MP3352 – INTEGRATED PHOTO FLASH CHARGER AND IGBT DRIVER

MP3352 Rev. 0.9

www.MonolithicPower.com

7

11/12/2008

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2008 MPS. All Rights Reserved.

APPLICATION INFORMATION

MP3352 controlled flyback charger operates in

critical conduction mode with peak current set by

ISET pin. Output voltage is divided down through

R1, R2 from the positive terminal of the

transformer secondary and compares with 1.20V

at FB pin. The low to high transition of CHARGE

pin will enable the flyback converter to switch.

Charger may enter DCM mode when charge is

close to full and actual OFF time is less than

RDYB will be pulled low once the flash capacitor

is charged to 300V, a value set by R2, R5, and

R8.

When the part is ready the internal

dissipation is reduced to just the circuits for IGBT

driver. Toggle CHARGE pin will start charge

again. Bringing CHARGE pin low terminates the

power delivery and put the part in shutdown. A

starved power source. If the ON time exceeds

DCM Comparator

DCM boundary is reached when V (FB) drops to

zero. The DCM comparator compares V (FB) and

a fixed offset voltage of 25mV to account for the

comparator delay.

Charge Speed

The

output

capacitor

charging

speed

is

determined by:

OUT

IN

LIM

charge

V

N

V

1

I

T

+

∝

Setting Peak Charge Current

SET

SET

50

R(K )

I(A)

Ω=

is 20kΩ.

Primary Inductance

The primary inductance is calculated based on

the minimum off time period:

peak

off

min,

out

primary

NI

T

V

L

≥

Turns Ratio

The minimum turns

ratio of the flyback

transformer is obtained as:

in

ds

out

V

V

V

N

−

≥

Table 1—Recommended Transformer Table

Part Number

Description

Size (L×W×H)

Vendor

TTRN-038S

T-19-060

Amax

6.4mm×7.7mm×4.0mm

TOKYO Coil

750310448

Amax

7mm×10mm×5mm

Wurth

Electronics

LDT565630T-042

only

5.8mm×5.8mm×3mm

TDK