LTC4354

5

4354f

PI FU CTIO S

DA, DB (Pins 1, 8): Drain Voltage Sense Inputs. These

pins sense source-drain voltage drop across the N-Chan-

nel MOSFETs. An external resistor is recommended to

protect these pins from transient voltages exceeding 80V

in extreme fault conditions. For Kelvin sensing, connect

these pins as close to the drains as possible. Connect to

pin to the positive side of the supply through a resistor. An

internal shunt regulator that can sink up to 20mA typically

GA, GB (Pins 4, 6): Gate Drive Outputs. Gate pins pull high

to 10V minimum, fully enhancing the N-Channel MOSFET,

when the load current creates more than 30mV of drop

across the FET. When the load current is small, the gates

are actively servoed to maintain a 30mV drop across the

MOSFET. If reverse current develops more than –60mV of

in less than 1µs. Quickly turning off the pass transistors

prevents excessive reverse currents. Leave the pins open

if unused.

device negative supply input and connects to the common

source connection of the N-Channel MOSFETs. It also

connects to the source voltage sense input of the servo

amplifiers. For Kelvin sensing, connect pin 5 as close to

the common source terminal of the MOSFETs as possible.

FAULT (Pin 7): Fault Output. Open drain output that

turn off an external LED or optocoupler. In the fault

condition, where the pass transistor is fully on and the

voltage drop across it is higher than the fault threshold, the

FAULT pin goes high impedance, turning on the LED or

optocoupler. This indicates that one or both of the pass

transistors have failed open or failed short creating a cross

conduction current in between the two power supplies.

and may be left open or connected to pins 2 and 5.

FU CTIO AL DIAGRA

DB

GB

DA

GA

30mV

BV = 11V

30mV

4354 FD01

FAULT

–

+

–

+

+

–

+

–

FAULT DETECTION

AMP B

AMP A

5

4

1

6

8

2

7

3