lt3468es5-trpbf Linear Technology Corporation, lt3468es5-trpbf Datasheet - Page 6

• Manufacturer Part Number: lt3468es5-trpbf
• Description: Lt3468-1 - Photoflash Capacitor Chargers In Thinsot?
• Manufacturer: Linear Technology Corporation

BLOCK DIAGRA
PI FU CTIO S
LT3468/LT3468-1/LT3468-2
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.
GND (Pin 2): Ground. Tie directly to local ground plane.
6
CHARGE
N
U
=
V
4
LT3468: R
LT3468-2: R
LT3468-1: R
MASTER
OUT
LATCH
OUT
31 5 .
Q3
U
3
DONE
+ 2
SHOT
is the desired output voltage.
ONE-
SENSE
Q
S
SENSE
SENSE
CHIP ENABLE
= 0.015Ω
Q
R
ENABLE
= 0.022Ω
= 0.03Ω
TO BATTERY
U
Q1
W
V
OUT
A2
COMPARATOR
+
–
C1
5
REFERENCE
V
IN
1.25V
Q2
R1
2.5k
60k
R2
Figure 1
SHOT
ONE-
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. This pin must be brought
high (>1V) to enable the part. 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. You may bring this
pin low during a charge cycle to halt charging at any time.
V
with a good quality ceramic capacitor. Input supply must
be 2.5V or higher.
IN
R
(Pin 5): Input Supply Pin. Must be locally bypassed
S
DCM COMPARATOR
Q
A1
A3
+
–
+
–
DRIVER
+
–
20mV
+–
36mV
PRIMARY
1
Q1
R
SW
SENSE
3486 BD
T1
2
D2
GND
SECONDARY
D1
+
C
PHOTOFLASH
CAPACITOR
V
OUT
OUT
346812fa