MIC2205 2MHz PWM Synchronous Buck Regulator with LDO Standby Mode General Description Features The Micrel MIC2205 is a high efficiency 2MHz PWM synchronous buck (step-down) regulator that features a LOWQ™ LDO standby mode that draws only 18µA of quiescent current. The MIC2205 allows an ultra-low noise, small size, and high efficiency solution for portable power applications. In PWM mode, the MIC2205 operates with a constant frequency 2MHz PWM control. 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 2.7V to 5.5V input and features internal power MOSFETs that can supply up to 600mA output current in PWM mode. It can operate with a maximum duty cycle of 100% for use in low-dropout conditions. The MIC2205 is available in the 3mm x 3mm MLF10L package with a junction operating range from –40°C to +125°C. Data sheets and support documentation can be found on Micrel’s web site at www.micrel.com. • 2.7 to 5.5V supply voltage • Light load LOWQ™ LDO mode 18µA quiescent current Low noise, 75µVrms • 2MHz PWM mode Output current to 600mA >95% efficiency 100% maximum duty cycle • Adjustable output voltage option down to 1V Fixed output voltage options available • Ultra-fast transient response • Stable with 1µF ceramic output capacitor • Fully integrated MOSFET switches • Micropower shutdown • Thermal shutdown and current limit protection • Pb-free 3mm x 3mm MLF-10L package • –40°C to +125°C junction temperature range Applications • Cellular phones • PDAs • USB peripherals ____________________________________________________________________________________________________ Typical Application MIC2205 V IN 2.7V to 5.5V C1 1µF LowQ C2 0.1µF 8 VIN SW 9 4 AVIN LDO 2 6 EN 7 LOWQ FB 5 3 BIAS 2.2µH R1 100k R2 125k VOUT C3 100pF C4 2.2µF PGND AGND GND 10 1 GND Adjustable Output Buck Regulator with LOWQ™ Mode 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 March 2005 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Ordering Information Part Number Output Voltage(1) Junction Temp. Range Package Lead Finish MIC2205YML Adj. –40° to +125°C 3x3 MLF-10L Pb-free MIC2205-1.58YML 1.58V –40° to +125°C 3x3 MLF-10L Pb-free Note: 1. Other Voltage options available. Contact Micrel for details. Pin Configuration 3mm x 3mm MLF-10L (ML) Pin Description Pin Number Pin Name 1 AGND 2 LDO LDO Output (Output): Connect to VOUT for LDO mode operation. 3 BIAS Internal circuit bias supply. Must be de-coupled to signal ground with a 0.1µF capacitor and should not be loaded. 4 AVIN Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND. 5 FB Feedback. Input to the error amplifier. For the Adjustable option, connect to the external resistor divider network to set the output voltage. For fixed output voltage options, connect to VOUT and an internal resistor network sets the output voltage. 6 EN Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 5µA. 7 _____ LOWQ 8 VIN Supply Voltage (Input): Supply voltage for the internal switches and drivers. 9 SW Switch (Output): Internal power MOSFET output switches. 10 PGND EP GND March 2005 Pin Function Analog (signal) Ground. Enable LDO Mode (Input): Logic low enables the internal LDO and disables the PWM operation. Logic high enables the PWM mode and disables the LDO mode. Power Ground. Ground, backside pad. 2 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) ............................................ +6V Output Switch Voltage (VSW) ............................... +6V Output Switch Current (ISW) ................................... 2A Logic Input Voltage (VEN,VLOWQ) .............. -0.3V to VIN Storage Temperature (Ts)................ -60°C to +150°C ESD Rating(3) ....................................................... 3kV Supply Voltage (VIN)............................