs when COAST is HIGH, and continue operating at the same nominal frequency until COAST goes LOW.
Table XV. HSYNC Output Polarity Settings
This function needs to be used along with the COAST
polarity override bit (Register 14, Bit 1).
Setting
SYNC
The power-up default value is CSTPOL = 1.
0
1
Logic 1 (Positive Polarity)
Logic 0 (Negative Polarity)
0F
A bit that determines the source of clamp timing.
The default setting for this register is 1. (This option
works on both the analog and digital interfaces.)
0E
Table XIX. Clamp Input Signal Source Settings
EXTCLMP
3 VSYNC Output Invert
0
Internally-Generated Clamp
1
Externally-Provided Clamp Signal
Table XVI. VSYNC Output Polarity Settings
A 0 enables the clamp timing circuitry controlled by
CLPLACE and CLDUR. The clamp position and duration is counted from the leading edge of Hsync.
Setting
VSYNC Output
0
1
Invert
No Invert
7 HSYNC Input Polarity
A bit that must be set to indicate the polarity of the HSYNC
signal that is applied to the PLL HSYNC input.
A 1 enables the external CLAMP input pin. The three
channels are clamped when the CLAMP signal is
active. The polarity of CLAMP is determined by the
CLAMPOL bit.
The power-up default value is EXTCLMP = 0.
0F
4 CLAMP Input Signal Polarity
A bit that determines the polarity of the externally provided CLAMP signal.
Table XVII. HSYNC Input Polarity Settings
Table XX. CLAMP Input Signal Polarity Settings
HSPOL
Function
EXTCLMP
Function
0
1
Active LOW
Active HIGH
0
1
Active LOW
Active HIGH
Active LOW is the traditional negative-going Hsync pulse.
All timing is based on the leading edge of Hsync, which is
the FALLING edge. The rising edge has no effect.
A Logic 0 means that the circuit will clamp when CLAMP
is HIGH, and it will pass the signal to the ADC when
CLAMP is LOW.
Active HIGH is inverted from the traditional Hsync, with a
positive-going pulse. This means that timing will be based on
the leading edge of Hsync, which is now the RISING edge.
A Logic 1 means that the circuit will clamp when CLAMP
is LOW, and it will pass the signal to the ADC when
CLAMP is HIGH.
The device will operate if this bit is set incorrectly, but the
internally generated clamp position, as established by
CLPOS, will not be placed as expected, which may generate clamping errors.
The power-up default value is CLAMPOL = 1.
0F
3 External Clock Select
A bit that determines the source of the pixel clock.
The power-up default value is HSPOL = 1.
0F
Function
One bit that inverts the polarity of the VSYNC output.
Table XVI shows the effect of this option.
The default setting for this register is 1. (This option
works on both the analog and digital interfaces.)
0F
5 Clamp Input Signal Source
Table XXI. External Clock Select Settings
6 COAST Input Polarity
A bit to indicate the polarity of the COAST signal that is
applied to the PLL COAST input.
Table XVIII. COAST Input Polarity Settings
CSTPOL
Function
0
1
Active LOW
Active HIGH
REV. 0
EXTCLK
Function
0
Internally Generated Clock
1
Externally Provided Clock Signal
A Logic 0 enables the internal PLL that generates the
pixel clock from an externally provided Hsync.
–31–
AD9887
of a single port (even port only), at the full data rate or
out of two ports (both even and odd ports), at one-half
the full data rate per port. A Logic 0 selects 1 pixel per
clock (even port only). A Logic 1 selects 2 pixels per clock
(both ports). See the Digital Interface Timing Diagrams,
Figures 29 to 32, for a visual representation of this function.
Note: This function operates exactly like the DEMUX
function on the analog interface.
A Logic 1 enables the external CKEXT input pin. In this
mode, the PLL Divide Ratio (PLLDIV) is ignored. The
clock phase adjust (PHASE) is still functional.
The power-up default value is EXTCLK = 0.
0F
2 Red Clamp Select
A bit that determines whether the red channel is clamped
to ground or to midscale. For RGB video, all three channels are referenced to ground. For YcbCr (or YUV), the
Y channel is referenced to ground, but the CbCr channels
are referenced to midscale. Clamping to midscale actually
clamps to Pin 118, RCLAMPV.
