LT3468 Linear Technology, LT3468 Datasheet - Page 9

• Manufacturer Part Number: LT3468
• Description: Photoflash Capacitor Charger in ThinSOT
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
Capacitor Selection
For the input bypass capacitor, a high quality X5R or X7R
type should be used. Make sure the voltage capability of
the part is adequate.
Output Diode Selection
The rectifying diode(s) should be low capacitance type
with sufficient reverse voltage and forward current rat-
ings. The peak reverse voltage that the diode(s) will see is
approximately:
The peak current of the diode is simply:
Table 3. Recommended Output Diodes
PART
GSD2004S
(Dual Diode)
BAV23S
(Dual Diode)
1SS306
(Dual Diode)
I
I
V
PK SEC
PK SEC
PK R
MAX REVERSE VOLTAGE
V
1 4 .
OUT
0 7 .
N
N
(LT3468)
(LT3468-1)
U
2x300
2x250
2x250
(V)
N V
•
IN
U
Table 4. Recommended Clamp Diodes
PART
ZHCS400
B0540W
MAX FORWARD CONTINUOUS CURRENT
W
MAX REVERSE VOLTAGE
U
(mA)
225
225
100
(V)
40
40
For the circuit of Figure 1 with V
I
recommended for most LT3468/LT3468-1 applications.
Another option is to use the BAV23S dual silicon diodes.
Toshiba makes a dual diode named 1SS306 which also
meets all the requirements. Table 3 shows the various
diodes and relevant specifications. Use the appropriate
number of diodes to achieve the necessary reverse break-
down voltage.
SW Pin Clamp Diode Selection
The diode D2 in Figure 1 is needed to clamp the SW node.
Due to the new control scheme of the LT3468/LT3468-1,
the SW node may go below ground during a switch cycle.
The clamp diode prevents the SW node from going too
far below ground. The diode is required for proper opera-
tion of the circuit. The recommended diode should be a
Schottky diode with at least a 500mA peak forward current
capability. Reverse voltage rating should be 40V or higher.
Table 4 shows various recommended clamping diodes.
PK-SEC
is 137mA. The GSD2004S dual silicon diode is
www.diodes.com
[phone]
www.zetex.com
[phone]
Diodes Inc.
CAPACITANCE
VENDOR
Zetex
(pF)
5
5
3
LT3468/LT3468-1
IN
www.semicon.toshiba.co.jp
of 5V, V
Philips Semiconductor
www.philips.com
www.vishay.com
[phone]
[phone]
[phone]
VENDOR
Toshiba
Vishay
PK-R
is 371V and
34681i
9