MIC2224 High Efficiency 2MHz PWM Buck Converter with DAC Input and 40mΩ Bypass Switch General Description Features The MIC2224 is a high efficiency 2MHz PWM synchronous buck switching regulator optimized for powering 2.5G and 3G CDMA RF Power Amplifiers. The output voltage of MIC2224 can be dynamically adjusted with an external DAC to maximize PA efficiency versus required output power. When the PA requires the highest power, the DAC can be used to enable a low on-resistance, 40mΩ, bypass switch that powers the PA directly from the battery. The 2MHz PWM operation of MIC2224 allows the smallest possible components. It also allows the device to easily meet stringent W-CDMA VOUT response specifications. The MIC2224 operates from a 2.7V to 5.5V input, making it ideal for single cell Li-Ion applications. The device features built-in power MOSFETs that can supply up to 600mA of output current in PWM mode, or over 1A in bypass mode. The MIC2224 can operate with a maximum duty cycle of 100% for use in low-dropout conditions. The MIC2224 has a junction temperature range of –40°C to +125°C and is available in a 10-pin 3mm x 3mm MLF® package. Data sheets and support documentation can be found on Micrel’s web site at www.micrel.com. • • • • • • • • • • • • • • 2.7V to 5.5V input voltage range DAC-adjustable output voltage down to 0.3V 600mA output current in PWM mode Internally protected 40mΩ bypass switch Allows direct connection of battery to load Over 95% efficient Fully integrated MOSFET switches Constant 2MHz PWM operation Internal soft-start 1% line and load regulation <1µA shutdown current Under-voltage lockout Thermal shutdown and current limit protection –40°C to +125°C junction temperature range Applications • Cellular phones • PDAs Typical Application GND 7 PGND GND 10 X 3 3.0 2.4 AC DAC AGND Bypass Mode 3.6 C2 1µF ENABLE D 6 4.2 V DAC 8, 9 VIN = 4.2V 1.8 1.2 = 4 VOUT 4.8 UT C1 1µF AVIN 5.4 VOUT O 5 SW VIN 1 L1 4.7µH V 2, 3 MIC2224 VOUT (V) VIN 2.6V to 5.5V 0.6 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 VDAC (V) 2MHz PWM Converter with DAC Input and 40mΩ Bypass Switch MLF and MicroLeadFrame are registered trademarks or 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 September 2006 1 M9999-091106 Micrel, Inc. MIC2224 Ordering Information(1) Part Number Output Voltage Junction Temp. Range Package Lead Finish MIC2224YML Adj. –40°C to +125°C 10-Pin 3mm x 3mm MLF® Pb-Free Pin Configuration SW 1 10 PGND VIN 2 9 VOUT VIN 3 8 VOUT EN 4 7 AGND AVIN 5 EP 6 DAC 10-Pin MLF® (ML) Pin Description Pin Number Pin Name 1 SW Switch (Output): Internal power MOSFET output switches. 2, 3 VIN Supply Voltage (Input): Requires bypass capacitor to GND. 4 EN A low level EN will power down the device, reducing the quiescent current to under 5µA (typ 1µA). 5 AVIN Supply Voltage (Input): Requires bypass capacitor to GND. 6 DAC DAC Control Input. Provides control of output voltage. The output voltage is 3 X the DAC voltage. (Ex. 0.5VDAC = 1.5VOUT). Bypass mode is enabled when the DAC voltage exceeds 1.2V. 7 AGND Signal Ground of chip. 8, 9 VOUT Source of Internal P-Channel MOSFET and Feedback of internal PWM regulator. 10 PGND Power Ground of chip. EP Exposed Pad September 2006 Pin Function Connect to ground. 2 M9999-091106 Micrel, Inc. MIC2224 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) ............................................... 0V to 6V Output Switch Voltage (VSW). ...........................................6V DAC Input Voltage (VDAC)............................ 