MIC2214 Datasheet, PDF (10/11 Pages) Micrel Semiconductor – Portable Power Management IC

MIC2214
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 MIC2214 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.
Adjustable Regulator Design
VOUT1
R1
ADJ1
VOUT2
ADJ2
R2
GND
Micrel
R1
R2
MIC2214 Adjustable Regulator Design
The MIC2214 allows the programming of the output voltages
1 and 2 anywhere between 1.25V and 5.5V, the maximum
operating rating of the part. Two resistors are required for
each output. Appropriate resistor values are required to
prevent the low quiescent current performance being com-
promised. Resistor values recommended are between 100kΩ
and 500kΩ.
The resistor values are calculated by:
R1 =
R2^{}
V_OUT
1.250
−
1^{}
where V_OUT is the desired output voltage. Calculate sepa-
rately for each output.
MIC2214
10
August 2004