LTC3537 datasheet(9/20 Pages) LINER

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LTC3537

3537fa

PIN FUNCTIONS

MODE (Pin 1): Logic Controlled Input for the Auto-Burst

Mode Feature.

MODE = High: PWM operation with Burst Mode

Operation

MODE = Low: PWM operation only

LBI (Pin 2): Low-Battery Comparator Non-Inverting Input.

(Comparator enabled with ENBST or ENLDO)

SGND (Pin 3): Signal Ground. Provide a short direct PCB

path between GND and the (–) side of the input and output

capacitors.

VINB (Pin 4): Input Supply for the Step-Up Converter.

Connect a minimum of 1μF ceramic decoupling capacitor

from this pin to ground.

PGDB (Pin 5): Power Good Indicator for the Boost Con-

verter. This is an open-drain output that sinks current when

VOUTB is greater than 94% of the programmed voltage.

ENBST (Pin 6): Logic controlled shutdown input for the

boost converter.

ENBST = High: Normal operation

ENBST = Low: Shutdown

PGDL (Pin 7): Power Good Indicator for the LDO Regulator.

This is an open-drain output that sinks current when VOLDO

is greater than 96% of the programmed voltage.

ENLDO (Pin 8): Logic Controlled Shutdown Input for the

LDO Regulator.

ENLDO = High: Normal operation

ENLDO = Low: Shutdown

FBB (Pin 9): Feedback Input to the gm Error Ampliﬁer

of the Boost Converter. Connect resistor divider tap to

this pin. The output voltage can be adjusted from 1.5V

to 5.25V by:

VOUTB = 1.2V • [1 + (R2/R1)]

FBL (Pin 10): Feedback Input to the gm Error Ampliﬁer of

the LDO. Connect resistor divider tap to this pin. The output

voltage can be adjusted from 0.6V (typical) to 5V by:

VOLDO = 0.6V • [1 + (R4/R3)]

VOLDO (Pin 11): LDO Regulator Output. PCB trace from

VOLDO to the output ﬁlter capacitor (1μF minimum) should

be as short and as wide as possible.

VINL (Pin 12): Input Supply for the LDO Regulator.

VOUTB (Pin 13): Output Voltage Sense Input and Drain

of the Internal Synchronous Rectiﬁer. PCB trace length

from VOUTB to the output ﬁlter capacitor (4.7μF minimum)

should be as short and wide as possible.

SW (Pin 14): Switch Pin. Connect the inductor between

SW and VINB. Keep these PCB trace lengths as short and

wide as possible to reduce EMI. If the inductor current falls

to zero or ENBST is low, an internal anti-ringing switch is

connected from SW to VINB to minimize EMI.

PGND (Pin 15): Power Ground. Provide a short direct

PCB path between GND and the (–) side of the input and

output capacitors.

LBO (Pin 16): Low-Battery Comparator Output. (Open-

Drain)

Exposed Pad (Pin 17): Power Ground. The Exposed Pad

must be soldered to the PCB.

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