GS2989 datasheet(12/20 Pages) SEMTECH

12 / 20 page

GS2989

Final Data Sheet

Rev.6

GENDOC-052133

July 2015

12 of 20

Semtech

www.semtech.com

The output signal presence function measures signal-edge energy to indicate that the

pre-driver to the serial data outputs is toggling.

4.6 Output Amplitude (RSET)

The output amplitude of the GS2989 can be adjusted by changing the value of the RSET

resistor as shown in Figure 4-1. For an 800mVpp output with a nominal ±7% tolerance, a

value of 750

Ω is required. A ±1% SMT resistor should be used.

The RSET resistor is part of an internal DC feedback loop in the GS2989. The resistor

should be placed as close as possible to the RSET pin, and connected directly to the VCC

plane (traces/wires may cause instability). In addition, the PCB capacitance should be

minimized at this node by removing the PCB groundplane beneath the RSET resistor

and the RSET pin.

Note: Care should be taken when considering layout of the RSET resistor. Please refer to

Section 5.1 for more details.

Table 4-4: Output Signal Presence Indicator

Pre-Driver Output

OSP Pin

Valid signal present

No valid signal present

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