LTC1647-2_15 datasheet(8/22 Pages) LINER

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LTC1647-1/

LTC1647-2/LTC1647-3

1647fa

PIN FUNCTIONS

VCC1 (LTC1647-3): Channel 1 Positive Supply Input.

The supply range for normal operation is 2.7V to 16.5V.

The supply current, ICC1, is typically 1mA. Channel 1’s

undervoltage lockout (UVLO) circuit disables GATE 1 until

the supply voltage at VCC1 is greater than VLKO (typically

2.45V). GATE 1 is held at ground potential until UVLO

deactivates. If ON1 is high and VCC1 is above the UVLO

threshold voltage, GATE 1 is pulled high by a 10μA current

source. If VCC1 falls below (VLKO – VLKH), GATE 1 is pulled

immediately to ground. The internal reference and the

common charge pump are powered from the higher of

the two VCC inputs, VCC1 or VCC2.

VCC2 (LTC1647-3): Channel 2 Positive Supply Input. See

VCC1 for functional description.

VCC: The Common Positive Supply Input for the LTC1647-1

and the LTC1647-2. VCC1 and VCC2 are internally connected

together.

GND: Chip Ground.

ON1: Channel 1 ON Input. The threshold at the ON1 pin is

set at 1.29V with 70mV hysteresis. If UVLO and the circuit

breaker of channel 1 are inactive, a logic high at ON1 enables

the 10μA charge pump current source, pulling the GATE

1 pin above VCC1. If the ON1 pin is pulled low, the GATE 1

pin is pulled to ground by a 50μA current sink.

ON1 resets channel 1’s electronic circuit breaker by pulling

ON1 low for greater than one tRESET period (50μs). A

low-to-high transition at ON1 restarts a normal GATE 1

pull-up sequence.

ON2: Channel 2 ON Input. See ON1 for functional

description.

FAULT1:Channel1Open-DrainFaultStatusOutput.FAULT1

pin pulls low after 0.3μs (tFAULT) if the circuit breaker

measures greater than 50mV across the sense resistor

connected between VCC1 and SENSE 1. If FAULT1 pulls

low, GATE 1 also pulls low. FAULT1 remains low until ON1

is pulled low for at least one tRESET period.

FAULT2: Channel 2 Open-Drain Fault Status Output. See

FAULT 1 for functional description.

SENSE1: Channel 1 Circuit Breaker Current Sense Input.

Load current is monitored by a sense resistor connected

between VCC1 and SENSE 1. The circuit breaker trips if the

voltage across the sense resistor exceeds 50mV (VCB). To

disable the circuit breaker, connect SENSE 1 to VCC1. In

order to obtain optimum performance, use Kelvin-sense

connections between the VCC and SENSE pins to the

current sense resistor.

SENSE2: Channel 2 Circuit Breaker Current Sense Input.

See SENSE 1 for functional description.

GATE1: Channel 1 N-channel MOSFET Gate Drive Output.

An internal charge pump guarantees at least 10V of gate

drive from a 5V supply. Two Zener clamps are incorporated

at the GATE 1 pin; one Zener clamps GATE 1 approximately

15V above VCC and the second Zener clamps GATE 1

appoximately 28V above GND. The rise time at GATE 1 is

set by an external capacitor connected between GATE 1

and GND and an internal 10μA current source provided

by the charge pump. The fall time at GATE 1 is set by

the 50μA current sink if ON1 is pulled low. If the circuit

breaker is tripped or the supply voltage hits the UVLO

threshold, a 50mA current sink rapidly pulls GATE 1 low.

An external 23V Zener from GATE1 to GND is required for

supply voltages (VCC1) greater than 10V.

GATE2: Channel 2 N-channel MOSFET Gate Drive Output.

See GATE 1 for functional description.

NC: No Connection.

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