0V to VIN +0.3V Output Switch Current (ISW)...........................................2.5A Logic Input Voltage (VEN) ............................ 0V to VIN +0.3V Storage Temperature (Ts) .........................–65°C to +150°C Supply voltage (VIN) ....................................... 2.7V to +5.5V Output Voltage (VOUT). ........................................ 0V to 5.5V DAC Input Voltage (VDAC).................................... 0.1V to VIN Junction Temperature (TJ) ........................ –40°C to +125°C Thermal Resistance MLF®-10 (θJA) ....................................................60°C/W Electrical Characteristics(4) VIN = VEN = 3.6V; VDAC = 0.6V; L = 4.7µH; COUT = 1µF; TA = 25°C, bold values indicate –40°C< TJ < +125°C, unless noted. Parameter Condition Min Typ Max Units 5.5 V 360 450 µA 1 5 µA 2.7 Supply Voltage Range Total Quiescent Current VDAC = 0.6V VOUT = 2.4V (regulator on, not switching) Shutdown Current VEN = 0V (regulator off) 100 Maximum Duty Cycle % Regulation 1.8 1.854 V 3.0V ≤ VIN ≤ 4.5, ILOAD= 10mA 0.05 0.5 %/V 0mA < IOUT < 500mA 0.2 ISW = -100mA, High-Side Switch ISW = 100mA , Low-Side Switch 0.55 0.6 0.75 0.85 Ω Ω 0.65 0.85 1.6 A 1.8 2 2.2 MHz 0.5 0.9 1.3 V Output Voltage VDAC = 0.6V, ILOAD =0mA Output Voltage Line Regulation Output Voltage Load Regulation 1.746 % Output Switch On-Resistance Current limit (Peak SW Current) Oscillator Frequency Enable / UVLO Enable Pin Threshold Enable Pin Hysteresis 30 Enable Pin Input Current EN high to 90% VOUT Under-Voltage Lockout Threshold (turn-on) UVLO Hysteresis mV 0.01 1 µA 25 50 µs 2.6 2.7 V 85 mV DAC Input DAC Input Current Output Voltage/DAC Voltage 0.15 (internally set) 2 3 µA V/V Bypass Switch 1.176 Bypass Switch Threshold Bypass Switch Hysteresis 1.2 1.224 35 V mV Bypass Transition Time 10 µs Bypass Switch On-Resistance 40 mΩ 5 Bypass Switch Leakage 1 Bypass Over-Current Limit Current Limit Retry Time Current Limit Retry Duty Cycle September 2006 3 1.4 2.5 µA A 32 µs 12.5 % M9999-091106 Micrel, Inc. Parameter MIC2224 Condition Min Typ Max Units Over Temperature Shutdown Shutdown Temperature 160 °C Over Temperature Shutdown Hysteresis 20 °C 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, 1.5k in series with 100pF. 4. Specification for packaged product only. September 2006 4 M9999-091106 Micrel, Inc. MIC2224 Typical Characteristics Efficiency 2.7VOUT 100 EFFICIENCY (%) 4.2VIN 80 75 75 70 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) 60 0 0.6 3.6VIN 4.2VIN 100 3VIN 90 80 70 65 60 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) 70 60 50 10 0 0 0.6 1.836 1.827 1.818 1.809 1.800 1.791 VOUT = 1.8V 1.782 VDAC = 0.6V VIN = 3.6V 1.773 0 100 200 300 400 500 600 LOAD CURRENT (mA) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 1.827 3.0 2.0 -40°C 25°C 1.5 1.0 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) 0.2 0.4 0.6 0.8 1.0 1.2 1.4 DAC VOLTAGE (V) September 2006 80 70 60 40 0 0.6 Output Voltage vs. Temperature 3.6VIN 4.2VIN 3.3 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) 0.6 VOUT/DAC vs. Temperature 3.2 2.05 2.00 1.95 1.90 1.80 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 5 3.0 2.9 2.7 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Frequency vs. Temperature 2.10 3.1 2.8 VDAC = 0.6V 1.85 0.5 90 3V IN 50 1.746 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) FREQUENCY (MHz) VOUT /DAC 4.2VIN 2.15 3.5 0 0 3.6VIN 1.773 1.764 1.755 2.20 0.6 100 1.791 1.782 4.0 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) Efficiency 0.6VOUT 