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Output On/Off Inhibit
+
+
INH
GND
GND
C
O
R
0.05W,1%
SET
C
I
PTN04050A
GND Adj
V
O
V
O
V
I
2
5
41
3
V
I
INH
t-Time=40ms/div
V (5V/Div)
O
I (1 A/Div)
I
V (2V/Div)
INH
INHRelease
PTN04050A
SLTS250 – SEPTEMBER 2005
For applications requiring output voltage on/off control, the PTN04050A power module incorporates an output
on/off Inhibit control (pin 3). The inhibit feature can be used wherever there is a requirement for the output
voltage from the regulator to be turned off.
The power module functions normally when the Inhibit pin is left open-circuit, providing a regulated output
whenever a valid source voltage is connected to V
I
with respect to GND.
Figure 17 shows the typical application of the inhibit function. Note the discrete transistor (Q1). The Inhibit
control has its own internal pullup to V
I
. An open-collector or open-drain (non-TTL) device is required to control
this input.
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. Figure 18 shows the typical rise in the output
voltage, following the turn off of Q1. The turn off of Q1 corresponds to the rise in the waveform, V
INH
. The
waveforms were measured with a 500-mA resistive load.
Note: The PTN04050A Inhibit control circuitry must not be shared with another module. Never connect a resistor
between the Inhibit pin and any voltage reference or GND.
Figure 17. Inhibit Circuit
Figure 18. Inhibit Waveform
12
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