LT3468 Ver la hoja de datos (PDF) - Linear Technology
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LT3468 Datasheet PDF : 12 Pages
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LT3468/LT3468-1/LT3468-2
APPLICATIO S I FOR ATIO
going too far below ground. The diode is required for
proper operation of the circuit. The recommended diode
should be a Schottky diode with at least a 500mA peak
forward current capability. The diode forward voltage drop
should be 600mV or less at 500mA of forward current.
Reverse voltage rating should be 40V or higher. Table 4
shows various recommended clamping diodes.
Table 4. Recommended Clamp Diodes
PART
MAX REVERSE VOLTAGE
(V)
ZHCS400
40
B0540W
40
MA2Z720
40
VENDOR
Zetex
(631) 360-2222
www.zetex.com
Diodes Inc.
(805) 446-4800
www.diodes.com
Panasonic
(408) 487-9510
www.panasonic.co.jp
Keep the area for the high voltage end of the secondary as
small as possible. Also note the larger than minimum
spacing for all high voltage nodes in order to meet break-
down voltage requirements for the circuit board. It is
imperative to keep the electrical path formed by C1, the
primary of T1, and the LT3468/LT3468-1/LT3468-2 as
short as possible. If this path is haphazardly made long, it
will effectively increase the leakage inductance of T1,
which may result in an overvoltage condition on the SW
pin.
VIN
R1
DONE
CHARGE
4
5
C1
D1
(DUAL DIODE)
3
•
COUT +
• T1
PHOTOFLASH
CAPACITOR
2
1
D2
Board Layout
The high voltage operation of the LT3468/LT3468-1/
LT3468-2 demands careful attention to board layout. You
will not get advertised performance with careless layout.
Figure 5 shows the recommended component placement.
3468 F05
Figure 5. Suggested Layout: Keep Electrical Path Formed by C1,
Transformer Primary and LT3468/LT3468-1/LT3468-2 Short.
TYPICAL APPLICATIO S
VIN
2.5V TO 8V
C1
4.7µF
T1
1:10.2
D1
1
4
2
5
+
R1
VIN
SW
D2
100k
LT3468
DONE
DONE
GND
320V
COUT
PHOTOFLASH
CAPACITOR
CHARGE
CHARGE
C1: 4.7µF, X5R OR X7R, 10V
T1: KIJIMA MUSEN PART# SBL-5.6-1, LPRI = 10µH, N = 10.2
D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES
D2: ZETEX ZHCS400 OR EQUIVALENT
R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
3468 F06
Figure 6. LT3468 Photoflash Charger Uses
High Efficiency 4mm Tall Transformer
10
VIN
2.5V TO 8V
C1
4.7µF
T1
1:10.2
D1
4
5
3
6
+
R1
100k
VIN
SW
D2
LT3468-1
DONE
DONE
GND
320V
COUT
PHOTOFLASH
CAPACITOR
CHARGE
CHARGE
C1: 4.7µF, X5R OR X7R, 10V
T1: KIJIMA MUSEN PART# SBL-5.6S-1, LPRI = 24µH, N = 10.2
D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES
D2: ZETEX ZHCS400 OR EQUIVALENT
R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
3468 F07
Figure 7. LT3468-1 Photoflash Charger Uses
High Efficiency 3mm Tall Transformer
346812f
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