MP3352 – INTEGRATED PHOTO FLASH CHARGER AND IGBT DRIVER

MP3352 Rev. 0.9

www.MonolithicPower.com

8

11/12/2008

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Setting Output Voltage

The output voltage is set by selecting the

resistive voltage divider ratio. If we use 1.2kΩ the

low side resistor (R8) of the voltage divider, we

can determine the high side resistor (R2, R5) by

the equation:

out

FB

25

8

FB

VV

1

RR

R

2V

−

==

Typical

values

are

R2=R5=150kΩ

and

R8=1.2kΩ.

Output Diode Selection

The reverse voltage of the output diode is

determined by:

in

out

D

NV

V

V

+

=

Quench Function

MP3352

has

build-in

quench

function

to

accurately control exposure time and preserve

power, thus to extend battery life.

When output capacitor is fully charged and

IGBTIN (pin14) is set high, internal IGBT driver

drives the gate of IGBT high and fires the flash

strobe. Once the photo transistor gets the flash

light, it starts to charge C and the voltage of C

represents the total exposure. IGBT will be off

when the voltage on C exceeds the control

voltage on QREF (Pin3)

MP3352

SW

RDYB

SW

FB

ISET

IGBTOUT

QREF

QSNS

GND

NC

NC

IGBTIN

PGND

PGND

CHARGE

VIN

Control Voltage

Photo Transistor

C

6

9

15

3

4

2

10

11

7

8

14

5

1

16

13

12

TYPICAL APPLICATION CIRCUIT

MP3352

VIN

CHARGE

Xenon Flash

RDYB

QREF

QSNS

GND

PGND

PGND

IGBTIN

IGBTOUT

ISET

FB

SW

SW

NC NC

T1

T2

Q2

Q1

VIN

CHAG

RDYB

QREF

QSNS

IGBTIN

VCC

6

9

15

3

4

2

10 11

7

8

14

5

1

16

13

12

+

Figure 2—Application Circuit for 2 Cell Li-Ion Battery Photo Flash Charger