Table XXVI. Pix Select Settings
Table XXII. Red Clamp Select Settings
Clamp
Function
0
1
Clamp to Ground
Clamp to Midscale (Pin 118)
10
A bit that determines whether the green channel is clamped
to ground or to midscale.
Table XXIII. Green Clamp Select Settings
Function
0
1
Clamp to Ground
Clamp to Midscale (Pin 109)
0 Blue Clamp Select
A bit that determines whether the blue channel is clamped
to ground or to midscale.
Table XXIV. Blue Clamp Select Settings
Clamp
Function
0
1
Clamp to Ground
Clamp to Midscale (Pin 99)
1 Pixel per Clock
2 Pixels per Clock
5, 4 Output Drive
Table XXVII. Output Drive Strength Settings
The default setting for this register is 0.
0F
0
1
These two bits select the drive strength for the high-speed
digital outputs (all data output and clock output pins).
Higher drive strength results in faster rise/fall times and in
general makes it easier to capture data. Lower drive strength
results in slower rise/fall times and helps to reduce EMI
and digitally generated power supply noise. The exact
timing speciﬁcations for each of these modes are speciﬁed
in Table VII.
1 Green Clamp Select
Clamp
Function
The default for this register is 0, 1 pixel per clock.
The default setting for this register is 0.
0F
Pix Select
Bit 5
Bit 4
Result
1
1
0
1
0
X
High Drive Strength
Medium Drive Strength
Low Drive Strength
The default for this register is 11, high drive strength. (This
option works on both the analog and digital interfaces.)
10
3 PDO—Power-Down Outputs
A bit that can put the outputs in a high impedance mode.
This applies only to the 48 data output pins and the two
data clock output pins.
Table XXVIII. Power-Down Output Settings
The default setting for this register is 0.
MODE CONTROL 2
10
7 Clk Inv Data Output Clock Invert
A control bit for the inversion of the output data clocks,
(Pins 134, 135). This function works only for the digital
interface. When not inverted, data is output on the rising
edge of the data clock. See timing diagrams to see how
this affects timing.
Function
0
1
Normal Operation
Three-State
The default for this register is 0. (This option works on
both the analog and digital interfaces.)
10
2 Sync Detect Polarity
This pin controls the polarity of the Sync Detect output
pin (Pin 136).
Table XXV. Clock Output Invert Settings
Clk Inv
Function
Table XXIX. Sync Detect Polarity Settings
0
1
Not Inverted
Inverted
Polarity
Function
0
1
Activity = Logic 1 Output
Activity = Logic 0 Output
The default for this register is 0, not inverted.
10
CKINV
6 Pix Select
This bit selects either 1 or 2 pixels per clock mode for the
digital interface. It determines whether the data comes out
–32–
The default for this register is 0. (This option works on
both the analog and digital interfaces.)
REV. 0
AD9887
Digital interface detection is determined by Bit 4 in this
register. If both interfaces are detected, the user can
determine which has priority via Bit 6 in register 12H.
The user can override this function via Bit 7 in Register 12H.
If the override bit is set to Logic 1, then this bit will be
forced to whatever the state of Bit 6 in Register 12H is set to.
SYNC DETECTION AND CONTROL
11
7 Analog Interface HSYNC Detect
This bit is used to indicate when activity is detected on
the HSYNC input pin (Pin 82). If HSYNC is held high or
low, activity will not be detected.
Table XXX. HSYNC Detection Results
Table XXXIV. Active Interface Results
11
Detect
Function
0
1
No Activity Detected
Activity Detected
Figure 38 shows where this function is implemented.
Bits 7, 6,
or 5
(Analog
Detection)
Bit 4
(Digital
Detection)
Override
AI
6 Analog Interface Sync-on-Green Detect
0
0
0
0
1
1
X
1
0
1
X
0
0
0
1
Soft
Power-Down
(Seek Mode)
1
0
Bit 6 in 12H
Bit 6 in 12H
This bit is used to indicate when sync activity is detected
on the Sync-on-Green input pin (Pin 108).
Table XXXI. Sync-on-Green Detection Results
Detect
Function
0
1
No Activity Detected
Activity Detected
Figure 38 shows where this function is implemented.
AI = 0 means Analog Interface.
AI = 1 means Digital Interface.
The override bit is in Register 12H, Bit 7.
