QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 646
STROBE CAPACITOR CHARGER, HIGH VOLTAGE SUPPLY
1
LT3420
DESCRIPTION
Demonstration circuit 646 is a DC-DC flyback
converter using the LT
®
3420EMS to rapidly charge an
output capacitor to 300V for photoflash applications.
It demonstrates a simple application circuit operating
in high efficiency and shows appropriate layout
techniques for the LT3420EMS. 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 digital cameras and high voltage
supplies that require high efficiency and small size.
Design files for this circuit board are available. Call the
LTC factory.
LT is a trademark of Linear Technology Corporation.
QUICK START PROCEDURE
Demonstration circuit 646 is easy to set up to evaluate the
performance of the LT3420EMS. Refer to Figure 1 for proper
measurement equipment setup and follow the procedure
below:
NOTE:
When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the V
IN
or
V
OUT
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.
Warning: Operate by high voltage trained personnel only
1.
With power off, connect input power source Vbatt to the
Vbatt and GND terminals. Input voltage is limited to
between 1.8V to 6V.
2.
Set JP1 to DISCONNECT position for separate input
power operation. Connect input power source Vcc to the
Vcc and GND terminals, and limit the input voltage from
2.3V to 6V.
3.
Connect load (a 220uF, 350V photoflash capacitor)
between the +Strobe Cap and –Strobe Cap terminals.
4.
Set JP2 to ON position to enable Charge operation.
5.
Slowly turn on power source Vbatt and Vcc. Check for the
proper output voltages. V
OUT
= 300V.
NOTE:
If there is no output, temporarily disconnect the
load and make sure that JP2 is set to ON position.
6.
For single source operation, set the input source selector
Jumper JP1 to CONNECT position. Remove the
connection of power source Vcc. Limit the input voltage
from 2.3V to 6V. Vcc will be powered from Vbatt.
7.
To shut down the circuit, connect the JP2 to OFF position.
The output capacitor charging is disabled.
