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LTC3539 Datasheet, PDF (6/12 Pages) Linear Technology – 2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters | |||
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LTC3539/LTC3539-2
PIN FUNCTIONS
SW (Pin 1): Switch Pin. Connect inductor between SW
and VIN. Keep PCB trace lengths as short and wide as pos-
sible to reduce EMI. If the inductor current falls to zero,
or SHDN is low, an internal anti-ring resistor is connected
from SW to VIN to minimize EMI.
PGND (Pin 2), GND (Pin 3): Signal and Power Ground.
Provide a short direct PCB path between PGND, GND and
the (â) side of the input and output capacitors.
VIN (Pin 4): Battery Input Voltage. Connect a minimum
of 2.2μF ceramic decoupling capacitor from this pin to
ground.
SHDN (Pin 5): Logic Controlled Shutdown Input. There
is an internal 4MΩ pull-down on this pin.
SHDN = High: Normal operation.
SHDN = Low: Shutdown, quiescent current <1μA.
FB (Pin 6): Feedback Input to the gm Error Ampliï¬er. Con-
nect resistor divider tap to this pin. The output voltage
can be adjusted from 1.5V to 5.25V by: VOUT = 1.20V â¢
[1 + (R2/R1)]
MODE (Pin 7): Burst Mode Pin. A logic controlled input
to select either automatic Burst Mode operation or forced
ï¬xed frequency operation.
MODE = High: Burst Mode operation at light loads
MODE = Low: Fixed frequency PWM Mode
VOUT (Pin 8): Output Voltage Sense and Drain of the
Internal Synchronous Rectiï¬er. PCB trace length from
VOUT to the output ï¬lter capacitor should be as short and
wide as possible.
Exposed Pad (Pin 9): The exposed pad must be soldered
to the PCB ground plane. It serves as another ground
connection, and as a means of conducting heat away
from the die.
BLOCK DIAGRAM
VIN
VOUT
VBEST
VB
OFF ON 5
SHUTDOWN
SHDN
SHUTDOWN
PWM BURST 7
MODE
VREF
UVLO
VREF
UVLO
START-UP
1MHz/2MHz CLK
OSC
THERMAL TSD
SHUTDOWN
EXPOSED PAD
9
VSEL
1
SW
4
VIN
WELL
SWITCH
GATE DRIVERS
AND
ANTI-CROSS
CONDUCTION
LOGIC AND
BURST MODE
CONTROL
PGND
2
IPK
COMPARATOR
3
SLOPE
IPK
COMPARATOR
IZERO
IZERO
COMPARATOR
VREF
FB
ERROR
AMPLIFIER/SLEEP
COMPARATOR
BURST
WAKE
GND
3
CLAMP
SOFT-START
8
VOUT
6
FB
3539 BD
VOUT
R2
R1
3539f
6
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