VOUT = 1.8V

PFM

TA = 25°C

IOUT = 0A

VIN = 5V

CSS = 4.7nF

Figure 9-32. Start-Up Timing

9.3 System Examples

9.3.1 Voltage Tracking

The SS/TR pin is externally driven by another voltage source to achieve output voltage tracking. The application

circuit is shown in Figure 9-33. From 0V to 0.6V, the internal reference voltage to the internal error amplifier

follows the SS/TR pin voltage. When the SS/TR pin voltage is above 0.6V, the voltage tracking is disabled and

the FB pin voltage is regulated at 0.6V. The device achieves ratiometric or coincidental (simultaneous) output

tracking, as shown in Figure 9-34.

The R2 value must be set properly to achieve accurate voltage tracking by taking the 2.5μA charging current into

account. 1kΩ or smaller is a sufficient value for R2. For decreasing SS/TR pin voltage, the device does not sink

current from the output when the device is in PFM mode. The resulting decrease of the output voltage can be

slower than the SS/TR pin voltage if the load is light.

When driving the SS/TR pin with an external voltage, do not exceed the voltage rating of the SS/TR pin which is

VIN+0.3V.

Vout1

Vout2

SS/TR

FB

R1

R2

R3

R4

TPSM8281x

Figure 9-33. Schematic for Output Voltage Tracking

Figure 9-34. Output Voltage Tracking

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TPSM82810, TPSM82813

SLUSDN6D – SEPTEMBER 2019 – REVISED JUNE 2026

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