incorporates Micrel’s Ripple Blocker active filter
technology. The MIC94305 provides high-frequency ripple
attenuation (switching noise rejection) for applications,
such as RF applications, where switching noise cannot be
tolerated by sensitive downstream circuits. The MIC94305
replaces a high-side switch, large filtering inductor, and
capacitors to save board area.
The MIC94305 operates from an input voltage of 1.8V to
3.6V, allowing true load switching of low-voltage power
rails in any electronic device. The output voltage (V
OUT
) is
set at a fixed drop from the input voltage.
Data sheets and support documentation can be found on
Micrel’s web site at:
www.micrel.com.
Requirements
The MIC94305 evaluation board requires an input power
supply that can deliver a minimum of 800mA at a voltage
range of 1.8V to 3.6V. The output load can be either active
or passive.
Precautions
The MIC94305 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 MIC94305.
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). Monitor the output voltage at
the VOUT terminal.
Ordering Information
Part Number
MIC94305YMT EV
Description
500mA Ripple Blocker Evaluation Board
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.
MIC94305 Evaluation Board
Power Supply Ripple Rejection (PSRR)
Measurements
Figure 1 shows the frequency response of the MIC94305.
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
MIC94305. The circuit shown in Figure 3 solves this
problem by using the MIC911 as a summing amplifier.
PSRR C
OUT
= 4.7µF
0
-10
-20
500mA
PSRR (dB)
-30
-40
-50
-60
-70
V
IN
= 2.5V + 40mVpp
-80
10
10
100
100
1K
10K
100K
1M
10M
1,000 10,000 100,00 1,000,0 10,000,
00
000
0
10mA
300mA
FREQUENCY (Hz)
Figure 1. MIC94305 Ripple 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 affects.
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.
MIC94305 Evaluation Board
Evaluation Board Schematic
Bill of Materials
Item
C1, C2
R1
R2
U1
Notes:
1. Samsung:
www.samsung.com.
2. Vishay:
www.vishay.com.
3.
Micrel, Inc.:
www.micrel.com.
Part Number
CL10A475K08NNNC
CRCW04022R25FKED
CRCW0402100KFKED
MIC943X5YMT
Manufacturer
Samsung
Vishay
Vishay
Micrel, Inc.
(3)
(1)
(2)
Description
Capacitor, 4.7µF Ceramic, 16V, X5R, Size 0603
Resistor, 2.25Ω, Size 0402
Resistor, 100kΩ, Size 0402
500mA LDO with Ripple Blocker Technology
Qty.
2
1
1
1
June 11, 2013
3
Revision 1.0
Micrel, Inc.
MIC94305 Evaluation Board
PCB Layout Recommendations
Top Layer
Bottom Layer
June 11, 2013
4
Revision 1.0
Micrel, Inc.
MIC94305 Evaluation Board
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB
http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
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