+2.7V to +5.5V Logic Input Voltage (VEN,VLOWQ) .............. -0.3V to VIN Junction Temperature (TJ) .............. –40°C to +125°C Junction Thermal Resistance 3x3 MLF-10L (θJA)................................... 60°C/W Electrical Characteristics (4) VIN = VEN = VLOWQ =3.6V; L = 2.2µH; COUT = 2.2µF; TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C Parameter Condition Min (turn-on) 2.45 Supply Voltage Range Under-Voltage Lockout Threshold Typ Max 5.5 V 2.55 2.65 V 2.7 UVLO Hysteresis 100 Units mV Quiescent Current, PWM mode VFB = 0.9 * VNOM (not switching) 690 900 µA Quiescent Current, LDO mode VLOWQ = 0V;IOUT = 0mA 16 29 µA Shutdown Current VEN = 0V 0.01 5 µA [Adjustable] Feedback Voltage ± 1% ± 2% (over temperature) 0.99 0.98 1 1.01 1.02 V [Fixed Output] Voltages Nominal VOUT tolerance -1 -2 +1 +2 % FB pin input current 1 VFB = 0.9 * VNOM Output Voltage Line Regulation VOUT > 2V; VIN = VOUT+300mV to 5.5V; ILOAD= 100mA VOUT < 2V; VIN = 2.7V to 5.5V; ILOAD= 100mA 0.13 Output Voltage Load Regulation, PWM Mode 20mA < ILOAD < 300mA 0.2 0.5 % Output Voltage Load Regulation, LDO Mode 100µA < ILOAD < 50mA VLOWQ = 0V 0.1 0.2 % Maximum Duty Cycle VFB ≤ 0.4V PWM Switch ONResistance ISW = 50mA VFB = 0.7VFB_NOM (High Side Switch) ISW = -50mA VFB = 1.1VFB_NOM (Low Side Switch) 0.75 1 nA Current Limit in PWM Mode 1.85 A % % 100 0.4 Ω 0.4 Oscillator Frequency 1.8 2 2.2 MHz LOWQ threshold voltage 0.5 0.85 1.3 V 0.1 2 µA 0.5 0.85 1.3 V 0.1 2 µA LOWQ Input Current Enable Threshold Enable Input Current LDO Dropout Voltage March 2005 IOUT = 50mA Note 5 110 3 mV M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Parameter Condition Min Output Voltage Noise LOWQ = 0V; COUT = 2.2µF, 10Hz to 100kHz LDO Current Limit LOWQ = 0V; VOUT = 0V (LDO Mode) Typ Max Units 75 µVrms 120 mA Over-Temperature Shutdown 160 °C Over-Temperature Hysteresis 20 °C 60 Notes 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5kΩ in series with 100pF. 4. Specification for packaged product only. 5. Dropout voltage is defined as the input-to-output differential at which the output voltage drops 2% below its nominal value that is initially measured at a 1V differential. For outputs below 2.7V, the dropout voltage is the input-to-output voltage differential with a minimum input voltage of 2.7V. March 2005 4 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Typical Characteristics – PWM Mode March 2005 5 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Typical Characteristics – PWM Mode (cont.) March 2005 6 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Typical Characteristics - LDO Mode March 2005 7 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Typical Characteristics – LDO Mode (cont.) March 2005 8 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Functional Diagram MIC2205 Block Diagram March 2005 9 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Functional Characteristics Load Transient PWM Mode Output Voltage AC Coupled (50mV/div) Output Current (100mA/div) LowQ = VIN Time 20 s/div Enable Transient PWM Mode VOUT (50mV/div) ENABLE (1V/div) LowQ = 0V Time 40 s/div March 2005 10 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Functional Characteristics March 2005 11 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Functional Description FB The feedback pin (FB) provides the control path to control the output. For adjustable versions, a resistor divider connecting the feedback to the output is used to adjust the desired output voltage. The output voltage is calculated as follows: VIN VIN provides power to the MOSFETs for the switch mode regulator section, along with the current limiting sensing. Due to the high switching speeds, a 1µF capacitor is recommended close to VIN and the power ground (PGND) pin for bypassing. Please