pth12050 Astec Powe, pth12050 Datasheet - Page 6

• Manufacturer Part Number: pth12050
• Description: Pth05020 5vin Single
• Manufacturer: Astec Powe

6. Operating Information
6.1 Overtemperature Protection (OTP)
Only the PTHxx020 and PTHxx030 series of products have
overtemperature protection. These products have an on-board
temperature sensor that protects the module’s internal circuitry
against excessively high temperatures. A rise in the internal
temperature may be the result of a drop in airflow, or a high ambient
temperature. If the internal temperature exceeds the OTP threshold
(see datasheet specifications), the module’s Inhibit control is
automatically pulled low. This disables the regulator allowing the
output voltage to drop to zero. (The external output capacitors will
be discharged by the load circuit). The recovery is automatic, and
begins with a soft-start power up. It occurs when the the sensed
temperature decreases by about 10°C below the trip point.
Note
The overtemperature protection is a last resort mechanism to prevent
thermal stress to the regulator. Operation at or close to the thermal
shutdown temperature is not recommended and will reduce the long-
term reliability of the module. Always operate the regulator within the
specified Safe Operating Area (SOA) limits for the worst-case
conditions of ambient temperature and airflow.
6.2 Overcurrent Protection
For protection against load faults, all modules incorporate output
overcurrent protection. Applying a load that exceeds the regulator’s
overcurrent threshold will cause the regulated output to shut down.
Following shutdown a module will periodically attempt to recover by
initiating a soft-start power-up. This is described as a “hiccup” mode
of operation, whereby the module continues in the cycle of
successive shutdown 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
automatically recovers and returns to normal operation.
6.3 Soft-Start Power-Up
modules to be directly controlled from the Track pin. However in a
stand-alone configuration, or when the Auto-Track feature is not
being used, the Track pin should be directly connected to the input
voltage, Vin (see Figure 6).
The Auto-Track feature allows the power-up of multiple PTH
C
1000µF
in
6 6
5V
GND
+
2
V
Figure 6 - Soft-Start Power-up
Inhibit
in
Up
10
3
Dn
GND
9
1
PTH05020
Track
File Name: an_pth05020.pdf Rev (05): 21 Dec 2005
8
7
Adjust
Sense
4
R
0.1W, 1%
V
5
set
out
698Ω
6
+
C
330µF
out
GND
3.3V
When the Track pin is connected to the input voltage the Auto-Track
function is permanently disengaged. This allows the module to
power up entirely under the control of its internal soft-start circuitry.
When power up is under soft-start control, the output voltage rises to
the set-point at a quicker and more linear rate.
From the moment a valid input voltage is applied, the soft-start
control introduces a short time delay (typically 5ms to 10ms) before
allowing the output voltage to rise. The output then progressively
rises to the module’s setpoint voltage. Figure 7 shows the soft-start
power-up characteristic of the 22A output product (PTH05020W),
operating from a 5V input bus and configured for a 3.3V output. The
waveforms were measured with a 5A resistive load, with Auto-Track
disabled. The initial rise in input current when the input voltage first
starts to rise is the charge current drawn by the input capacitors.
Power-up is complete within 15ms
HORIZ SCALE:5 ms/Div
PTH05020 Single Series | Application Note 156
Figure 7 - Power-up Characteristic
Vout (1V/Div)
Iin (5A/Div)
Vin (1V/Div)