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LTC1753

1753fa

FU CTIO TABLES

Table 2. Rated Output Voltage (cont)

INPUT PIN

RATED OUTPUT

VID4

VID3

VID2

VID1

VID0

VOLTAGE (V)

0011

1.90

0010

1.95

0001

2.00

0000

2.05

1111

SHDN

1110

2.1

1101

2.2

1100

2.3

1011

2.4

1010

2.5

1001

2.6

1000

2.7

0111

2.8

0110

2.9

0101

3.0

0100

3.1

0011

3.2

0010

3.3

0001

3.4

0000

3.5

* With external pull-up resistor

** With respect to the output voltage selected in Table 2

X Don’t care

Table 2. Rated Output Voltage

INPUT PIN

RATED OUTPUT

VID4

VID3

VID2

VID1

VID0

VOLTAGE (V)

1111

1.30

1110

1.35

1101

1.40

1100

1.45

1011

1.50

1010

1.55

1001

1.60

1000

1.65

0111

1.70

0110

1.75

0101

1.80

0100

1.85

Table 1. PWRGD and FAULT Logic

INPUT

OUTPUT*

OUTEN

VSENSE**

FAULT

PWRGD

< 97%

> 97%

< 103%

>103%

> 113%

OVERVIEW

The LTC1753 is a voltage feedback, synchronous switch-

ing regulator controller (see Block Diagram) designed for

use in high power, low voltage step-down (buck) convert-

ers. It includes an on-chip DAC to control the output

voltage, a PWM generator, a precision reference trimmed

±1%, two high power MOSFET gate drivers and all the

necessary feedback and control circuitry to form a com-

plete switching regulator circuit.

The LTC1753 includes a current limit sensing circuit that

uses the upper external power MOSFET as a current

sensing element, eliminating the need for an external

sense resistor. Once the current comparator, CC, detects

an overcurrent condition, the duty cycle is reduced by

discharging the soft-start capacitor through a voltage-

controlled current source. Under severe overloads or

output short circuit conditions, the chip will be repeatedly

forced into soft-start until the short is removed, prevent-

ing the external components from being damaged. Under

output overvoltage conditions, the MOSFET drivers will be

disabled permanently until the chip power supply is

recycled or the OUTEN pin is toggled.

OUTEN can optionally be connected to an external nega-

tive temperature coefficient (NTC) thermistor placed near

the external MOSFETs or the microprocessor. Two thresh-

old levels are provided internally. When OUTEN drops to

1.7V, the G1 and G2 pins will be forced low. If OUTEN is

pulled below 1.2V, the LTC1753 will go into shutdown

mode, cutting the supply current to a minimum. If thermal

shutdown is not required, OUTEN can be connected to a

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