MCP1603-ADJISLASHOS datasheet(13/26 Pages) MICROCHIP

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DS22042A-page 13

MCP1603

4.3

Soft Start

The output of the MCP1603 is controlled during start-

up. This control allows for a very minimal amount of

VOUT overshoot during start-up from VIN rising above

the UVLO voltage or SHDN being enabled.

4.4

Overtemperature Protection

Overtemperature protection circuitry is integrated in the

MCP1603. This circuitry monitors the device junction

temperature and shuts the device off, if the junction

temperature exceeds the typical 150°C threshold. If

this threshold is exceeded, the device will automatically

restart once the junction temperature drops by

approximately 10°C. The soft start is reset during an

overtemperture condition.

4.5

Overcurrent Protection

Cycle-by-cycle current limiting is used to protect the

MCP1603 from being damaged when an external short

circuit is applied. The typical peak current limit is

860 mA. If the sensed current reaches the 860 mA

limit, the P-Channel MOSFET is turned off, even if the

output voltage is not in regulation. The device will

attempt to start a new switching cycle when the internal

oscillator sets the internal RS latch.

4.6

Enable/Disable Control

The SHDN pin is used to enable or disable the

MCP1603. When the SHDN pin is pulled low, the

device is disabled. When pulled high the device is

enabled and begins operation provided the input

voltage is not below the UVLO threshold or a fault

condition exists.

4.7

Undervoltage Lockout (UVLO)

The UVLO feature uses a comparator to sense the

input voltage (VIN) level. If the input voltage is lower

than the voltage necessary to properly operate the

MCP1603, the UVLO feature will hold the converter off.

When VIN rises above the necessary input voltage, the

UVLO is released and soft start begins. Hysteresis is

built into the UVLO circuit to compensate for input

impedance. For example, if there is any resistance

between the input voltage source and the device when

it is operating, there will be a voltage drop at the input

to the device equal to IIN x RIN. The typical hysteresis

is 140 mV.

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