LTC4359CDCB-TRMPBF データシートの表示（PDF） - Linear Technology

部品番号

コンポーネント説明

メーカー

LTC4359CDCB-TRMPBF

Ideal Diode Controller with Reverse Input Protection

Linear Technology 

LTC4359

Operation

The LTC4359 controls an external N-channel MOSFET to

form an ideal diode. The GATE amplifier (see Block Dia-

gram) senses across IN and OUT and drives the gate of the

MOSFET to regulate the forward voltage to 30mV. As the

load current increases, GATE is driven higher until a point

is reached where the MOSFET is fully on. Further increases

in load current result in a forward drop of RDS(ON)• ILOAD.

If the load current is reduced, the GATE amplifier drives

the MOSFET gate lower to maintain a 30mV drop. If the

input voltage is reduced to a point where a forward drop

of 30mV cannot be supported, the GATE amplifier drives

the MOSFET off.

In the event of a rapid drop in input voltage, such as an

input short circuit fault or negative-going voltage spike,

reverse current temporarily flows through the MOSFET.

This current is provided by any load capacitance and by

other supplies or batteries that feed the output in diode-

OR applications.

The FPD COMP (Fast Pull Down Comparator) quickly

responds to this condition by turning the MOSFET off in

300ns, thus minimizing the disturbance to the output bus.

The IN, SOURCE, GATE and SHDN pins are protected

against reverse inputs of up to –40V. The NEGATIVE COMP

detects negative input potentials at the SOURCE pin and

quickly pulls GATE to SOURCE, turning off the MOSFET

and isolating the load from the negative input.

When pulled low the SHDN pin turns off most of the internal

circuitry, reducing the quiescent current to 9µA and hold-

ing the MOSFET off. The SHDN pin may be either driven

high or left open to enable the LTC4359. If left open, an

internal 2µA current source pulls SHDN high. In applica-

tions where Q1 is replaced with back-to-back MOSFETs,

the SHDN pin serves as an on/off control for the forward

path, as well as enabling the diode function.

Applications Information

Blocking diodes are commonly placed in series with supply

inputs for the purpose of ORing redundant power sources

and protecting against supply reversal. The LTC4359

replaces diodes in these applications with a MOSFET to

reduce both the voltage drop and power loss associated

with a passive solution. The curve shown on page 1 illus-

trates the dramatic improvement in power loss achieved in

a practical application. This represents significant savings

in board area by greatly reducing power dissipation in the

pass device. At low input voltages, the improvement in

forward voltage loss is readily appreciated where head-

room is tight, as shown in Figure 2.

The LTC4359 operates from 4V to 80V and withstands

an absolute maximum range of –40V to 100V without

damage. In automotive applications the LTC4359 operates

through load dump, cold crank and two-battery jumps,

and it survives reverse battery connections while also

protecting the load.

A 12V/20A ideal diode application is shown in Figure 1.

Several external components are included in addition to

the MOSFET, Q1. Ideal diodes, like their non-ideal coun-

terparts, exhibit a behavior known as reverse recovery.

In combination with parasitic or intentionally introduced

inductances, reverse recovery spikes may be generated by

an ideal diode during commutation. D1, D2 and R1 protect

against these spikes which might otherwise exceed the

LTC4359’s –40V to 100V survival rating. COUT also plays

a role in absorbing reverse recovery energy. Spikes and

protection schemes are discussed in detail in the Input

Short Circuit Faults section.

Q1

BSC028N06NS

VIN

12V

D1

SMAT70A

70V

D2

IN SOURCE

GATE OUT

SMAJ24A

24V

SHDN

LTC4359

VSS

VOUT

12V

20A

COUT

47nF

4359 F01

R1

1k

Figure 1. 12V/20A Ideal Diode with Reverse Input Protection

4359f

7

Share Link: