DC711A-C - ANALOG DEVICES - Product.Network

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC711

PHOTOFLASH CAPACITOR CHARGER, HIGH VOLTAGE SUPPLY

LT3468ES5/ LT3468ES5-1/ LT3468ES5-2

DESCRIPTION

Demonstration circuit DC711 is a DC-DC flyback

converter using the highly integrated LT3468ES5/

LT3468ES5-1/ LT3468ES-2 to rapidly charge a

photoflash capacitor up to 320V for photoflash

applications. It demonstrates a simple application

circuit operating in high efficiency and shows

appropriate layout techniques for the

LT3468ES5/LT3468ES5-1/LT3468ES5-2. The circuit

uses small surface mount components and has very

small board space compared to conventional

solutions. This demonstration circuit is particularly

useful for applications such as camera flash, PDA and

cell phone flash and high voltage power supplies that

require high efficiency and extremely small size.

Design files for this circuit board are available.

Call the LTC factory.

LT is a trademark of Linear Technology Corporation

Table 1.

Demo board Assembly versions

ASSEMBLY VERSIONS U1 I

SW-PK

(PEAK SWITCH CURRENT

LIMIT)

DC711A-A LT3468ES5 1.4A

DC711A-B LT3468ES5-1 0.7A

DC711A-C LT3468ES5-2 1A

QUICK START PROCEDURE

Demonstration circuit DC711 is easy to set up to

evaluate the performance of the LT3468ES5

(LT3468ES5-1/-2). Refer to Figure 1 for proper

measurement equipment setup and follow the proce-

dure below:

NOTE:

When measuring the input voltage ripple, care

must be taken to avoid a long ground lead on the os-

cilloscope probe. Measure the input voltage ripple by

touching the probe tip directly across the VIN or

VOUT and GND terminals. See Figure 2 for proper

scope probe technique.

NOTE:

For safe operation, always shield the circuit

when power is on, and always discharge the high

voltage output capacitor after power is off.

With power off, connect input power source Vbatt

to the VIN and GND terminals. Input voltage is lim-

ited to between 2.5V to 8V.

Connect a function generator to the Charge and

GND terminals. Input voltage is limited to between

2.5V to 8V. A low (<0.3V) to high (>1V) transition

on the Charge pin will initiate charge cycle.

Connect load (such as a 70uF, 330V photoflash ca-

pacitor) between the +Strobe Cap and –Strobe Cap

terminals.

Slowly turn on power source Vbatt. Turn on the

pulse generator to send an edge triggered one-shot

from low (<0.3V) to high (>1V) to enable charge

operation. Check for the proper output voltages.

Vout= 320V.

Measure the charge time (VOUT rise time from 0V

to 320V) from scope. The photoflash capacitor

should be pre-charged a few times before the

measurement test due to its memory characteris-

tic.

For single source operation, connect Charge termi-

nal to VIN through an on/off switch. Toggle the

switch to enable charge operation. Warning: Oper-

ate by high voltage trained personnel only.