MIC37122 Evaluation Board
High-Performance, 1A, Low-Noise,
Low Dropout Regulator
General Description
The MIC37122 is a high-performance low-noise, low
dropout regulator. The MIC37122 is capable of sourcing
1A output current and offers high-PSRR and low output
noise, which makes the IC an ideal general purpose
LDO regulator for consumer applications such as set-top
boxes and gaming consoles.
The MIC37122 offers 2.5% accuracy, dropout of less
than 400mV at 1A, and low ground current (typically
250µA). The MIC37122 can also be put into zero-off-
mode current state, drawing little current when disabled.
Additionally, an output load discharge feature allows the
MIC37122 to discharge large capacitive loads through a
low impedance path to ground upon disabling the LDO
regulator.
The MIC37122 has an operating junction temperature
range of
−40°C
to
+125°C
and is available in lead-free
®
(RoHS-compliant) SOIC-8 and 2.0mm
×
2.0mm MLF
packages. The MLF
®
package occupies only 4mm
2
of
PCB area, an 86% reduction in board area compared to
SOIC-8 packaging.
Datasheets and support documentation can be found on
Micrel’s web site at:
www.micrel.com.
Getting Started
1.
Connect an external supply to V
IN
terminal.
Apply
desired input voltage to the V
IN
and ground (GND)
terminals of the evaluation board, paying careful
attention to polarity and supply voltage. An ammeter
may be placed between the input supply and the V
IN
terminal to the evaluation board. Ensure that the
supply voltage is monitored at the V
IN
terminal. The
ammeter and/or power lead resistance can reduce
the voltage supplied to the input.
2.
Connect the load to the V
OUT
and GND terminals.
The load can be either passive (resistive) or active
(as in an electronic load). An ammeter can be
placed between the load and the V
OUT
terminal.
Ensure that the output voltage is monitored at the
V
OUT
terminal. The V
OUT
can be adjusted by
changing the feedback resistors (see
Output
Voltage
section in this data sheet).
3.
Enable the MIC37122.
The enable (EN) pin is
provided on the evaluation board with a 10k pull-up
resistor. The output of the MIC37122 may be turned
off by shorting the EN pin to ground. An external
connection on the board provides easy access to
the EN pin. Removing the pull-up resistor and
leaving the EN pin floating will cause the regulator
to operate in an indeterminate state.
Requirements
The MIC37122 evaluation board requires a single input
power supply. The V
IN
power supply must be able to
deliver 2.375V to 5.5V with more than 1A capability. The
output load can either be an active or passive load.
Output Voltage
The output voltage on the MIC37122 evaluation board is
adjustable. The output is set by adjusting the feedback
resistors (R1 and R2) and can be calculated as follows:
Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the V
IN
terminal may damage the device. Additionally, the
maximum V
IN
operating voltage of the MIC37122
evaluation board is 5.5V. Exceeding 5.5V on V
IN
could
permanently damage the device.
V
OUT
=
V
REF
×
⎜
1
+
⎛
⎝
R1
⎞
R2
⎠
⎟
With V
REF
= 1.0V:
R2
=
R1
V
OUT
−
1.0V
MLF and
MicroLeadFrame
are trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
October 2011
M9999-101211-A
Micrel, Inc.
MIC37122 Evaluation Board
Bill of Materials
Item
C1, C2
Part Number
C0805C106K8PACTU
GRM21BR60J106ME19
C3216X5ROJ476M
C4, C6
C5
R1
R2
R3
R4
U1
Notes:
Manufacturer
Kemet
(1)
Description
10µF/10V ceramic capacitor, X5R, size 0805
47µF/6.3V ceramic capacitor, X5R, size 1206
(greater or lesser capacitance value or larger case
size is acceptable)
Large value electrolytic capacitor
100Ω film resistor, size 0805, 1%
124Ω film resistor, size 0805, 1%
0Ω film resistor, size 0805, 1%
10kΩ film resistor, size 0805, 1%
High-Performance, 1A, Low-Noise, Low Dropout
Regulator
Qty.
2
Murata
(2)
TDK
(3)
Murata
(3)
AVX
⎯
Vishay
Vishay
Vishay
(5)
(5)
(5)
(5)
(4)
GRM31CR60J476ME19L
12066D476MAT2A
⎯
CRCW08051000F
CRCW08051240F
CRCW080500R0F
CRCW08051002F
MIC37122YM
DNP
DNP
1
1
1
1
1
Vishay
Micrel, Inc.
(6)
1.
2.
3.
4.
5.
6.
Kemet:
www.kemet.com.
Murata:
www.murata.com.
TDK:
www.tdk.com.
AVX:
www.avx.com.
Vishay:
www.vishay.com.
Micrel, Inc.:
www.micrel.com.
October 2011
3
M9999-101211-A
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