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UNDERVOLTAGE LOCKOUT (UVLO)

R

V

kW

(5)

GND

2

3

+

GND

Inhibit/

UVLO

10

UDG−06059

PTH04T230/231W

PTH04T230W, PTH04T231W

SLTS271A – SEPTEMBER 2006 – REVISED OCTOBER 2006

The PTH04T230/231W power modules incorporate an input undervoltage lockout (UVLO). The UVLO feature

prevents the operation of the module until there is sufficient input voltage to produce a valid output voltage. This

enables the module to provide a clean, monotonic power-up for the load circuit, and also limits the magnitude of

current drawn from the regulator’s input source during the power-up sequence.

control is overridden, and the module does not produce an output. The hysteresis voltage, which is the

difference between the ON and OFF threshold voltages, is set at 500 mV. The hysteresis prevents start-up

oscillations, which can occur if the input voltage droops slightly when the module begins drawing current from

the input source.

The UVLO feature of the PTH04T230/231W module allows for limited adjustment of the ON threshold voltage.

The adjustment is made via the Inhbit/UVLO Prog control pin (pin 10) using a single resistor (see figure below).

When pin 10 is left open circuit, the ON threshold voltage is internally set to its default value, which is 1.95 volts.

The ON threshold might need to be raised if the module is powered from a tightly regulated 5-V bus. Adjusting

the threshold prevents the module from operating if the input bus fails to completely rise to its specified

regulation voltage.

and it may only be adjusted to a higher value.

2.5

3.0

3.5

4.0

4.5

154

71.5

53.6

33.2

26.7

Figure 18. Undervoltage Lockout

22

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