MIC5190
Micrel
Functional Diagram
VCC1
INTERNAL
VOLTAGE
REGULATOR
50mV
VIN
IS
CURRENT LIMIT
AMPLIFIER
VCC2
EN
ENABLE
OUTPUT
CONTROL
AND
LEVEL
SHIFT
OUT
PGND
FB
0.5V
ERROR
AMPLIFIER
COMP
SGND
Figure 1. MIC5190 Block Diagram
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 0.9V min to 5.5V max.
ISENSE
The ISENSE pin is the other input to the current limit com-
parator. 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 0.9V 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 se-
lected.
Output
The output drives the external N-Channel MOSFET and is
powered from V
CC
. 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.
Enable
The MIC5190 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 0.5V
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 com-
plete 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 MIC5190 is in the
“Designing with the MIC5190” section.
SGND, PGND
SGND is the internal signal ground which provides an iso-
lated 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 2005
6
M9999-120105
MICREL [ MICREL SEMICONDUCTOR ]
