MIC69301/02 Evaluation Board Low VIN, Low VOUT 3A LDO Regulator General Description This evaluation board can be used to evaluate several of Micrel’s new, low-voltage, high-current, low-dropout linear voltage regulators. The MIC69301WR is a 3A LDO in an SPAK package with a fixed output voltage that offers the added functionality of an enable pin and an error flag output. The MIC69302WR is an adjustable version of the MIC69301WR in a SPAK package and it also has the added functionality of an enable pin, allowing the user to disable the device and put it into a zero-current off mode state. Requirements The evaluation board requires a power supply capable of supplying a minimum of 3A of output current. The maximum voltage of that power supply should be at least 5V. The evaluation board has jumpers to set the output voltage to: 3.3V, 2.5V, 1.8V or 1.5V. The output voltage can also be set to a different value by using the adjustable version (MIC69302) and by choosing R1 and R2 as detailed on the right. The MIC69301 has an input voltage range of 1.65V to 5.5V, therefore it is not limited to just 5V systems. Circuit Description The MIC69301 regulator is simple to implement, requiring only an output capacitor for proper operation. An input capacitor is required when the supply is greater than 4 inch away from the device. The evaluation board includes an input capacitor within 1 inch of the device. This is the recommended maximum distance away from the device that a capacitor should be placed. A minimum of 10µF of output capacitance is required for the MIC69301. Using large values of capacitance at the input and output will help to improve transient response. MIC69301/MIC69302 The MIC69301 circuit implements an error flag, an enable function, and sense pin. The enable function allows the user to put the device into a zero-current off state when the regulator is not required. The enable pin is an activehigh pin and needs to be pulled high (≥2V) to enable the device and pulled low (≤0.8V) to disable the device. The error flag function is a voltage monitor that indicates when the output falls out of regulation for any reason. The error flag output is an open-collector output, which is active-low, and requires a pull-up resistor for proper operation. R1 is a zero ohm resistor. All berg jumpers on JP2 must be left open. Boards assembled with the MIC69301 have a 100kΩ pull-up resistor from FLG to the output voltage. The MIC69302 is an adjustable regulator that implements an enable pin that allows the user to disable the device. The enable pin is also active-high and requires that pin to be pulled high to turn-on the output and pulled low to disable the output. A jumper (JP1) is available to tie that pin to either the input or to ground. The output voltage of the MIC69302 is adjustable down to 0.5V. The board is set-up with four set voltage options, A through D. A fifth option is available that can be custom set. The equation to set the output voltage is as follows: R1 ⎞ ⎛ VOUT = VREF ⎜1 + ⎟ R2 ⎠ ⎝ VREF = 0.5V On the board as it stands, R1 is set to 10kΩ. Using the equation and knowing that R1 = 10kΩ, a custom voltage can be determined by solving for R2 and placing an 0805 or 1206 resistor in the slot prepared and labeled E. ⎛ ⎞ VREF R2 = ⎜⎜ × R1⎟⎟ ⎝ VOUT − VRE F ⎠ ⎛ ⎞ 0.5V R2 = ⎜⎜ × 10k Ω ⎟⎟ ⎝ VOUT − 0.5 V ⎠ Leaving all jumpers open sets the output voltage to 0.5V. The MIC69302WR adjustable output evaluation board can be configured into a fixed output version in the following way: R6 = 10kΩ R1, R2, R3, R4, R5 Open Remove all jumpers from JP2 Replace U1 with MIC69301WR Minimum Load All of the devices require a minimum load of 10mA. A resistor is included on the board to provide a minimum load of 10mA. The resistor value is different depending on the voltage option that the board has. The MIC69301 has a 140Ω resistor to maintain approximately 10mA at 1.4V output voltage. The 140Ω resistor can be changed to set a 10mA load depending upon the desired output voltage. 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 M9999-053008-A Micrel, Inc. MIC69301/03 Evaluation Board Ordering Information Part Number Description MIC69302WR EV Evaluation board with the adjustable output MIC69302 device with Enable pin Evaluation Board Schematic R6 10k U1 MIC69301/02WR J1 +VIN VIN VOUT 4 C1 10µF/6.3V 1 EN FLG/ADJ 5 J6 2 D 1 C 4 B 3 A 6 R5 6.04k 5 R4 9.76k 8 R3 22.1k 7 3 R2 48.7k J2 GND A: B: C: D: VOUT = 1.5V VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V J3 GND Option for Fixed VOUT (MIC69301-xxWR) R6 = 10k R1, R2, R3, R4, R5 = Open Remove all jumpers from JP1 May 2008 J3 VOUT C2 10µF/6.3V R1 10k GND J5 EN 2 Option for Adjustable VOUT (MIC69302WR) R6 = Open Select desired output voltage with berg jumper on JP1 2 M9999-053008-A Micrel, Inc. MIC69301/02 Evaluation Board Bill of Materials Item C1, C2 Part Number R2 R3 Description Qty 10µF/6.3V, X7R, Ceramic Capacitor 2 (1) C2012X5R0J106K TDK 0805D106MAT2A AVX(2) GRM21CR70J106KA01B Murata(3) VJ0805Y106KXYAT R1, R6 Manufacturer (4) Vishay CRCW08051002FRT1 Vishay(4) 10k, 1%, 1/10W, 0805 Resistor 2 CRCW08054991FRT1 (4) 4.99k, 1%, 1/10W, 0805Resistor 1 (4) 3.83k, 1%, 1/10W, 0805Resistor 1 (4) CRCW08053831FRT1 Vishay Vishay R4 CRCW08052491FRT1 Vishay 2.49k, 1%, 1/10W, 0805Resistor 1 R5 CRCW08051781FRT1 Vishay(4) 1.78k, 1%, 1/10W, 0805Resistor 1 MIC69301WR Micrel(5) Low VIN, Low VOUT 3A LDO Regulator 1 U1 MIC69302WR Notes: 1. TDK: www.tdk.com 2. AVX: www.avx.com 3. Murata: www.murata.com 4. Vishay Dale: www.vishay.com 5. Micrel: www.micrel.com May 2008 3 M9999-053008-A Micrel, Inc. MIC69301/02 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer May 2008 4 M9999-053008-A Micrel, Inc. MIC69301/02 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. © 2007 Micrel, Incorporated. May 2008 5 M9999-053008-A