MIC37110 Datasheet, PDF (14/20 Pages) Micrel Semiconductor – High-Performance, Low-Noise, 1A LDOs

Micrel, Inc.
Application Information
The MIC37110/2 and MIC37120/2 are high-performance,
low-noise, low-voltage regulators suitable for moderate
current consumer applications such as mobile phones,
set-top boxes, and gaming consoles. The MIC37110/2
and MIC37120/2 are capable of sourcing 1A output, offer
high PSRR and low output noise. With a 400mV dropout
voltage at full load and over temperature, these ICs are
especially valuable in battery-powered systems and as
high-efficiency noise filters in post-regulator applications.
The MIC37110/12 and MIC37120/22 regulators are fully
protected from damage due to fault conditions. Linear
current limiting is provided. Output current during overload
conditions is constant. Thermal shutdown disables the
device when the die temperature exceeds the maximum
safe operating temperature. The output structure of these
regulators allows voltages in excess of the desired output
voltage to be applied without reverse current flow.
Figure 1. Capacitor Requirements
Output Capacitor
The MIC37110/2 and MIC37120/2 requires an output
capacitor to maintain stability and improve transient
response. The MIC37110/2 and MIC37120/2 require a
2.2µF or greater output capacitor to maintain stability.
Larger capacitor values may be used but the device is
optimized for 2.2µF and optimum performance is
achieved with the use of low ESR ceramic capacitors.
Ultra-low ESR ceramic capacitors are recommended for
output capacitance of 10µF or greater to help improve
transient response and noise reduction at high frequency.
X7R/X5R dielectric-type ceramic capacitors are
recommended because of their temperature performance.
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 operating 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.
MIC37110/MIC37112
MIC37120/MIC37122
Input Capacitor
An input capacitor of 1µF or greater is recommended
when the device is more than four inches away from the
bulk AC supply capacitance or when the supply is a
battery. Small, surface mount, ceramic chip capacitors
can be used for bypassing. Larger values will help to
improve ripple rejection by bypassing the input to the
regulator, further improving the integrity of the output
voltage. Place the external capacitors for the input/output
as close to the IC as possible. See Figure 1.
Enable Input
The TMLF-6 (Thin MLF) and SOIC-8 package options
feature an active-high enable input (EN) that allows for
ON/OFF control of the regulator. Current drain reduces
to “zero” when the device is shutdown, with only
microamperes of leakage current. The EN input has
TTL/CMOS compatible thresholds for simple logic
interfacing. EN may be directly tied to V_IN.
Transient Response and 3.3V to 2.5V or 2.5V to 1.8V,
1.65V or 1.5V Conversion
The MIC37110/02 and MIC37120/22 have excellent
transient response to variations in input voltage and load
current. The device has been designed to respond
quickly to load current variations and input voltage
variations. Large output capacitors are not required to
obtain this performance. A standard 10µF output
capacitor (ceramic) is all that is required. Larger values
help to improve performance even further.
December 2012
14
M9999-121312-A