5V/3.3V/3V or Adjustable, High-Efficiency,

6

_______________________________________________________________________________________

MAX649

LINE-TRANSIENT RESPONSE

250

µs/div

A

B

A: INPUT VOLTAGE (7V & 12V), 5V/div

B: 5V OUT, AC COUPLED, 100mV/div

_____________________________Typical Operating Characteristics (continued)

MAX649

LOAD-TRANSIENT RESPONSE

250

µs/div

A

B

A: LOAD CURRENT (100mA & 1A), 500mA/div

B: 5V OUTPUT VOLTAGE, AC COUPLED, 50mV/div

______________________________________________________________Pin Description

Positive power-supply input

V+

5

CS

6

Gate drive for external P-channel MOSFET. EXT swings between V+ and GND.

EXT

7

Ground

GND

8

1.5V reference output that can source 100µA. Bypass with 0.1µF.

REF

4

SHDN

3

PIN

FB

2

OUT

1

FUNCTION

NAME

Sense input for fixed 5V, 3.3V, or 3V output operation. OUT is internally connected to the on-chip voltage divider.

Although it is connected to the output of the circuit, the OUT pin does not supply current.

Feedback input. Connect to GND for fixed-output operation. Connect a resistor divider between OUT, FB,

and GND for adjustable-output operation. See

Setting the Output Voltage section.

Active-high TTL/CMOS logic-level input. Part is placed in shutdown when SHDN is driven high. In shutdown mode,

the reference and the external MOSFET are turned off, and OUT = 0V. Connect to GND for normal operation.

Current-sense input. Connect current-sense resistor between V+ and CS. When the voltage across the

resistor equals the current-limit trip level, the external MOSFET is turned off.

MAX649

SHUTDOWN RESPONSE TIME

1ms/div

A

B

A: SHDN INPUT VOLTAGE (0V & 5V), 2V/div

B: 5V OUTPUT VOLTAGE, 2V/div