11
This bit is used to determine which HSYNC should be
used for the analog interface, the HSYNC input or Syncon-Green. It uses Bits 7 and 6 in this register for inputs
in determining which should be active. Similar to the previous bit, if both HSYNC and SOG are detected the user
can determine which has priority via Bit 4 in Register
12H. The user can override this function via Bit 5 in
Register 12H. If the override bit is set to Logic 1, this
bit will be forced to whatever the state of Bit 4 in Register
12H is set to.
Warning: If no sync is present on the green video input,
normal video may still trigger activity.
11
5 Analog Interface VSYNC Detect
This bit is used to indicate when activity is detected on
the VSYNC input pin (Pin 81). If VSYNC is held high or
low, activity will not be detected.
Table XXXII. VSYNC Detection Results
Detect
Function
0
1
No Activity Detected
Activity Detected
Table XXXV. Active HSYNC Results
Figure 38 shows where this function is implemented.
11
4 Digital Interface Clock Detect
This bit is used to indicate when activity is detected on
the digital interface clock input.
Table XXXIII. Digital Interface Clock Detection Results
Detect
Function
0
1
No Activity Detected
Activity Detected
The sync processing block diagram shows where this
function is implemented.
11
Bit 7
(HSYNC
Detect)
Bit 6
(SOG
Detect)
Override
AHS
0
0
1
1
X
0
1
0
1
X
0
0
0
0
1
Bit 4 in 12H
1
0
Bit 4 in 12H
Bit 4 in 12H
AHS = 0 means use the HSYNC pin input for HSYNC.
AHS = 1 means use the SOG pin input for HSYNC.
The override bit is in Register 12H, Bit 5.
11
1 AVS—Active VSYNC
This bit is used to determine which VSYNC should be
used for the analog interface; the VSYNC input or output
from the sync separator. If both VSYNC and composite
SOG are detected, VSYNC will be selected. The user can
override this function via Bit 3 in Register 12H. If the
override bit is set to Logic 1, this bit will be forced to whatever the state of Bit 2 in Register 12H is set to.
3 Active Interface
This bit is used to indicate which interface should be
active, analog, or digital. It checks for activity on the
analog interface and for activity on the digital interface,
then determines which should be active according to
Table XXXIV. Speciﬁcally, analog interface detection
is determined by OR-ing Bits 7, 6, and 5 in this register.
REV. 0
2 AHS—Active HSYNC
–33–
AD9887
Table XXXVI. Active VSYNC Results
Bit 5
(VSYNC
Detect)
Override
0
1
X
0
0
1
Table XL. Active HSYNC Select Settings
Select
Result
AVS
0
1
HSYNC Input
Sync-on-Green Input
0
1
Bit 2 in 12H
The default for this register is 0.
12
12
7 AIO—Active Interface Override
This bit is used to override the automatic interface selection (Bit 3 in Register 11H). To override, set this bit to
Logic 1. When overriding, the active interface is set via
Bit 6 in this register.
Table XLI. Active VSYNC Override Settings
Table XXXVII. Active Interface Override Settings
AIO
Result
0
1
Autodetermines the Active Interface
Override, Bit 6 Determines the Active Interface
12
Analog Interface
Digital Interface
12
2 Active VSYNC Select
Select
Result
0
1
VSYNC Input
Sync Separator Output
1 COAST Select
This bit is used to select the active COAST source. The
choices are the COAST input pin or VSYNC. If VSYNC
is selected, the additional decision of using the VSYNC
input pin or the output from the sync separator needs to
be made (Bits 3, 2).
The default for this register is 0.
12
Autodetermines the Active VSYNC
Override, Bit 2 Determines the Active VSYNC
The default for this register is 0.
Table XXXVIII. Active Interface Select Settings
0
1
0
1
Table XLII. Active VSYNC Select Settings
This bit is used under two conditions. It is used to select
the active interface when the override bit is set (Bit 7).
Alternately, it is used to determine the active interface
when not overriding but both interfaces are detected.
Result
Result
This bit is used to select the active VSYNC when the
override bit is set (Bit 3).
6 AIS—Active Interface Select
AIS
Override
The default for this register is 0.
The default for this register is 0.
12
3 Active VSYNC Override
This bit is used to override the automatic VSYNC selection
(Bit 1 in Register 11H). To override, set this bit to Logic 1.
When overriding, the active interface is set via Bit 2 in
this register.
