GS9092ACNE3 datasheet(49/63 Pages) GENNUM

49 / 63 page

GS9092A GenLINX® III 270Mb/s Serializer for SDI and

DVB-ASI

Data Sheet

34715 - 4

May 2010

49 of 63

3.10 Serial Digital Output

The GS9092A contains an integrated current mode differential serial digital output

buffer/cable driver, capable of driving 800mV into two single ended 75Ω loads. Output

pins SDO and SDO provide a single differential serial digital output. Alternatively, two

75Ω connections can be driven using single ended drive.

To enable the output, SDO_EN must be set HIGH by the application layer. Setting the

SDO_EN signal LOW will cause the SDO and SDO output pins to become high

impedance, resulting in reduced device power consumption.

With suitable external return loss matching circuitry, the GS9092A's serial digital

outputs will provide a minimum output return loss of 15dB.

The output buffer / cable driver uses a separate power supply of +1.8V DC supplied via

the CD_VDD and CD_GND pins.

3.10.1 Output Swing

Nominally, the voltage swing of the serial digital output is 800mVp-p single-ended into

a 75Ω load. This is set externally by connecting the RSET pin to CD_VDD through a

resistor. The output swing may be adjusted by altering the value of the RSET resistor.

SMPTE-compliant cable driver operation can be achieved at +1.8V operation by

connecting external pull-up resistors from the differential output to the +1.8V source.

3.10.2 Serial Digital Output Mute Control

The GS9092A will automatically mute the serial digital output when RESET is LOW. In

this case, the SDO and SDO signals are set to the last logic state.

3.10.3 Output Return Loss Measurement

Under normal operating conditions the cable connected to the BNC connector will

provide a 75Ω load. Under this loaded condition, the outputs of the device swing

between VCC-0.4V and VCC-1.2V. When a 75Ω load is not connected to the BNC

connector, the outputs of the device will swing between VCC and VCC - 1.6V. The

difference in output swing is shown in Figure 3-10.

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