TI1 ADC08DL502 Low power, 8-bit, dual 500 msps a/d converter Datasheet

ADC08DL502
Low Power, 8-Bit, Dual 500 MSPS A/D Converter
General Description
Features
The ADC08DL502 is a dual, low power, high performance,
CMOS analog-to-digital converter. The ADC08DL502 digitizes signals to 8 bits of resolution at sample rates up to 500
MSPS. Consuming a typical 1.2 Watts in demultiplex mode at
500 MSPS from a single 1.9 Volt supply, this device is guaranteed to have no missing codes over the full operating
temperature range. The unique folding and interpolating architecture, the fully differential comparator design, the innovative design of the internal sample-and-hold amplifier and
the calibration schemes enable a very flat response of all dynamic parameters beyond Nyquist, producing a high 7.5
Effective Number of Bits (ENOB) with a 125 MHz input signal
and a 500 MHz sample rate while providing a 10−18 Code
Error Rate (C.E.R.)
The converter typically consumes 3.3 mW in the Power Down
Mode and is available in a lead-free 144-lead LQFP and operates over the modified Industrial (-40°C ≤ TA ≤ +70°C)
temperature range.
■ Single +1.9V ±0.1V Operation
■ Duty Cycle Corrected Sample Clock
Key Specifications
■
■
■
■
■
■
Resolution
Max Conversion Rate
Code Error Rate
ENOB @ 125 MHz Input
DNL
Power Consumption
— Operating in 1:2 Demux Output
— Power Down Mode
8 Bits
500 MSPS
10−18 (typ)
7.5 Bits (typ)
±0.15 LSB (typ)
1.25W (typ)
3.3 mW (typ)
Applications
■
■
■
■
■
Satellite Modems
Digital Oscilloscopes
Direct RF Down Conversion
Communications Systems
Test Instrumentation
Ordering Information
Industrial Temperature Range (-40°C < TA < +70°C)
NS Package
ADC08DL502CIVV/NOPB
Lead-free 144-Pin LQFP
Block Diagram
30174153
© 2012 Texas Instruments Incorporated
301741 SNAS582
www.ti.com
ADC08DL502 Low Power, 8-Bit, Dual 500 MSPS A/D Converter
March 23, 2012
ADC08DL502
Pin Configuration
30174101
www.ti.com
2
Pin Functions
Pin No.
5
31
Symbol
Equivalent Circuit
Description
Output Voltage Amplitude and Serial Interface Clock. Tie this
pin high for normal differential DCLK and data amplitude.
Ground this pin for a reduced differential output amplitude
and reduced power consumption. When the extended
control mode is enabled, this pin functions as the SCLK input
which clocks in the serial data. OutV functionality: (Note 16)
OutV / SCLK
A logic high on the PDQ pin puts only the "Q" ADC into the
Power Down mode. PDQ functionality: (Note 16)
PDQ
OutEdge / DDR /
SDATA
DCLK Edge Select, Double Data Rate Enable and Serial
Data Input. This input sets the output edge of DCLK+ at
which the output data transitions. When this pin is floating or
connected to 1/2 the supply voltage, DDR clocking is
enabled. When the extended control mode is enabled, this
pin functions as the SDATA input. OutEdge functionality:
(Note 16)
17
DCLK_RST /
DCLK_RST+
DCLK Reset. When single-ended DCLK_RST is selected by
floating or setting pin 58 logic high, a positive pulse on this
pin is used to reset and synchronize the DCLK outputs of
multiple converters. When differential DCLK_RST is
selected by setting pin 58 logic low, this pin receives the
positive polarity of a differential pulse signal used to reset
and synchronize the DCLK outputs of multiple converters.
DCLK_RST, DCLK_RST+ functionality: (Note 16)
28
PD
Power Down Pins. A logic high on the PD pin puts the entire
device into the Power Down Mode. PD functionality: (Note
16)
32
CAL
Calibration Cycle Initiate. A minimum tCAL_L input clock
cycles logic low followed by a minimum of tCAL_H input clock
cycles high on this pin initiates the calibration sequence.
6
3
www.ti.com
ADC08DL502
Pin Descriptions and Equivalent Circuits
ADC08DL502
Pin Functions
Pin No.
Symbol
Equivalent Circuit
Description
FSR/ALT_ECE/
DCLK_RST-
Full Scale Range Select, Alternate Extended Control Enable
and DCLK_RST-. This pin has three functions. It can
conditionally control the ADC full-scale voltage, enable the
extended control mode, or become the negative polarity
signal of a differential pair in differential DCLK_RST mode.
If pin 58 and pin 47 are floating or at logic high, this pin can
be used to set the full-scale-range or can be used as an
alternate extended control enable pin . When used as the
FSR pin, a logic low on this pin sets the full-scale differential
input range to a reduced VIN input level. A logic high on this
pin sets the full-scale differential input range to a higher VIN
input level. To enable the extended control mode, whereby
the serial interface and control registers are employed, allow
this pin to float or connect it to a voltage equal to VA/2. Note
that pin 47 overrides the extended control enable of this pin.
When pin 58 is held at logic low, this pin acts as the
DCLK_RST- pin. When in differential DCLK_RST mode,
there is no pin-controlled FSR and the full-scale-range is
defaulted to the higher VIN input level. FSR, ALT_ECE,
DCLK_RST- functionality: (Note 16)
141
CalDly / SCS
Calibration Delay and Serial Interface Chip Select. With a
logic high or low on pin 16, and a logic high on pin 47, this
pin functions as Calibration Delay and sets the number of
input clock cycles after power up before calibration begins
With pin 16 floating, and a logic low on pin 47, this pin acts
as the enable pin for the serial interface input and the CalDly
value becomes "0" (short delay with no provision for a long
power-up calibration delay). CalDly functionality: (Note 16)
20
21
CLK+
CLK−
LVDS Clock input pins for the ADC. The differential clock
signal must be a.c. coupled to these pins. The input signal is
sampled on the falling edge of CLK+.
16
VINI+
VINI−
13
12
24
25
www.ti.com
Analog signal inputs to the ADC. The differential full-scale
input range of this input is programmable using the FSR pin
16 in normal mode and the Input Full-Scale Voltage Adjust
register in the extended control mode. Refer to the VIN
specification in the Converter Electrical Characteristics for
the full-scale input range in the normal mode.
VINQ+
VINQ−
4
Pin No.
Symbol
Equivalent Circuit
Description
9
VCMO
Common Mode Voltage. This pin is the common mode
output in d.c. coupling mode and also serves as the a.c.
coupling mode select pin. When d.c. coupling is used, the
voltage output at this pin is required to be the common mode
input voltage at VIN+ and VIN− when d.c. coupling is used.
This pin should be grounded when a.c. coupling is used at
the analog inputs. This pin is capable of sourcing or sinking
100 μA.
33
VBG
Bandgap output voltage capable of 100 μA source/sink and
can drive a load up to 80 pF. VBG functionality: (Note 16)
140
CalRun
Calibration Running indication. This pin is at a logic high
when calibration is running. CalRun functionality: (Note 16)
34
REXT
External bias resistor connection. Nominal value is 4.7 kΩ
(±0.1%) to ground.
40
41
47
58
Tdiode_P
Tdiode_N
Temperature Diode Positive (Anode) and Negative
(Cathode). These pins may be used for die temperature
measurements, however no specified accuracy is implied or
guaranteed. Noise coupling from adjacent output data
signals has been shown to affect temperature
measurements using this feature. Tdiode_P, Tdiode_N
functionality: (Note 16)
ECE
Extended Control Enable. This pin always enables and
disables Extended Control Enable. When this pin is set logic
high, the extended control mode is inactive and all control of
the device must be through control pins only . When it is set
logic low, the extended control mode is active. This pin
overrides the Extended Control Enable signal set using pin
16.
DRST_SEL
DCLK_RST select. This pin selects whether the DCLK is
reset using a single-ended or differential signal. When this
pin is floating or logic high, the DCLK_RST operation is
single-ended and pin 16 functions as FSR/ALT_ECE. When
this pin is logic low, the DCLK_RST operation becomes
differential with functionality on pin 17 (DCLK_RST+) and pin
16 (DCLK_RST-). When in differential DCLK_RST mode,
there is no pin-controlled FSR and the full-scale-range is
defaulted to the higher VIN input level. When pin 47 is set
logic low, the extended control mode is active and the FullScale Voltage Adjust registers can be programmed.
DRST_SEL functionality: (Note 16)
5
www.ti.com
ADC08DL502
Pin Functions
ADC08DL502
Pin Functions
Pin No.
Symbol
93 / 88
94 / 87
95 / 86
96 / 85
99 / 82
100 / 81
101 / 80
102 / 79
103 / 78
104 / 77
105 / 76
106 / 75
114 / 67
115 / 66
116 / 65
117 / 64
DI7− / DQ7−
DI7+ / DQ7+
DI6− / DQ6−
DI6+ / DQ6+
DI5− / DQ5−
DI5+ / DQ5+
DI4− / DQ4−
DI4+ / DQ4+
DI3− / DQ3−
DI3+ / DQ3+
DI2− / DQ2−
DI2+ / DQ2+
DI1− / DQ1−
DI1+ / DQ1+
DI0− / DQ0−
DI0+ / DQ0+
I and Q channel LVDS Data Outputs that are not delayed in
the output demultiplexer. Compared with the DId and DQd
outputs, these outputs represent the later time samples.
These outputs should always be terminated with a 100 Ω
differential resistor.
118 / 63
119 / 62
120 / 61
121 / 60
125 / 56
126 / 55
127 / 54
128 / 53
129 / 52
130 / 51
131 / 50
132 / 49
136 / 45
137 / 44
138 / 43
139 / 42
DId7− / DQd7−
DId7+ / DQd7+
DId6− / DQd6−
DId6+ / DQd6+
DId5− / DQd5−
DId5+ / DQd5+
DId4− / DQd4−
DId4+ / DQd4+
DId3− / DQd3−
DId3+ / DQd3+
DId2− / DQd2−
DId2+ / DQd2+
DId1− / DQd1−
DId1+ / DQd1+
DId0− / DQd0−
DId0+ / DQd0+
I and Q channel LVDS Data Outputs that are delayed by one
CLK cycle in the output demultiplexer. Compared with the
DI/DQ outputs, these outputs represent the earlier time
sample. These outputs should be terminated with a 100 Ω
differential resistor when enabled. In non-demultiplexed
mode, these outputs are disabled and are high impedance
when enabled. When disabled, these outputs must be left
floating.
OR+/DCLK2+
OR-/DCLK2-
Out Of Range output. A differential high at these pins
indicates that the differential input is out of range (outside the
range ±VIN/2 as programmed by the FSR pin in nonextended control mode or the Input Full-Scale Voltage Adjust
register setting in the extended control mode). DCLK2 is the
exact mirror of DCLK and should output the same signal at
the same rate. DCLK2+/- functionality: (Note 16)
DCLK+
DCLK-
Data Clock. Differential Clock outputs used to latch the
output data. Delayed and non-delayed data outputs are
supplied synchronous to this signal. In 1:2 demultiplexed
mode, this signal is at 1/2 the input clock rate in SDR mode
and at 1/4 the input clock rate in the DDR mode. By default,
the DCLK outputs are not active during the termination
resistor trim section of the calibration cycle. If a system
requires DCLK to run continuously during a calibration cycle,
the termination resistor trim portion of the cycle can be
disabled by setting the Resistor Trim Disable (RTD) bit to
logic high in the Extended Configuration Register (address
9h). This disables all subsequent termination resistor trims
after the initial trim which occurs during the power on
calibration. Therefore, this output is not recommended as a
system clock unless the resistor trim is disabled. When the
device is in the non-demultiplexed mode, DCLK can only be
in DDR mode and the signal is at 1/2 the input clock rate.
89
90
92
91
www.ti.com
Equivalent Circuit
Description
6
Pin No.
Symbol
Equivalent Circuit
4, 7, 10, 15,
18, 19, 22,
27, 30, 39,
142
Description
VA
NONE
Analog power supply pins. Bypass these pins to ground.
46, 57, 68,
83, 98, 113,
124, 135
VDR
NONE
Output Driver power supply pins. Bypass these pins to DR
GND.
2, 3, 8, 11,
14, 23, 26,
29, 35
GND
NONE
Ground return for VA.
48, 59, 70,
74, 84, 97,
107, 111,
122, 133
DR GND
NONE
Ground return for VDR.
1, 36, 37,
38, 69, 71,
72, 73, 108,
109, 110,
143, 144
NC
NONE
Not Connected. These pins are not bonded and may be left
floating or connected to any potential.
112, 123,
134
DNC
NONE
Do Not Connect. These pins are used for internal purposes
and should not be connected, i.e. left floating. Do not ground.
7
www.ti.com
ADC08DL502
Pin Functions
ADC08DL502
Absolute Maximum Ratings
Operating Ratings
Ambient Temperature Range (Note
23)
Supply Voltage (VA)
Driver Supply Voltage (VDR)
Common Mode Input Voltage
VIN+, VIN− Voltage Range
(Maintaining Common Mode)
(Note 1, Note 2)
If Military/Aerospace specified devices are required,
please contact the Texas Instruments Sales Office/
Distributors for availability and specifications.
