MCP1603B datasheet(16/34 Pages) MICROCHIP

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MCP1603/B/L

DS22042B-page 16

 2007-2012 Microchip Technology Inc.

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/B/L device family. 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/B/L device family 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/B/L. When the SHDN pin is pulled low, the

device is disabled. When pulled high, the device is

enabled and begins operation, unless the input voltage

is 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 xRIN. The typical hysteresis

is 140 mV.

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