LT3468 데이터 시트보기 (PDF) - Linear Technology
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LT3468 Datasheet PDF : 12 Pages
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LT3468/LT3468-1/LT3468-2
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:
N = VOUT + 2
31. 5
Where: VOUT is the desired output voltage.
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.
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.
VIN (Pin 5): Input Supply Pin. Must be locally bypassed
with a good quality ceramic capacitor. Input supply must
be 2.5V or higher.
BLOCK DIAGRA
TO BATTERY
C1
T1
D1
PRIMARY
SECONDARY
D2
VOUT
DONE
3
5 VIN
R2
60k
SW
1
Q3
DCM COMPARATOR
MASTER
LATCH
Q
S
Q1
ENABLE
Q
R
+
A2
–
Q2
R1
2.5k
1.25V
REFERENCE
CHARGE
4
ONE-
SHOT
VOUT COMPARATOR
CHIP ENABLE
LT3468: RSENSE = 0.015Ω
LT3468-2: RSENSE = 0.022Ω
LT3468-1: RSENSE = 0.03Ω
ONE-
SHOT
+
A3
–
–+ 36mV
DRIVER
S
R
Q
Q1
Figure 1
+
A1
–
20mV
+–
RSENSE
GND
2
3486 BD
6
+ COUT
PHOTOFLASH
CAPACITOR
346812f
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