Supply Voltage (VA, VDR)
Supply Difference
VDR - VA
Voltage on Any Input Pin
(Except VIN+, VIN- )
Voltage on VIN+, VIN(Maintaining Common Mode)
Ground Difference
|GND - DR GND|
Input Current at Any Pin (Note
3)
Package Input Current (Note 3)
Junction Temperature
2.2V
0V to 100 mV
−0.15V to (VA +0.15V)
ESD Susceptibility (Note 4)
Human Body Model
Machine Model
Charged Device Model
Storage Temperature
(Note 1, Note 2)
−40°C ≤ TA ≤ +70°C
+1.8V to +2.0V
+1.8V to VA
VCMO ± 50 mV
0V to 2.15V
(100% duty cycle)
0V to 2.5V
(10% duty cycle)
Ground Difference
(|GND − DR GND|)
CLK Pins Voltage Range
Differential CLK Amplitude
Common Mode Input Voltage
-0.15 to 2.5V
0V to 100 mV
±25 mA
±50 mA
0V
0V to VA
0.4VP-P to 2.0VP-P
VCMO - 50mV < VCMI
< VCMO + 50mV
Package Thermal Resistance
TJ ≤ 145°C
2500V
250V
1000V
−65°C to +150°C
Package
θJA
θJC
psiJB
144-Lead,
LQFP
43.6°C / W
12.5°C / W
39.0°C / W
Soldering
process
must
comply
with
National
Semiconductor’s Reflow Temperature Profile specifications.
Refer to www.national.com/packaging. (Note 5)
Converter Electrical Characteristics
The following specifications apply after calibration for VA = VDR = 1.9V; OutV = 1.9V; VIN FSR (a.c. coupled) = differential 840
mVP-P; CL = 10 pF; Differential, a.c. coupled Sine Wave Input Clock, fCLK = 500 MHz at 0.5 VP-P with 50% duty cycle; VBG = Floating;
Extended Control Mode default values; DDR 0° Mode; REXT = 4700 Ω ±0.1%; 1:2 Output Demultiplex; Duty Cycle Stabilizer on.
Boldface limits apply for TA = TMIN to TMAX. All other limits TA = 25°C, unless otherwise noted. (Note 6, Note 7).
TABLE 1. Static Converter Characteristics
Symbol
Parameter
Conditions
Typ
Resolution with No Missing
Codes
Lim
Units
(Limits)
8
Bits
INL
Integral Non-Linearity
(Best fit)
DC Coupled, 1 MHz Sine Wave
Overanged, SDR, Non-ECM,
FSR = High
±0.3
±0.9
LSB
(max)
DNL
Differential Non-Linearity
DC Coupled, 1 MHz Sine Wave
Overanged, SDR, Non-ECM,
FSR = High
±0.15
±0.75
LSB
(max)
VOFF
Offset Error
SDR, Non-ECM Mode
−0.45
LSB
VOFF_ADJ
Input Offset Adjustment Range Extended Control Mode
(Note 18)
±45
mV
PFSE
Positive Full-Scale Error
(Note 9)
±25
mV (max)
NFSE
Negative Full-Scale Error
(Note 9)
±25
mV (max)
Out of Range Output Code
(VIN+) − (VIN−) > + Full Scale
255
(VIN+) − (VIN−) < − Full Scale
0
www.ti.com
8
Symbol
Parameter
FPBW
Full Power Bandwidth
Gain Flatness
Conditions
Typ
Lim
Units
(Limits)
2.0
GHz
d.c. to 248 MHz
±0.8
dBFS
d.c. to 500 MHz
±1.0
dBFS
10−18
Error/
Sample
C.E.R.
Code Error Rate
NPR
Noise Power Ratio
(Note 21)
38.4
dB
IMD3
3rd order Intermodulation
Distortion
fIN1 =111.47 MHz @ −7dBFS
fIN2 =121.47 MHz @ −7dBFS
71.4
dBFS
Noise Floor
(Note 22)
Effective Number of Bits
AIN = 125 MHz @ -0.5dBFS
7.5
AIN = 248 MHz @ -0.5dBFS
7.6
Signal-to-Noise Plus Distortion AIN = 125 MHz @ -0.5dBFS
Ratio
AIN = 248 MHz @ -0.5dBFS
46.9
Signal-to-Noise Ratio
AIN = 125 MHz @ -0.5dBFS
47.8
AIN = 248 MHz @ -0.5dBFS
48.5
AIN = 125 MHz @ -0.5dBFS
-54.2
AIN = 248 MHz @ -0.5dBFS
-54.8
dB (max)
AIN = 125 MHz @ -0.5dBFS
−60
dB
AIN = 248 MHz @ -0.5dBFS
-59
dB
AIN = 125 MHz @ -0.5dBFS
−68
dB
AIN = 248 MHz @ -0.5dBFS
-60
dB
Spurious-Free dynamic Range AIN = 125 MHz @ -0.5dBFS
58.5
AIN = 248 MHz @ -0.5dBFS
59.1
64.4
dBc
-135.4
dBm/Hz
-133.3
ENOB
SINAD
SNR
THD
2nd Harm
3rd Harm
SFDR
Total Harmonic Distortion
Second Harmonic Distortion
Third Harmonic Distortion
9
dBFS/Hz
6.8
bits
bits (min)
42.4
47.6
dB
dB (min)
43.5
dB
dB (min)
-49
49
dB
dB
dB (min)
www.ti.com
ADC08DL502
TABLE 2. Dynamic Converter Characteristics
ADC08DL502
TABLE 3. Analog Input/Output and Reference Characteristics
Symbol
Parameter
Conditions
Typ
Lim
Units
(Limits)
900
mVP-P
Analog Inputs
VIN_FSR
Analog Differential Input Full
Scale Range
Non-Extended Control Mode (Note 16)
FSR Pin High, SDR
840
FSR Pin Low, SDR
650
mVP-P
FS_ADJ(15:7) = 1111 1111 1b
840
mVP-P
FS_ADJ(15:7) = 1000 0000 0b
(default)
700
mVP-P
Extended Control Mode (Note 18)
CIN
RIN
FS_ADJ(15:7) = 0000 0000 0b
560
mVP-P
Analog Input Capacitance
(Note 10, Note 11, Note 20)
Differential
0.02
pF
Each input pin to ground
1.6
pF
Differential Input Resistance
Measured at D.C.
140
Ω
Common Mode Output
VCMO
Common Mode Output Voltage ICMO = ±100 µA
1.26
0.9
V (min)
1.6
V (max)
Bandgap Reference
VBG
Bandgap Reference Output
Voltage
IBG = ±100 µA
TC_VBG
Bandgap Reference Voltage
Temperature Coefficient
TA = −40°C to +70°C,
IBG = ±100 µA
CLOAD VBG
Maximum Bandgap Reference
load Capacitance
www.ti.com
1.26
V
28
ppm/°C
80
10
pF
Symbol
Parameter
Conditions
Typ
Offset Match
X-TALK
Lim
Units
(Limits)
1
LSB
Positive Full-Scale Match
Zero offset selected in Control
Register
1
LSB
Negative Full-Scale Match
Zero offset selected in Control
Register
1
LSB
Phase Matching (I, Q)
fIN = 500 MHz
<1
Degree
Crosstalk from I (Aggressor) to Aggressor = 467 MHz F.S.
Q (Victim) Channel
Victim = 100 MHz F.S.
−65
dB
Crosstalk from Q (Aggressor) to Aggressor = 467 MHz F.S.
I (Victim) Channel
Victim = 100 MHz F.S.
−65
dB
TABLE 5. Sampling Clock Characteristics
Symbol
Parameter
Conditions
Typ
Lim
Units
(Limits)
VIN_CLK
Differential Clock Input Level
Sine Wave Clock
0.6
0.4
VP-P (min)
2.0
VP-P
(max)
0.4
VP-P (min)
2.0
VP-P
(max)
Square Wave Clock
0.6
RIN_CLK
Sampling Clock Input
Impedance
Measured at D.C.
100
Ω
CIN_CLK
Input Capacitance
(Note 10, Note 11)
Differential
0.02
pF
Each input to ground
1.5
pF
1.2
V
VOSI
Input Offset Voltage
11
www.ti.com
ADC08DL502
TABLE 4. I-Channel to Q-Channel Characteristics
ADC08DL502
TABLE 6. Digital Control and Output Pin Characteristics
Symbol
Parameter
Conditions
Typ
Lim
Units
(Limits)
0.69 x VA
V (min)
Digital Control Pins
VIH
Logic High Input Voltage (Note PD,CAL, OutV, PDQ, ECEb,
12)
DRST_SEL
VIL
Logic Low Input Voltage (Note PD,CAL, OutV, PDQ, ECEb,
12)
DRST_SEL
OUTEDGE, FSR, CalDly
OUTEDGE, FSR, CalDly
CIN_DIG
Input Capacitance
(Note 11, Note 13)
0.815 x VA
V (min)
0.28 x VA
V (max)
0.21 x VA
V (max)
Each input to ground
1.2
pF
Measured differentially, OutV =
VA,
VBG = Floating (Note 15, Note
16)
590
Measured differentially, OutV =
GND, VBG = Floating (Note 15,
Note 16)
432
mVP-P
±1
mV
VBG = Floating
0.8
V
VBG = VA (Note 15, Note 16)
1.2
V
±1
mV
±4
mA
Digital Output Pins
VOD
LVDS Differential Output
Voltage
400
mVP-P
(min)
850
mVP-P
(max)
ΔVO DIFF
Change in LVDS Output Swing
Between Logic Levels
VOS
Output Offset Voltage
ΔVOS
Output Offset Voltage Change
Between Logic Levels
IOS
Output Short Circuit Current
ZO
Differential Output Impedance
100
Ω
VOH
CalRun H level output
IOH = −400 µA (Note 12)
1.65
V
VOL
CalRun L level output
IOH = 400 µA (Note 12)
0.15
V
Output+ & Output−
connected to 0.8V
Differential DCLK Reset Pins (DCLK_RST) (Note 17)
VCMI_DRST
DCLK_RST Common Mode
Input Voltage
1.25
V
VID_DRST
Differential DCLK_RST Input
Voltage
VIN_CLK
VP-P
RIN_DRST
Differential DCLK_RST Input
Resistance
100
Ω
TABLE 7. Power Supply Characteristics
Typ
Lim
Units
(Limits)
PD = Low
494
650
mA (max)
PD = High
1.7
Symbol
Parameter
Conditions
IA
Analog Supply Current
1:2 Demux Output
IDR
PC
www.ti.com
Output Driver Supply Current
Power Consumption
mA
1:2 Demux Output
PD = Low
168
PD = High
0.054
275
mA (max)
mA
1:2 Demux Output
PD = Low
1.25
PD = High
3.3
12
1.61
W (max)
mW
Symbol
Parameter
Conditions
Typ
Lim
Units
(Limits)
Sampling Clock (CLK)
fCLK (max)
Maximum Sampling Clock
Frequency
500
MHz
fCLK (min)
Minimum Sampling Clock
Frequency
200
MHz
Sampling Clock Duty Cycle
200 MHz ≤ fCLK ≤ 500 MHz
(Note 12)
50
20
% (min)
80
% (max)
tCL
Sampling Clock Low Time
(Note 11)
1000
400
ps (min)
tCH
Sampling Clock High Time
(Note 11)
1000
400
ps (min)
DCLK_RST (Note 17)
tSR
Setup Time DCLK_RST±
(Note 12) Differential
DCLK_RST
90
ps
tHR
Hold Time DCLK_RST±
(Note 12) Differential
DCLK_RST
30
ps
tPWR
Pulse Width DCLK_RST±
(Note 11)
4
CLK±
Cycles
(min)
Data Clock (DCLK)
DCLK Duty Cycle
(Note 11)
50
45
% (min)
55
% (max)
tLHT
Differential Low-to-High
Transition Time
10% to 90%
150
ps
tHLT
Differential High-to-Low
Transition Time
10% to 90%
150
ps
tOSK
DCLK-to-Data Output Skew
50% of DCLK transition to 50%
of Data transition
±50
ps
tSU
Data-to-DCLK Set-Up Time
DDR Mode, 90° DCLK (Note
11)
750
ps
tH
DCLK-to-Data Hold Time
DDR Mode, 90° DCLK (Note
11)
890
ps
Input CLK+ Fall to Acquisition
of Data
1.6
ns
0.4
ps (rms)
4.0
ns
Data Input-to-Output
tAD
Sampling (Aperture) Delay
tAJ
Aperture Jitter
tOD
Input Clock-to Data Output
Delay (in addition to Pipeline
Delay)
tLAT
Pipeline Delay (Latency) in 1:2 DI Outputs
Demux Mode
DId Outputs
(Note 11, Note 14)
DQ Outputs
50% of Input Clock transition to
50% of Data transition
13
14
13
DQd Outputs
14
Pipeline Delay (Latency) in
Non-Demux Mode
(Note 11, Note 14)
DI Outputs
13
DQ Outputs
13
tORR
Over Range Recovery Time
Differential VIN step from ±1.2V
to 0V to get accurate
conversion
tWU
PD low to Rated Accuracy
Conversion (Wake-Up Time)
(Note 11)
13
Sampling
Clock
Cycles
1
Sampling
Clock
Cycle
500
ns
www.ti.com
ADC08DL502
TABLE 8. AC Electrical Characteristics
ADC08DL502
TABLE 9. Serial Port Interface
Symbol
Parameter
Conditions
fSCLK
Serial Clock Frequency
(Note 11)
Typ
Lim
15
Units
(Limits)
MHz
Serial Clock Low Time
33.3
ns (min)
Serial Clock High Time
33.3
ns (min)
tSSU
Serial Data to Serial Clock
Rising Setup Time
(Note 11)
2.5
ns (min)
tSH
Serial Data to Serial Clock
Rising Hold Time
(Note 11)
1
ns (min)
tSCS
CS to Serial Clock Rising Setup
Time
2.5
ns
tHCS
CS to Serial Clock Falling Hold
Time
1.5
ns
TABLE 10. Calibration
Symbol
Parameter
Conditions
Typ
Lim
tCAL
Calibration Cycle Time
Rtrim enabled
1.4 x 106
1.62 x 106
Rtrim disabled
106
106
1.2 x
1.35 x
tCAL_L
CAL Pin Low Time
(Note 11)
1280
tCAL_H
CAL Pin High Time
(Note 11)
1280
tCalDly
Calibration Delay determined
by CalDly pin (Note 11)
CalDly = Low (Note 16)
226
CalDly = High (Note 16)
232
Units
(Limits)
Clock
Cycles
(max)
Clock
Cycles
(min)
Clock
Cycles
(max)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. There is no guarantee of operation at the Absolute Maximum
Ratings. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications
and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics
may degrade when the device is not operated under the listed test conditions.