AVS = 1 means Sync separator.
AVS = 0 means VSYNC input.
The override bit is in Register 12H, Bit 3.
5 Active Hsync Override
Table XLIII. COAST Select Settings
This bit is used to override the automatic Hsync selection
(Bit 2 in Register 11H). To override, set this bit to Logic
1. When overriding, the active Hsync is set via Bit 4 in
this register.
Select
Result
0
1
COAST Input Pin
VSYNC (See Above Text)
Table XXXIX. Active Hsync Override Settings
The default for this register is 0.
Override
Result
0
1
Autodetermines the Active Interface
Override, Bit 4 Determines the Active Interface
12
The default for this register is 0.
12
4 Active Hsync Select
This bit is used under two conditions. It is used to select
the active Hsync when the override bit is set (Bit 5). Alternately, it is used to determine the active Hsync when not
overriding but both Hsyncs are detected.
0 PWRDN
This bit is used to put the chip in full power-down. This
powers down both interfaces. See the section on Power
Management for details of which blocks are actually
powered down. Note, the chip will be unable to detect
incoming activity while fully powered-down.
Table XLIV. Power-Down Settings
Select
Result
0
1
Power-Down
Normal Operation
The default for this register is 1.
–34–
REV. 0
AD9887
DIGITAL CONTROL
13
7:0 Sync Separator Threshold
This register is used to set the responsiveness of the sync
separator. It sets how many pixel clock pulses the sync
separator must count to before toggling high or low. It
works like a low-pass ﬁlter to ignore Hsync pulses in order
to extract the Vsync signal. This register should be set to
some number greater than the maximum Hsync pulsewidth.
Table XLVIII. Detected HSYNC Input Polarity Status
15
CONTROL BITS
14
2 Scan Enable
This register is used to enable the scan function. When
enabled, data can be loaded into the AD9887 outputs
serially with the scan function. The scan function utilizes
three pins (SCANIN, SCANOUT, and SCANCLK). These
pins are described in Table I.
14
0
Scan Function Disabled
1
Scan Function Enabled
15
6 VSYNC Output Polarity Status
Vsync Polarity
Status
Result
0
1
Vsync Polarity is Active Low.
Vsync Polarity is Active High.
5 Coast Input Polarity Status
The default for scan enable is 0 (disabled).
1 Coast Input Polarity Override
Table L. Detected Coast Input Polarity Status
Table XLVI. Coast Input Polarity Override Settings
Override Bit
Result
0
Coast Polarity Determined by Chip
1
Coast Polarity Determined by User
16
0 HSYNC Input Polarity Override
This register is used to override the internal circuitry that
determines the polarity of the Hsync signal going into
the PLL.
Result
0
Hsync Polarity Determined by Chip
1
Hsync Polarity Determined by User
17
0
1
Coast Polarity is Negative.
Coast Polarity is Positive.
7–3 Sync-on-Green Slicer Threshold
7–0 Pre-Coast
This register allows the Coast signal to be applied prior
to the Vsync signal. This is necessary in cases where preequalization pulses are present. The step size for this
control is one Hsync period.
The default is 0.
18
7–0 Post-Coast
This register allows the coast signal to be applied following to the Vsync signal. This is necessary in cases where
post-equalization pulses are present. The step size for this
control is one Hsync period.
The default for Hsync polarity override is 0 (polarity
determined by chip).
7 HSYNC Input Polarity Status
This bit reports the status of the Hsync input polarity
detection circuit. It can be used to determine the polarity
of the Hsync input. The detection circuit’s location is
shown in the Sync Processing Block Diagram (Figure 38).
Result
The default setting is 23 and corresponds to a threshold
value of 70 mV.
Table XLVII. HSYNC Input Polarity Override Settings
Override Bit
Coast Polarity
Status
This register allows the comparator threshold of the
Sync-on-Green slicer to be adjusted. This register adjusts
the comparator threshold in steps of 10 mV. A setting of zero
results in a 330 mV threshold. The setting of 31 results in
a 10 mV threshold.
The default for coast polarity override is 0 (polarity
determined by chip).
15
Hsync Polarity is Negative.
Hsync Polarity is Positive.
This bit reports the status of the coast input polarity
detection circuit. It can be used to determine the polarity of the coast input. The detection circuit’s location is
shown in the Sync Processing Block Diagram (Figure 38).
