Gennum GS1508-CKAE3 Hdtv cable driver Datasheet

HD-LINX ™ GS1508
HDTV Cable Driver
PRELIMINARY DATA SHEET
DESCRIPTION
• SMPTE 292M compliant
The GS1508 is a first generation very high speed bipolar
integrated circuit designed to drive two 75Ω co-axial
cables. The GS1508 is a SMPTE 292M compliant cable
driver that directly interfaces with other Gennum HDTV
devices and can also be used as a general purpose high
speed cable driver.
• dual cable driving outputs optimized for driving data
up to 1.485Gb/s
• ±7% tolerance output
• >17dB output return loss
• minimum external components
• seamless interface with the HD-LINX™ family of
products
• low power
• standard packaging
APPLICATIONS
1.485Gb/s HDTV Serial Digital Receiver Interfaces for:
Routers, Distribution Amplifiers, Switchers, and other
transmitting equipment.
The GS1508 features two complementary outputs whose
amplitude is controlled within a precise ±7% variation. The
output amplitude can be varied by adjusting the RSET
resistor value.
The serial inputs can be AC coupled. The GS1508 is a low
power device that does not require external pull down
resistors. The GS1508 is packaged in an 8 pin SOIC and
operates from a single 5V power supply.
ORDERING INFORMATION
PART NUMBER
PACKAGE
TEMPERATURE
GS1508-CKA
8 pin SOIC
0°C to 70°C
GS1508-CTA
8 pin Tape and Reel
0°C to 70°C
BANDGAP REFERENCE AND BIASING CIRCUIT
SDI
INPUT
DIFFERENTIAL
PAIR
RSET
SDO
OUTPUT STAGE &
CONTROL
SDI
SDO
PATENT PENDING
BLOCK DIAGRAM
Revision Date: March 2000
Document No. 522 - 02 - 03
GENNUM CORPORATION P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3
Tel. +1 (905) 632-2996 Fax. +1 (905) 632-5946 E-mail: [email protected]
www.gennum.com
GS1508
FEATURES
ABSOLUTE MAXIMUM RATINGS
TA = 25°C unless otherwise indicated
PARAMETER
VALUE
Supply Voltage
5.5V
Input Voltage Range (any input)
-0.3 to (VCC +0.3)V
GS1508
Operating Temperature Range
0°C to 70°C
Storage Temperature
-65°C to 150°C
Power Dissipation
300mW
Lead Temperature (soldering, 10 sec)
260°C
Input ESD Voltage
2000V
DC ELECTRICAL CHARACTERISTICS
VCC = 5V, TA = 0°C to 70°C unless otherwise shown.
Specifications assume 800mV output amplitude level settings into end terminated 75Ω transmission lines. Data Rate = 1485Mb/s unless otherwise shown.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VCC
4.75
5.00
5.25
V
1
PD
-
215
265
mW
1
IS
-
43
54
mA
1
VCM,IN
2.5+(VDIFF/2)
-
VCC-(VDIFF/2)
V
2
VCM,OUT
-
VCC-VOUT
-
V
2
Supply Voltage
System Power
Consumption
Driving two
75Ω cables
Supply Current
Common Mode Input
Voltage Range
Common Mode Output
Voltage Range
TEST
LEVEL
SYMBOL
NOTES
AC ELECTRICAL CHARACTERISTICS
VCC = 5V, TA = 0°C to 70°C unless otherwise shown.
Specifications assume 800mV output amplitude levels into end terminated 75Ω transmission lines. Data Rate = 1485Mb/s unless otherwise shown.
PARAMETER
CONDITIONS
SYMBOL
Serial Digital Rate
Additive Jitter
TYP
MAX
UNITS
DC
1485
-
Mb/s
-
5
-
psRMS
1
3
1485Mb/s
NOTES
TEST
LEVEL
MIN
1
Differential Input
VDIFF
150
-
800
mV
diff p-p
2
Differential Output
VOUT
750
800
850
mV
p-p
1
tR, tF
-
120
250
ps
2
1
Mismatch in Output Rise/Fall
Times
-
15
30
ps
4
Overshoot
-
1
8
%
4
Duty Cycle Distortion
-
15
30
ps
1
-
17
-
dB
Output Rise/Fall Times
Output Return Loss
(20% - 80%)
5MHz to 1485MHz
NOTES:
TEST LEVELS:
1. RMS additive jitter measured using Pseudo Random bit sequence (2
23
- 1).
1. 100% tested at 25°C.
2. Guaranteed by design.
2. Measured with Gennum Evaluation Board (EB1508).
3. Correlated Value.
4. Tested with EB1508
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2
4
PIN CONNECTIONS
1
SDI
2
VEE
3
RSET
4
GS1508
TOP
VIEW
8
SDO
7
SDO
6
GND
5
VCC
GS1508
SDI
PIN DESCRIPTIONS
NUMBER
SYMBOL
TYPE
DESCRIPTION
1, 2
SDI, SDI
I
Serial data inputs (non-inverting and inverting).
3
VEE
P
Most negative supply voltage.