Note 2: All voltages are measured with respect to GND = DR GND = 0V, unless otherwise specified.
Note 3: When the input voltage at any pin exceeds the power supply limits (that is, less than GND or greater than VA), the current at that pin should be limited to
25 mA. The 50 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 25 mA to
two. This limit is not placed upon the power, ground and digital output pins.
Note 4: Human body model is 100 pF capacitor discharged through a 1.5 kΩ resistor. Machine model is 220 pF discharged through ZERO Ohms. Charged device
model simulates a pin slowly acquiring charge (such as from a device sliding down the feeder in an automated assembler) then rapidly being discharged.
Note 5: Reflow temperature profiles are different for lead-free and non-lead-free packages.
Note 6: The analog inputs are protected as shown below. Input voltage magnitudes beyond the Absolute Maximum Ratings may damage this device.
30174104
Note 7: To guarantee accuracy, it is required that VA and VDR be well bypassed. Each supply pin must be decoupled with separate bypass capacitors. Additionally,
achieving rated performance requires that the backside exposed pad be well grounded.
Note 8: Typical figures are at TA = 25°C, and represent most likely parametric norms. Test limits are guaranteed to National's AOQL (Average Outgoing Quality
Level).
www.ti.com
14
Note 10: The analog and clock input capacitances are die capacitances only. Additional package capacitances of 0.65 pF differential and 0.95 pF each pin to
ground are isolated from the die capacitances by lead and bond wire inductances.
Note 11: This parameter is guaranteed by design and is not tested in production.
Note 12: This parameter is guaranteed by design and/or characterization and is not tested in production.
Note 13: The digital control pin capacitances are die capacitances only. Additional package capacitance of 1.6 pF each pin to ground are isolated from the die
capacitances by lead and bond wire inductances.
Note 14: Each of the two converters of the ADC08DL502 has two LVDS output buses, which each clock data out at one half the sample rate. The data at each
bus is clocked out at one half the sample rate. The second bus (D0 through D7) has a pipeline latency that is one Input Clock cycle less than the latency of the
first bus (Dd0 through Dd7) in 1:2 demux mode.
Note 15: Tying VBG to the supply rail will increase the output offset voltage (VOS) by 400 mV (typical), as shown in the VOS specification above. Tying VBG to the
supply rail will also affect the differential LVDS output voltage (VOD), causing it to increase by 40 mV (typical).
Note 16: This pin/bit functionality is not tested in production test; performance is tested in the specified/default mode only.
Note 17: This feature functionality is not tested in production test; performance is tested in the specified/default mode only.
Note 18: Only the end points of the range, not the full sweep, are tested in production test.
Note 19: Coarse and intermediate step size are tested in major steps only in production test; fine step size is not tested.
Note 20: The differential and pin-to-ground input capacitances are lumped capacitance values from design; they are defined as shown below.
30174168
Note 21: The NPR was measured using an Agilent N6030A Arbitrary Waveform Generator (ARB) to generate the input signal. The "noise" portion of the signal
was created by tones spaced at 500 kHz and the "notch" was a 12.5 MHz absence of tones centered at 175 MHz.
Note 22: For the case where the inputs are shorted or terminted with 50Ω, the LSB of the ADC never transitions because the Noise Floor is limited by quantization
noise, not thermal noise. Therefore, the Noise Floor was measured with a low-level wideband input from 10 MHz to 30 MHz; the noise floor was measured in the
band from 126 MHz to 175 MHz.
Note 23: The 4-layer standard JEDEC thermal test board or 4LJEDEC is 4"x3" in size. The board has two embedded copper layers which cover roughly the same
size as the board. The copper thickness for the four layers, starting from the top one, is 2 oz., 1 oz., 1 oz., 2 oz. Detailed description of the board can be found
in the JESD 51-7 standard.
15
www.ti.com
ADC08DL502
Note 9: Calculation of Full-Scale Error for this device assumes that the actual reference voltage is exactly its nominal value. Full-Scale Error for this device,
therefore, is a combination of Full-Scale Error and Reference Voltage Error. For relationship between Gain Error and Full-Scale Error, see Specification Definitions
for Gain Error.
ADC08DL502
Specification Definitions
APERTURE (SAMPLING) DELAY is the amount of delay,
measured from the sampling edge of the Clock input, after
which the signal present at the input pin is sampled inside the
device.
APERTURE JITTER (tAJ) is the variation in aperture delay
from sample to sample. Aperture jitter shows up as input
noise.
CODE ERROR RATE (C.E.R.) is the probability of error and
is defined as the probable number of word errors on the ADC
output per unit of time divided by the number of words seen
in that amount of time. A C.E.R. of 10-18 corresponds to a
statistical error in one word about every four (4) years.
CLOCK DUTY CYCLE is the ratio of the time that the clock
waveform is at a logic high to the total time of one clock period.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of
the maximum deviation from the ideal step size of 1 LSB.
Measured at sample rate = 500 MSPS with a 1MHz input
sinewave.
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE
BITS) is another method of specifying Signal-to-Noise and
Distortion Ratio, or SINAD. ENOB is defined as
(SINAD − 1.76) / 6.02 and says that the converter is equivalent to a perfect ADC of this (ENOB) number of bits.
FULL POWER BANDWIDTH (FPBW) is a measure of the
frequency at which the reconstructed output fundamental
drops 3 dB below its low frequency value for a full-scale input.
GAIN ERROR is the deviation from the ideal slope of the
transfer function. It can be calculated from Offset and FullScale Errors:
Positive Gain Error = Offset Error − Positive Full-Scale
Error
Negative Gain Error = −(Offset Error − Negative FullScale Error)
Gain Error = Negative Full-Scale Error − Positive FullScale Error = Positive Gain Error + Negative Gain Error
INTEGRAL NON-LINEARITY (INL) is a measure of worst
case deviation of the ADC transfer function from an ideal
straight line drawn through the ADC transfer function. The
deviation of any given code from this straight line is measured
from the center of that code value step. The best fit method
is used
INTERMODULATION DISTORTION (IMD) is the creation of
additional spectral components as a result of two sinusoidal
frequencies being applied to the ADC input at the same time.
It is defined as the ratio of the power in the second and third
order intermodulation products to the power in one of the
original frequencies. IMD is usually expressed in dBFS.
LSB (LEAST SIGNIFICANT BIT) is the bit that has the smallest value or weight of all bits. This value is
30174146
FIGURE 1.
LVDS OUTPUT OFFSET VOLTAGE (VOS) is the midpoint
between the D+ and D− pins output voltage with respect to
ground, i.e., [(VD+) + ( VD−)] / 2.
MISSING CODES are those output codes that are skipped
and will never appear at the ADC outputs. These codes cannot be reached with any input value.
MSB (MOST SIGNIFICANT BIT) is the bit that has the largest
value or weight. Its value is one half of full scale.
NEGATIVE FULL-SCALE ERROR (NFSE) is a measure of
how far the first code transition is from the ideal 1/2 LSB above
a differential −VIN/2. For the ADC08DL502 the reference voltage is assumed to be ideal, so this error is a combination of
full-scale error and reference voltage error.
OFFSET ERROR (VOFF) is a measure of how far the midscale point is from the ideal zero voltage differential input.
Offset Error = Actual Input causing average of 8k samples to
result in an average code of 127.5.
OUTPUT DELAY (tOD) is the time delay (in addition to
Pipeline Delay) after the falling edge of CLK+ before the data
update is present at the output pins.
OVER-RANGE RECOVERY TIME is the time required after
the differential input voltages goes from ±1.2V to 0V for the
converter to recover and make a conversion with its rated accuracy.
PIPELINE DELAY (LATENCY) is the number of input clock
cycles between initiation of conversion and when that data is
presented to the output driver stage. New data is available at
every clock cycle, but the data lags the conversion by the
Pipeline Delay plus the tOD.
POSITIVE FULL-SCALE ERROR (PFSE) is a measure of
how far the last code transition is from the ideal 1-1/2 LSB
below a differential +VIN/2. For the ADC08DL502 the reference voltage is assumed to be ideal, so this error is a combination of full-scale error and reference voltage error.
POWER SUPPLY REJECTION RATIO (PSRR) can be one
of two specifications. PSRR1 (DC PSRR) is the ratio of the
change in full-scale error that results from a power supply
voltage change from 1.8V to 2.0V. PSRR2 (AC PSRR) is a
measure of how well an a.c. signal injected on the power supply is rejected from the output and is measured with a 125
MHz, 50 mVP-P signal riding upon the power supply. It is the
ratio of the output amplitude of that signal at the output to its
amplitude on the power supply pin. PSRR is expressed in dB.
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in
dB, of the rms value of the input signal at the output to the rms
value of the sum of all other spectral components below onehalf the sampling frequency, not including harmonics or d.c.
SIGNAL TO NOISE PLUS DISTORTION (S/(N+D) or
SINAD) is the ratio, expressed in dB, of the rms value of the
input signal at the output to the rms value of all of the other
VFS / 2N
where VFS is the differential full-scale amplitude VIN as set by
the FSR input and "n" is the ADC resolution in bits, and which
is 8 for the ADC08DL502.
LOW VOLTAGE DIFFERENTIAL SIGNALING (LVDS)
DIFFERENTIAL VOLTAGE (VID and VOD) is two times the
absolute value of the difference between the VD+ and VD −
signals; each measured with respect to Ground.
www.ti.com
16
where Af1 is the RMS power of the fundamental (output) frequency and Af2 through Af10 are the RMS power of the first 9
harmonic frequencies in the output spectrum.
– Second Harmonic Distortion (2nd Harm) is the difference, expressed in dB, between the RMS power in the input
frequency seen at the output and the power in its 2nd harmonic level at the output.
– Third Harmonic Distortion (3rd Harm) is the difference
expressed in dB between the RMS power in the input frequency seen at the output and the power in its 3rd harmonic
level at the output.
17
www.ti.com
ADC08DL502
spectral components below half the input clock frequency, including harmonics but excluding d.c.
SPURIOUS-FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the rms values of the input
signal at the output and the peak spurious signal, where a
spurious signal is any signal present in the output spectrum
that is not present at the input, excluding d.c.
TOTAL HARMONIC DISTORTION (THD) is the ratio expressed in dB, of the rms total of the first nine harmonic levels
at the output to the level of the fundamental at the output. THD
is calculated as
ADC08DL502
Transfer Characteristic
30174122
FIGURE 2. Input / Output Transfer Characteristic
www.ti.com
18
ADC08DL502
Timing Diagrams
30174114
FIGURE 3. ADC08DL502 Timing — SDR Clocking in 1:2 Demultiplexed Mode
30174159
FIGURE 4. ADC08DL502 Timing — DDR Clocking in 1:2 Demultiplexed Mode
19
www.ti.com
ADC08DL502
30174161
FIGURE 5. ADC08DL502 Timing — DDR Clocking in Non-Demultiplexed Mode
30174119
FIGURE 6. Serial Interface Timing
30174120
FIGURE 7. Clock Reset Timing in DDR Mode
www.ti.com
20
ADC08DL502
30174123
FIGURE 8. Clock Reset Timing in SDR Mode with OUTEDGE Low
30174124
FIGURE 9. Clock Reset Timing in SDR Mode with OUTEDGE High
30174125
FIGURE 10. Power-up Calibration and On-Command Calibration Timing
21
www.ti.com
INL vs. CODE
INL vs. AMBIENT TEMPERATURE
30174164
30174165
DNL vs. CODE
DNL vs. AMBIENT TEMPERATURE
30174166
30174167
POWER CONSUMPTION vs. CLOCK FREQUENCY
GAIN STABILITY vs. DIE TEMPERATURE
1.6
1.4
POWER (W)
ADC08DL502
Typical Performance Characteristics VA = VDR = 1.9V, fCLK = 500 MHz, fIN = 125 MHz, TA= 25°C, I
channel, 1:2 Demux Mode (1:1 Demux Mode has similar performance), unless otherwise stated.
1.2
1.0
0.8
0
100
200
300
400
CLOCK FREQUENCY (MHz)
500
30174181
www.ti.com
30174195
22
CROSSTALK vs. SOURCE FREQUENCY
30174198
30174163
SPECTRAL RESPONSE AT fIN = 125 MHz
SPECTRAL RESPONSE AT fIN = 248 MHz
0
0
-20
-20
AMPLITUDE (dBFS)
MAGNITUDE (dBFS)
ADC08DL502
SIGNAL GAIN vs. INPUT FREQUENCY
-40
-60
-80
-40
-60
-80
-100
-100
0
50
100
150
200
FREQUENCY (MHz)
250
0
30174187
50
100
150
200
FREQUENCY (MHz)
250
30174188
23
www.ti.com
ADC08DL502
portant part of this chip's functionality and is required in order
to obtain adequate performance. In addition to the requirement to be run at power-up, an on-command calibration must
be run whenever the sense of the FSR pin is changed. For
best performance, we recommend that an on-command calibration be run 20 seconds or more after application of power
and whenever the operating temperature changes significantly relative to the specific system performance requirements. See 2.4.2.2 On-Command Calibration for more
information. Calibration can not be initiated or run while the
device is in the power-down mode. See 1.1.7 Power Down for
information on the interaction between Power Down and Calibration.