This register is used to override the internal circuitry that
determines the polarity of the coast signal going into
the PLL.
14
0
1
Table XLIX. Detected VSYNC Input Polarity Status
Table XLV. Scan Enable Settings
Result
Result
This bit reports the status of the Vsync output polarity
detection circuit. It can be used to determine the polarity
of the Vsync input. The detection circuit’s location is
shown in the Sync Processing Block Diagram (Figure 38).
The default for this register is 32.
Scan Enable
Hsync Polarity
Status
The default is 0.
19
7–0 Test Register
Must be set to default.
1A
7–0 Test Register
Must be set to 41H for proper operation.
REV. 0
–35–
AD9887
1B
7–0 Test Register
Must be set to 10H for proper operation.
1C
7–2 Test Bits
Must be set to 6FH for proper operation.
1C
1 Output Format Mode Select
A bit that configures the output data in 4:2:2 mode. This
mode can be used to reduce the number of data lines used
from 24 down to 16 for applications using YUV, YCbCr,
or YPbPr graphics signals. A timing diagram for this mode is
shown on page 22. Recommended input and output configurations are shown in Table LI. In 4:2:2 mode, the red
and blue channels can be interchanged to help satisfy
board layout or timing requirements, but the green channel
must be configured for Y.
Table LI. 4:2:2 Output Mode Select
Select
Output Mode
1
4:4:4
1
4:2:2
Bit 7
A6
(MSB)
Bit 6
A5
Bit 5
A4
Bit 4
A3
Bit 3
A2
Bit 2
A1
Bit 1
A0
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
1
1
0
1
0
1
For each byte of data read or written, the MSB is the ﬁrst bit of
the sequence.
Channel
Input
Connection
Output
Format
Red
Green
Blue
V
Y
U
U/V
Y
High Impedance
1–0 Test Bits
Must be set to default.
2-WIRE SERIAL CONTROL PORT
A 2-wire serial interface control interface is provided. Up to four
AD9887 devices may be connected to the 2-wire serial interface,
with each device having a unique address.
The 2-wire serial interface comprises a clock (SCL) and a bidirectional data (SDA) pin. The Analog Flat Panel Interface acts
as a slave for receiving and transmitting data over the serial
interface. When the serial interface is not active, the logic levels
on SCL and SDA are pulled HIGH by external pull-up resistors.
Data received or transmitted on the SDA line must be stable for
the duration of the positive-going SCL pulse. Data on SDA must
change only when SCL is LOW. If SDA changes state while SCL
is HIGH, the serial interface interprets that action as a start or
stop sequence.
There are five components to serial bus operation:
•
•
•
•
•
Table LIII. Serial Port Addresses
Data Transfer via Serial Interface
Table LII. 4:2:2 Input/Output Configuration
1C
eighth bit). The R/W bit indicates the direction of data transfer,
read from (1) or write to (0) the slave device. If the transmitted
slave address matches the address of the device (set by the state of
the SA1-0 input pins in Table LIII, the AD9887 acknowledges by
bringing SDA LOW on the 9th SCL pulse. If the addresses do not
match, the AD9887 does not acknowledge.
Start Signal
Slave Address Byte
Base Register Address Byte
Data Byte to Read or Write
Stop Signal
When the serial interface is inactive (SCL and SDA are HIGH)
communications are initiated by sending a start signal. The start
signal is a HIGH-to-LOW transition on SDA while SCL is
HIGH. This signal alerts all slaved devices that a data transfer
sequence is coming.
If the AD9887 does not acknowledge the master device during a
write sequence, the SDA remains HIGH so the master can
generate a stop signal. If the master device does not acknowledge
the AD9887 during a read sequence, the AD9887 interprets this
as “end of data.” The SDA remains HIGH so the master can
generate a stop signal.
Writing data to speciﬁc control registers of the AD9887 requires
that the 8-bit address of the control register of interest be written
after the slave address has been established. This control register
address is the base address for subsequent write operations. The
base address autoincrements by one for each byte of data written
after the data byte intended for the base address. If more bytes
are transferred than there are available addresses, the address will
not increment and remain at its maximum value of 1Dh. Any base
address higher than 1Dh will not produce an acknowledge signal.
Data is read from the control registers of the AD9887 in a similar
manner. Reading requires two data transfer operations:
The base address must be written with the R/W bit of the slave
address byte LOW to set up a sequential read operation.
