LTC4353 データシートの表示（PDF） - Linear Technology

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LTC4353

Dual Low Voltage Ideal Diode Controller

Linear Technology 

LTC4353

Operation

The LTC4353 controls N-channel MOSFETs to emulate

two ideal diodes. When enabled, each servo amplifier

(SA1, SA2) controls the gate of the external MOSFET to

servo its forward voltage drop (VFWD = VIN – OUT) to VFR.

The gate voltage rises to enhance the MOSFET if the load

current causes the drop to exceed VFR. For large output

currents, the MOSFET gate is driven fully on and the volt-

age drop is equal to IFET • RDS(ON).

In the case of an input supply short-circuit, when the

MOSFET is conducting, a large reverse current starts

flowing from the load towards the input. SA detects this

failure condition as soon as it appears, and turns off the

MOSFET by rapidly pulling down its gate.

SA quickly pulls up the gate whenever it senses a large for-

ward voltage drop. An external capacitor between the CPO

and VIN pins is needed for fast gate pull-up. This capacitor

is charged up, at device power-up, by the internal charge

pump. The stored charge is used for the fast gate pull-up.

The GATE pin sources current from the CPO pin and sinks

current to the VIN and GND pins. Clamps limit the GATE

and CPO voltages to 12V above and a diode below VIN.

Internal switches pull the ONST pins low when the GATE to

VIN voltage exceeds 0.7V to indicate that power is passing

through the MOSFET.

LDO is a low dropout regulator that generates a 5V supply

at the VCC pin from the highest VIN input. When both VIN

are below 2.9V, an external supply in the 2.9V to 6V range

is required at the VCC pin.

VCC and EN pin comparators, CP1 to CP3, control power

passage. The MOSFET is held off whenever the EN pin is

above 0.6V, or the VCC pin is below 2.55V. A high on both

EN pins lowers the current consumption of the device.

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