In normal operation, calibration is performed just after application of power and whenever a valid calibration command is
given, which is holding the CAL pin low for at least tCAL_L clock
cycles, then hold it high for at least another tCAL_H clock cycles
as defined in the Converter Electrical Characteristics. The
time taken by the calibration procedure is specified as tCALin
Converter Electrical Characteristics. Holding the CAL pin high
upon power up will prevent the calibration process from running until the CAL pin experiences the above-mentioned
tCAL_L clock cycles followed by tCAL_H clock cycles.
CalDly (pin 141) is used to select one of two delay times that
apply from the application of power to the start of calibration.
This calibration delay time is depedent on the setting of the
CalDly pin and is specified as tCalDly in the Converter Electrical
Characteristics. These delay values allow the power supply
to come up and stabilize before calibration takes place. If the
PD pin is high upon power-up, the calibration delay counter
will be disabled until the PD pin is brought low. Therefore,
holding the PD pin high during power up will further delay the
start of the power-up calibration cycle. The best setting of the
CalDly pin depends upon the power-on settling time of the
power supply.
The CAL bit does not reset itself to zero automatically, but
must be manually reset before another calibration event can
be initiated. If no further calibration event is desired, the CAL
bit may be left high indefinitely, with no negative consequences. The RTD bit setting is critical for running a calibration event with the Clock Phase Adjust enabled. If initiating a
calibration event while the Clock Phase Adjust is enabled, the
RTD bit must be set to high, or no calibration will occur. If
initiating a calibration event while the Clock Phase Adjust is
not enabled, a normal calibration will occur, regardless of the
setting of the RTD bit.
1.0 Functional Description
NOT ALL OF THE PINS, BITS, AND FEATURES WHICH
ARE MENTIONED IN THIS SECTION ARE TESTED IN
PRODUCTION TEST. SEE (Note 16, Note 17, Note 18, Note
19) IN THE PIN DESCRIPTIONS, THE CONVERTER ELECTRICAL CHARACTERISTICS, Table 13, Table 14, AND
THE REGISTER DESCRIPTION FOR A DETAILED EXPLANATION OF WHAT IS TESTED. IF THE SYSTEM APPLICATION REQUIRES ADDITIONAL FEATURES OF THE
PRODUCT TO BE TESTED, CONTACT YOUR NATIONAL
SALES REPRESENTATIVE.
The ADC08DL502 is a versatile A/D Converter with an innovative architecture permitting very high speed operation. The
controls available ease the application of the device to circuit
solutions. Optimum performance requires adherence to the
provisions discussed here and in the Applications Information
Section.
While it is generally poor practice to allow an active pin to float,
pins 6 and 16 of the ADC08DL502 are designed to be left
floating without jeopardy. In all discussions throughout this
data sheet, whenever a function is called by allowing a control
pin to float, connecting that pin to a potential of one half the
VA supply voltage will have the same effect as allowing it to
float.
1.1 OVERVIEW
The ADC08DL502 uses a calibrated folding and interpolating
architecture that achieves 7.5 effective bits. The use of folding
amplifiers greatly reduces the number of comparators and
power consumption. Interpolation reduces the number of
front-end amplifiers required, minimizing the load on the input
signal and further reducing power requirements. In addition
to other things, on-chip calibration reduces the INL bow often
seen with folding architectures. The result is an extremely
fast, high performance, low power converter.
The analog input signal that is within the converter's input
voltage range is digitized to eight bits at speeds of 200 MSPS
to 500 MSPS. Differential input voltages below negative fullscale will cause the output word to consist of all zeroes.
Differential input voltages above positive full-scale will cause
the output word to consist of all ones. Either of these conditions at either the "I" or "Q" input will cause the OR (Out of
Range) output to be activated. This single OR output indicates
when the output code from one or both of the channels is below negative full scale or above positive full scale.
Each converter has a selectable output demultiplexer which
feeds two LVDS buses. If the 1:2 demultiplexed mode is selected, the output data rate is reduced to half the input sample
rate on each bus. When non-demultiplexed mode is selected,
that output data rate on channels DI and DQ are at the same
rate as the input sample clock.
The output levels may be selected to be normal or reduced.
Using reduced levels saves power but could result in erroneous data capture of some or all of the bits, especially at
higher sample rates and in marginally designed systems.
1.1.2 Acquiring the Input
In 1:2 demux mode, data is acquired at the falling edge of CLK
+ (pin 20) and the digital equivalent of that data is available
at the digital outputs 13 input clock cycles later for the DI and
DQ output buses and 14 input clock cycles later for the DId
and DQd output buses. There is an additional internal delay
called tOD before the data is available at the outputs. See the
Timing Diagram. The ADC08DL502 will convert as long as
the input clock signal is present. The fully differential comparator design and the innovative design of the sample-andhold amplifier, together with calibration, enables a very flat
SINAD/ENOB response beyond 1 GHz. The ADC08DL502
output data signaling is LVDS and the output format is offset
binary.
1.1.1 Calibration
A calibration is performed upon power-up and can also be
invoked by the user upon command. Calibration trims the
analog input differential termination resistor and minimizes
full-scale error, offset error, DNL and INL, resulting in maximizing SNR, THD, SINAD (SNDR) and ENOB. Internal bias
currents are also set with the calibration process. All of this is
true whether the calibration is performed upon power up or is
performed upon command. Running the calibration is an im-
www.ti.com
1.1.3 Control Modes
Much of the user control can be accomplished with several
control pins that are provided. Examples include initiation of
the calibration cycle, power down mode and full scale range
setting. However, the ADC08DL502 also provides an Extend24
In the Extended Control mode, programming the Input FullScale Voltage Adjust register allows the input full-scale range
to be adjusted as described in 1.4 REGISTER DESCRIPTION and 2.2 THE ANALOG INPUT.
1.1.5 Clocking
The ADC08DL502 must be driven with an a.c. coupled, differential clock signal. 2.3 THE CLOCK INPUTS describes the
use of the clock input pins. A differential LVDS output clock is
available for use in latching the ADC output data into whatever
device is used to receive the data.
The ADC08DL502 offers two output clocking options. These
are a choice of which DCLK edge the output data transitions
on, and a choice of Single Data Rate (SDR) or Double Data
Rate (DDR) outputs.
The ADC08DL502 also has the option to use a duty cycle
corrected clock receiver as part of the input clock circuit. This
feature is enabled by default and provides improved ADC
clocking. This circuitry allows the ADC to be clocked with a
signal source having a duty cycle ratio of 20% / 80% (worst
case).
1.1.4 The Analog Inputs
The ADC08DL502 must be driven with a differential input signal. Operation with a single-ended signal is not allowed. It is
important that the inputs either be a.c. coupled to the inputs
with the VCMO pin grounded, or d.c. coupled with the VCMO pin
left floating. An input common mode voltage equal to the
VCMO output must be provided when d.c. coupling is used.
Two full-scale range settings are provided with pin 16 (FSR).
A high on pin 16 causes an input full-scale range setting of a
higher VIN input level, while grounding pin 16 causes an input
full-scale range setting of a reduced VIN input level. The fullscale range setting operates equally on both ADCs.
TABLE 11. Input Channel Samples Produced at Data Outputs in 1:2 Demultiplexed Mode**
Data Outputs
(Always sourced with respect to fall of DCLK+)
DI
"I" Input Sampled with Fall of CLK 13
cycles earlier.
DId
"I" Input Sampled with Fall of CLK 14
cycles earlier.
DQ
"Q" Input Sampled with Fall of CLK 13
cycles earlier.
DQd
"Q" Input Sampled with Fall of CLK 14
cycles after being sampled.
* Note that, in the non-demultiplexed mode, the DId and DQd outputs are disabled and are high impedance.
TABLE 12. Input Channel Samples Produced at Data Outputs in Non-Demultiplexed Mode
Data Outputs
(Sourced with respect to fall of DCLK+)
DI
"I" Input Sampled with Fall of CLK 13 cycles earlier.
DId
No output.
DQ
"Q" Input Sampled with Fall of CLK 13 cycles earlier.
DQd
No output.
relationship with the output data independent of the demultiplexer selection. For 1:2 Demux DDR 0° Mode, there are four,
as opposed to three cycles of CLK systematic delay from the
Synchronizing Edge to the start of tOD. See 1.5 MULTIPLE
ADC SYNCHRONIZATIONfor more details.
1.1.5.2 OutEdge and Demultiplex Control Setting
To help ease data capture in the SDR mode, the output data
may be caused to transition on either the positive or the negative edge of the output data clock (DCLK). In the nonextended control mode, this is chosen with the OutEdge input
(pin 6). A high on the OutEdge input pin causes the output
data to transition on the rising edge of DCLK+, while grounding this input causes the output to transition on the falling edge
of DCLK+. See 2.4.3 Output Edge Synchronization. When in
the extended control mode, the OutEdge is selected using the
OED bit in the Configuration Register. This bit has two functions. In the single data rate (SDR) mode, the bit functions as
OutEdge and selects the DCLK edge with which the data
transitions. In the Double Data Rate (DDR) mode, this bit selects whether the device is in non-demultiplex or 1:2 demultiplex mode. In the DDR case, the DCLK has a 0° phase
1.1.5.3 Single Data Rate and Double Data Rate
A choice of single data rate (SDR) or double data rate (DDR)
output is offered. With single data rate the output clock
(DCLK) frequency is the same as the data rate of the two output buses. With double data rate the DCLK frequency is half
the data rate and data is sent to the outputs on both edges of
DCLK. DDR clocking is enabled in non-Extended Control
mode by allowing pin 6 to float.
25
www.ti.com
ADC08DL502
ed Control mode whereby a serial interface is used to access
register-based control of several advanced features. The Extended Control mode is not intended to be enabled and
disabled dynamically. Rather, the user is expected to employ
either the normal control mode or the Extended Control mode
at all times. When the device is in the Extended Control mode,
pin-based control of several features is replaced with registerbased control and those pin-based controls are disabled.
These pins are OutV (pin 5), OutEdge/DDR (pin 6), FSR (pin
16) and CalDly (pin 141). See 1.2 NORMAL/EXTENDED
CONTROL for details on the Extended Control mode.
ADC08DL502
pins (positive and negative) are put into a high impedance
state and the devices power consumption is reduced to a
minimal level. The DCLK+/- and OR +/- are not tri-stated, they
are weakly pulled down to ground internally. Therefore when
both I and Q are powered down the DCLK +/- and OR +/should not be terminated to a DC voltage.
A high on the PDQ pin will power down the "Q" channel and
leave the "I" channel active. There is no provision to power
down the "I" channel independently of the "Q" channel. Upon
return to normal operation, the pipeline will contain meaningless information.
If the PD input is brought high while a calibration is running,
the device will not go into power down until the calibration
sequence is complete. However, if power is applied and PD
is already high, the device will not begin the calibration sequence until the PD input goes low. If a manual calibration is
requested while the device is powered down, the calibration
will not begin at all. That is, the manual calibration input is
completely ignored in the power down state. Calibration will
function with the "Q" channel powered down, but that channel
will not be calibrated if PDQ is high. If the "Q" channel is subsequently to be used, it is necessary to perform a calibration
after PDQ is brought low.
1.1.6 The LVDS Outputs
The data outputs, the Out Of Range (OR) and DCLK, are
LVDS. The electrical specifications of the LVDS outputs are
compatible with typical LVDS receivers available on ASIC and
FPGA chips; but they are not IEEE or ANSI communications
standards compliant due to the low +1.9V supply used this
chip. User is given the choice of a lower signal amplitude
mode with OutV control pin or the OV control register bit. For
short LVDS lines and low noise systems, satisfactory performance may be realized with the OutV input low, which results
in lower power consumption. If the LVDS lines are long and/
or the system in which the ADC08DL502 is used is noisy, it
may be necessary to tie the OutV pin high.
The LVDS data output have a typical common mode voltage
when the VBG pin is unconnected and floating. This common
mode voltage can be increased by tying the VBG pin to VA if a
higher common mode is required.
IMPORTANT NOTE: Tying the VBG pin to VA will also increase the differential LVDS output voltage by up to 40 mV.
1.1.7 Power Down
The ADC08DL502 is in the active state when the Power Down
pin (PD) is low. When the PD pin is high, the device is in the
power down mode. In this power down mode the data output
www.ti.com
26
TABLE 13. Features and Modes
Feature
Normal Control Mode
Extended Control Mode
SDR or DDR Clocking
Selected with pin 6
Selected with nDE in the Configuration Register
(Addr-1h; bit-10).
DDR Clock Phase (Note 17)
Not Selectable (0° Phase Only)
Selected with DCP in the Configuration Register
(Addr-1h; bit-11).
SDR Data transitions with
rising or falling DCLK edge
SDR Data transitions with rising edge
Selected with OED in the Configuration Register
of DCLK+ when pin 6 is high and on
(Addr-1h; bit-8).
falling edge when low.
LVDS output level (Note 17)
Normal differential data and DCLK
amplitude selected when pin 5 is high Selected with OV in the Configuration Register
(Addr-1h; bit-9).
and reduced amplitude selected
when low.
Power-On Calibration Delay
(Note 17)
Short delay selected when pin 141 is
low and longer delay selected when Short delay only.
high.
Full-Scale Range (Note 18)
Normal input full-scale range
selected when pin 16 is high and
reduced range when low. Selected
range applies to both channels.
Up to 512 step adjustments over a nominal range
specified in 1.4 REGISTER DESCRIPTION. Separate
range selected for I- and Q-Channels. Selected using
Full Range Registers (Addr-3h and Bh; bit-7 thru 15).
