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MIC2090

Current Limiting Power Distribution Switches

Micrel 

Micrel, Inc.

Figure 3. IOUT in Current Limiting for VOUT > 1.8V

MIC2090/MIC2091

Under-Voltage Lock Out (UVLO)

The MIC2090/MIC2091 switches have an Under-Voltage

Lock Out (UVLO) feature that will shut down the switch

in a reproducible way when the input power supply

voltage goes too low. The UVLO circuit disables the

output until the supply voltage exceeds the UVLO

threshold. Hysteresis in the UVLO circuit prevents noise

and finite circuit impedance from causing chatter during

turn-on and turn-off. While disable by the UVLO circuit,

the output switch (power MOSFET) is OFF and no circuit

functions, such as FAULT/ or EN, are considered to be

valid or operative.

OGI (Output Greater than Input)

The internal MOSFET switch turns off when it senses an

output voltage that is greater than the input voltage.

This feature prevents continuous current from flowing

from the output to the input.

If the output voltage rises above VIN by the OGI

threshold voltage (typically 85mV), the internal MOSFET

switch turns off after a period of time, specified in the

electrical characteristics table as OGITIME. The FAULT/

pin remains high during and after an OGI event.

Figure 5 shows the output voltage, input current and

FAULT/ pin voltage when the output voltage is raised

above the input. Reverse current flows through the

internal MOSFET switch for the OGITIME period, until the

internal MOSFET switch is turned off and the input

current goes to 0A.

Figure 4. IOUT in Current Limiting for VOUT < 1.8V

July 2011

Figure 5. OGI Event

17

M9999-070611-B

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