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| LTC3400-1 Datasheet, PDF (4/12 Pages) Linear Technology – 600mA, 1.2MHz Micropower Synchronous Boost Converter in ThinSOT | |||
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LTC3400-1
PI FU CTIO S
SW (Pin 1): Switch Pin. Connect inductor between SW
and VIN. Optional Schottky diode is connected between
SW and VOUT. Keep these PCB trace lengths as short and
wide as possible to reduce EMI and voltage overshoot. If
the inductor current falls to zero, or SHDN is low, an
internal 100⦠antiringing switch is connected from SW to
VIN to minimize EMI.
GND (Pin 2): Signal and Power Ground. Provide a short
direct PCB path between GND and the (â) side of the output
capacitor(s).
FB (Pin 3): Feedback Input to the gm Error Amplifier.
Connect resistor divider tap to this pin. The output voltage
can be adjusted from 2.5V to 5V by:
VOUT = 1.23V ⢠[1 + (R1/R2)]
SHDN (Pin 4): Logic Controlled Shutdown Input.
SHDN = High: Normal free running operation, 1.2MHz
typical operating frequency.
SHDN = Low: Shutdown, quiescent current < 1µA.
100⦠connected between SW and VIN. VIN is connected
to VOUT through the internal P-channel MOSFET syn-
chronous rectifier and external inductor.
Typically, SHDN should be connected to VIN through a 1M
pull-up resistor.
VOUT (Pin 5): Output Voltage Sense Input and Drain of the
Internal Synchronous Rectifier MOSFET. Bias is derived
from VOUT. PCB trace length from VOUT to the output filter
capacitor(s) should be as short and wide as possible. VOUT
is connected to VIN in shutdown through the internal
P-channel MOSFET synchronous rectifier.
VIN (Pin 6): Battery Input Voltage. The device gets its
start-up bias from VIN. Once VOUT exceeds VIN, bias
comes from VOUT. Thus, once started, operation is com-
pletely independent from VIN. Operation is only limited by
the output power level and the batteryâs internal series
resistance.
BLOCK DIAGRA
+ SINGLE
CELL
INPUT
6 VIN
START-UP
OSC
CIN
1µF
A A/B
MUX
B
L1
4.7µH
1 SW
VOUT
GOOD
2.3V
0.45â¦
OPTIONAL
SCHOTTKY
VOUT
5
3.3V
OUTPUT
RAMP
GEN
1.2MHz
PWM
CONTROL
PWM
COMPARATOR
SLOPE
COMP
SHUTDOWN
SYNC
DRIVE
CONTROL
Σ
SLEEP
Burst Mode
OPERATION
CONTROL
RC
80k
CC
150pF
CP2
2.5pF
0.35â¦
CURRENT
SENSE
CFF
(OPTIONAL)
gm
ERROR
AMP
FB
3
1.23V
REF
R1
1.02M
1%
(EXTERNAL)
COUT
4.7µF
R2
604k
1%
(EXTERNAL)
4
SHDN
4
SHUTDOWN
CONTROL
SHUTDOWN
2 GND
34001 BD
34001f
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