Input Offset Adjust (Note 18)
Not possible
512 steps of adjustment using the Input Offset register
specified in 1.4 REGISTER DESCRIPTION for each
channel using Input Offset Registers (Addr-2h and Ah;
bit-7 thru 15).
Test Pattern
Not possible
A test pattern can be made present at the data outputs
by setting TPO to 1b in Extended Configuration
Register (Addr-9h; bit-15).
Resistor Trim Disable
Not possible
The DCLK outputs will continuously be present when
RTD is set to 1b in Extended Configuration Register
(Addr-9h; bit-14 to 7).
Selectable Output
Demultiplexer
Not possible
If the device is set in DDR, the output can be
programmed to be non-demultiplex. When OED in
Configuration Register is set 1b (Addr-1h; bit-8), this
selects non-demultiplex. If OED is set 0b, this selects
1:2 demultiplex.
Second DCLK Output (Note
17)
Not possible
The OR outputs can be programmed to become a
second DCLK output when nSD is set 0b in
Configuration Register (Addr-1h; bit-13).
The sampling clock phase can be manually adjusted
through the Coarse and Intermediate Register (AddrFh; bit-15–7) and Fine Register (Addr-Eh; bit-15 to 8).
Sampling Clock Phase Adjust
Not possible
(Note 19)
27
www.ti.com
ADC08DL502
ting pin 47 to logic low. If pin 47 is floating and pin 58 is floating
or logic high, pin 16 can be used to enable the extended control mode. The choice of control modes is required to be a
fixed selection and is not intended to be switched dynamically
while the device is operational.
Table 13 shows how several of the device features are affected by the control mode chosen.
1.2 NORMAL/EXTENDED CONTROL
The ADC08DL502 may be operated in one of two modes. In
the simpler standard control mode, the user affects available
configuration and control of the device through several control
pins. The "extended control mode" provides additional configuration and control options through a serial interface and a
set of 9 registers. Extended control mode is selected by set-
ADC08DL502
The default state of the Extended Control Mode is set upon
power-on reset (internally performed by the device) and is
shown in Table 14.
TABLE 14. Extended Control Mode Operation (Pin 41 Logic Low or Pin 14 Floating)
Feature
Extended Control Mode Default State
SDR or DDR Clocking
DDR Clocking
DDR Clock Phase (Note 17)
Data changes with DCLK edge (0° phase)
LVDS Output Amplitude (Note 17)
Higher value indicated in Electrical Table
Calibration Delay (Note 17)
Short Delay
Full-Scale Range (Note 18)
700 mV nominal for both channels
Input Offset Adjust (Note 18)
No adjustment for either channel
Test Pattern
Not present at output
Resistor Trim Disable
Trim enabled, DCLK not continuously present at output
Selectable Output Demultiplexer
1:2 demultiplex
Second DCLK Output (Note 17)
Not present, pins 89 and 90
function as OR+ and OR-
Sampling Clock Phase Adjust (Note 19)
No adjustment for fine, intermediate or coarse
IMPORTANT NOTE: Do not write to the Serial Interface when
calibrating the ADC. Doing so will impair the performance of
the device until it is re-calibrated correctly. Programming the
serial registers will also reduce dynamic performance of the
ADC for the duration of the register access time.
1.3 THE SERIAL INTERFACE
IMPORTANT NOTE: During the initial write using the serial interface, all nine registers must be written with desired or default values. Subsequent writes to single
registers are allowed.
The 3-pin serial interface is enabled only when the device is
in the Extended Control mode. The pins of this interface are
Serial Clock (SCLK), Serial Data (SDATA) and Serial Interface Chip Select (SCS). Nine write only registers are accessible through this serial interface.
SCS: This signal should be asserted low while accessing a
register through the serial interface. Setup and hold times with
respect to the SCLK must be observed.
SCLK: Serial data input is accepted at the rising edge of this
signal. There is no minimum frequency requirement for SCLK.
SDATA: Each register access requires a specific 32-bit pattern at this input. This pattern consists of a header, register
address and register value. The data is shifted in MSB first.
Setup and hold times with respect to the SCLK must be observed. See the Timing Diagram.
Each Register access consists of 32 bits, as shown in Figure
6 of the Timing Diagrams. The fixed header pattern is 0000
0000 0001 (eleven zeros followed by a 1). The loading sequence is such that a "0" is loaded first. These 12 bits form
the header. The next 4 bits are the address of the register that
is to be written to and the last 16 bits are the data written to
the addressed register. The addresses of the various registers are indicated in Table 15.
Refer to the Register Description (1.4 REGISTER DESCRIPTION) for information on the data to be written to the registers.
Subsequent register accesses may be performed immediately, starting with the 33rd SCLK. This means that the SCS input
does not have to be de-asserted and asserted again between
register addresses. It is possible, although not recommended,
to keep the SCS input permanently enabled (at a logic low)
when using extended control.
Control register contents are retained when the device is put
into power-down mode.
www.ti.com
TABLE 15. Register Addresses
4-Bit Address
Loading Sequence:
A3 loaded after Fixed Header pattern, A0 loaded last
A3 A2 A1
28
A0 Hex
Register Addressed
0
0
0
0
0h
Calibration
0
0
0
1
1h
Configuration
0
0
1
0
2h
"I" Ch Offset
0
0
1
1
3h
"I" Ch Full-Scale Voltage
Adjust
0
1
0
0
4h
Reserved
0
1
0
1
5h
Reserved
0
1
1
0
6h
Reserved
0
1
1
1
7h
Reserved
1
0
0
0
8h
Reserved
1
0
0
1
9h
Extended Configuration
1
0
1
0
Ah
"Q" Ch Offset
1
0
1
1
Bh
"Q" Ch Full-Scale Voltage
Adjust
1
1
0
0
Ch
Reserved
1
1
0
1
Dh
Reserved
1
1
1
0
Eh
Sampling Clock Phase
Fine Adjust
1
1
1
1
Fh
Sample Clock Phase
Intermediate and Coarse
Adjust
Bit 11
Bit 10
Calibration Register
Addr: 0h (0000b)
Write only (0x7FFF)
D15
D14
D13
D12
D11
D10
D9
D8
CAL
1
1
1
1
1
1
1
D7
D6
D5
D4
D3
D2
D1
D0
1
1
1
1
1
1
1
1
Bit 15
Bit 9
CAL: Calibration Enable. When this bit is set
1b, an on-command calibration cycle is
initiated. This function is exactly the same as
issuing an on-command calibration using the
CAL pin. (Note 16)
POR State: 0b
Must be set to 1b
Bits 14:0
Bit 8
Configuration Register
Addr: 1h (0001b)
Write only (0xB2FF)
D15
D14
D13
D12
D11
D10
D9
D8
1
0
nSD
DCS DCP
nDE
OV
OED
D7
D6
D5
D4
D3
D2
D1
D0
1
1
1
1
1
1
1
1
Bit 15
Bit 14
Bit 13
Bit 12
Must be set to 1b
Must be set to 0b
nSD: Second DCLK Output Enable. When
this bit is 1b, the device only has one DCLK
output and one OR output. When this bit is
0b, the device has two identical DCLK
outputs and no OR output. (Note 16)
POR State: 1b
DCS: Duty Cycle Stabilizer. When this bit is
set to 1b, a duty cycle stabilization circuit is
applied to the clock input. When this bit is set
to 0b the stabilization circuit is disabled.
(Note 16)
POR State: 1b
Bits 7:0
DCP: DDR Clock Phase. This bit only has an
effect in the DDR mode. When this bit is set
to 0b, the DCLK edges are time-aligned with
the data bus edges ("0° Phase"). When this
bit is set to 1b, the DCLK edges are placed
in the middle of the data bit-cells ("90°
Phase"), using the one-half speed DCLK
shown in Figure 4 as the phase reference.
(Note 16)
POR State: 0b
nDE: DDR Enable. When this bit is set to 0b,
data bus clocking follows the DDR (Double
Data Rate) mode whereby a data word is
output with each rising and falling edge of
DCLK. When this bit is set to a 1b, data bus
clocking follows the SDR (single data rate)
mode whereby each data word is output with
either the rising or falling edge of DCLK , as
determined by the OutEdge bit.
POR State: 0b
OV: Output Voltage. This bit determines the
LVDS outputs' voltage amplitude and has the
same function as the OutV pin that is used in
the normal control mode. When this bit is set
to 1b, the standard output amplitude is used.
When this bit is set to 0b, the reduced output
amplitude is used. (Note 16)
POR State: 1b
OED: Output Edge and Demultiplex Control.
This bit has two functions. When the device
is in SDR mode, this bit selects the DCLK
edge with which the data words transition
and has the same effect as the OutEdge pin
in the Non-extended control mode. When this
bit is set to 1b, the data outputs change with
the rising edge of DCLK+. When this bit is set
to 0b, the data output changes with the falling
edge of DCLK+. When the device is in DDR
mode, this bit selects the non-demultiplexed
mode when set to 1b. When the bit set to 0b,
the device is programmed into the
Demultiplexed mode. If the device is in DDR
and Non-Demultiplexed Mode, then the
DCLK has a 0° phase relationship with the
data; it is not possible to select the 90° phase
relationship.
POR State: 0b
Must be set to 1b
IMPORTANT NOTE: It is recommended that this register
should only be written upon power-up initialization as writing
it may cause disturbance on the DCLK output as this signal's
basic configuration is changed.
29
www.ti.com
ADC08DL502
1.4 REGISTER DESCRIPTION
NOT ALL OF THE PINS, BITS, AND FEATURES WHICH
ARE MENTIONED IN THIS SECTION ARE TESTED IN
PRODUCTION TEST. SEE (Note 16, Note 17, Note 18, Note
19) IN THE PIN DESCRIPTIONS, THE CONVERTER ELECTRICAL CHARACTERISTICS, Table 13, Table 14, AND
THE REGISTER DESCRIPTION FOR A DETAILED EXPLANATION OF WHAT IS TESTED. IF THE SYSTEM APPLICATION REQUIRES ADDITIONAL FEATURES OF THE
PRODUCT TO BE TESTED, CONTACT YOUR NATIONAL
SALES REPRESENTATIVE.
Nine write-only registers provide several control and configuration options in the Extended Control Mode. These registers have no effect when the device is in the Normal Control
Mode. Each register description below also shows the PowerOn Reset (POR) state of each control bit.
ADC08DL502
I-Channel Offset (Note 18)
Addr: 2h (0010b)
D15
D14
Extended Configuration Register
Addr: 9h (1001b)
Write only (0x007F)
D13
(MSB)
D12
D11
D10
D9
Offset Value
Write only (0x03FF)
D8
D15
D14
D13
D12
D11
D10
D9
D8
(LSB)
TPO
RTD
0
0
0
0
1
1
D7
D6
D5
D4
D3
D2
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
Sign
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Bits 15:8
Bit 7
Bits 6:0
Offset Value. The input offset of the IChannel ADC is adjusted linearly and
monotonically by the value in this field. 00h
provides a nominal zero offset, while FFh
provides a nominal 45 mV of offset. Thus,
each code step provides 0.176 mV of offset.
POR State: 0000 0000 b
Sign bit. 0b gives positive offset, 1b gives
negative offset, resulting in total offset
adjustment of ±45 mV.
POR State: 0b
Must be set to 1b
Bit 15
POR State: 0b
Bit 14
D15
D14
Write only (0x807F)
D13
(MSB)
D12
D11
D10
D9
Bit 13:10
Must be set to 0b
Bits 9:0
Must be set to 1b
Q-Channel Offset (Note 18)
D8
Addr: Ah (1010b)
Adjust Value
D7
D6
D5
D4
D3
D2
D1
D0
D15
(LSB)
1
1
1
1
1
1
1
(MSB)
Bits 15:7
Bits 6:0
www.ti.com
Full Scale Voltage Adjust Value. The input fullscale voltage or gain of the I-Channel ADC is
adjusted linearly and monotonically with a 9 bit
data value. The adjustment range is ±20% of the
nominal 700 mVP-P differential value.
0000 0000 0
560 mVP-P
1000 0000 0
Default Value
1111 1111 1
700 mVP-P
RTD: Resistor Trim Disable. When this bit is
set to 1b, the input termination resistor is not
trimmed during the calibration cycle and the
DCLK output remains enabled. Note that the
ADC is calibrated regardless of this setting.
POR State: 0b
I-Channel Full-Scale Voltage Adjust (Note 18)
Addr: 3h (0011b)
TPO: Test Pattern Output. When this bit is set
1b, the ADC is disengaged and a test pattern
generator is connected to the outputs
including OR. This test pattern will work with
the device in the SDR, DDR and the nondemultiplex output modes.
D14
D11
D10
D9
Offset Value
D8
(LSB)
D6
D5
D4
D3
D2
D1
D0
Sign
1
1
1
1
1
1
1
840 mVP-P
Bit 7
Bits 6:0
30
D12
D7
Bits 15:8
For best performance, it is recommended that the
value in this field be limited to the range of 0110
0000 0b to 1110 0000 0b. i.e., limit the amount of
adjustment to ±15%. The remaining ±5%
headroom allows for the ADC's own full scale
variation. A gain adjustment does not require ADC
re-calibration.
POR State: 1000 0000 0b (no adjustment)
Must be set to 1b
D13
Write only (0x007F)
Offset Value. The input offset of the QChannel ADC is adjusted linearly and
monotonically by the value in this field. 00h
provides a nominal zero offset, while FFh
provides a nominal 45 mV of offset. Thus,
each code step provides about 0.176 mV of
offset.
POR State: 0000 0000 b
Sign bit. 0b gives positive offset, 1b gives
negative offset.
