Datasheet

INH
Control
INH/UVLO
VIN
R
UVLO1
R
UVLO2
A_VOUT
V
IN
GND
U1
LMZ34002
www.ti.com SNVS989A –JULY 2013–REVISED SEPT 2013
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, an external level-shifter is required to interface with the pin
because in a positive-to-negative buck-boost supply, the INH pin is referenced to VOUT, not GND. Adding a
level-shifter (U1) as shown in Figure 42, allows the INH control to be refernced to GND. A recommended level-
shifter part # is DCX144EH-7 from Diodes Inc.
Pulling the input of U1 to GND applies a low voltage to the inhibit control pin and disables the output of the
supply, shown in Figure 43. Releasing the input of U1 enables the device, which executes a soft-start power-up
sequence, as shown in Figure 44. The device produces a regulated output voltage within 10 ms. The waveforms
were measured with a 1.5-A constant current load.
Figure 42. Typical Inhibit Control
Figure 43. Inhibit Turn-Off Figure 44. Inhibit Turn-On
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