MIC5190
Micrel
Functional Diagram
INTERNAL
VOLTAGE
REGULATOR
VCC1
VIN
IS
50mV
CURRENT LIMIT
AMPLIFIER
VCC2
OUTPUT
CONTROL
AND
EN
ENABLE
OUT
LEVEL
SHIFT
PGND
FB
0.5V
ERROR
AMPLIFIER
SGND
COMP
Figure 1. MIC5190 Block Diagram
Enable
Functional Description
The MIC5190 comes with an active-high enable pin that
allowstheregulatortobedisabled.Forcingtheenablepinlow
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.
VIN
The VIN pin is connected to the N-Channel drain. VIN is the
inputpowerbeingsuppliedtotheoutput. Thispinisalsoused
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.
FB
ISENSE
The feedback pin is used to sense the output voltage for
regulation. The feedback pin is compared to an internal 0.5V
referenceandtheoutputadjuststhegatevoltageaccordingly
to maintain regulation. Since the feedback biasing current is
typically 13µA, smaller feedback resistors should be used to
minimize output voltage error.
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.
COMP
VCC1, VCC2
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.
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
13.2VandbothVCCpinsshouldbetiedtogether.Ensurethat
the voltage supplied is greater than a gate-source threshold
above the output voltage for the N-Channel MOSFET se-
lected.
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.
Output
The output drives the external N-Channel MOSFET and is
powered from V . The output can sink and source over
CC
PGND is the power ground and is the grounding path for the
output driver.
150mAofcurrenttodriveeitheranN-ChannelMOSFEToran
external NPN transistor. The output drive also has short
circuit current protection.
December 2005
6
M9999-120105
MICREL [ MICREL SEMICONDUCTOR ]
