MIC94305 Evaluation Board 500mA Switch with Ripple Blocker™ Technology General Description The MIC94305 is an integrated load switch that 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 (VOUT) 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. 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 Description MIC94305YMT EV 500mA Ripple Blocker Evaluation Board Precautions The MIC94305 evaluation board does not have reverse polarity protection. Applying a negative voltage to the VIN terminal may damage the device. 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 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. Figure 1 shows the frequency response of the MIC94305. PSRR COUT = 4.7µF 0 -10 PSRR (dB) -20 500mA -30 -40 300mA -50 -60 -70 VIN = 2.5V + 40mVpp 10mA -80 10 10 100 100 1K 10,000 10K 100,00 100K 1,000,0 1M 10,000, 10M 1,000 00 000 0 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 VSUPPLY (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 VSUPPLY 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. 1kΩ 1kΩ 1kΩ VOUT = VSUPPLY + VNETWORKANALYZER 1 + 1kΩ + 1kΩ 1kΩ 1kΩ + 1kΩ 1 1 VOUT = VSUPPLY + VNETWORKANALYZER (2) 2 2 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. June 11, 2013 VOUT = VSUPPLY + VNETWORKANALYZER Eq. 1 2 Revision 1.0 Micrel, Inc. MIC94305 Evaluation Board Evaluation Board Schematic Bill of Materials Item Part Number C1, C2 CL10A475K08NNNC R1 CRCW04022R25FKED R2 CRCW0402100KFKED U1 MIC943X5YMT Manufacturer Samsung (1) (2) Vishay Vishay (3) Micrel, Inc. Description Qty. Capacitor, 4.7µF Ceramic, 16V, X5R, Size 0603 2 Resistor, 2.25Ω, Size 0402 1 Resistor, 100kΩ, Size 0402 1 500mA LDO with Ripple Blocker Technology 1 Notes: 1. Samsung: www.samsung.com. 2. Vishay: www.vishay.com. 3. Micrel, Inc.: www.micrel.com. 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. © 2013 Micrel, Incorporated. June 11, 2013 5 Revision 1.0