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LTC1421/LTC1421-2.5

TYPICAL PERFORMANCE CHARACTERISTICS

CPON Voltage vs Source Current

(Charge Pump On)

SOURCE CURRENT (mA)

– 0.5

– 1.0

– 1.5

– 2.0

1421 G10

– 2.5

– 3.0

VCCLO = 5V

VCCHI = 12V

ICCLO Supply Current

vs VCCLO Voltage

VCCLO VOLTAGE (V)

610

1421 G11

812

VCCHI = 12V

PIN FUNCTIONS

CON1 (Pin 1): TTL Level Input with a Pull-Up to VCCLO.

Together with CON2, it is used to indicate board connec-

tion. The pin must be tied to ground on the host side of the

connector. When using staggered connector pins, CON1

and CON2 must be the shortest and must be placed at

opposite corners of the connector. Board insertion is

assumed after CON1 and CON2 are both held low for 20ms

after power-up.

CON2 (Pin 2): TTL Level Input with a Pull-Up to VCCLO.

Together with CON1 it is used to indicate board connec-

tion.

POR (Pin 3): TTL Level Input with a Pull-Up to VCCLO.

When the pin is pulled low for at least 20ms, a hard reset

is generated. Both VOUTLO and VOUTHI will turn off at a

controlled rate. A power-up sequence will not start until

the POR pin is pulled high. If POR is pulled high before

VOUTLO and VOUTHI are fully discharged, a power-up

sequence will not begin until the voltage at VOUTLO and

VOUTHI are below VTRIP. The electronic circuit breaker will

be reset by pulling POR low.

FAULT (Pin 4): Open Drain Output to GND with a Weak

Pull-Up to VCCLO. The pin is pulled low when an overcur-

rent fault is detected at VOUTLO or VOUTHI.

DISABLE (Pin 5): CMOS Output. The signal is used to

disable the board’s data bus during insertion or removal.

PWRGD (Pin 6): Open Drain Output to GND with a Weak

Pull-Up to VCCLO. The pin is pulled low immediately after

VOUTLO falls below its reset threshold voltage. The pin is

pulled high immediately after VOUTLO rises above its reset

threshold voltage.

RESET (Pin 7): Open Drain Output to GND with a Weak

Pull-Up to VCCLO. The pin is pulled low when a reset

condition is detected. A reset will be generated when any

of the following conditions are met: Either CON1 or CON2

is high, POR is pulled low, VCCLO or VCCHI are below their

respective undervoltage lockout thresholds, PWRGD goes

low or an overcurrent fault is detected at VOUTLO or

VOUTHI. RESET will go high 200ms after PWRGD goes

high. On power failure, RESET will go low 32

µs after

PWRGD goes low.

REF (Pin 8): The Reference Voltage Output. VOUT = 1.232V

±1%. The reference can source up to 5mA of current. A

µF bypass capacitor is recommended.

CPON (Pin 9): CMOS Output That Can Be Pulled Below

Ground. CPON is pulled high when the internal charge

pumps for GATELO and GATEHI are turned on. CPON is

pulled low when the charge pumps are turned off. The pin

can be used to control an external MOSFET for a – 5V to

– 12V supply.

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