QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 661
PHOTOFLASH CAPACITOR CHARGER, HIGH VOLTAGE SUPPLY
LT3468ES5/LT3468ES5-1
DESCRIPTION
Demonstration circuit 661 is a DC/DC flyback
converter
using
the
highly
integrated
LT
®
3468ES5/LT
®
3468ES5-1 to rapidly charge a pho-
toflash capacitor up to 320V for photoflash applica-
tions. It demonstrates a simple application circuit op-
erating in high efficiency and shows appropriate lay-
out techniques for the LT3468ES5/LT3468ES5-1. 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 re-
quire 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
DC661A-A
DC661A-B
U1
LT3468ES5
LT3468ES5-1
I
SW-PK
(PEAK SWITCH CURRENT
LIMIT)
1.4A
0.6A
QUICK START PROCEDURE
Demonstration circuit 661 is easy to set up to evalu-
ate the performance of the LT3468ES5/LT3468ES5-1.
Refer to Figure 1 for proper measurement equipment
setup and follow the procedure below:
NOTE:
When measuring the input or output voltage
2.
Connect second power source Vcharge to the
Charge and Gnd terminal. Input voltage is limited
to 2.5V to 8V.
3.
Connect load (a 220uF, 350V photoflash capacitor)
ripple, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or out-
put 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
between the +STROBE CAP and -STROBE CAP
terminals.
4.
Slowly turn on power source Vin. Turn Vcharge on
to enable charge operation. Check for the proper
output voltages. Vout= 320V
NOTE:
If there is no output, temporarily disconnect
when power is on, and always discharge the high
voltage output capacitor after power is off.
1.
With power off, connect input power source Vin to
the load and make sure that Vcharge is applied to
Charge terminal.
5.
For single source operation, connect Charge termi-
the Vin and Gnd terminals. Input voltage is limited
to 2.5V to 8V.
nal to Vin through an on/off switch. Turn on the
switch to enable charge operation.
Warning: Operate by high voltage trained personnel
only.
1
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