refer to layout recommendations. ⎛ R1 ⎞ VOUT = VREF × ⎜ + 1⎟ ⎝ R2 ⎠ AVIN Analog VIN (AVIN) provides power to the LDO section and the bias through an internal 6 Ohm resistor. AVIN and VIN must be tied together. Careful layout should be considered to ensure high frequency switching noise caused by VIN is reduced before reaching AVIN. where VREF is equal to 1.0V. A feedforward capacitor is recommended for most designs using the adjustable output voltage option. To reduce battery current draw, a 100K feedback resistor is recommended from the output to the FB pin (R1). Also, a feedforward capacitor should be connected between the output and feedback (across R1). The large resistor value and the parasitic capacitance of the FB pin can cause a high frequency pole that can reduce the overall system phase margin. By placing a feedforward capacitor, these effects can be significantly reduced. Feedforward capacitance (CFF) can be calculated as follows: LDO The LDO pin is the output of the linear regulator and should be connected to the output. In LOWQ mode (LOWQ<1.5V), the LDO provides the output voltage. In PWM mode (LOWQ>1.5V) the LDO pin is high impedance. EN The enable pin provides a logic level control of the output. In the off state, supply current of the device is greatly reduced (typically <1µA). Also, in the off state, the output drive is placed in a "tri-stated" condition, where both the high side P-channel Mosfet and the low-side N-channel are in an “off” or non-conducting state. Do not drive the enable pin above the supply voltage. CFF = For fixed options A feed forward capacitor from the output to the FB pin is required. Typically a 100pF small ceramic capacitor is recommended SW The switch (SW) pin connects directly to the inductor and provides the switching current nessasary to operate in PWM mode. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes. LOWQ The LOWQ pin provides a logic level control between the internal PWM mode and the low noise linear regulator mode. With LOWQ pulled low (<0.5V), quiescent current of the device is greatly reduced by switching to a low noise linear regulator mode that has a typical IQ of 18µA. In linear (LDO) mode the output can deliver 60mA of current to the output. By placing LOWQ high (>1.5V), this transitions the device into a constant frequency PWM buck regulator mode. This allows the device the ability to efficiently deliver up to 600mA of output current at the same output voltage. PGND Power ground (PGND) is the ground path for the high current PWM mode. The current loop for the power ground should be as small as possible and separate from the Analog ground (AGND) loop. Refer to the layout considerations for more details. SGND Signal ground (SGND) is the ground path for the biasing and control circuitry. The current loop for the signal ground should be separate from the Power ground (PGND) loop. Refer to the layout considerations for more details. BIAS The BIAS pin supplies the power to the internal power to the control and reference circuitry. The bias is powered from AVIN through an internal 6Ω resistor. A small 0.1µF capacitor is recommended for bypassing. March 2005 1 2π × R1× 160kHz 12 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Applications Information Output Capacitor Even though the MIC2205 is optimized for a 2.2µF output capacitor, output capacitance can be varied from 1µF to 4.7µF. The MIC2205 utilizes type III internal compensation and utilizes an internal high frequency zero to compensate for the double pole roll off of the LC filter. For this reason, larger output capacitors can create instabilities. X5R or X7R dielectrics are recommended for the output capacitor. Y5V dielectrics lose most of their capacitance over