Notes on Use of Auto-Track™

V

I = 5 V

Vo

1 = 3.3 V

R

SET1

+

Vo

2 = 1.8 V

U1

U2

+

PTH04T240W

V

I

V

O

+Sense

GND

V

O Adj

PTH04T230W

V

I

V

O

+Sense

−Sense

GND

AutoTrack

V

O Adj

R

SET2

TurboTrans

TurboTrans

AutoTrack

C4

V

CC

GND

SENSE

MR

CT

RESET

6

5

3

4

1

2

TPS3808G50

C3

4700 pF

0.1

µF

−Sense

1.21 k

Ω

4.75 k

Ω

CO1

CO2

CI1

CI2

U3

RTT

RTT

PTH04T240W, PTH04T241W

www.ti.com ...................................................................................................................................................... SLTS276D – OCTOBER 2006 – REVISED JULY 2009

1. The Track pin voltage must be allowed to rise above the module set-point voltage before the module

regulates at its adjusted set-point voltage.

2. The Auto-Track function tracks almost any voltage ramp during power up, and is compatible with ramp

speeds of up to 1 V/ms.

3. The absolute maximum voltage that may be applied to the Track pin is the input voltage VI.

4. The module cannot follow a voltage at its track control input until it has completed its soft-start initialization.

This takes about 20 ms from the time that a valid voltage has been applied to its input. During this period, it

is recommended that the Track pin be held at ground potential.

5. The Auto-Track function is disabled by connecting the Track pin to the input voltage (VI). When Auto-Track is

disabled, the output voltage rises according to its softstart rate after input power has been applied.

6. The Auto-Track pin should never be used to regulate the module's output voltage for long-term, steady-state

operation.

Figure 24. Sequenced Power Up and Power Down Using Auto-Track

Copyright © 2006–2009, Texas Instruments Incorporated

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