MIC2205 Evaluation Board High Efficiency 2Mhz Step-Down Converter with LOW™ Mode General Description The Micrel MIC2205 is a high efficiency 2MHz PWM synchronous step-down switching regulator that features a LOWQ™ LDO standby mode that draws only 18µA of quiescent current. The MIC2205 features an ultra-low noise, small size, and high efficiency solution for portable power applications. In PWM mode, the MIC2205 operates at a constant frequency of 2MHz. Under light load conditions, such as in system sleep or standby modes, the PWM switching operation can be disabled to reduce switching losses. In this light load LOWQ™ mode, the LDO maintains the output voltage and draws only 18µA of quiescent current. The LDO mode of operation saves battery life while not introducing spurious noise and high ripple as experienced with pulse skipping or bursting mode regulators. The MIC2205 operates from a 2.7V to 5.5V input and features internal power MOSFETs that can supply up to 600mA of output current in PWM mode. It can operate with a maximum duty cycle of 100% for use in low-dropout conditions. Requirements The MIC2205 evaluation board requires an input power source that is able to deliver greater than 1A at 2.7V. The output load can either be an active or passive source. Precautions The evaluation board does not have reverse polarity protection. Applying a negative voltage to the VIN terminal may damage the device. In addition, the maximum operating voltage of the MIC2205 evaluation board is 5.5V. Exceeding 6V on the input could damage the device. Getting Started 1. Connect an external supply to VIN terminal. Apply desired input voltage to the VIN and ground terminals of the evaluation board, paying careful attention to polarity and supply voltage (2.7V ≤ VIN ≤ 5.5V). An ammeter may be placed between the input supply and the VIN terminal to the evaluation board. Be sure to monitor the supply voltage at the VIN terminal. The ammeter and/or power lead resistance can reduce the voltage supplied to the input. 2. Connect the load to the VOUT and ground terminals. The load can be either passive (resistive) or active (electronic load). An ammeter can be placed between the load and the VOUT terminal. Ensure the output voltage is monitored at the VOUT terminal. The default output voltage is set to 1.8V. This can be adjusted by changing the feedback resistors. (see Output Voltage). 3. Enable the MIC2205. Apply a 1.3V or greater voltage source to the enable pin. LOWQ 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 M9999-051606 May 2006 (408) 955-1690 Micrel, Inc MIC2205 Evaluation Board LOWQTM The MIC2205 is a 600mA PWM power device that utilizes a LOWQ™ light load mode to maximize battery efficiency in light load conditions. This is achieved with a LOWQ™ control pin that when pulled low, (Remove JP1), shuts down all the biasing and drive current for the PWM regulator, drawing only 18µA of operating current. This allows the output to be regulated through the LDO output that is capable of providing 60mA of output current. This method has the advantage of producing a clean, low current, ultra low noise output in LOWQ™ mode. During LOWQ™ mode, the SW node becomes high impedance, blocking current flow. Other methods of reducing quiescent current, such as pulse frequency modulation (PFM) or bursting techniques, create large amplitude, low frequency ripple voltages that can be detrimental to system operation. Output Voltage The output voltage on the MIC2205 evaluation board is adjustable. The output voltage is controlled by the feedback resistors (R1 and R2) and can be calculated as follows: ⎛ R1 ⎞ + 1⎟ VOUT = 1.0V × ⎜ ⎝ R2 ⎠ The evaluation board is initially adjusted to 1.8V, but can easily be modified by removing R2 and replacing it with the value that yields the desired output voltage. (Removing R2 sets the output to 1.0V). R2 = May 2006 100kΩ ⎛ VOUT ⎞ ⎜⎜ − 1⎟⎟ ⎝ 1.0V ⎠ When more than 60mA is required, the LOWQ pin can be forced high, (Connect JP1), causing the MIC2205 to enter PWM mode. In this case, the LDO output makes a "hand-off" to the PWM regulator virtually without any variation in output voltage. The LDO output then turns off allowing up to 600mA of current to be efficiently supplied through the PWM output to the load. 2 M9999-051606 (408) 955-1690 Micrel, Inc. MIC2205 Evaluation Board VIN 2.7V to 5.5V 8 R3 10K C2 0.1µF 4 6 C1 1µF R4 10K C3 0.1µF GND MIC2205BML/YML VIN SW AVIN LDO EN 7 LOWQ 3 BIAS AGND 1 9 VOUT 1.8V L1 2.2µH 600mA 2 C5 2.2µF R1 100K FB PGND 5 C4 120pF R2 124K 10 GND Bill of Material MIC2205 Evaluation Board Ref Des Part Number 06036D475MAT2A C1608X5R0J475M C1005X5R1C104K GRM155R61C104K C1005X5R1C104K GRM155R61C104K VJ0402A121KXJAT 06036D225MAT2A GRM188R60J225KE19D C1608X5R1A225K LQH32CN2R2M53 VLF3010AT-2R2M1R0 CBC2016T2R2M CRCW04021003FRT1 CRCW04021243FRT1 CRCW04021002FRT1 CRCW04021002FRT1 MIC2205BML/YML* C1 C2 C3 C4 C5 L1 R1 R2 R3 R4 U1 Description Manufacturer 4.7µF 6.3V X5R 0603 Ceramic Capacitor 0.1µF 16V X5R 0402 Ceramic Capacitor 0.1µF 16V X7R 0402 Ceramic Capacitor 0.1µF 16V X5R 0402 Ceramic Capacitor 0.1µF 16V X7R 0402 Ceramic Capacitor 120pF 16V X7R 0402 Ceramic Capacitor 2.2µF 6.3V X5R 0603 Ceramic Capacitor 2.2µF 10V X5R 0603 Ceramic Capacitor 2.2µH 790mA Inductor 2.2µH 100mA Inductor 2.2µH 750mA Inductor 100kΩ 1% 0402 Resistor 124kΩ 1% 0402 Resistor 10kΩ 1% 0402 Resistor 10kΩ 1% 0402 Resistor 2MHz PWM Step-Down Converter/LDO TDK Murata TDK Murata TDK Murata Vishay AVX Murata TDK Murata TDK Taiyo Yuden Vishay Vishay Vishay Vishay Micrel Notes: 1. AVX: www.avx.com 2. Murata: www.murata.com 3. TDK: www.tdk.com 4. Vishay: www.vishay.com 5. Taiyo Yuden: www.t-yuden.co 6. Micrel, Inc.: www.micrel.com * Micrel IC = Pb-Free May 2006 3 M9999-051606 (408) 955-1690 Micrel, Inc. MIC2205 Evaluation Board Printed Circuit Board Layouts May 2006 Figure 1a. Top Silkscreen Figure 1b. Top Layer Figure 1c. Bottom Silkscreen Figure 1d. Bottom Layer 4 M9999-051606 (408) 955-1690 Micrel, Inc. MIC2205 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 This 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. © 2005 Micrel Incorporated May 2006 5 M9999-051606 (408) 955-1690