Q1

INH

Control

INH/UVLO

VIN

AGND

V

IN

TPS84250

SLVSAR6 – AUGUST 2012

www.ti.com

Output On/Off Inhibit (INH)

The INH pin provides electrical on/off control of the device. Once the INH pin voltage exceeds the threshold

voltage, the device starts operation. If the INH pin voltage is pulled below the threshold voltage, the regulator

stops switching and enters low quiescent current state.

The INH pin has an internal pull-up current source, allowing the user to float the INH pin for enabling the device.

If an application requires controlling the INH pin, use an open drain/collector device, or a suitable logic gate to

interface with the pin.

Figure 32 shows the typical application of the inhibit function. The Inhibit control has its own internal pull-up to

VIN potential. An open-collector or open-drain device is recommended to control this input.

Turning Q1 on applies a low voltage to the inhibit control (INH) pin and disables the output of the supply, shown

in Figure 33. If Q1 is turned off, the supply executes a soft-start power-up sequence, as shown in Figure 34. A

regulated output voltage is produced within 5 ms. The waveforms were measured with a 2-A constant current

load.

Figure 32. Typical Inhibit Control

Figure 33. Inhibit Turn-Off

Figure 34. Inhibit Turn-On

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