5

LTC1515 Series

Terminal.

ESR capacitor as close as possible to the pin for best

performance.

either 3V/5V, 3.3V/5V or adjustable using an external

a

≥ 10µF low ESR capacitor as close as possible to the pin

for best performance.

SI PLIFIED

Regulator Operation

The regulator section of the LTC1515, LTC1515-3/5 and

LTC1515-3.3/5 consists of a charge pump, reference,

comparator and some logic. The divided down output

voltage is compared to the internal reference voltage.

When the divided output drops below the reference volt-

age, the charge pump is enabled, which boosts the output

back into regulation. Hysteresis in the comparator forces

the regulator to burst on and off and causes approximately

100mV of peak-to-peak ripple to appear at the output. By

enabling the charge pump only when needed, the parts

achieve high efficiencies with low output load currents.

Each part’s charge pump has a unique architecture that

allows the input voltage to be either stepped up or stepped

down to produce a regulated output. Internal circuitry

charge pump operating mode. In addition, the effective

output impedance of the charge pump is internally

adjusted to prevent large inrush currents and allow for a

wide input voltage range. When the input voltage is lower

than the output voltage, the charge pump operates as a

step-up voltage doubler. When the input voltage is greater

than the output, the charge pump operates as a step-down

gated switch.

+

–

+

–

1.232V

650kHz

OSCILLATOR

RESET

COUNTER

STEP-UP/STEP-DOWN

CHARGE PUMP

SHDN

POR

GND

(LTC1515-X)

(LTC1515-X)

LTC1515 • BD

FB

(LTC1515)

5/3

(LTC1515-X)

EN

EN