MP62350/MP62351 –CURRENT-LIMITED POWER DISTRIBUTION SWITCHES

MP62350/MP62351 Rev. 0.91

www.MonolithicPower.com

9

9/18/2009

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© 2009 MPS. All Rights Reserved.

DETAILED DESCRIPTION

Over Current

When the load exceeds trip current (minimum

threshold current triggering constant-current

mode) or a short is present, MP62350/MP62351

switches into to a constant-current mode (current

limit value). MP62350/MP62351 will be shutdown

only if the overcurrent condition stays long

enough to trigger thermal protection.

Trigger

overcurrent

protection

for

different

overload conditions occurring in applications:

1) The output has been shorted or overloaded

before the device is enabled or input applied.

MP62350/MP62351 detects the short or

overload and immediately switches into a

constant-current mode.

2) A short or an overload occurs after the device

is enabled. After the current-limit circuit has

been tripped (reached the trip current

threshold), the device switches into constant-

current mode. However, high current may

flow for a short period of time before the

current-limit circuit can react.

3) Output current has been gradually increased

beyond the recommended operating current.

The load current rises until the trip current

threshold is reached or until the thermal limit

of

the

device

is

exceeded.

The

MP62350/MP62351 is capable of delivering

current up to the trip current threshold without

damaging the device. Once the trip threshold

has been reached, the device switches into

its constant-current mode.

Flag Response

The FLAG pin is an open drain configuration.

This FAULT will report a fail mode after an 8ms

deglitch timeout. This is used to ensure that no

false fault signals are reported. This internal

deglitch circuit eliminates the need for extend

components. The FLAG pin is not deglitched

during an over temp. or a voltage lockout.

Thermal Protection

The purpose of thermal protection is to prevent

damage in the IC by allowing exceptive current to

flow

and

heating

the

junction.

The

die

temperature is internally monitored until the

thermal limit is reached. Once this temperature is

reached, the switch will turn off and allow the

chip to cool. The switch has a built-in hysteresis.

Under-voltage Lockout (UVLO)

This circuit is used to monitor the input voltage to

ensure that the MP62350/MP62351 is operating

correctly. This UVLO circuit also ensures that

there is no operation until the input voltage

reaches the minimum spec.

Enable

The logic pin disables the chip to reduce the

supply current. The device will operate once the

enable signal reaches the appropriate level. The

input is compatible with both COMS and TTL.