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| LTC3533 Datasheet, PDF (7/16 Pages) Linear Technology – 2A Wide Input Voltage Synchronous Buck-Boost DC/DC Converter | |||
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BLOCK DIAGRAM
VIN
1.8V TO 5.5V
SW1
SW2
SW A
SW B
GATE
DRIVERS
AND
ANTI-CROSS
CONDUCTION
SW D
â0.5A
SW C
ISENSE
AMP
REVERSE
CURRENT
LIMIT
LTC3533
VOUT
R1
RT
RT
+
4.5A
â
+
1.6V
â
SUPPLY
CURRENT
LIMIT
UVLO
PWM
LOGIC
AND
OUTPUT
PHASING
PWM
COMPARATORS
OSC
ERROR
AMP
1.22V
FB
CLAMP
VC
R2
SLEEP
BURST
BURST MODE
OPERATION
CONTROL
0 = BURST MODE
1 = FIXED FREQUENCY
GND
RUN
RUN/SS RSS
VIN
CSS
3533 BD
OPERATION
The LTC3533 provides high efï¬ciency, low noise power
for a wide variety of handheld electronic devices. The LTC
proprietary topology allows input voltages above, below
or equal to the output voltage by properly phasing the
output switches. The error ampliï¬er output voltage on VC
determines the output duty cycle of the switches. Since
VC is a ï¬ltered signal, it provides rejection of frequencies
well below the switching frequency. The low RDS(ON), low
gate charge synchronous switches provide high frequency
pulse width modulation control at high efï¬ciency. High
efï¬ciency is achieved at light loads when Burst Mode
operation is entered and the LTC3533âs quiescent current
drops to a low 40µA.
LOW NOISE FIXED FREQUENCY OPERATION
Oscillator
The frequency of operation is programmed by an external
resistor from RT to ground, according to the following
equation:
f(kHz) = 33,170/RT(k)
3533f
7
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