5V or Adjustable, Low-Voltage,

Step-Up DC-DC Controller

6

_______________________________________________________________________________________

______________________________________________________________Pin Description

PIN

NAME

FUNCTION

1

EXT

Gate Drive for External N-Channel Power Transistor

2

OUT

3

FB

4

SHDN

5

REF

6

AGND

Analog Ground

7

GND

High-Current Ground Return for the Output Driver

8

CS

Power-Supply and Voltage-Sense Input. Always connect OUT to circuit output.

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 the input voltage (due to the DC path from the input voltage to the output). 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 AGND.

1.5V

REFERENCE

Q

TRIG

Q

S

F/F

R

Q

TRIG

LOW-VOLTAGE

OSCILLATOR

2.5V

0.1V

MAX ON-TIME

ONE-SHOT

MIN OFF-TIME

ONE-SHOT

CURRENT-SENSE

AMPLIFIER

DUAL-MODE

COMPARATOR

FB

REF

50mV

ERROR

COMPARATOR

SHDN

OUT

LOW-VOLTAGE

START-UP

COMPARATOR

EXT

CS

BIAS

CIRCUITRY

N

MAX608

2.3

µs

16

µs

Figure 1. Functional Diagram