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Up

Dn

Sense

V =12V

I

ASIC

VC ORE

VC CI O

I 2

O

PTH12010L

1

10

4

5

6

2

3

9

Tra ck

GND

Inhibit

7

Vadj

Sense

+

V 1=3.3V

O

V 2=1.8V

O

R1

2kW

R5

10k0

R4

100kW

R3

11k0

R1

130 W

C2

330 F

m

C4

330 F

m

C6

0.68 F

m

C5

0.1 F

m

C3

330 F

m

C1

330 F

m

+

+

PTH12020W

7

10

4

5

6

2

3

9

Tra ck

V

I

V

I

V

O

V

O

GND

Inhibit

1

Adjust

+

TL7702B

V

CC

GND

SENSE

RESIN

REF

CT

RESET

RESET

8

7

2

1

3

5

6

4

+

8

8

PTH12010W, PTH12010L

SLTS205G – JUNE 2003 – REVISED FEBRUARY 2007

Figure 18. Application Circuit Demonstrating Prebias Startup

Notes:

1. Output prebias holdoff is an inherent feature to all PTH120x0L and PTV120x0W/L modules. It has now

been incorporated into all modules (including W-suffix modules with part numbers of the form

PTH120x0W), with a production lot date code of 0423 or later.

2. The prebias start-up feature is not compatible with Auto-Track. If the rise in the output is limited by the

voltage applied to the Track control pin, the output sinks current during the period that the track control

voltage is below that of the back-feeding source. For this reason, it is recommended that Auto-Track be

disabled when not being used. This is accomplished by connecting the Track pin to the input voltage, VI.

This raises the Track pin voltage well above the set-point voltage prior to the module’s start up, thereby,

defeating the Auto-Track feature.

3. To further ensure that the regulator's output does not sink current when power is first applied (even with a

ground signal applied to the Inhibit control pin), the input voltage must always be greater than the applied

prebias source. This condition must exist throughout the power-up sequence of the power system.

19

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