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POWER-UP INTO A NON-PREBIASED OUTPUT — AUTO-TRACK™ FUNCTION
UDG−06074
R
SET
2 kΩ
0.1 W
1 %
C
O
330 µF
C
I
560 µF
2
8 1 7
3910
PTH12060W
4
6
+
GND
L
O
A
D
Q1
BSS138
1=Turn−Off
+
Margin
Down
Margin
Up
Inhibit
Track GND GND VoAdj
5
V
O
V
O
V
O
Sense
V
I
PTH12010W , PTH12010L
SLTS205G – JUNE 2003 – REVISED FEBRUARY 2007
The Auto-Track function is unique to the PTH/PTV family, and is available with all POLA products. Auto-Track
was designed to simplify the amount of circuitry required to make the output voltage from each module power up
and power down in sequence. The sequencing of two or more supply voltages during power up is a common
requirement for complex mixed-signal applications that use dual-voltage VLSI ICs such as the TMS320™ DSP
family, microprocessors, and ASICs.
Basic Power-Up using Auto-Track™
For applications requiring output voltage on/off control, each series of the PTH family incorporates the track
control pin. The Auto-Track feature should be used instead of the inhibit feature wherever there is a requirement
for the output voltage from the regulator to be turned on/off.
Figure 12 shows the typical application for basic start-up. Note the discrete transistor (Q1). The track input has
its own internal pull-up to a potential of 5 V to 13.2 V The input is not compatible with TTL logic devices. An
open-collector (or open-drain) discrete transistor or supply voltage supervisor (TPS3808 or TPS7712) is
recommended for control.
Figure 12. Basic Start-up Control Circuit
Turning on Q1 applies a low voltage to the track control pin and disables the output of the module. If Q1 is then
turned off, the output ramps immediately to the regulated output voltage. A regulated output voltage is produced
within 35 ms. With the initial application of the input source voltage, the track pin must be held low (Q1 turned
ON) for at least 40 ms. Figure 13 shows the typical rise in both the output voltage and input current, following
the turn off of Q1. The turn off of Q1 corresponds to the rise in the waveform, Q1 Vds. The waveforms were
measured with a 10-A constant current load.
14
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