MIC2219 Datasheet, PDF (9/10 Pages) Micrel Semiconductor – Dynamically Adjustable Dual uCap LDO

MIC2219
Functional Diagram
VIN
EN1
LDO1
EN2
CBYP
Reference
LDO2
GND
MIC2219 Fixed Voltage Block Diagram
OUT1
FB1
OUT2
FB2
Micrel, Inc.
Functional Description
The MIC2219 is a high performance, low quiescent current
power management IC consisting of two µCap low-dropout
regulators. The first regulator is capable of sourcing 150mA
at output voltages from 1.25V to 5V. The second regulator is
capable of sourcing 300mA of current at output voltages from
1.25V to 5V.
Enable 1 and 2
The enable inputs allow for logic control of both output
voltages with individual enable inputs. The enable input is
active high, requiring 1.8V for guaranteed operation. The
enable input is CMOS logic and cannot by left floating.
Input Capacitor
Good bypassing is recommended from input to ground to
help improve AC performance. A 1µF capacitor or greater
located close to the IC is recommended.
Bypass Capacitor
The internal reference voltage of the MIC2219 can be by-
passed with a capacitor to ground to reduce output noise and
increase power supply rejection (PSRR). A quick-start fea-
ture allows for quick turn-on of the output voltage regardless
of the size of the capacitor. The recommended nominal
bypass capacitor is 0.01µF, but it can be increased without
limit.
Output Capacitor
Each regulator output requires a 1µF ceramic output capaci-
tor for stability. The output capacitor value can be increased
to improve transient response, but performance has been
optimized for a 1µF ceramic type output capacitor.
X7R/X5R dielectric-type ceramic capacitors are recom-
mended because of their temperature performance. X7R-
type capacitors change capacitance by 15% over their oper-
ating temperature range and are the most stable type of
ceramic capacitors. Z5U and Y5V dielectric capacitors change
value by as much as 50% and 60% respectively over their
operating temperature ranges. To use a ceramic chip capaci-
tor with Y5V dielectric, the value must be much higher than an
X7R ceramic capacitor to ensure the same minimum capaci-
tance over the equivalent operating temperature range.
April 2005
9
M9999-042105