Digitally Adjustable LCD Bias Supply

4

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PIN

NAME

FUNCTION

1

V+

+2V to +6V Input Voltage to power the MAX749 and external circuitry. When using an external

P-channel MOSFET, V+ must exceed the MOSFET’s gate threshold voltage.

2

ADJ

Logic Input. When CTRL is high, a rising edge on ADJ increments an internal counter. When CTRL is

low, the counter is reset to mid-scale when ADJ is high. When ADJ is low, the counter does not

change (regardless of activity on CTRL) as long as V+ is applied.

3

CTRL

Logic Input. When CTRL and ADJ are low, the MAX749 is shut down, but the counter is not reset.

When CTRL is low, the counter is reset to mid-scale when ADJ is high. The device is always on when

CTRL is high.

4

FB

5

GND

Ground

6

DLOW

Output Driver Low. Connect to DHI when using an external P-channel MOSFET. When using an

mum base-drive current.

7

DHI

Output Driver High. Connect to the gate of the external P-channel transistor, or to the base of the

external PNP transistor.

8

CS

Current-Sense Input. The external transistor is turned off when current through the sense resistor,

OUTPUT

VOLTAGE

LOAD

CURRENT

10mA/div

0mA

LOAD-TRANSIENT RESPONSE

TRANSISTOR = ZTX750

50

µs/div

TRANSISTOR = ZTX750

OUTPUT

VOLTAGE

INPUT

VOLTAGE

1 V/div

0V

LINE-TRANSIENT RESPONSE

TRANSISTOR = ZTX750

50ms/div

____________________________Typical Operating Characteristics (continued)

______________________________________________________________Pin Description