10.17 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 pullup 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. Using a voltage superviser to control the INH pin allows control of the turnon and turnoff of the device as opposed to relying on the ramp up or down if the input voltage source.

Figure 26 shows the typical application of the inhibit function. Turning Q1 on applies a low voltage to the inhibit control (INH) pin and disables the output of the supply, shown in Figure 27. If Q1 is turned off, the supply executes a soft-start power-up sequence, as shown in Figure 28. A regulated output voltage is produced within 2 ms. The waveforms were measured with a 5-A constant current load.

Figure 26. Typical Inhibit Control

Figure 27. Inhibit Turnoff

Figure 28. Inhibit Turnon