LTC3429 Datasheet, PDF (5/12 Pages) Linear Technology – 600mA, 500kHz Micropower Synchronous Boost Converter with Output Disconnect

LTC3429/LTC3429B
PI FU CTIO S
SW (Pin 1): Switch Pin. Connect inductor between SW
and V_IN. 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
150Ω antiringing switch is connected from SW to V_IN to
minimize EMI.
GND (Pin 2): Signal and Power Ground. Provide a short
direct PCB path between GND and the (–) side of the output
capacitor(s).
FB (Pin 3): Feedback Input to the g_m Error Amplifier.
Connect resistor divider tap to this pin. The output voltage
can be adjusted from 2.5V to 5V by:
V_OUT = 1.23V • [1 + (R1/R2)]
SHDN (Pin 4): Logic Controlled Shutdown Input.
SHDN = High: Normal free running operation, 500kHz
typical operating frequency.
SHDN = Low: Shutdown, quiescent current < 1µA.
Output capacitor can be completely discharged through
the load or feedback resistors. A 150Ω resistor is
internally connected between SW and V_IN.
V_OUT (Pin 5): Output Voltage Sense Input and Drain of the
Internal Synchronous Rectifier MOSFET. Bias is derived
from V_OUT. PCB trace length from V_OUT to the output filter
capacitor(s) should be as short and wide as possible. V_OUT
is completely disconnected from V_IN when SHDN is low
due to the output disconnect feature.
V_IN (Pin 6): Battery Input Voltage. The device gets its
start-up bias from V_IN. Once V_OUT exceeds V_IN, bias
comes from V_OUT. Thus, once started, operation is com-
pletely independent from V_IN. Operation is only limited by
the output power level and the battery’s internal series
resistance.
BLOCK DIAGRA
+
1V TO 4.4V
6 V_IN
L1
C_IN
1 SW
START-UP
OSC
A A/B
MUX
B
V_OUT
GOOD
2.3V
0.45Ω
V_IN
WELL
SWITCH
V_OUT
5
2.5V TO 5V
RAMP
GEN
500kHz
PWM
CONTROL
PWM
COMPARATOR
SLOPE
COMP
SLEEP
Burst Mode
OPERATION
CONTROL
SYNC
DRIVE
CONTROL
Σ
0.35Ω
CURRENT
SENSE
C_PL
(OPTIONAL)
R1
R_C
80k
C_C
150pF
C_P2
2.5pF
g_m
ERROR
AMP
FB
3
1.23V
REF
R2
C_OUT
SHDN
4
SHUTDOWN
CONTROL
SHUTDOWN
2 GND
3429 BD
3429fa
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