MIC47100 Evaluation Board 1A Low Voltage LDO Regulator General Description The demonstration board can be used to evaluate the MIC47100. The MIC47100, a 1A, high speed, low dropout linear regulator, utilizes a split supply input to regulate low output voltages. It is offered in an 8-pin power MSOP and 2mm x 2mm MLF® packages. The MIC47100 is also offered in fixed and adjustable output versions. Please check the datasheet for all available variations. The evaluation board accommodates the adjustable version. Requirements The MIC47100 requires two power supplies, one to provide a minimum of 1A to the VIN and the other to provide VBIAS current. VBIAS, requiring relatively light current, provides power to the control portion of the MIC47100. Bypassing on the BIAS pin is recommended to improve performance of the regulator during line and load transients. Small ceramic capacitors from VBIAS-to-ground help reduce high frequency noise from being injected into the control circuitry from the bias and are good design practices. Circuit Description The MIC47100 high speed regulator is easy to use. It requires an output capacitor of 1µF or greater to maintain stability. The design is optimized for use with low ESR ceramic chip capacitors. An input capacitor is required when the power supply is more than 4-inches away from the device. All evaluation boards include an input capacitor within 1-inch of the device. This is the maximum recommended distance from the device that the capacitor should be placed. The evaluation board has a 10µF ceramic on the VIN pin. Although this is much larger than required for the device, this was designed to allow for the long inductive test leads that will be attached to the evaluation board. The output can be selected by using the evaluation board jumper. The available output options on the evaluation board are 1.0V, 1.2V, 1.5V and 1.8V. Also, a 0.8V output can be obtained by removing the jumper altogether. Any of the four bottom feedback resistors can be substituted to obtain a different output voltage. The equation to set the output is as follows: ⎛ R1 ⎞ VOUT = VREF ⎜ + 1⎟ ⎝ R2 ⎠ VREF = 0.7 R1 on the evaluation board is set to 1k. Due to the high bandwidth of the MIC47100, larger values of R1 and the parasitic capacitance of the feedback pin introduce an additional pole. For R1 values greater than 1k, a feed forward capacitor across R1 will help improve stability margin. Since R1 on the evaluation board is set to 1k, the formula for adjusting the output to the desired level is as following: ⎛V ⎞ R2 = ⎜⎜ REF − VREF ⎟⎟ × R1 ⎝ VOUT ⎠ ⎛ 0.7V ⎞ − 0.7V ⎟⎟ × 1k R2 = ⎜⎜ ⎝ VOUT ⎠ Ordering Information Part Number Description MIC47100YML EV Evaluation board for the MIC47100YML device MLF and MicroLeadFrame are registered 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 May 2008 M9999-050508-A Micrel, Inc. MIC47100 Evaluation Board Evaluation Board Schematic Bill of Materials Item Part Number Manufacturer (1) Description Qty. C1, C3 GRM40 XR5 105K 10 Murata 0.1µF, 10V capacitor 2 C2 GRM235Y5V106Z10 Murata(1) 10µF, 10V capacitor 1 Vishay Dale (2) 1kΩ, 1%, 1/10W, 0805 resistor 1 (2) 2.32kΩ, 1%, 1/10W, 0805 resistor 1 1.43kΩ, 1%, 1/10W, 0805 resistor 1 Vishay Dale (2) 887Ω, 1%, 1/10W, 0805 resistor 1 Vishay Dale (2) 634Ω, 1%, 1/10W, 0805 resistor 1 (3) 1A Low Voltage LDO Regulator 1 R1 CRCW08051001FRT1 R2 CRCW08052321FRT1 Vishay Dale R3 CRCW08051431FRT1 Vishay Dale(2) R4 R5 U1 CRCW0805887FRT1 CRCW08056340FRT1 MIC47100YML Micrel, Inc. Notes: 1. Murata: www.murata.com 2. Vishay Dale: www.vishay.com 3. Micrel, Inc.: www.micrel.com May 2008 2 M9999-050508-A Micrel, Inc. MIC47100 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer May 2008 3 M9999-050508-A Micrel, Inc. MIC47100 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 The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. 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. © 2008 Micrel, Incorporated. May 2008 4 M9999-050508-A