AIC1652

MICROPOWER INVERTING DC/DC CONVERTER

SPEC NO: DS-1652-02 DEC 27, 00

ANALOG INTEGRATIONS CORPORATION

www.analog.com.tw

4F, 9 Industry E. 9th Road, Science-based IndustrialPark , Hsinchu, Taiwan, R.O.C.

TEL: (8863)577-2500 FAX:(8863)577-2510

4

PIN 1:

VIN

- 2.4V to 7V input supply voltage.

PIN 2:

VREF - 1.22V reference output. Bypass with

a

0.047

µF capacitor to GND.

Sourcing capability is guaranteed to

be greater than 250

µA.

PIN 3:

SHDN - Logic input to shutdown the chip.

>1.5V = normal operation,

GND = shutdown

In shutdown mode DLOW and DHI

pins are at high level.

PIN 4:

FB

- Feedback signal input to sense

ground. Connecting a resistor R1 to

yields the output voltage:

PIN 5:

GND - Power ground.

PIN 6: DLOW - Driver sinking output. Connected to

DHI when using an external P-

channel MOSFET. When using an

external

PNP

bipolar

transistor,

connect a resistor RB from this pin

inductor and PNP bipolar transistor.

By adjusting the RB value, efficiency

can be optimized.

PIN 7: DHI

- Driver sourcing output. Connect to

gate

of

the

external

P-channel

MOSFET or base of the PNP bipolar

transistor.

PIN 8:

CL

- Current-limit input. This pin clamps

the switch peak current to prevent

over-current damage to the external

switch.

2

4

6

8

0

0.2

0.4

0.6

0.8

100

µH

120

µH

150

µH

180

µH

220

µH

Inductor Value

Typical Application Circuit

The typical application circuit generates an adjustable

negative voltage for contrast bias of LCD displays. Effi-

ciency and output power can be optimized by using ap-

propriate inductor and switch. The following formulas

provide a guideline for determining the optimal component

values:

L

=

(11.1 0.15

V )

V

I

V

IN

IN

OUT

OUT

−

×

×

×

PNP :

V

V

V

CEO

IN

OUT

>

+

I

200

I

V

C, MAX

OUT

IN

≥

×

V

0. 4 V at I

= 200

I

V

CE

C

OUT

IN

<

×

and

10

β =

RB

RB in

Ω