LTC2923

1

2923fa

(4mm × 3mm) DFN Packages

Power Supply

Tracking Controller

The LTC

tracking and sequencing requirements. By selecting a few

resistors, the supplies can be configured to ramp-up and

ramp-down together or with voltage offsets, time delays

or different ramp rates.

By introducing currents into the feedback nodes of two

independent switching regulators, the LTC2923 causes

their outputs to track without inserting any pass element

losses. Because the currents are controlled in an open-

loop manner, the LTC2923 does not affect the transient

response or stability of the supplies. Furthermore, it

presents a high impedance when power-up is complete,

effectively removing it from the DC/DC circuit.

For systems that require a third supply, one supply can be

controlled with a series FET. This optional series FET can

also control a supply that does not allow direct access to

its feedback resistors (e.g., a power module) or a supply

whose output cannot be forced to ground (e.g., a 3-termi-

nal linear regulator). When the FET is used, an electronic

circuit breaker provides protection from short-circuit

conditions.

Q1

10nF

138k

3.3V

16.5k

887k

35.7k

1.8V

3.3V

16.5k

412k

13k

100k

ON

RAMPBUF

TRACK1

TRACK2

FB1

GATE

LTC2923

GND

2923 TA01

RAMP

412k

2.5V

887k

DC/DC

IN

FB = 1.235V

OUT

DC/DC

IN

FB = 0.8V

OUT

FB2

SDO

STATUS

1V/DIV

1ms/DIV

2923 TA02

3.3V

2.5V

1.8V

1V/DIV

3.3V

2.5V

1.8V

1ms/DIV

2923 F08b

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

APPLICATIO S

, LTC and LT are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Patents Pending.