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MIC5191_06 Datasheet, PDF (7/15 Pages) Micrel Semiconductor – Ultra High-Speed, High-Current Active Filter / LDO Controller
Micrel, Inc.
Functional Description
VIN
The VIN pin is connected to the N-Channel drain. VIN is
the input power being supplied to the output. This pin is
also used to power the internal current limit comparator
and compare the ISENSE voltage for current limit. The
voltage range is from 1.0V min to 5.5V max.
ISENSE
The ISENSE pin is the other input to the current limit
comparator. The output current is limited when the
ISENSE pin's voltage is 50mV less than the VIN pin. In
cases where there is a current limited source and there
isn’t a need for current limit, this pin can be tied directly
to VIN. Its operating voltage range, like the VIN pin, is
1.0V min to 5.5V max.
VCC1, VCC2
VCC1 supplies the error amplifier and internal reference,
while VCC2 supplies the output gate drive. For this
reason, ensure these pins have good input capacitor
bypassing for better performance. The operating range
is from 4.5V to 13.2V and both VCC pins should be tied
together. Ensure that the voltage supplied is greater than
a gate-source threshold above the output voltage for the
N-Channel MOSFET selected.
Output
The output drives the external N-Channel MOSFET and
is powered from VCC. The output can sink and source
over 150mA of current to drive either an N-Channel
MOSFET or an external NPN transistor. The output drive
also has short-circuit current protection.
MIC5191
Enable
The MIC5191 comes with an active-high enable pin that
allows the regulator to be disabled. Forcing the enable
pin low disables the regulator and sends it into a low off-
mode-current state. Forcing the enable pin high enables
the output voltage. The enable pin cannot be left floating;
a floating enable pin may cause an indeterminate state
on the output.
FB
The feedback pin is used to sense the output voltage for
regulation. The feedback pin is compared to an internal
1.0V reference and the output adjusts the gate voltage
accordingly to maintain regulation. Since the feedback
biasing current is typically 13µA, smaller feedback
resistors should be used to minimize output voltage
error.
COMP
COMP is the external compensation pin. This allows
complete control over the loop to allow stability for any
type of output capacitor, load currents and output
voltage. A detailed explanation of how to compensate
the MIC5191 is in the “Designing with the MIC5191”
section.
SGND, PGND
SGND is the internal signal ground which provides an
isolated ground path from the high current output driver.
The signal ground provides the grounding for noise
sensitive circuits such as the current limit comparator,
error amplifier and the internal reference voltage.
PGND is the power ground and is the grounding path for
the output driver.
December 2006
7
M9999-122206