GS2972 Datasheet, PDF (85/125 Pages) Semtech Corporation – 3G/HD/SD-SDI Serializer with Complete SMPTE Audio & Video Support

4.12.1 Output Signal Interface Levels
The Serial Digital Output signals (SDO and SDO pins), of the device meet the amplitude
requirements as defined in SMPTE ST 424 for an unbalanced generator (single-ended).
The signal amplitude is controlled to better than +/-7% of the nominal level defined in
SMPTE ST 424, when an external 750Ω 1% resistor is connected between the RSET pin
of the device and VCC.
The output signal amplitude can be reduced to less than 1/10th of the nominal
amplitude, defined above, by increasing the value of the resistor connected between the
RSET pin of the device and VCC.
These requirements are met across all ambient temperature and power supply
operating conditions described in Section 2.
The output amplitude of the GS2972 can be adjusted by changing the value of the R_SET
resistor as shown in Table 4-29. For a 800mV_pp output a value of 750Ω is required.
A ±1% SMT resistor should be used.
The R_SET resistor is part of the high speed output circuit of the GS2972. The resistor
should be placed as close as possible to the RSET pin. In addition, an anti-pad should be
used underneath the resistor.
Table 4-29: R_SET Resistor Value vs. Output Swing
R_SET Resistor Values (Ω)
995
824
750
680
Output Swing (mV_pp)
608
734
800
884
4.12.2 Overshoot/Undershoot
The serial digital output signal overshoot and undershoot is controlled to be less that 7%
of the output signal amplitude, when operating as an unbalanced generator
(single-ended).
This requirement is met for nominal signal amplitudes as defined by SMPTE ST 292.
This requirement is met regardless of the output slew rate setting of the device.
This requirement is met across all ambient temperature and power supply operating
conditions described in Section 2.
This requirement is summarized in Table 4-30:
Table 4-30: Serial Digital Output - Overshoot/Undershoot
Parameter
Symbol
Conditions
Min
Typ
Serial output overshoot /undershoot
−
−
−
0
Max
7
Units
%
GS2972 3G/HD/SD-SDI Serializer with Complete
SMPTE Audio & Video Support
Final Data Sheet Rev. 9
GENDOC-047479 September 2013
www.semtech.com
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