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 2 522 - 02 - 03 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) 3 522 - 02 - 03 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. 4 522 - 02 - 03 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. 5 522 - 02 - 03 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 522 - 02 - 03 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 7 522 - 02 - 03 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 8