MIC2213

Micrel, Inc.

M9999-101705

10

October 2005

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 MIC2213 can be by-

passed with a capacitor to ground to reduce output noise and

increase power supply rejection (PSRR).Aquick-start feature

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-

mendedbecauseoftheirtemperatureperformance.X7R-type

capacitors change capacitance by 15% over their operating

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 operat-

ing temperature ranges. To use a ceramic chip capacitor with

Y5V dielectric, the value must be much higher than a X7R

ceramic capacitor to ensure the same minimum capacitance

over the equivalent operating temperature range.

Adjustable Regulator Design

VOUT1

ADJ1

R1

R2

ADJ2

VOUT2

R2

R1

GND

MIC2213 Adjustable Regulator Design

The MIC2213 allows the programming of the output voltages

1 and 2 anywhere between 1.25V and 5.5V, the maximum

operatingratingofthepart.Tworesistorsarerequiredforeach

output. Appropriate resistor values are required to prevent

the low quiescent current performance being compromised.

Resistor values recommended are between 100kΩ and

500kΩ.

The resistor values are calculated by:

R1 = R2

1.250

– 1

rately for each output.