POR State: 0b
Must be set to 1b
D15
D14
D13
Addr: 1110
Write only (0x807F)
D12
(MSB)
D11
D10
D9
D8
D15
Adjust Value
D14
Write only (0x00FF)
D13
(MSB)
D12
D11
D10
D9
Fine Phase Adjust
D8
(LSB)
D7
D6
D5
D4
D3
D2
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
(LSB)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Bits 15:7
Full Scale Voltage Adjust Value. The input
full-scale voltage or gain of the I-Channel
ADC is adjusted linearly and monotonically
with a 9 bit data value. The adjustment range
is ±20% of the nominal 700 mVP-P differential
value.
0000 0000 0
560 mVP-P
Bits 6:0
1000 0000 0
700 mVP-P
1111 1111 1
840 mVP-P
Bits 15:8
Fine Phase Adjust. The phase of the ADC
sampling clock is adjusted monotonically by
the value in this field. 00h provides a nominal
zero phase adjustment, while FFh provides a
nominal 50 ps of delay. Thus, each code step
provides approximately 0.2 ps of delay.
POR State: 0000 0000b
Bits 7:0
Must be set to 1b
Sample Clock Phase Intermediate/Coarse Adjust (Note
19)
For best performance, it is recommended
that the value in this field be limited to the
range of 0110 0000 0b to 1110 0000 0b. i.e.,
limit the amount of adjustment to ±15%. The
remaining ±5% headroom allows for the
ADC's own full scale variation. A gain
adjustment does not require ADC recalibration.
POR State: 1000 0000 0b (no adjustment)
Must be set to 1b
Addr: Fh (1111b)
D15
POL
D14
D13
Write only (0x007F)
D12
D11
D10
D9
(MSB) Coarse Phase Adjust
D8
IPA
D7
D6
D5
D4
D3
D2
D1
D0
(LSB)
1
1
1
1
1
1
1
Bit 15
Polarity Select. When this bit is selected, the
polarity of the ADC sampling clock is
inverted.
POR State: 0b
Bits 14:10 Coarse Phase Adjust. Each code value in
this field delays the sample clock by
approximately 65 ps. A value of 00000b in
this field causes zero adjustment.
POR State: 00000b
31
Bits 9:7
Intermediate Phase Adjust. Each code value
in this field delays the sample clock by
approximately 11 ps. A value of 000b in this
field causes zero adjustment. Maximum
combined adjustment using Coarse Phase
Adjust and Intermediate Phase adjust is
approximately 2.1ns.
POR State: 000b
Bits 6:0
Must be set to 1b
www.ti.com
ADC08DL502
Sample Clock Phase Fine Adjust (Note 19)
Q-Channel Full-Scale Voltage Adjust (Note 18)
Addr: Bh (1011b)
ADC08DL502
reset state conditions). Therefore, depending upon when the
DCLK_RST signal is asserted, there may be a narrow pulse
on the DCLK line during this reset event. When the
DCLK_RST signal is de-asserted in synchronization with the
CLK rising edge, there are three or four CLK cycles of systematic delay and the next CLK falling edge synchronizes the
DCLK output with those of other ADC08DL502s in the system. The DCLK output is enabled again after a constant delay
(relative to the input clock frequency) which is equal to the
CLK input to DCLK output delay (tOD). The device always exhibits this delay characteristic in normal operation. The user
has the option of using a single-ended DCLK_RST signal, but
a differential DCLK_RST is strongly recommended due to its
superior timing specifications.
As shown in Figure 7, Figure 8, and Figure 9 of the Timing
Diagrams, there is a delay from the deassertion of
DCLK_RST to the reappearance of DCLK, which is equal to
several cycles of CLK plus tOD. Note that the deassertion of
DCLK_RST is not latched in until the next falling edge of CLK.
For 1:2 Demux DDR 0° Mode, there are four CLK cycles of
delay; for all other modes, there are three CLK cycles of delay.
If the device is not programmed to allow DCLK to run continuously, DCLK will become inactive during a calibration cycle.
Therefore, it is strongly recommended that DCLK only be
used as a data capture clock and not as a system clock.
The DCLK_RST pin should NOT be brought high while the
calibration process is running (while CalRun is high). Doing
so could cause a digital glitch in the digital circuitry, resulting
in corruption and invalidation of the calibration.
1.4.1 Note Regarding Clock Phase Adjust
This is a feature intended to help the system designer remove
small imbalances in clock distribution traces at the board level
when multiple ADCs are used. Please note, however, that
enabling this feature will reduce the dynamic performance
(ENOB, SNR, SFDR) some finite amount. The amount of
degradation increases with the amount of adjustment applied.
The user is strongly advised to (a) use the minimal amount of
adjustment; and (b) verify the net benefit of this feature in his
system before relying on it.
1.4.2 Note Regarding Extended Mode Offset Correction
When using the I or Q channel Offset Adjust registers, the
following information should be noted.
For offset values of +0000 0000 and −0000 0000, the actual
offset is not the same. By changing only the sign bit in this
case, an offset step in the digital output code of about 1/10th
of an LSB is experienced. This is shown more clearly in the
Figure below.
1.6 ADC TEST PATTERN
To aid in system debug, the ADC08DL502 has the capability
of providing a test pattern at the four output ports completely
independent of the input signal. The ADC is disengaged and
a test pattern generator is connected to the outputs including
OR. Each port is given a unique 8-bit word, alternating between 1's and 0's as described in Table 16 and Table 17.
30174130
TABLE 16. Test Pattern by Output Port in
1:2 Demultiplex Mode
FIGURE 11. Extended Mode Offset Behavior
Time
1.5 MULTIPLE ADC SYNCHRONIZATION
The ADC08DL502 has the capability to precisely reset its
sampling clock input to DCLK output relationship as determined by the user-supplied DCLK_RST pulse. This allows
multiple ADCs in a system to have their DCLK (and data) outputs transition at the same time with respect to the shared
CLK input that all the ADCs use for sampling.
The DCLK_RST signal must observe some timing requirements that are shown in Figure 7, Figure 8 and Figure 9 of the
Timing Diagrams. The DCLK_RST pulse must be of a minimum width and its deassertion edge must observe setup and
hold times with respect to the CLK input rising edge. The duration of the DCLK_RST pulse affects the length of time that
the digital output will take before providing valid data again
after the end of the reset condition. Therefore, the DCLK_RST
pulse width should be made reasonably short within the system application constraints. These timing specifications are
listed as tRH, tRS, and tPWR in the Converter Electrical Characteristics.
The DCLK_RST signal can be asserted asynchronous to the
input clock. If DCLK_RST is asserted, the DCLK output is held
in a designated state. The state in which DCLK is held during
the reset period is determined by the mode of operation (SDR/
DDR) and the setting of the Output Edge configuration pin or
bit. (Refer to Figure 7, Figure 8 and Figure 9 for the DCLK
www.ti.com
Qd
Id
Q
I
OR
T0
01h
02h
03h
04h
0
T1
FEh
FDh
FCh
FBh
1
T2
01h
02h
03h
04h
0
T3
FEh
FDh
FCh
FBh
1
T4
01h
02h
03h
04h
0
T5
01h
02h
03h
04h
0
T6
FEh
FDh
FCh
FBh
1
T7
01h
02h
03h
04h
0
T8
FEh
FDh
FCh
FBh
1
T9
01h
02h
03h
04h
0
T10
01h
02h
03h
04h
0
T11
...
...
...
...
...
Comments
Pattern
Sequence
n
Pattern
Sequence
n+1
Pattern
Sequence n
+2
With the part programmed into the non-demultiplex mode, the
test pattern’s order will be as described in Table 17.
32
Time
Q
I
OR
T0
01h
02h
0
T1
FEh
FDh
1
T2
01h
02h
0
T3
01h
02h
0
T4
FEh
FDh
1
T5
FEh
FDh
1
T6
01h
02h
0
T7
01h
02h
0
T8
FEh
FDh
1
T9
01h
02h
0
T10
01h
02h
0
T11
FEh
FDh
1
T12
01h
02h
0
T13
01h
02h
0
T14
FEh
FDh
1
T15
...
...
...
Comments
Pattern
Sequence
n
Pattern
Sequence
n+1
33
www.ti.com
ADC08DL502
It is possible for the I and the Q channels' test patterns to be
not synchronized. Either I and Id or Q and Qd patterns may
be slipped by one DCLK.
To ensure that the test pattern starts synchronously in each
port, set DCLK_RST while writing the Test Pattern Output bit
in the Extended Configuration Register. The pattern appears
at the data output ports when DCLK_RST is cleared low. The
test pattern will work at speed and will work with the device in
the SDR, DDR and the non-demultiplex output modes.
TABLE 17. Test Pattern by Output Port in
Non-demultiplex Mode
ADC08DL502
When the inputs are a.c. coupled, the VCMO output must be
grounded, as shown in Figure 12. This causes the on-chip
VCMO voltage to be connected to the inputs through on-chip
50 kΩ resistors.
IMPORTANT NOTE: An Analog input channel that is not used
should be connected to ac-ground (ie, capacitors to ground)
when the inputs are a.c. coupled. Do not connect an unused
analog input directly to ground.
2.0 Applications Information
2.1 THE REFERENCE VOLTAGE
The voltage reference for the ADC08DL502 is derived from a
1.254V bandgap reference, a buffered version of which is
made available at pin 33, VBG, for user convenience.
This output has an output current capability of ±100 μA and
should be buffered if more current than this is required.
There is no provision for the use of an external reference voltage, but the full-scale input voltage can be adjusted through
a Configuration Register in the Extended Control mode, as
explained in 1.2 NORMAL/EXTENDED CONTROL.
Differential input signals up to the chosen full-scale level will
be digitized to 8 bits. Signal excursions beyond the full-scale
range will be clipped at the output. These large signal excursions will also activate the OR output for the time that the
signal is out of range. See 2.2.2 Out Of Range (OR) Indication.
One extra feature of the VBG pin is that it can be used to raise
the common mode voltage level of the LVDS outputs. The
output offset voltage (VOS) is at its nominal value when the
VBG pin is used as an output or left unconnected. To raise the
LVDS offset voltage, the VBG pin can be connected directly to
the supply rails.
30174144
FIGURE 12. Differential Input Drive
When the d.c. coupled mode is used, a common mode voltage must be provided at the differential inputs. This common
mode voltage should track the VCMO output pin. Note that the
VCMO output potential will change with temperature. The common mode output of the driving device should track this
change.
IMPORTANT NOTE: An analog input channel that is not used
should be tied to the VCMO voltage when the inputs are d.c.
coupled. Do not connect unused analog inputs to ground.
Full-scale distortion performance falls off rapidly as the
input common mode voltage deviates from VCMO. This is
a direct result of using a very low supply voltage to minimize power. Keep the input common voltage within 50
mV of VCMO.
Performance is as good in the d.c. coupled mode as it is in
the a.c. coupled mode, provided the input common mode
voltage at both analog inputs remain within 50 mV of VCMO.
2.2 THE ANALOG INPUT
The analog input is a differential one to which the signal
source may be a.c. coupled or d.c. coupled. In the normal
mode, the full-scale input range is selected using the FSR pin
as specified in the Converter Electrical Characteristics. In the
Extended Control mode, the full-scale input range is selected
by programming the Full-Scale Voltage Adjust register
through the Serial Interface. For best performance when adjusting the input full-scale range in the Extended Control, refer
to 1.4 REGISTER DESCRIPTION for guidelines on limiting
the amount of adjustment
Table 18 gives the input to output relationship with the FSR
pin high when the normal (non-extended) mode is used. With
the FSR pin grounded, the millivolt values in Table 18 are
reduced to 75% of the values indicated. In the Enhanced
Control Mode, these values will be determined by the full
scale range and offset settings in the Control Registers.
2.2.1 Handling Single-Ended Input Signals
There is no provision for the ADC08DL502 to adequately process single-ended input signals. The best way to handle
single-ended signals is to convert them to differential signals
before presenting them to the ADC. The easiest way to accomplish single-ended to differential signal conversion is with
an appropriate balun-connected transformer, as shown in
Figure 13.
TABLE 18. Differential Input To Output Relationship
(Non-Extended Control Mode, FSR High)
VIN+
VIN−
Output Code
VCM − 217.5 mV
VCM + 217.5 mV
0000 0000
VCM − 109 mV
VCM + 109 mV
0100 0000
VCM
VCM
0111 1111 /
1000 0000
VCM + 109 mV
VCM − 109 mV
1100 0000
VCM + 217.5 mV
VCM − 217.5 mV
1111 1111
2.2.1.1. a.c. Coupled Input
The easiest way to accomplish single-ended a.c. input to differential a.c. signal is by using an appropriate balun, as shown
in Figure 13.
The buffered analog inputs simplify the task of driving these
inputs and the RC pole that is generally used at sampling ADC
inputs is not required. If it is desired to use an amplifier circuit
before the ADC, use care in choosing an amplifier with adequate noise and distortion performance and adequate gain at
the frequencies used for the application.
Note that a precise d.c. common mode voltage must be
present at the ADC inputs. This common mode voltage,
VCMO, is provided on-chip when a.c. input coupling is used
and the input signal is a.c. coupled to the ADC.
www.ti.com
34
30174143
FIGURE 13. Single-Ended to Differential Signal
Conversion Using a Balun
2.2.1.2. d.c. Coupled Input
When d.c. coupling to the ADC08DL502 analog inputs is required, single-ended to differential conversion may be easily
accomplished with the LMH6555, as shown inFigure 14. In
such applications, the LMH6555 performs the task of singleended to differential conversion while delivering low distortion
and noise, as well as output balance, that supports the operation of the ADC08DL502. Connecting the ADC08DL502
VCMO pin to the VCM_REF pin of the LMH6555, through an appropriate buffer, will ensure that the common mode input
voltage is as needed for optimum performance of the ADC08DL502. The LMV321 was chosen to buffer VCMD for its
low voltage operation and reasonable offset voltage.