Reading (the R/W bit of the slave address byte HIGH) begins at
the previously established base address. The address of the read
register autoincrements after each byte is transferred.
To terminate a read/write sequence to the AD9887, a stop signal must be sent. A stop signal comprises a LOW-to-HIGH
transition of SDA while SCL is HIGH.
A repeated start signal occurs when the master device driving
the serial interface generates a start signal without ﬁrst generating a stop signal to terminate the current communication. This
is used to change the mode of communication (read, write)
between the slave and master without releasing the serial interface lines.
Serial Interface Read/Write Examples
Write to one control register
➥Start signal
➥Slave Address byte (R/W bit = LOW)
➥Base Address byte
➥Data byte to base address
➥Stop signal
The ﬁrst eight bits of data transferred after a start signal comprising
a 7-bit slave address (the ﬁrst seven bits) and a single R/W bit (the
–36–
REV. 0
AD9887
SDA
tBUFF
tDSU
tDHO
tSTASU
tSTAH
tSTOSU
tDAL
SCL
tDAH
Figure 36. Serial Port Read/Write Timing
Write to four consecutive control registers
➥Start signal
➥Slave Address byte (R/W bit = LOW)
➥Base Address byte
➥Data byte to base address
➥Data byte to (base address + 1)
➥Data byte to (base address + 2)
➥Data byte to (base address + 3)
➥Stop signal
THEORY OF OPERATION (SYNC PROCESSING)
This section is devoted to the basic operation of the sync processing engine (refer to Figure 37 Sync Processing Block Diagram).
Sync Slicer
The purpose of the sync slicer is to extract the sync signal from
the green graphics channel. A sync signal is not present on all
graphics systems, only those with “sync-on-green.” The sync
signal is extracted from the green channel in a two step process.
First, the SOG input is clamped to its negative peak (typically
0.3 V below the black level). Next, the signal goes to a comparator with a trigger level that is 0.15 V above the clamped level.
The “sliced” sync is typically a composite sync signal containing
both Hsync and Vsync.
Read from one control register
➥Start signal
➥Slave Address byte (R/W bit = LOW)
➥Base Address byte
➥Start signal
➥Slave Address byte (R/W bit = HIGH)
➥Data byte from base address
➥Stop signal
Sync Separator
A sync separator extracts the Vsync signal from a composite
sync signal. It does this through a low-pass ﬁlter-like or integratorlike operation. It works on the idea that the Vsync signal stays
active for a much longer time than the Hsync signal, so it rejects
any signal shorter than a threshold value, which is somewhere
between an Hsync pulsewidth and a Vsync pulsewidth.
Read from four consecutive control registers
➥Start signal
➥Slave Address byte (R/W bit = LOW)
➥Base Address byte
➥Start signal
➥Slave Address byte (R/W bit = HIGH)
➥Data byte from base address
➥Data byte from (base address + 1)
➥Data byte from (base address + 2)
➥Data byte from (base address + 3)
➥Stop signal
SDA
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
ACK
SCL
Figure 37. Serial Interface—Typical Byte Transfer
Table LIV. Control of the Sync Block Muxes via the
Serial Register
Mux
Nos.
Serial Bus
Control Bit
1 and 2
12H: Bit 4
3
12H: Bit 1
4
12H: Bit 2
5, 6, and 7 11H: Bit 3
REV. 0
Control
Bit
State
Result
0
1
0
1
0
1
0
1
Pass Hsync
Pass Sync-on-Green
Pass Coast
Pass Vsync
Pass Vsync
Pass Sync Separator Signal
Pass Digital Interface Signals
Pass Analog Interface Signals
The sync separator on the AD9887 is simply an 8-bit digital
counter with a 5 MHz clock. It works independently of the
polarity of the composite sync signal. (Polarities are determined
elsewhere on the chip.) The basic idea is that the counter counts
up when Hsync pulses are present. But since Hsync pulses are
relatively short in width, the counter only reaches a value of N
before the pulse ends. It then starts counting down eventually
reaching 0 before the next Hsync pulse arrives. The speciﬁc
value of N will vary for different video modes, but will always be
less than 255. For example with a 1 µs width Hsync, the counter
will only reach 5 (1 µs/200 ns = 5). Now, when Vsync is present
on the composite sync the counter will also count up. However,
since the Vsync signal is much longer, it will count to a higher
number M. For most video modes, M will be at least 255. So,
Vsync can be detected on the composite sync signal by detecting
when the counter counts to higher than N. The speciﬁc count
that triggers detection (T) can be programmed through the
serial register (0fh).
