MIC94325/45/55
Evaluation Board
500mA LDO with
Ripple Blocker Technology
General Description
The MIC943x5 Ripple Blocker™ is a monolithic integrated
circuit that provides low-frequency ripple attenuation
(switching noise rejection) to a regulated output voltage.
This is important for applications, such as RF applications,
where switching noise cannot be tolerated by sensitive
downstream circuits. The MIC94325/45/55 maintains high
power supply ripple rejection (PSRR) with input voltage
operating near the output voltage level to improve overall
system efficiency.
The MIC943x5 operates from an input voltage of 1.8V to
3.6V. The MIC943x5 options include fixed (MIC94345/55)
or adjustable (MIC94325) output voltages. The MIC94355
version offers an auto-discharge to discharge the output
capacitor when the part is disabled.
Datasheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Requirements
The MIC94325/45/55 evaluation board requires an input
power supply that can deliver greater than 800mA at a
voltage range of 1.8V to 3.6V. The output load can be
either active or passive.
Precautions
The MIC94325/45/55 evaluation board does not have
reverse polarity protection. Applying a negative voltage to
the VIN terminal may damage the device.
Getting Started
1.
Connect an External Supply to VIN.
Apply the desired input voltage to the VIN and ground
terminal of the evaluation board, paying careful
attention to polarity and supply voltage (1.8V ≤ VIN ≤
3.6V).
2.
Enable/Disable the MIC94325/45/55.
The evaluation board is supplied with a 100kΩ pull-up
resistor to VIN, which makes the on state the default.
To disable the output, jumper the EN terminal to
ground.
3.
Connect the Load.
Connect the load to the VOUT terminal and the ground
terminal. The load can be either passive (resistor) or
active (electronic load). Be sure to monitor the output
voltage at the VOUT terminal.
Ordering Information
Part Number
MIC94325YMT EV
MIC94355-4YMT EV
MIC94355-FYMT EV
MIC94355-GYMT EV
MIC94355-MYMT EV
MIC94355-SYMT EV
Description
500mA LDO Ripple Blocker
Evaluation Board
500mA LDO Ripple Blocker
Evaluation Board (V
OUT
= 1.2V)
500mA LDO Ripple Blocker
Evaluation Board (V
OUT
= 1.5V)
500mA LDO Ripple Blocker
Evaluation Board (V
OUT
= 1.8V)
500mA LDO Ripple Blocker
Evaluation Board (V
OUT
= 2.8V)
500mA LDO Ripple Blocker
Evaluation Board (V
OUT
= 3.3V)
Ripple Blocker is a trademark of Micrel, 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
June 11, 2013
Revision 1.0
Micrel, Inc.
MIC94325/45/55 Evaluation Board
Power Supply Ripple Rejection (PSRR)
Measurements
Figure 1 shows the frequency response of the MIC94325.
PSRR measurements can be made using either dedicated
PSRR test equipment or a PSRR interface board and a
network analyzer. The network analyzer can sweep the AC
frequency and perform a comparison measurement of the
amplitude on the input and output. With this method, the
network analyzer is configured for an A/R measurement.
The problem comes when trying to impose the network
analyzer’s AC signal with the DC input voltage to the
MIC94325/45/55. The circuit shown in Figure 3 solves this
problem by using the MIC911 as a summing amplifier.
MIC94325 PSRR
C
OUT
= 4.7µF C
FF
= 3.3nF
-20
-30
-40
-50
500mA
V
IN
= 2.7V
C
OUT
= 4.7µF
C
FF
= 3.3nF
PSRR (dB)
-60
-70
-80
-90
-100
-110
-120
10
10
300mA
10mA
100
100
1K
10K
100K
1M
10M
1,000 10,000 100,00 1,000,0 10,000,
0
00
000
FREQUENCY (Hz)
Figure 1. MIC94325 Rippled Blocker Frequency Response
For high-frequency measurements (above 1MHz), pay
careful attention to the test set-up configuration because it
is easy to introduce noise into the grounds. That gives
inaccurate measurements, as shown in Figure 2.
Figure 3. Network Analyzer Set-Up
The summing amplifier adds the V
SUPPLY
(DC voltage) and
the network analyzer’s AC signal. Because the network
analyzer’s source is 50Ω impedance, it may be neglected.
The DC voltage seen at the non-inverting side is half of the
V
SUPPLY
voltage. The output is gained up by 2 with the 1kΩ
resistor divider to the non-inverting side. This sums the AC
and DC voltages with an overall gain of 1.
Figure 2. High-Frequency Noise on Measurement System
The inductance of test probes connected to the evaluation
board at higher frequencies is a factor that can create a
differential between the device under test and test
measurement system grounds. Adding a low-value resistor
(2Ω) in series with the input capacitor to ground and using
a test measurement system that can make differential
measurements will help to reduce these effects.
1k
Ω
1k
Ω
1k
Ω
V
OUT
=
V
SUPPLY
+
V
NETWORKANALYZER
1
+
1k
Ω +
1k
Ω
1k
Ω
1k
Ω +
1k
Ω
1
1
V
OUT
=
V
SUPPLY
+
V
NETWORKANALYZER
(
2
)
2
2
V
OUT
=
V
SUPPLY
+
V
NETWORKANALYZER
Eq. 1
June 11, 2013
2
Revision 1.0
Micrel, Inc.
MIC94325/45/55 Evaluation Board
Evaluation Board Schematic (Adjustable)
Bill of Materials
Item
C1, C2
C3
R1, R2, R4
R3
U1
Notes:
1. Samsung:
www.samsung.com.
2. TDK:
www.tdk.com.
3. Vishay:
www.vishay.com.
4.
Micrel, Inc.:
www.micrel.com.
Part Number
CL10A475K08NNNC
C1608X7R2AP/NK
CRCW0402100KFKED
CRCW04022R00FKED
MIC943X5YMT
Manufacturer
Samsung
TDK
(2)
(3)
(3)
(4)
(1)
Description
Capacitor, 4.7µF Ceramic, 16V, X5R, Size 0603
Capacitor, 10nF Ceramic, 50V, X7R, Size 0603
Resistor, 100kΩ, Size 0402
Resistor, 2.0Ω, Size 0402
500mA LDO with Ripple Blocker Technology
Qty.
2
1
3
1
1
Vishay
Vishay
Micrel, Inc.
June 11, 2013
3
Revision 1.0
Micrel, Inc.
MIC94325/45/55 Evaluation Board
Evaluation Board Schematic (Fixed)
Bill of Materials
Item
C1, C2
R1
R2
U1
Notes:
5. Samsung:
www.samsung.com.
6. Vishay:
www.vishay.com.
7.
Micrel, Inc.:
www.micrel.com.
Part Number
CL10A475K08NNNC
CRCW04022R0FKED
CRCW0402100KFKED
MIC94355-XYMT
Manufacturer
Samsung
Vishay
Vishay
(5)
(6)
(6)
(7)
Description
Capacitor, 4.7µF Ceramic, 16V, X5R, Size 0603
Resistor, 2.0Ω, Size 0402
Resistor, 100kΩ, Size 0402
500mA LDO with Ripple Blocker Technology
Qty.
2
2
1
Micrel, Inc.
June 11, 2013
4
Revision 1.0
Micrel, Inc.
MIC94325/45/55 Evaluation Board
PCB Layout Recommendations (MIC94325)
Top Layer
Bottom Layer
June 11, 2013
5
Revision 1.0
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