Be sure to limit output current from the ADC08DL502 VCMO
pin to 100 μA
Figure 13 is a generic depiction of a single-ended to differential signal conversion using a balun. The circuitry specific to
the balun will depend upon the type of balun selected and the
overall board layout. It is recommended that the system designer contact the manufacturer of the balun they have selected to aid in designing the best performing single-ended to
differential conversion circuit using that particular balun.
When selecting a balun, it is important to understand the input
architecture of the ADC. There are specific balun parameters
of which the system designer should be mindful. A designer
should match the impedance of their analog source to the
ADC08DL502's on-chip differential input termination resistor.
The range of this termination resistor is described in the electrical table as the specification RIN.
Also, the phase and amplitude balance are important. The
lowest possible phase and amplitude imbalance is desired
30174155
FIGURE 14. Example of Servoing the Analog Input with VCMO
In Figure 14, RADJ- and RADJ+ are used to adjust the differential
offset that can be measured at the ADC inputs VIN+ / VIN- with
LMH6555's input terminated to ground as shown but not driven and with no RADJ resistors applied. An unadjusted positive
offset with reference to VIN- greater than |15mV| should be
reduced with a resistor in the RADJ- position. Likewise, an unadjusted negative offset with reference to VIN- greater than
|15mV| should be reduced with a resistor in the RADJ+ position.
Table 19 gives suggested RADJ- and RADJ+ values for various
unadjusted differential offsets to bring the VIN+ / VIN- offset
back to within |15mV|.
TABLE 19. D.C. Coupled Offset Adjustment
35
Unadjusted Offset Reading
Resistor Value
0mV to 10mV
no resistor needed
11mV to 30mV
20.0kΩ
31mV to 50mV
10.0kΩ
51mV to 70mV
6.81kΩ
71mV to 90mV
4.75kΩ
91mV to 110mV
3.92kΩ
www.ti.com
ADC08DL502
when selecting a balun. The phase imbalance should be no
more than ±2.5° and the amplitude imbalance should be limited to less than 1dB at the desired input frequency range.
Finally, when selecting a balun, the VSWR (Voltage Standing
Wave Ratio), bandwidth and insertion loss of the balun should
also be considered. The VSWR aids in determining the overall
transmission line termination capability of the balun when interfacing to the ADC input. The insertion loss should be
considered so that the signal at the balun output is within the
specified input range of the ADC as described in the Converter Electrical Characteristics as the specification VIN.
ADC08DL502
problems, keep the clock level within the range specified as
VID in the Converter Electrical Characteristics.
The low and high times of the input clock signal can affect the
performance of any A/D Converter. The ADC08DL502 features a duty cycle clock correction circuit which can maintain
performance over temperature. The ADC will meet its performance specification if the input clock high and low times are
maintained within the duty cycle range as specified in the
Converter Electrical Characteristics.
High speed, high performance ADCs such as the ADC08DL502 require a very stable input clock signal with minimum phase noise or jitter. ADC jitter requirements are defined
by the ADC resolution (number of bits), maximum ADC input
frequency and the input signal amplitude relative to the ADC
input full scale range. The maximum jitter (the sum of the jitter
from all sources) allowed to prevent a jitter-induced reduction
in SNR is found to be
2.2.2 Out Of Range (OR) Indication
When the conversion result is clipped the Out of Range output
is activated such that OR+ goes high and OR- goes low. This
output is active as long as accurate data on either or both of
the buses would be outside the range of 00h to FFh. Note that
when the device is programmed to provide a second DCLK
output, the OR signals become DCLK2. Refer to 1.4 REGISTER DESCRIPTION
2.2.3 Full-Scale Input Range
As with all A/D Converters, the input range is determined by
the value of the ADC's reference voltage. The reference voltage of the ADC08DL502 is derived from an internal band-gap
reference. The FSR pin controls the effective reference voltage of the ADC08DL502 such that the differential full-scale
input range at the analog inputs is a normal amplitude with
the FSR pin high, or a reduced amplitude with FSR pin low as
defined by the specification VIN in the Converter Electrical
Characteristics. Best SNR is obtained with FSR high, but better distortion and SFDR are obtained with the FSR pin low.
The LMH6555 of is Figure 14 suitable for any Full Scale
Range.
tJ(MAX) = (VINFSR / VIN(P-P)) x (1/(2(N+1) x π x fIN))
where tJ(MAX) is the rms total of all jitter sources in seconds,
VIN(P-P) is the peak-to-peak analog input signal, VINFSR is the
full-scale range of the ADC, "N" is the ADC resolution in bits
and fIN is the maximum input frequency, in Hertz, at the ADC
analog input.
Note that the maximum jitter described above is the RSS sum
of the jitter from all sources, including that in the ADC input
clock, that added by the system to the ADC input clock and
input signals and that added by the ADC itself. Since the effective jitter added by the ADC is beyond user control, the best
the user can do is to keep the sum of the externally added
input clock jitter and the jitter added by the analog circuitry to
the analog signal to a minimum.
Input clock amplitudes above those specified in the Converter
Electrical Characteristics may result in increased input offset
voltage. This would cause the converter to produce an output
code other than the expected 127/128 when both input pins
are at the same potential.
2.3 THE CLOCK INPUTS
The ADC08DL502 has differential LVDS clock inputs, CLK+
and CLK−, which must be driven with an a.c. coupled, differential clock signal. Although the ADC08DL502 is tested and
its performance is guaranteed with a differential 1 GHz clock,
it typically will function well with input clock frequencies indicated in the Converter Electrical Characteristics. The clock
inputs are internally terminated and biased. The input clock
signal must be capacitively coupled to the clock pins as indicated in Figure 15.
Operation up to the sample rates indicated in the Converter
Electrical Characteristics is typically possible if the maximum
ambient temperatures indicated are not exceeded. Operating
at higher sample rates than indicated for the given ambient
temperature may result in reduced device reliability and product lifetime. This is because of the higher power consumption
and die temperatures at high sample rates. Important also for
reliability is proper thermal management . See 2.6.2 Thermal
Management.
2.4 CONTROL PINS
Six control pins (without the use of the serial interface) provide
a wide range of possibilities in the operation of the ADC08DL502 and facilitate its use. These control pins provide
Full-Scale Input Range setting, Calibration, Calibration Delay,
Output Edge Synchronization choice, LVDS Output Level
choice and a Power Down feature.
2.4.1 Full-Scale Input Range Setting
The input full-scale range can be selected with the FSR control input (pin 16) in the normal mode of operation. The input
full-scale range is specified as VIN in the Converter Electrical
Characteristics. In the extended control mode, the input fullscale range may be programmed using the Full-Scale Adjust
Voltage register. See 2.2 THE ANALOG INPUT for more information.
30174147
FIGURE 15. Differential (LVDS) Input Clock Connection
2.4.2 Calibration
The ADC08DL502 calibration must be run to achieve specified performance. The calibration procedure is run upon power-up and can be run any time on command. The calibration
procedure is exactly the same whether there is an input clock
present upon power up or if the clock begins some time after
application of power. The CalRun output indicator is high
while a calibration is in progress. Note that the DCLK outputs
are not active during a calibration cycle by default and therefore are not recommended as system clock unless the Resistor Trim Disable feature is used (Reg.9h). The DCLK
The differential input clock line pair should have a characteristic impedance of 100 Ω and (when using a balun), be
terminated at the clock source in that (100 Ω) characteristic
impedance. The input clock line should be as short and as
direct as possible. The ADC08DL502 clock input is internally
terminated with an untrimmed 100 Ω resistor.
Insufficient input clock levels will result in poor dynamic performance. Excessively high clock levels could cause a
change in the analog input offset voltage. To avoid these
www.ti.com
36
Note that the calibration delay selection is not possible in the
Extended Control mode and the short delay time is used.
2.4.2.1 Power-On Calibration
Power-on calibration begins after a time delay following the
application of power. This time delay is determined by the
setting of CalDly, as described in the Calibration Delay Section, below.
The calibration process will be not be performed if the CAL
pin is high at power up. In this case, the calibration cycle will
not begin until the on-command calibration conditions are
met. The ADC08DL502 will function with the CAL pin held
high at power up, but no calibration will be done and performance will be impaired. A manual calibration, however, may
be performed after powering up with the CAL pin high. See
On-Command Calibration 2.4.2.2 On-Command Calibration.
The internal power-on calibration circuitry comes up in an unknown logic state. If the input clock is not running at power up
and the power on calibration circuitry is active, it will hold the
analog circuitry in power down and the power consumption
will typically be less than 200 mW. The power consumption
will be normal after the clock starts.
2.4.3 Output Edge Synchronization
DCLK signals are available to help latch the converter output
data into external circuitry. The output data can be synchronized with either edge of these DCLK signals. That is, the
output data transition can be set to occur with either the rising
edge or the falling edge of the DCLK signal, so that either
edge of that DCLK signal can be used to latch the output data
into the receiving circuit.
When OutEdge (pin 6) is high, the output data is synchronized
with (changes with) the rising edge of the DCLK+ (pin 92).
When OutEdge is low, the output data is synchronized with
the falling edge of DCLK+.
At the very high speeds of which the ADC08DL502 is capable,
slight differences in the lengths of the DCLK and data lines
can mean the difference between successful and erroneous
data capture. The OutEdge pin is used to capture data on the
DCLK edge that best suits the application circuit and layout.
Reliable data capture can be achieved by using just one
DCLK+/- signal for the full 32 signal data bus. However, if desired, the user may configure the OR+/- output as the second
DCLK+/- output instead.
2.4.2.2 On-Command Calibration
To initiate an on-command calibration, bring the CAL pin high
for a minimum of tCAL_H input clock cycles after it has been
low for a minimum of tCAL_L input clock cycles. Holding the
CAL pin high upon power up will prevent execution of poweron calibration until the CAL pin is low for a minimum of
tCAL_L input clock cycles, then brought high for a minimum of
another tCAL_H input clock cycles. The calibration cycle will
begin tCAL_H input clock cycles after the CAL pin is thus
brought high. The CalRun signal should be monitored to determine when the calibration cycle has completed.
The minimum tCAL_L and tCAL_H input clock cycle sequence is
required to ensure that random noise does not cause a calibration to begin when it is not desired. As mentioned for best
performance, a calibration should be performed 20 seconds
or more after power up and repeated when the operating
temperature changes significantly relative to the specific system design performance requirements.
By default, On-Command calibration also includes calibrating
the input termination resistance and the ADC. However, since
the input termination resistance, once trimmed at power-up,
changes marginally with temperature, the user has the option
to disable the input termination resistor trim, which will guarantee that the DCLK is continuously present at the output
during subsequent calibration. The Resistor Trim Disable can
be programmed in register (address: 1h, bit 13) when in the
Extended Control mode. Refer to for register programming
information.
2.4.4 LVDS Output Level Control
The output level can be set to one of two levels with OutV (pin
5). The strength of the output drivers is greater with OutV high.
With OutV low there is less power consumption in the output
drivers, but the lower output level means decreased noise
immunity.
For short LVDS lines and low noise systems, satisfactory performance may be realized with the OutV input low. If the LVDS
lines are long and/or the system in which the ADC08DL502
is used is noisy, it may be necessary to tie the OutV pin high.
2.4.6 Power Down Feature
The Power Down pins (PD and PDQ) allow the ADC08DL502
to be entirely powered down (PD) or the "Q" channel to be
powered down and the "I" channel to remain active. See 1.1.7
Power Down for details on the power down feature.
The digital data (+/-) output pins are put into a high impedance
state when the PD pin for the respective channel is high. Upon
return to normal operation, the pipeline will contain meaningless information and must be flushed.
If the PD input is brought high while a calibration is running,
the device will not go into power down until the calibration
sequence is complete. However, if power is applied and PD
is already high, the device will not begin the calibration sequence until the PD input goes low. If a manual calibration is
requested while the device is powered down, the calibration
will not begin at all. That is, the manual calibration input is
completely ignored in the power down state.
2.4.2.3 Calibration Delay
The CalDly input (pin 141) is used to select one of two delay
times after the application of power to the start of calibration,
as described in 1.1.1 Calibration. The calibration delay values
allow the power supply to come up and stabilize before calibration takes place. With no delay or insufficient delay, calibration would begin before the power supply is stabilized at
its operating value and result in non-optimal calibration coefficients. If the PD pin is high upon power-up, the calibration
delay counter will be disabled until the PD pin is brought low.
Therefore, holding the PD pin high during power up will further
delay the start of the power-up calibration cycle. The best
setting of the CalDly pin depends upon the power-on settling
time of the power supply.
2.5 THE DIGITAL OUTPUTS
The ADC08DL502 normally demultiplexes the output data of
each of the two ADCs on the die onto two LVDS output buses
(total of four buses, two for each ADC). For each of the two
converters, the results of successive conversions started on
the odd falling edges of the CLK+ pin are available on one of
the two LVDS buses, while the results of conversions started
on the even falling edges of the CLK+ pin are available on the
other LVDS bus. This means that, the word rate at each LVDS
bus is 1/2 the ADC08DL502 input clock rate and the two buses must be multiplexed to obtain the entire 1 GSPS conversion result.
37
www.ti.com
ADC08DL502
outputs are continuously present at the output only when the
Resistor Trim Disable is active.
ADC08DL502
Since the minimum recommended input clock rate for this
device is 200 MSPS, the effective rate can be reduced to as
low as 100 MSPS by using the results available on just one
of the the two LVDS buses and a 200 MHz input clock, decimating the 200 MSPS data by two.
There is one LVDS output clock pair (DCLK+/−) available for
use to latch the LVDS outputs on all buses. However, the user
has the option to configure the OR+/- output as a second
DCLK+/- pair. Whether the data is sent at the rising or falling
edge of DCLK is determined by the sense of the OutEdge pin,
as described in 2.4.3 Output Edge Synchronization.
DDR (Double Data Rate) clocking can also be used. In this
mode a word of data is presented with each edge of DCLK,
reducing the DCLK frequency to 1/4 the input clock frequency.
See the Timing Diagram section for details.
The OutV pin is used to set the LVDS differential output levels.
See 2.4.4 LVDS Output Level Control.
The output format is Offset Binary. Accordingly, a full-scale
input level with VIN+ positive with respect to VIN− will produce
an output code of all ones, a full-scale input level with VIN−
positive with respect to VIN+ will produce an output code of all
zeros and when VIN+ and VIN− are equal, the output code will
vary between codes 127 and 128. A non-multiplexed mode of
operation is available for those cases where the digital ASIC
is capable of higher speed operation.
Many linear regulators will produce output spiking at poweron unless there is a minimum load provided. Active devices
draw very little current until their supply voltages reach a few
hundred millivolts. The result can be a turn-on spike that can
destroy the ADC08DL502, unless a minimum load is provided
for the supply. The 100 Ω resistor at the regulator output provides a minimum output current during power-up to ensure
there is no turn-on spiking.
In the circuit of Figure 16, an LM317 linear regulator is satisfactory if its input supply voltage is 4V to 5V . If a 3.3V supply
is used, an LM1086 linear regulator is recommended.
30174154
FIGURE 16. Non-Spiking Power Supply
The output drivers should have a supply voltage, VDR, that is
within the range specified in the Operating Ratings table. This
voltage should not exceed the VA supply voltage.
If the power is applied to the device without an input clock
signal present, the current drawn by the device might be below 200 mA. This is because the ADC08DL502 gets reset
through clocked logic and its initial state is unknown. If the
reset logic comes up in the "on" state, it will cause most of the
analog circuitry to be powered down, resulting in less than
100 mA of current draw. This current is greater than the power
down current because not all of the ADC is powered down.
The device current will be normal after the input clock is established.
2.6 POWER CONSIDERATIONS
A/D converters draw sufficient transient current to corrupt
their own power supplies if not adequately bypassed. A
33 µF capacitor should be placed within an inch (2.5 cm) of
the A/D converter power pins. A 0.1 µF capacitor should be
placed as close as possible to each VA pin, preferably within
one-half centimeter. Leadless chip capacitors are preferred
because they have low lead inductance.
The VA and VDR supply pins should be isolated from each
other to prevent any digital noise from being coupled into the
analog portions of the ADC. A ferrite choke, such as the JW
Miller FB20009-3B, is recommended between these supply
lines when a common source is used for them.
As is the case with all high speed converters, the ADC08DL502 should be assumed to have little power supply
noise rejection. Any power supply used for digital circuitry in
a system where a lot of digital power is being consumed
should not be used to supply power to the ADC08DL502. The
ADC supplies should be the same supply used for other analog circuitry, if not a dedicated supply.
2.6.2 Thermal Management
The ADC08DL502 is capable of impressive speeds and performance at very low power levels for its speed. However, the
power consumption is still high enough to require attention to
thermal management. For reliability reasons, the die temperature should be kept to a maximum of 130°C. That is, TA
(ambient temperature) plus ADC power consumption times
θJA (junction to ambient thermal resistance) should not exceed 130°C. This is not a problem if the ambient temperature
is kept to a maximum of +70°C as specified in the Operating
Ratings section.
To help minimize junction temperature, it is recommended
that a simple heat sink be built into the PCB. This is done by
including a copper area of about 2 square inches (6.5 square
cm) on the opposite side of the PCB. This copper area may
be plated or solder coated to prevent corrosion, but should
not have a conformal coating, which could provide some thermal insulation. Thermal vias should be used to connect this
bottom copper area to a copper pour on top of the PCB in the
area underneath the ADC, where room allows. These thermal
vias act as "heat pipes" to carry the thermal energy from the
device side of the board to the opposite side of the board
where it can be more effectively dissipated. The use of 9 to
16 thermal vias is recommended.
The thermal vias should be placed on a 1.2 mm grid spacing
and have a diameter of 0.30 to 0.33 mm. Such voids could
increase the thermal resistance between the device and the
2.6.1 Supply Voltage
The ADC08DL502 is specified to operate with a supply voltage of 1.9V ±0.1V. It is very important to note that, while this
device will function with slightly higher supply voltages, these
higher supply voltages may reduce product lifetime.
No pin should ever have a voltage on it that is in excess of the
supply voltage or below ground by more than 150 mV, not
even on a transient basis. This can be a problem upon application of power and power shut-down. Be sure that the supplies to circuits driving any of the input pins, analog or digital,
do not come up any faster than does the voltage at the ADC08DL502 power pins.
The Absolute Maximum Ratings should be strictly observed,
even during power up and power down. A power supply that
produces a voltage spike at turn-on and/or turn-off of power
can destroy the ADC08DL502. The circuit of Figure 16 will
provide supply overshoot protection.
www.ti.com
38
2.9.1 Non-Extended Control Mode Operation
Non-extended control mode operation means that the Serial
Interface is not active and all controllable functions are controlled with various pin settings. Pin 47 is the primary control
of the extended control enable function. When pin 47 is logic
high, the device is in the non-extended control mode. If pin 47
is floating and pin 58 is floating or logic high, the extended
control enable function is controlled by pin 16. The device has
functions which are pin programmable when in the non-extended control mode. An example is the full-scale range is
controlled in the non-extended control mode by setting pin 16
high or low. Table 20 indicates the pin functions of the ADC08DL502 in the non-extended control mode.
2.7 LAYOUT AND GROUNDING
Proper grounding and proper routing of all signals are essential to ensure accurate conversion. A single ground plane
should be used, instead of splitting the ground plane into analog and digital areas.
Since digital switching transients are composed largely of
high frequency components, the skin effect tells us that total
ground plane copper weight will have little effect upon the
logic-generated noise. Total surface area is more important
than is total ground plane volume. Coupling between the typically noisy digital circuitry and the sensitive analog circuitry
can lead to poor performance that may seem impossible to
isolate and remedy. The solution is to keep the analog circuitry well separated from the digital circuitry.
High power digital components should not be located on or
near any linear component or power supply trace or plane that
services analog or mixed signal components as the resulting
common return current path could cause fluctuation in the
analog input “ground” return of the ADC, causing excessive
noise in the conversion result.
Generally, we assume that analog and digital lines should
cross each other at 90° to avoid getting digital noise into the
analog path. In high frequency systems, however, avoid
crossing analog and digital lines altogether. The input clock
lines should be isolated from ALL other lines, analog AND
digital. The generally-accepted 90° crossing should be avoided as even a little coupling can cause problems at high
frequencies. Best performance at high frequencies is obtained with a straight signal path.
The analog input should be isolated from noisy signal traces
to avoid coupling of spurious signals into the input. This is
especially important with the low level drive required of the
ADC08DL502. Any external component (e.g., a filter capacitor) connected between the converter's input and ground
should be connected to a very clean point in the analog
ground plane. All analog circuitry (input amplifiers, filters, etc.)
should be separated from any digital components.
TABLE 20. Non-Extended Control Mode Operation
(Pin 47 Floating and Pin 58 Floating or Logic High)
Pin
Low
High
Floating
5
Reduced VOD
Normal VOD
n/a
6
OutEdge = Neg
OutEdge = Pos
DDR
141
CalDly Short
CalDly Long
n/a
Normal VIN
Extended
Control
Mode
Reduced VIN
16
Pin 5 can be either high or low in the non-extended control
mode. See 1.2 NORMAL/EXTENDED CONTROL for more
information.
Pin 6 can be high or low or can be left floating in the nonextended control mode. In the non-extended control mode,
pin 6 high or low defines the edge at which the output data
transitions. See 2.4.3 Output Edge Synchronization for more
information. If this pin is floating, the output clock (DCLK) is a
DDR (Double Data Rate) clock (see 1.1.5.3 Single Data Rate
and Double Data Rate) and the output edge synchronization
is irrelevant since data is clocked out on both DCLK edges.
Pin 141, if it is high or low in the non-extended control mode,
sets the calibration delay.
TABLE 21. Extended Control Mode Operation
(Pin 47 Logic Low or Pin 16 Floating and Pin 58 Floating
or Logic High)
2.8 DYNAMIC PERFORMANCE
The ADC08DL502 is a.c. tested and its dynamic performance
is guaranteed. To meet the published specifications and avoid
jitter-induced noise, the clock source driving the CLK input
must exhibit low rms jitter. The allowable jitter is a function of
the input frequency and the input signal level, as described in
2.3 THE CLOCK INPUTS.
It is good practice to keep the ADC input clock line as short
as possible, to keep it well away from any other signals and
to treat it as a transmission line. Other signals can introduce
jitter into the input clock signal. The clock signal can also introduce noise into the analog path if not isolated from that
path.
Best dynamic performance is obtained when the exposed pad
at the back of the package has a good connection to ground.
This is because this path from the die to ground is a lower
impedance than offered by the package pins.
Pin
Function
5
SCLK (Serial Clock)
6
SDATA (Serial Data)
141
SCS (Serial Interface Chip Select)
2.10 COMMON APPLICATION PITFALLS
Failure to write all register locations when using extended control mode. When using the serial interface, all nine
address locations must be written at least once with the default or desired values before calibration and subsequent use
of the ADC.
Driving the inputs (analog or digital) beyond the power
supply rails. For device reliability, no input should go more
than 150 mV below the ground pins or 150 mV above the
supply pins. Exceeding these limits on even a transient basis
may not only cause faulty or erratic operation, but may impair
device reliability. It is not uncommon for high speed digital
circuits to exhibit undershoot that goes more than a volt below
ground. Controlling the impedance of high speed lines and
terminating these lines in their characteristic impedance
should control overshoot.
2.9 USING THE SERIAL INTERFACE
The ADC08DL502 may be operated in the non-extended control (non-Serial Interface) mode or in the extended control
mode. Table 20 and Table 21 describe the functions of pins
5, 6, 16 and 141 in the non-extended control mode and the
extended control mode, respectively.
39
www.ti.com
ADC08DL502
thermal land on the board, which would cause the device to
run hotter.
ADC08DL502
Care should be taken not to overdrive the inputs of the ADC08DL502. Such practice may lead to conversion inaccuracies and even to device damage.
Incorrect analog input common mode voltage in the d.c.
coupled mode. As discussed in 1.1.4 The Analog Inputs and
2.2 THE ANALOG INPUT, the Input common mode voltage
must remain within 50 mV of the VCMO output , which has a
variability with temperature that must also be tracked. Distortion performance will be degraded if the input common mode
voltage is more than 50 mV from VCMO .
Using an inadequate amplifier to drive the analog input.
Use care when choosing a high frequency amplifier to drive
the ADC08DL502 as many high speed amplifiers will have
higher distortion than will the ADC08DL502, resulting in overall system performance degradation.
Driving the VBG pin to change the reference voltage. As
mentioned in 2.1 THE REFERENCE VOLTAGE, the reference voltage is intended to be fixed by FSR pin or Full-Scale
Voltage Adjust register settings. Over driving this pin will not
change the full scale value, but can otherwise upset operation.
www.ti.com
Driving the clock input with an excessively high level
signal. The ADC input clock level should not exceed the level
described in the Operating Ratings Table or the input offset
could change.
Inadequate input clock levels. As described in 2.3 THE
CLOCK INPUTS, insufficient input clock levels can result in
poor performance. Excessive input clock levels could result
in the introduction of an input offset.
Using a clock source with excessive jitter, using an excessively long input clock signal trace, or having other
signals coupled to the input clock signal trace. This will
cause the sampling interval to vary, causing excessive output
noise and a reduction in SNR performance.
Failure to provide adequate heat removal. As described in
2.6.2 Thermal Management, it is important to provide adequate heat removal to ensure device reliability. This can be
done either with adequate air flow or the use of a simple heat
sink built into the board.
40
ADC08DL502
Physical Dimensions inches (millimeters) unless otherwise noted
NOTES: UNLESS OTHERWISE SPECIFIED
REFERENCE JEDEC REGISTRATION MS-026, VARIATION BFB.
144-Lead, Low Profile, Quad, Flatpack (LQFP)
Order Number ADC08DL502CIVV
NS Package Number VNG144A
41
www.ti.com
ADC08DL502 Low Power, 8-Bit, Dual 500 MSPS A/D Converter
Notes
www.ti.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Applications
Audio
www.ti.com/audio
Automotive and Transportation www.ti.com/automotive
Amplifiers
amplifier.ti.com
Communications and Telecom www.ti.com/communications
Data Converters
dataconverter.ti.com
Computers and Peripherals
www.ti.com/computers
DLP® Products
www.dlp.com
Consumer Electronics
www.ti.com/consumer-apps
DSP
dsp.ti.com
Energy and Lighting
www.ti.com/energy
Clocks and Timers
www.ti.com/clocks
Industrial
www.ti.com/industrial
Interface
interface.ti.com
Medical
www.ti.com/medical
Logic
logic.ti.com
Security
www.ti.com/security
Power Mgmt
power.ti.com
Space, Avionics and Defense
www.ti.com/space-avionics-defense
Microcontrollers
microcontroller.ti.com
Video and Imaging
www.ti.com/video
RFID
www.ti-rfid.com
OMAP Mobile Processors
www.ti.com/omap
Wireless Connectivity
www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2012, Texas Instruments Incorporated