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Soft-Start Power UP

12 V

CIN

1,000 mF

COUT

330 mF

GND

GND

3.3 V

RSET

, 2 kW

0.1 W, 1 %

PTH12020W

7

10

4

5

6

2

3

9

Track

GND

Inhibit

1

Adjust

8

Up Dn

Sense

Vin (5 V/Div)

Vo (1 V/Div)

Iin (5 A/Div)

HORIZ SCALE 5 ms/Div

PTH12020W/L

SLTS208E–MAY 2003–REVISED OCTOBER 2005

For simple point-of-use applications, the PTH12050 (6 A) provides operating features such as an on/off inhibit,

output voltage trim, pre-bias start-up and over-current protection. The PTH12060 (10 A), and PTH12010 (12 A)

include an output voltage sense, and margin up/down controls. Then the higher output current, PTH12020 (18 A)

and PTH12030 (26 A) products incorporate overtemperature shutdown protection.

The PTV12010 and PTV12020 are similar parts offered in a vertical, single in-line pin (SIP) profile, at slightly

lower current ratings.

the task of sequencing the supply voltages in a power system. This and other features are described in the

following sections.

The Auto-Track feature allows the power-up of multiple PTH 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

Figure 12. Power-Up Application Circuit

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.

Figure 13. Power-Up Waveforms

From the moment a valid input voltage is applied, the soft-start control introduces a short time delay

(typically 8 ms–15 ms) before allowing the output voltage to rise. The output then progressively rises to the

(PTH12020W), operating from a 12-V input bus and configured for a 3.3-V output. The waveforms were

measured with a 5-A resistive load and the Auto-Track feature 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

25 ms.

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