Once Vsync has been detected, there is a similar process to detect
when it goes inactive. At detection, the counter ﬁrst resets to 0,
then starts counting up when Vsync goes away. Similar to the
previous case, it will detect the absence of Vsync when the
counter reaches the threshold count (T). In this way, it will
reject noise and/or serration pulses. Once Vsync is detected to
be absent, the counter resets to 0 and begins the cycle again.
–37–
AD9887
ACTIVITY
DETECT
SYNC STRIPPER
NEGATIVE PEAK
CLAMP
SYNC SEPARATOR
COMP
SYNC
INTEGRATOR
VSYNC
1/S
SOG
MUX 1
HSYNC IN
SOG OUT
PLL
ACTIVITY
DETECT
POLARITY
DETECT
HSYNC OUT
HSYNC
CLOCK
GENERATOR
MUX 2
HSYNC OUT
PIXEL CLOCK
COAST
COAST
MUX 3
POLARITY
DETECT
AD9887
VSYNC IN
VSYNC OUT
ACTIVITY
DETECT
POLARITY
DETECT
MUX 4
Figure 38. Sync Processing Block Diagram
PCB LAYOUT RECOMMENDATIONS
The AD9887 is a high-performance, high-speed analog device.
As such, to get the maximum performance out of the part it is
important to have a well laid-out board. The following is a guide
for designing a board using the AD9887.
Analog Interface Inputs
Using the following layout techniques on the graphics inputs is
extremely important:
that placing a series ferrite bead prior to the 75 Ω termination
resistor is helpful in ﬁltering out excess noise. Speciﬁcally, the
part used was the # 2508051217Z0 from Fair-Rite, but each
application may work best with a different bead value. Alternately,
placing a 100 Ω to 120 Ω resistor between the 75 Ω termination
resistor and the input coupling capacitor can also be beneficial.
Digital Interface Inputs
Minimize the trace length running into the graphics inputs. This
is accomplished by placing the AD9887 as close as possible to
the graphics VGA connector. Long input trace lengths are undesirable because they will pick up more noise from the board and
other external sources.
Each differential input pair (RXO+, RXO–, RXC+, RXC–, etc.)
should be routed together using 50 Ω strip line routing techniques and should be kept as short as possible. No other
components should be placed on these inputs; for example, no
clamping diodes. Every effort should also be made to route
these signals on a single layer (component layer) with no vias.
Power Supply Bypassing
Place the 75 Ω termination resistors as close to the AD9887
chip as possible. Any additional trace length between the termination resistors and the input of the AD9887 increases the
magnitude of reflections, which will corrupt the graphics signal.
Use 75 Ω matched impedance traces. Trace impedances other
than 75 Ω will also increase the chance of reflections.
The AD9887 has very high input bandwidth, (330 MHz). While
this is desirable for acquiring a high resolution PC graphics
signal with fast edges, it means that it will also capture any high
frequency noise present. Therefore, it is important to reduce the
amount of noise that gets coupled to the inputs. Avoid running
any digital traces near the analog inputs.
Due to the high bandwidth of the AD9887, sometimes low-pass
ﬁltering the analog inputs can help to reduce noise. (For many
applications, ﬁltering is unnecessary.) Experiments have shown
It is recommended to bypass each power supply pin with a
0.1 µF capacitor. The exception is in the case where two or
more supply pins are adjacent to each other. For these groupings of powers/grounds, it is only necessary to have one bypass
capacitor. The fundamental idea is to have a bypass capacitor
within about 0.5 cm of each power pin. Also, avoid placing the
capacitor on the opposite side of the PC board from the AD9887,
as that interposes resistive vias in the path.
The bypass capacitors should be physically located between the
power plane and the power pin. Current should flow from the
power plane to the capacitor to the power pin. Do not make the
power connection between the capacitor and the power pin.
Placing a via underneath the capacitor pads, down to the power
plane, is generally the best approach.
