LT3468 Linear Technology, LT3468 Datasheet - Page 5

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

PI FU CTIO S
SW (Pin 1): Switch Pin. This is the collector of the internal
NPN Power switch. Minimize the metal trace area con-
nected to this pin to minimize EMI. Tie one side of the
primary of the transformer to this pin. The target output
voltage is set by the turns ratio of the transformer.
Choose Turns Ratio N by the following equation:
Where: V
You must tie a Schottky diode from GND to SW, with the
anode at GND for proper operation of the circuit. Please
refer to the applications section for further information.
N
U
V
OUT
OUT
31 5 .
U
is the desired output voltage.
2
U
GND (Pin 2): Ground. Tie directly to local ground plane.
DONE (Pin 3): Open NPN Collector Indication Pin. When
target output voltage is reached, NPN turns on. This pin
needs a pull-up resistor or current source.
CHARGE (Pin 4): Charge Pin. A low (<0.3V) to high (>1V)
transition on this pin puts the part into power delivery
mode. Once the target output voltage is reached, the part
will stop charging the output. Toggle this pin to start
charging again. Ground to shut down.
V
with a good quality ceramic capacitor. Input supply must
be 2.5V or higher.
IN
(Pin 5): Input Supply Pin. Must be locally bypassed
LT3468/LT3468-1
34681i
5