LTC2925

4

2925f

TYPICAL PERFOR A CE CHARACTERISTICS

2

8

9

10

12

11

34

2925 G03

56

2.9

1.3

1.4

1.5

5

2925 G01

1.2

1.1

1.0

3.5

4

4.5

5.5

0

0

0.2

0.4

0.6

0.8

1.0

1

234

2925 G02

5

supply input range is 2.9V to 5.5V. An undervoltage

lockout circuit resets the part when the supply is below

capacitor.

SENSEP (Pin 2/Pin 23): Circuit Breaker Positive Sense

Input. SENSEP and SENSEN measure the voltage across

the sense resistor and trigger the circuit breaker function

when the current exceeds the level programmed by the

sense resistor for longer than a short circuit timer cycle

SENSEN (Pin 3/Pin 24): Circuit Breaker Negative Sense

Input. SENSEN connects to the low side of the current

sense resistor. SENSEP and SENSEN monitor the current

through the external FET by measuring the voltage across

the sense resistor. The circuit breaker turns off the FET

when the sense voltage exceeds 50mV for longer than a

short circuit timer cycle (see SCTMR). If the short-circuit

timer times out, the GATE pin will be pulled low immedi-

ately to protect the FET. If unused, tie SENSEN and

ON (Pin 4/Pin 1): On Control Input. The ON pin has a

threshold of 1.23V with 75mV of hysteresis. An active high

will cause 10

µA to flow from the GATE pin, ramping up the

supplies. An active low pulls 10

µA from the GATE pin,

ramping the supplies down. Pulling the ON pin below 0.4V

resets the electronic circuit breaker in the LTC2925. If a

powered.

SDTMR (Pin 5/Pin 2): Shutdown Timer. A capacitor from

SDTMR to GND sets the delay time between the ON pin

transitioning high (which releases the SDx pins) and the

supplies beginning to ramp-up. Float SDTMR when it is

unused.

SD1, SD2, SD3 (Pins 6, 7, 8/Pins 3, 4, 5): Outputs for

Slave Supply Shutdowns. The SDx pins are open-drain

outputs that hold the shutdown (RUN/SS) pins of the slave

supplies low until the ON pin is pulled above 1.23V. The

SDx pins will be pulled low again when RAMP <100mV and

ON <1.23V. If a slave supply is capable of operating with

an input supply that is lower than the LTC2925’s minimum

operating voltage of 2.9V, the SDx pins can be used to hold

off the slave supplies. Each SDx pin is capable of sinking

greater than 1mA with supplies as low as 2.3V.

RAMPBUF (Pin 9/Pin 6): Ramp Buffer Output. Provides a

low impedance buffered version of the signal on the RAMP

pin. This buffered output drives the resistive dividers that

connect to the TRACKx pins. Limit the capacitance at the

RAMPBUF pin to less than 100pF.