–38–
REV. 0
AD9887
It is particularly important to maintain low noise and good
stability of PVD (the clock generator supply). Abrupt changes in
PVD can result in similarly abrupt changes in sampling clock
phase and frequency. This can be avoided by careful attention
to regulation, ﬁltering, and bypassing. It is highly desirable to
provide separate regulated supplies for each of the analog circuitry groups (VD and PVD).
Some graphic controllers use substantially different levels of
power when active (during active picture time) and when idle
(during horizontal and vertical sync periods). This can result in
a measurable change in the voltage supplied to the analog
supply regulator, which can in turn produce changes in the
regulated analog supply voltage. This can be mitigated by regulating the analog supply, or at least PVD, from a different, cleaner
power source (for example, from a 12 V supply).
It is also recommended to use a single ground plane for the
entire board. Experience has repeatedly shown that the noise
performance is the same or better with a single ground plane.
Using multiple ground planes can be detrimental because each
separate ground plane is smaller, and long ground loops can result.
NE
PLA
ND
U
O
GR
GI
AD988
7
DIG
ITA
L
E
AC
DI
POWER PLANE
TPUT TR
OU
ANALOG
In some cases, using separate ground planes is unavoidable. For
those cases, it is recommended to at least place a single ground
plane under the AD9887. The location of the split should be at
the receiver of the digital outputs. For this case it is even more
important to place components wisely because the current loops
will be much longer (current takes the path of least resistance).
An example of a current loop:
TA
L
GRO
UND P
LANE
REC
DIGITAL DATA
EIV E
R
Figure 39. Example of a Current Loop
REV. 0
PLL
Place the PLL loop ﬁlter components as close to the FILT pin
as possible.
Do not place any digital or other high-frequency traces near
these components.
Use the values suggested in the data sheet with 10% tolerances
or less.
Outputs (Both Data and Clocks)
Try to minimize the trace length that the digital outputs have to
drive. Longer traces have higher capacitance, which require
more current that causes more internal digital noise.
Shorter traces reduce the possibility of reflections.
Adding a series resistor of value 50 Ω–200 Ω can suppress reflections, reduce EMI, and reduce the current spikes inside of the
AD9887. If series resistors are used, place them as close to the
AD9887 pins as possible (try not to add vias or extra length to
the output trace in order to get the resistors closer).
If possible, limit the capacitance that each of the digital outputs
drives to less than 10 pF. This can easily be accomplished by
keeping traces short and by connecting the outputs to only one
device. Loading the outputs with excessive capacitance will
increase the current transients inside of the AD9887 creating
more digital noise on its power supplies.
Digital Inputs
The digital inputs on the AD9887 were designed to work with
3.3 V signals.
Any noise that gets onto the Hsync input trace will add jitter to
the system. Therefore, minimize the trace length and do not run
any digital or other high-frequency traces near it.
Voltage Reference
Bypass with a 0.1 µF capacitor. Place as close to the AD9887
pin as possible. Make the ground connection as short as possible.
REFOUT is easily connected to REFIN with a short trace. Avoid
making this trace any longer than it needs to be.
When using an external reference, the REFOUT output, while
unused, still needs to be bypassed with a 0.1 µF capacitor in
order to avoid ringing.
–39–
AD9887
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
160-Lead MQFP
(S-160)
0.160 (4.07)
MAX
0.041 (1.03)
0.035 (0.88)
0.029 (0.73)
120
121
81
80
0.998
(25.35)
BSC SQ
TOP VIEW
(PINS DOWN)
SEATING
PLANE
0.004 (0.10)
MAX
C01026–0-10/01(0)
1.238 (31.45)
1.228 (31.20) SQ
1.219 (30.95)
1.106 (28.10)
1.102 (28.00) SQ
1.098 (27.90)
PIN 1
160
0.010 (0.25)
MIN
0.145 (3.67)
0.135 (3.42)
0.125 (3.17)
41
40
1
0.026 (0.65)
BSC*
LEAD PITCH
0.015 (0.38)
0.012 (0.30) LEAD WIDTH
0.009 (0.22)
PRINTED IN U.S.A.
*THE ACTUAL POSITION OF EACH LEAD IS WITHIN 0.0047 (0.12) FROM ITS
IDEAL POSITION WHEN MEASURED IN THE LATERAL DIRECTION.
CENTER FIGURES ARE TYPICAL UNLESS OTHERWISE NOTED.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS. INCH DIMENSIONS
ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE
ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
–40–
REV. 0

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