Datasheet

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
V
OUT
overshoot during start-up from V
IN
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 (V
IN
) 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 V
IN
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 I
IN
xR
IN
. The typical hysteresis
is 140 mV.