LT1672 datasheet(7/22 Pages) LINER

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LTC3108

3108fb

VAUX (Pin 1/Pin 2): Output of the Internal Rectiﬁer Cir-

cuit and VCC for the IC. Bypass VAUX with at least 1μF of

capacitance. An active shunt regulator clamps VAUX to

5.25V (typical).

VSTORE (Pin 2/Pin 3): Output for the Storage Capacitor

or Battery. A large capacitor may be connected from this

pin to GND for powering the system in the event the input

voltage is lost. It will be charged up to the maximum VAUX

clamp voltage. If not used, this pin should be left open

or tied to VAUX.

VOUT (Pin 3/Pin 4): Main Output of the Converter. The

voltage at this pin is regulated to the voltage selected by

VS1 and VS2 (see Table 1). Connect this pin to an energy

storage capacitor or to a rechargeable battery.

VOUT2 (Pin 4/Pin 5): Switched Output of the Converter.

Connect this pin to a switched load. This output is open

until VOUT2_EN is driven high, then it is connected to

VOUT through a 1.3Ω P-channel switch. If not used, this

pin should be left open or tied to VOUT. The peak current

in this output is limited to 0.3A typical.

VLDO (Pin 5/Pin 6): Output of the 2.2V LDO. Connect a

2.2μF or larger ceramic capacitor from this pin to GND.

If not used, this pin should be tied to VAUX.

PGD (Pin 6/Pin 7): Power Good Output. When VOUT is

within 7.5% of its programmed value, PGD will be pulled

up to VLDO through a 1MΩ resistor. If VOUT drops 9%

below its programmed value PGD will go low. This pin

can sink up to 100μA.

VS2 (Pin 7/Pin 10): VOUT Select Pin 2. Connect this pin

to ground or VAUX to program the output voltage (see

Table 1).

VS1 (Pin 8/Pin 11): VOUT Select Pin 1. Connect this pin

to ground or VAUX to program the output voltage (see

Table 1).

VOUT2_EN (Pin 9/Pin 12): Enable Input for VOUT2. VOUT2

will be enabled when this pin is driven high. There is an

internal 5M pull-down resistor on this pin. If not used,

this pin can be left open or grounded.

C1 (Pin 10/Pin 13): Input to the Charge Pump and Rectiﬁer

Circuit. Connect a capacitor from this pin to the secondary

winding of the step-up transformer.

C2 (Pin 11/Pin 14): Input to the N-Channel Gate Drive

Circuit. Connect a capacitor from this pin to the secondary

winding of the step-up transformer.

SW (Pin 12/Pin 15): Drain of the Internal N-Channel

Switch. Connect this pin to the primary winding of the

transformer.

GND (Pins 1, 8, 9, 16) SSOP Only: Ground

GND (Exposed Pad Pin 13) DFN Only: Ground. The DFN

exposed pad must be soldered to the PCB ground plane.

It serves as the ground connection, and as a means of

conducting heat away from the die.

Table 1. Regulated Voltage Using Pins VS1 and VS2

VS2

VS1

VOUT

GND

2.35V

GND

VAUX

3.3V

VAUX

GND

4.1V

VAUX

PIN FUNCTIONS (DFN/SSOP)

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