temperature and are therefore, not recommended. In addition to a 2.2µF, a small 10nF is recommended close to the load for high frequency filtering. Smaller case size capacitors are recommended due to there lower ESR and ESL. The MIC2205 is a 600mA PWM power supply 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, 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, 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. When more than 60mA is required, the LOWQ pin can be forced high, causing the MIC2205 to enter PWM mode. In this case, the LDO output makes a "hand-off" to the PWM regulator with virtually no 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. Inductor Selection The MIC2205 is designed for use with a 2.2µH inductor. Proper selection should ensure the inductor can handle the maximum average and peak currents required by the load. Maximum current ratings of the inductor are generally given in two methods; permissible DC current and saturation current. Permissible DC current can be rated either for a 40°C temperature rise or a 10% to 20% loss in inductance. Ensure that the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. Peak inductor current can be calculated as follows: Input Capacitor A minimum 1µF ceramic is recommended on the VIN pin for bypassing. X5R or X7R dielectrics are recommended for the input capacitor. Y5V dielectrics lose most of their capacitance over temperature and are therefore, not recommended. A minimum 1µF is recommended close to the VIN and PGND pins for high frequency filtering. Smaller case size capacitors are recommended due to their lower ESR and ESL. Please refer to layout recommendations for proper layout of the input capacitor. March 2005 IPK = IOUT 13 ⎛ V VOUT ⎜⎜1 − OUT VIN ⎝ + 2× f ×L ⎞ ⎟ ⎟ ⎠ M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Layout Recommendations Top Bottom Note: The above figures demonstrate the recommended layout for the MIC2205 adjustable option. March 2005 14 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 MIC2205 V IN 2.7V to 5.5V C1 1µF LowQ C2 0.1µF 8 VIN SW 9 4 AVIN LDO 2 6 EN FB 5 7 LOWQ 3 BIAS 2.2µH R1 100k VOUT C3 100pF C4 2.2µF R2 125k PGND AGND 10 GND 1 GND Adjustable Output MIC2205 V IN 2.7V to 5.5V C1 1µF LowQ C2 0.1µF 8 VIN SW 9 4 AVIN LDO 2 6 EN FB 5 7 LOWQ 3 BIAS 2.2µH VOUT C3 100pF C4 2.2µF PGND AGND GND 10 1 GND Fixed Output Item Part Number Description Manufacturer C1 06036D105MAT2 GRM185R60J105KE21D 1µF Ceramic Capacitor X5R, 6.3V 0603 1µF Ceramic Capacitor X5R, 6.3V 0603 AVX (4) Murata 1 C4 06036D225MAT2 GRM188R61A225KE34 2.2µF Ceramic Capacitor X5R, 10V 0603 2.2µF Ceramic Capacitor X5R, 10V 0603 AVX (4) Murata 1 C3 VJ0402A101KXAA 100pF Ceramic Capacitor Vishay 1 C2 0201ZD103MAT2 GRM033R10J103KA01D 10nF Ceramic Capacitor 6.3V 0201 10nF Ceramic Capacitor 6.3V 0201 AVX (4) Murata 1 L1 LQH32CN2R2M53K CDRH2D14-2R2 2.2µH Inductor 97mΩ 3.2mmx2.5mmx1.55mm 2.2µH Inductor 94mΩ 3.2mmx3.2mmx1.55mm Murata (2) Sumida CRCW04021002F 100kΩ 1% 0402 Vishay Dale (1) R1 (1) (3) Qty (4) 1 (3) 1 (3) R2 CRCW04026652F CRCW04021243F CRCW04022003F CRCW04024023F 66.5 kΩ 1% 0402 For 2.5VOUT 124 kΩ 1% 0402 For 1.8 VOUT 200 kΩ 1% 0402 For 1.5 VOUT 402 kΩ 1% 0402 For 1.2 VOUT Open For 1.0 VOUT U1 MIC2205BML 2MHz Synchronous Buck Regulator with LOWQ Vishay Dale (3) Vishay Dale (3) Vishay Dale (3) Vishay Dale (3) Vishay Dale TM Mode Micrel, Inc. (5) 1 Notes: 1. For adjustable version only. 2. Sumida Tel: 408-982-9660 3. Murata Tel: 949-916-4000 4. Vishay Tel: 402-644-4218 5. Micrel, Inc. Tel: 408-944-0800 March 2005 15 M9999-031105 www.micrel.com Micrel, Inc. MIC2205 Package Information 10-Lead MLF™ (ML) 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. © 2004 Micrel, Incorporated. March 2005 16 M9999-031105 www.micrel.com