LTC7825

7

Rev. A

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PIN FUNCTIONS

VHIGH (Pins 1, 28): Switched Capacitor Converter High

Side Voltage Input. Connect capacitors from VHIGH to GND

and to VLOW for high efficiency operation.

SWH (Pins 2, 3): High Side Switching Node. Connect to

the flying capacitors.

VLOW (Pins 4, 5): Switched Capacitor Converter Low Side

Voltage Input. Connect capacitors from VLOW to GND.

SWL (Pins 6, 7): Low Side Switching Node. Connect to

the flying capacitors.

PGND (Pins 8, 9, 10, 11 ): Power Ground.

VOUT (Pins 12, 13, 14): Output of the Internal Disconnect

MOSFET Connected to VLOW. The input short protection is

achieved by turning off the internal disconnect MOSFET.

If internal disconnect is not needed, VOUT may be short

to VLOW externally for higher efficiency.

BOOSTL, BOOSTH (Pins 15, 22): Bootstrapped Supplies

to the floating Drivers. Capacitors are connected between

the BOOSTH to SWH and BOOSTL to SWL pins.

TIMER (Pin 16): Connecting a capacitor between this pin

and ground sets the amount of time of soft start-up. It

also sets the short-circuit retry time. See the Applications

Information section for details.

RUN (Pin 17): Digital Run Control Input. Forcing RUN

below 1.2V shuts down the controller. When RUN pin is

higher than 1.2V, internal circuitry starts up. A 1µA pull-

up current flows out of RUN pin when RUN is below 1.2V

and an additional 4.5µA current flowing out of RUN pin

when RUN is above 1.2V.

HYS_PRGM (Pin 18): A resistor connected between

this pin and ground will set the window threshold of the

window comparator that monitors the voltage difference

across VHIGH/2 and VLOW. Tying this pin to GND or INTVCC

sets the window to 240mV or 400mV, respectively. There

is a 10µA current flowing throughout this pin.

FL5V (Pin 19): Floating 5V power for the internal driver

and control circuit. A 0.1µF ~ 1µF ceramic capacitor or

other low ESR capacitor is required from this pin to the

VLOW pin.

FREQ (Pin 20): Frequency Set Pin. There is a precision

10μA current flowing out of this pin. A resistor to ground

sets a voltage which in turn programs the frequency. Tying

this pin to GND or INTVCC sets the default 300kHz/600kHz

switching frequency. See the Applications Information

section for the detailed information.

FAULT (Pin 21): This is an open-drain output. FAULT is

pulled to ground when the VLOW voltage is out of the

VHIGH/2 window threshold.

SGND (Pin 23): Signal Ground. All small-signal compo-

nents should connect to this ground. Connect this pin with

PGND pins on the PCB.

EXTVCC (Pin 24): External Power Input to an Internal

LDO Connected to the INTVCC. This LDO supplies INTVCC

power, bypassing the internal LDO powered from VCC

whenever EXTVCC is higher than 5V and VCC is higher

than 6V. Do not float or exceed 14V on this pin.

INTVCC (Pin 25): Output of the Internal Linear Low

Dropout Regulator. The driver and control circuits are

powered from this voltage source. Must be bypassed to

power ground with a minimum of 4.7µF ceramic or other

low ESR capacitor. Do not use the INTVCC pin for any

other ICs.

VCC (Pin 26): Power supply for drivers and internal charg-

ing circuit. A bypass capacitor should be tied between this

pin and the GND pin.

OVG (Pin 27): Optional input over voltage protection pin.

connect this pin to the gate of the external N-channel

MOSFET. If the VHIGH voltage is higher than 26V, the

OVG turns off the external MOSFET. If not used, leave

this pin floating.