5V/12V/15V or Adjustable, High-Efficiency,

_______________________________________________________________________________________

7

A: SHDN, 2V/div

MAX770

EXITING SHUTDOWN

A

B

0

0

200

µs/div

______________________________________________________________Pin Description

____________________________Typical Operating Characteristics (continued)

PIN

NAME

FUNCTION

MAX773

1

—

EXT

Gate drive for external N-channel power transistor

2

3

V+

3

6

FB

4

7

SHDN

5

8

REF

6

—

AGND

Analog ground

7

9

GND

High-current ground return for the output driver

8

11

CS

—

1

V12

—

2

V5

MAX770

MAX771

MAX772

Power-supply input. Also acts as a voltage-sense point when in bootstrapped mode for the

MAX770/MAX771/MAX772, or as a shunt regulator when SGND is connected to ground for the

MAX773. Bypass to SGND with 0.1

µF when using the shunt regulator.

Feedback input for adjustable-output operation. Connect to ground for fixed-output operation. Use

a resistor divider network to adjust the output voltage. See

Setting the Output Voltage section.

below V+ (due to the DC path from V+ to the output) and the supply current drops to 5

µA

maximum. Connect to ground for normal operation.

1.5V reference output that can source 100

µA for external loads. Bypass to GND with 0.1µF.

The reference is disabled in shutdown.

Positive input to the current-sense amplifier. Connect the current-sense resistor between CS and GND.

Leave unconnected for adjustable-output operation.

unconnected for adjustable-output operation.

—

4

LBO

—

5

LBI

Input to the internal low-battery comparator. Tie to GND or V+ if not used.

—

10

SGND

Shunt regulator ground. Leave unconnected if the shunt regulator is not used.

Low-battery output is an open-drain output that goes low when LBI is less than 1.5V. Connect to V+

through a pull-up resistor. Leave floating if not used. LBO is high impedance in shutdown mode.