LTC3539-2_15 Datasheet, PDF (6/14 Pages) Linear Technology – 2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters

LTC3539/LTC3539-2
PIN FUNCTIONS
SW (Pin 1): Switch Pin. Connect inductor between SW
and V_IN. 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 V_IN to minimize EMI.
PGND (Pin 2), GND (Pin 3): Signal and Power Ground.
Provide a short direct PCB path between PGND, GND and
the (–) side of the input and output capacitors.
V_IN (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 g_m Error Amplifier.
Connect resistor divider tap to this pin. The output volt-
age can be adjusted from 1.5V to 5.25V by: V_OUT = 1.20V
• [1 + (R2/R1)]
MODE (Pin 7): Burst Mode Pin. A logic controlled input
to select either automatic Burst Mode operation or forced
fixed frequency operation.
MODE = High: Burst Mode operation at light loads
MODE = Low: Fixed frequency PWM Mode
V_OUT (Pin 8): Output Voltage Sense and Drain of the
Internal Synchronous Rectifier. PCB trace length from
V_OUT to the output filter 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
V_IN
V_OUT
V_BEST
V_B
OFF ON 5
SHUTDOWN
SHDN
SHUTDOWN
PWM BURST 7
MODE
V_REF
UVLO
V_REF
UVLO
START-UP
1MHz/2MHz ^CLK
OSC
THERMAL ^TSD
SHUTDOWN
EXPOSED PAD
9
V_SEL
1
SW
4
V_IN
WELL
SWITCH
GATE DRIVERS
AND
ANTI-CROSS
CONDUCTION
LOGIC AND
BURST MODE
CONTROL
PGND
2
I_PK
COMPARATOR
Σ
SLOPE
I_PK
COMPARATOR
I_ZERO
I_ZERO
COMPARATOR
V_REF
FB
ERROR
AMPLIFIER/SLEEP
COMPARATOR
BURST
WAKE
GND
3
CLAMP
SOFT-START
8
V_OUT
6
FB
3539 BD
V_OUT
R2
R1
35392fc
6
For more information www.linear.com/3539/3539-2