Datasheet

Application Notes
For technical support and further information visit http://power.ti.com
Figure 3-2
Figure 3-3
Vo (2 V/Div)
Iin (1 A/Div)
Vinh (10 V/Div)
HORIZ SCALE: 5 ms/Div
Power-Up Characteristics
When configured per the standard application, the
PTH12000x power modules produce a regulated out-
put voltage whenever of a valid input voltage is applied
from V
in
(pin 2), with respect to GND (pin 1). During
the power-up period, internal soft-start circuitry slows the
rate that the output voltage rises. This reduces the in-rush
current drawn from the input source. The soft-start cir-
cuitry also introduces a short time delay (typically 12 ms)
into the power-up characteristic. The delay is from the
point that a valid input source is recognized, to the initial
rise of the output voltage. Figure 3-1 shows the power-
up characteristic of the PTH12000W with the output
voltage set to 5-V. The waveforms were measured with a
2-A resistive load. The initial rise in input current when
the input voltage first starts to rise is the charge current
drawn by the input capacitors.
Figure 3-1
Vin (5 V/Div)
Vo (5 V/Div)
Iin (2 A/Div)
HORIZ SCALE: 5 ms/Div
Over-Current Protection
For protectection against load faults, this series incorpo-
rates output over-current protection. Applying a load that
exceeds the module’s over-current threshold will cause
the regulated output to shut down. Following shut down
the module will periodically attempt to recover by initi-
ating a soft-start power-up. This is often described as a
“hiccup” mode of operation, whereby the module con-
tinues in the cycle of successive shut down and power up
until the load fault is removed. During this period, the
average current flowing into the fault is significantly
reduced. Once the fault is removed, the module auto-
matically recovers and returns to normal operation.
Output On/Off Inhibit
The inhibit control (pin 3) is used wherever there is a
requirement to turn off the regulator output while input
power is applied.
PTH12000 Series
PTH12000W
V
IN
4
52
3
L
O
A
D
C
IN
100 µF
+
Co
1
100 µF
+
1 =Inhibit
GND GND
V
OUT
Q
1
BSS138
R
SET
280
1%
1
The power modules function normally when the Inhibit
pin is left open-circuit, providing a regulated output
whenever a valid source voltage is connected to V
in
with
respect to GND.
Figure 3-2 shows the typical application of the inhibit
function. Note the discrete transistor (Q
1
). The Inhibit
pin has its own internal pull-up to V
in
potential. An
open-collector or open-drain device is recommended to
control this input.
Turning Q
1
on applies a low voltage to the inhibit control
and disables the output of the module. If Q
1
is then turned
off, the module will execute a soft-start power-up. A
regulated output voltage is produced within 25 msec.
Figure 3-3 shows the typical rise in both the output volt-
age and input current, following the turn-off of Q
1
. The
turn off of Q
1
corresponds to the rise in the waveform,
V
inh
. The waveforms were measured with a 5-V output
and 2-A resistive load.