www.ti.com

OUTPUT ON/OFF INHIBIT

PTH12060W

V

I

V

O

V

1

10

4

5

6

2

3

C

330 F

O

m

C

560 F

I

m

1=Inhibit

GND

9

8

Q1

BSS138

R

2k

0.1W

1%

SET

W

7

GND

L

O

A

D

t − Time − 10 ms/div

REMOTE SENSE

PTH12030W/L

SLTS211F – MAY 2003 – REVISED FEBRUARY 2007

For applications requiring output voltage on/off control, each series of the PTH family incorporates an output

Inhibit control pin. The inhibit feature can be used wherever there is a requirement for the output voltage from

the regulator to be turned off.

The power modules function normally when the Inhibit pin is left open-circuit, providing a regulated output

Figure 12 shows the typical application of the inhibit function. Note the discrete transistor (Q1). The Inhibit input

has its own internal pull-up to a potential of 5 V to 13.2 V (see footnotes to specification table). The input is not

compatible with TTL logic devices. An open-collector (or open-drain) discrete transistor is recommended for

control.

Figure 12. Inhibit Control Circuit

Figure 13. Power-Up from Inhibit Control

Turning Q1 on applies a low voltage to the Inhibit control pin and disables the output of the module. If Q1 is then

turned off, the module executes a soft-start power-up sequence. A regulated output voltage is produced within

25 ms Figure 13 shows the typical rise in both the output voltage and input current, following the turn-off of Q1.

constant current load.

regulation performance of the module by allowing it to compensate for any IR voltage drop between its output

and the load. An IR drop is caused by the high output current flowing through the small amount of pin and trace

resistance.

application circuit). If a sense pin is left open-circuit, an internal low-value resistor (15-

Ω or less) connected

between the pin and and the output node, ensures the output remains in regulation.

This should be limited to a maximum of 0.3 V.

Note: The remote sense feature is not designed to compensate for the forward drop of nonlinear or

frequency dependent components that may be placed in series with the converter output. Examples include

OR-ing diodes, filter inductors, ferrite beads, and fuses. When these components are enclosed by the

remote sense connection, they are effectively placed inside the regulation control loop, which can adversely

affect the stability of the regulator.

14

Submit Documentation Feedback