LTC3450 datasheet(6/12 Pages) LINER

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LTC3450

3450fa

PI FU CTIO S

C3+ (Pin 1): Charge Pump Inverter Flying Capacitor Posi-

tive Node. The charge pump inverter flying capacitor is

connected between C3+ and C3–. The voltage on C3+ will

alternate between GND and VINV at an approximate 50%

duty cycle while the inverting charge pump is operating.

Use a 10nF or larger X5R type ceramic capacitor for best

results.

C3– (Pin 2): Charge Pump Inverter Flying Capacitor Nega-

tive Node. The charge pump inverter flying capacitor is

connected between C3+ and C3–. The voltage on C3– will

alternate between GND and VNEG at an approximate 50%

duty cycle while the inverting charge pump is operating.

Use a 10nF or larger X5R type ceramic capacitor for best

results.

VNEG (Pin 3): Charge Pump Inverter Output. VNEG can be

either – 5V or –10V depending on where VINV is con-

nected. VNEG should be bypassed to GND with at 0.1µF or

larger X5R type ceramic capacitor. VNEG can also be

configured for –15V with two external low current Schottky

diodes (see Applications section).

MODE (Pin 4): Drive MODE high to force the LTC3450 into

high power (scan) mode. Drive MODE low to force the

LTC3450 into low power (blank) mode. The output volt-

ages remain active with the MODE pin driven low but with

reduced output current capability. MODE must be pulled

up to VIN or higher on initial application of power in order

for proper initialization to occur.

SHDN (Pin 5): Master Shutdown Input for the LTC3450.

Driving SHDN low disables all IC functions and reduces

quiescent current from the battery to less than 2µA. Each

generated output voltage is actively discharged to GND in

shutdown through internal pull down devices. An optional

RC network on SHDN provides a slower ramp up of the

boost converter inductor current during startup (soft-start).

VIN (Pin 6): Input Supply to the LTC3450. Connect VIN to

a voltage source between 1.5V and 4.6V. Bypass VIN to

GND with a 2.2µF X5R ceramic capacitor.

VOUT (Pin 7): Main 5.1V Output of the Boost Regulator and

Input to the Voltage Doubler Stage. Bypass VOUT with a low

ESR, ESL ceramic capacitor (X5R type) between 2.2µF and

10µF.

SW (Pin 8): Switch Pin. Connect the inductor between SW

and VIN. Keep PCB trace lengths as short and wide as

possible to reduce EMI and voltage overshoot. If the

inductor current falls to zero, the internal P-channel

MOSFET synchronous rectifier is turned off to prevent

reverse charging of the inductor and an internal switch

connects SW to VIN to reduce EMI.

GND (Pin 9): Signal and Power Ground for the LTC3450.

Provide a short direct PCB path between GND and the

output filter capacitor(s) on VOUT, V2X, V3X and VNEG.

C1– (Pin 10): Charge Pump Doubler Flying Capacitor

Negative Node. The charge pump doubler flying capacitor

is connected between C1+ and C1–. The voltage on C1– will

alternate between GND and VOUT at an approximate 50%

duty cycle while the charge pump is operating. Use a 10nF

or larger X5R type ceramic capacitor for best results.

C1+ (Pin 11): Charge Pump Doubler Flying Capacitor

Positive Node. The charge pump doubler flying capacitor

is connected between C1+ and C1–. The voltage on C1+ will

alternate between VOUT and V2X at an approximate 50%

duty cycle while the charge pump is operating. Use a 10nF

or larger X5R type ceramic capacitor for best results.

V2X (Pin 12): Charge Pump Doubler Output. This output

is 10.2V (nom) at no load and is capable of delivering up

to 500µA to a load. V2X should be bypassed to GND with

a 0.47µF X5R type ceramic capacitor.

C2– (Pin 13): Charge Pump Tripler Flying Capacitor Nega-

tive Node. The charge pump tripler flying capacitor is

connected between C2+ and C2–. The voltage on C2– will

alternate between GND and VOUT at an approximate 50%

duty cycle while the charge pump is operating. Use a 10nF

or larger X5R type ceramic capacitor for best results.

C2+ (Pin 14): Charge Pump Tripler Flying Capacitor Posi-

tive Node. The charge pump tripler flying capacitor is

connected between C2+ and C2–. The voltage on C2+ will

alternate between V2X and V3X at an approximate 50%

duty cycle while the charge pump is operating. Use a 10nF

or larger X5R type ceramic capacitor for best results.

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