LTC4412HV datasheet(8/12 Pages) LINER

8 / 12 page

LTC4412HV

sn4412hv 4412hvfs

VIN and SENSE Pin Usage

Since the analog controller’s thresholds are small (

±20mV),

the VIN and SENSE pin connections should be made in a

way to avoid unwanted I • R drops in the power path. Both

pins are protected from negative voltages.

GATE Pin Usage

The GATE pin controls the external P-channel MOSFET

connected between the VIN and SENSE pins when the load

current is supplied by the power source at VIN. In this

mode of operation, the internal current source, which is

responsible for pulling the GATE pin up, is limited to a few

microamps (IG(SRC)). If external opposing leakage cur-

rents exceed this, the GATE pin voltage will reach the

clamp voltage (VGON) and VDS will be smaller. The internal

current sink, which is responsible for pulling the GATE pin

down, has a higher current capability (IG(SNK)). With an

auxiliary supply input pulling up on the SENSE pin and

exceeding the VIN pin voltage by 20mV (VRTO), the device

enters the reverse turn-off mode and a much stronger

current source is available to oppose external leakage

currents and turn off the MOSFET (VGOFF).

While in forward regulation, if the on resistance of the

MOSFET is too high to maintain forward regulation, the

GATE pin will maximize the MOSFET’s VGS to that of the

clamp voltage (VGON). The clamping action takes place

between the higher of VIN or VSENSE and the GATE pin.

Status Pin Usage

During normal operation, the open-drain STAT pin can be

biased at any voltage between ground and 36V regardless

of the supply voltage to the LTC4412HV. It is usually

connected to a resistor whose other end connects to a

voltage source. In the forward regulation mode, the STAT

pin will be open (IS(OFF)). When a wall adaptor input or

other auxiliary supply is connected to that input, and the

voltage on SENSE is higher than VIN + 20mV (VRTO), the

system is in the reverse turn-off mode. During this mode

of operation the STAT pin will sink 10

µA of current

(IS(SNK)). This will result in a voltage change across the

resistor, depending on the resistance, which is useful to

turn on an auxiliary P-channel MOSFET or signal to a

microcontroller that an auxiliary power source is con-

nected. External leakage currents, if significant, should be

accounted for when determining the voltage across the

resistor when the STAT pin is either on or off.

Control Pin Usage

This is a digital control input pin with low threshold

voltages (VIL,VIH) for use with logic powered from as little

as 1V. During normal operation, the CTL pin can be biased

at any voltage between ground and 36V, regardless of the

supply voltage to the LTC4412HV. A logical high input on

this pin forces the gate to source voltage of the primary

P-channel MOSFET power switch to a small voltage (VGOFF).

This will turn the MOSFET off and no current will flow from

the primary power input at VIN if the MOSFET is configured

so that the drain to source diode is not forward biased. The

high input also forces the STAT pin to sink 10

µA of current

(IS(SNK)). See the Typical Applications for various ex-

amples on using the STAT pin. A 3.5

µA internal pull-down

current (ICTL) on the CTL pin will insure a logical low level

input if the pin should be open.

Protection

Most of the application circuits shown provide some

protection against supply faults such as shorted, low or

reversed supply inputs. The fault protection does not

protect shorted supplies but can isolate other supplies and

the load from faults. A necessary condition of this protec-

tion is for all components to have sufficient breakdown

voltages. In some cases, if protection of the auxiliary input

(sometimes referred to as the wall adapter input) is not

required, then the series diode or MOSFET may be elimi-

nated.

Internal protection for the LTC4412HV is provided to

prevent damaging pin currents and excessive internal self

heating during a fault condition. These fault conditions can

be a result of any LTC4412HV pins shorted to ground or to

a power source that is within the pin’s absolute maximum

voltage limits. Both the VIN and SENSE pins are capable of

being taken significantly below ground without current

drain or damage to the IC (see Absolute Maximum Voltage

Limits). This feature allows for reverse-battery condition

without current drain or damage. This internal protection

is not designed to prevent overcurrent or overheating of

external components.

APPLICATIO S I FOR ATIO

LTC4412HV 数据表(PDF) 8 Page - Linear Technology

LTC4412HV 数据表(HTML) 8 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12

数据表下载