4
RSET
I
Output amplitude control resistor.
5
VCC
P
Most positive supply voltage.
6
GND
P
Not connected internally. Connect to Ground. Used for isolation.
7, 8
SDO, SDO
O
Serial data outputs (non-inverting and inverting).
INPUT / OUTPUT CIRCUITS
VCC
5k
SDO SDO
SDI
SDI
20k
+
RSET
Fig. 1 (Pins 1 and 2)
Fig. 2 (Pins 7 and 8)
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DETAILED DESCRIPTION
INPUT INTERFACING
SDI/SDI are high impedance differential inputs. (See
Figure 1 for equivalent input circuit).
GS1508
Several conditions must be observed when interfacing to
these inputs:
1. The differential input signal amplitude must be between
150 and 800mVpp.
2. The common mode voltage range must be as specified
in the DC Characteristics table. For a 400mV input from
the GS1504 HD cable equalizer, this corresponds to a
common mode voltage range of between 2.7 and 4.8
volts.
3. For input trace lengths longer than approximately 1cm,
the inputs should be terminated as shown in the Typical
Application Circuit.
Fig. 3 Output Optimized for Waveform Symmetry
L=8.2nH, R=75 (Typical ORL=13.5dB)
The GS1508 inputs are self biased, allowing for simple AC
coupling to the device. For serial digital HDTV, a minimum
capacitor value of 4.7µF should be used to allow coupling
of pathological test signals. A tantalum capacitor is
recommended.
OUTPUT INTERFACING
The GS1508 outputs are current mode, and will drive
800mV into a 75 ohm load. These outputs are protected
from accidental static damage with internal static protection
diodes.
The SMPTE 292M standard requires that the output of a
cable driver have a source impedance of 75Ω and a return
loss of at least 15dB between 5Mhz and 1.485GHz.
Fig. 4 Output Optimized for Return Loss
L=12nH, C=0.5pF, R=75 (Typical ORL=18dB)
In order for an HD SDI output circuit using the GS1508 to
meet this specification, the output circuit shown in the
Typical Application Circuit is recommended.
Figures 3 and 4 show the eye diagram of the GS1508
output for two different output compensation conditions.
Figure 4 shows the GS1508 output optimized for wideband
return loss of 18dB. Figure 3 shows the GS1508 output
optimized for output waveform symmetry. In this case the
output may not exhibit a return loss of 15dB.
The values of LCOMP and CCOMP will vary depending on PCB
layout, but typical values are 12nH and 0.5pF respectively.
The small value of CCOMP can be easily swamped by
parasitic PCB capacitance, so it is recommended that the
ground plane be removed under the GS1508 output
circuitry (see the Application Information section in this data
sheet for further details). A 4.7µF capacitor is used for AC
coupling the output of the GS1508. This value is chosen to
ensure that pathological signals can be coupled without a
significant DC component occurring.
When measuring return loss at the GS1508 output it is
necessary to take the measurement for both a logic high
and a logic low output condition. This is because the output
protection diodes act as a varactor (voltage controlled
capacitor) as shown in Figure 5.
Consequently, the output capacitance of the GS1508 is
dependent on the logic state of the output.
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1.000
GS1508
0.800
SDO
0.600
0.400
GS1508
OUTPUT SWING
SDO
0.200
0.000
0.0000
Fig. 5 Static Protection Diodes
0.0050
0.0100
0.0150
0.0200
0.0250
1 / RSET (mho)
OUTPUT RETURN LOSS MEASUREMENT
Fig. 6 GS1508 Output Amplitude vs. 1/R SET
To perform a practical return loss measurement, it is
necessary to force the GS1508 output to a DC high or low
condition. The actual measured return loss will be based on
the outputs being static at VCC or VCC-1.6V. Under normal
operating conditions the outputs of the GS1508 swing
between VCC-0.4V and VCC-1.2V, so the measured value of
return loss will not represent the actual operating return
loss.
TABLE 1: RSET vs VOUT
A simple method of calculating the values of actual
operating return loss is to interpolate the two return loss
measurements. In this way, the values of return loss are
estimated at VCC-0.4V and VCC-1.2V based on the
measurements at VCC and VCC-1.6V.
RSET R
1/RSET
OUTPUT SWING
500.0
0.0020
0.095
150.0
0.0067
0.298
75.0
0.0133
0.575
53.6
0.0187
0.785
43.2
0.0231
0.937
NOTE: For reliable operation of the GS1508 over the full
temperature range, do not use an RSET value below 49.9Ω.
The two values of return loss (high and low) will typically
differ by several decibels. If the measured return loss is RH
for logic high and RL for logic low, then the two values can
be interpolated as follows:
RIH = RH- (RH-RL)/4 and
RIL = RL+(RH-RL)/4
where RIH is the interpolated logic high value and RIL is the
interpolated logic low value.
For example, if RH = -18dB and RL = -14dB, then the
interpolated values are RIH = -17dB and RIL = -15dB.
