MIC68220_10 Datasheet, PDF (12/17 Pages) Micrel Semiconductor – Dual 2A LDO Regulator

Micrel
Applications Information
Enable Input
The MIC68220 features a TTL/CMOS compatible
positive logic enable input for on/off control of the
device. High (>1V) enables the regulator while low
(<.2V) disables the regulator. In shutdown the
regulator consumes very little current (only a few
microamperes of leakage). For simple applications the
enable (EN) can be connected to V_IN (IN). While
MIC68220 only requires a few µA’s of enable current
to turn on, actual enable pin current will depend on the
overdrive (voltage exceeding 1V) in each particular
application.
Enable Connections for Logic Driven input
Enable Connection for V_IN-Driven and/or Slow
Risetime Inputs
MIC68220
Input Capacitor
An input capacitor of 1µF or greater is recommended
when the device is more than 4 inches away from the
bulk supply capacitance, or when the supply is a
battery. Small surface mount chip capacitors can be
used for the bypassing. The capacitor should be place
within 1 inch of the device for optimal performance.
Larger values will help to improve ripple rejection by
bypassing the regulator input, further improving the
integrity of the output voltage.
Output Capacitor
The MIC68220 requires an output capacitor for stable
operation. As a µCap LDO, the MIC68220 can
operate with ceramic output capacitors of 4.7µF or
greater with ESR’s ranging from a 0mΩ to over
300mΩ. Values of greater than 4.7µF improve
transient response and noise reduction at high
frequency. X7R/X5R dielectric-type ceramic
capacitors are recommended because of their
superior temperature performance. X7R-type
capacitors change capacitance by 15% over their
operating temperature range and are the most stable
type of ceramic capacitors. Larger output
capacitances can be achieved by placing tantalum or
aluminum electrolytics in parallel with the ceramic
capacitor. For example, a 100µF electrolytic in parallel
with a 4.7µF ceramic can provide the transient and
high frequency noise performance of a 100µF ceramic
at a significantly lower cost. Specific
undershoot/overshoot performance will depend on
both the values and ESR/ESL of the capacitors.
September 2010
12
M9999-092310-C