OUTPUT AMPLITUDE ADJUSTMENT
The output amplitude of the GS1508 can be adjusted by
changing the value of the RSET resistor as shown in Figure 6
and Table 1. For an 800mVp-p output with a nominal ±7%
tolerance, a value of 53.6% is required. A ±1% SMT resistor
should be used.
The RSET resistor is part of the high speed output circuit of
the GS1508. The resistor should be placed as close as
possible to the RSET pin. In addition, PCB capacitance
should be minimized at this node by removing the PCB
groundplane beneath the RSET resistor and the RSET pin.
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TYPICAL APPLICATION CIRCUIT
VCC
100n
PECL INPUT
SDI
GS1508
SDI
+
SDO
GS1508
VEE
OUT
75
6
GND
VCC
5
4
RSET
LCOMP
CCOMP
VCC
53.6
0µ1
All resistors in ohms,
all capacitors in farads,
unless otherwise shown.
TABLE 2: Typical Application Circuit Component Values
COMPONENT
VALUE
COMMENT
RSET
53.6
For 800mV Output
Z0
50Ω
For 50Ω PCB trace impedance
LCOMP
12nH
Typical value. Component value will vary depending on PCB layout.
CCOMP
0.5pF
Typical value. Component value will vary depending on PCB layout.
APPLICATION INFORMATION
PCB LAYOUT
Special attention must be paid to component layout when
designing serial digital interfaces for HDTV. Figures 8
through 11 show the artwork for a four layer printed circuit
evaluation board for the GS1508. The schematic is shown in
Figure 7. An FR-4 dielectric can be used, however,
controlled impedance transmission lines are required for
PCB traces longer than approximately 1cm. Note the
following PCB artwork features used to optimize
performance:
PCB trace width for HD rate signals is closely matched to
SMT component width to minimize reflections due to
change in trace impedance
The PCB ground plane is removed under the GS1508
output components to minimize parasitic capacitance.
The PCB ground plane is removed under the GS1508 RSET
pin and resistor to minimize parasitic capacitance
Input and output BNC connectors are surface mounted inline to eliminate a transmission line stub caused by a BNC
mounting via High speed traces are curved to minimize
impedance changes due to change of PCB trace width.
6
+
4µ7
1n
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4µ7
7
3
Z0
LCOMP
75
SDO
2
Z0
75
8
1
75
CCOMP
OUT
GS1508 EVALUATION BOARD
VCC
C1 1µ
TP1
C2 100n
C3 1n
TP2
GS1508
VCC
C16
1n
R12
50
C14
R13
50
C10
R8
75
100n
1µ
EDGEMNT_BNC
C13
J6
EDGEMNT_BNC 1µ
R9
75
C17 0p5
R7
75
U2
J7
L2 10n
L3 10n
SDI SDO
RSET VCC
J4
4µ7
SDI SDO
VEE GND
C11
VCC
C15
10n
EDGEMNT_BNC
C12
J5
R10
4µ7
EDGEMNT_BNC
75
C18 0p5
R11
53.6
All resistors in ohms,
all capacitors in farads,
unless otherwise shown.
Fig. 7 Schematic Diagram for the GS1508 Evaluation Board
Fig. 8 Top Layer of EB1508 PCB Layout
Fig. 10 Ground Layer of EB1508 PCB Layout
Fig. 9 Power Layer of EB1508 PCB Layout
Fig. 11 Bottom Layer of EB1508 PCB Layout
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PACKAGE DIMENSIONS
1.91
MAX
5.00 MAX.
1.27 MAX
0.49 MAX
5
8
GS1508
4.0
MAX
0.25
MAX
6.20
MAX
4
1
0.25
MAX
=
=
=
0.60 MAX
3.81 ±0.05
8-pin SOIC
All dimensions are in millimetres
3 spaces
@ 1.27 ±0.05
CAUTION
ELECTROSTATIC
SENSITIVE DEVICES
DO NOT OPEN PACKAGES OR HANDLE
EXCEPT AT A STATIC-FREE WORKSTATION
DOCUMENT IDENTIFICATION
REVISION NOTES:
PRELIMINARY DATA SHEET
This product is in production. Gennum reserves the right to make
changes to the product and to the documentation.
Updated ordering information; Replaced evaluation board diagrams;
Updated pin descriptions; Added note to Table 1.
For the latest product information, visit www.gennum.com
GENNUM JAPAN CORPORATION
C-101, Miyamae Village, 2-10-42 Miyamae, Suginami-ku
Tokyo 168-0081, Japan
Tel. +81 (03) 3334-7700 Fax. +81 (03) 3247-8839
GENNUM CORPORATION
MAILING ADDRESS:
P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3
Tel. +1 (905) 632-2996 Fax. +1 (905) 632-5946
GENNUM UK LIMITED
25 Long Garden Walk, Farnham, Surrey, England GU9 7HX
Tel. +44 (0)1252 747 000 Fax +44 (0)1252 726 523
SHIPPING ADDRESS:
970 Fraser Drive, Burlington, Ontario, Canada L7L 5P5
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.
© Copyright August 1998 Gennum Corporation. All rights reserved. Printed in Canada.
522 - 02 - 03
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