1.818 1.809 1.800 Output Voltage vs. DAC Voltage 125°C 50 0 0.6 40 30 20 Load Regulation 2.5 65 60 55 Efficiency 0.9VOUT EFFICIENCY (%) 85 80 75 EFFICIENCY (%) 3VIN 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) 3.6VIN 4.2VIN 75 70 65 100 95 90 4.5 4VIN 80 Efficiency 1.2VOUT 55 50 0 3.5VIN 85 EFFICIENCY (%) 70 0 90 3VIN 90 85 80 VOUT /DAC EFFICIENCY (%) 85 3.6VIN 100 95 3VIN 95 EFFICIENCY (%) 3VIN 95 90 Efficiency 1.5VOUT 450 QUIESCENT CURRENT (µA) 100 Efficiency 1.8VOUT Quiescent Current vs. Temperature 400 350 300 250 200 150 100 50 VIN = 3.6V 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) M9999-091106 Micrel, Inc. MIC2224 Typical Characteristics (cont.) 400 ENABLE THRESHOLD (V) QUIESCENT CURRENT (µA) 450 Quiescent Current vs. Temperature 350 300 250 200 150 100 50 0 2.7 3.26 3.82 4.38 4.94 SUPPLY VOLTAGE (V) September 2006 5.5 1.5 1.4 Enable Threshold vs. Supply Voltage 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 2.7 3.26 3.82 4.38 4.94 SUPPLY VOLTAGE (V) 6 5.5 M9999-091106 Micrel, Inc. MIC2224 Functional Characteristics Bypass Mode Transient Bypass Mode Transient 0V DAC Voltage (500mV/div) DAC Voltage (500mV/div) 0V 0V 0V Current Limit Transient (Bypass Mode) Current Limit Transient (PWM Mode) Output Voltage (2V/div) Time 10µs Output Voltage (2V/div) Time 10µs VIN = 3.6V VDAC = 1.3V L = 4.7µH COUT = 1µF 0V VIN = 3.6V VDAC = 1.3V L = 4.7µH COUT = 1µF Output Current (500mA/div) Output Current (500mA/div) 0V 0mA 0mA Time 2ms Time 100µs Enable Transient Load Transient VIN = 3.6V VDAC = 0.6V L = 4.7µH COUT = 1µF Output Voltage (100mV/div) Output Voltage (1V/div) VIN = 4.2V L = 4.7µH COUT = 1µF Output Voltage (2V/div) Output Voltage (2V/div) VIN = 4.2V L = 4.7µH COUT = 1µF VIN = 3.6V VDAC = 0.6V L = 4.7µH COUT = 1µF Enable Voltage (1V/div) Output Current (100mA/div) 0V 0mA 0V Time 10µs September 2006 Time 10µs 7 M9999-091106 Micrel, Inc. MIC2224 Functional Characteristics (cont.) Output Voltage Transient Output Voltage (1V/div) Output Voltage (1V/div) Output Voltage Transient 0V DAC Voltage (500mV/div) DAC Voltage (500mV/div) 0V VIN = 3.6V L = 4.7µH COUT = 1µF 0V VIN = 3.6V L = 4.7µH COUT = 1µF 0V Time 10µs Time 10µs VIN = 3.6V VDAC = 0.6V IOUT = 600mA L = 4.7µH COUT = 1µF Switch Voltage (2V/div) Output Voltage Ripple AC Coupled (10mV/div) Switch Voltage - Output Ripple Time 400nµs September 2006 8 M9999-091106 Micrel, Inc. MIC2224 Functional Diagram VIN VOUT 1.2V AVIN SW DRIVER DAC EN 80k 40k AGND PGND MIC2224 Block Diagram September 2006 9 M9999-091106 Micrel, Inc. MIC2224 VOUT The VOUT pin connects the internal bypass drain and the feedback signal to the output. The bypass applies the input voltage through a low resistance (40mΩ typical) P-Channel MOSFET switch. The feedback signal provides the control path to set the output at 3X the DAC voltage. Functional Description 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. SW The switch (SW) pin connects directly to the inductor and provides the switching current necessary to operate in PWM mode. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes. AVIN Analog VIN (AVIN) provides power to the internal reference and control section. 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. 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. DAC The DAC pin is the control pin that sets the output voltage. The Output voltage is 3X the voltage set on the DAC pin. When 1.2V or greater is applied to the DAC pin, the MIC2224 enters bypass mode. In bypass mode, the input supply is connected to the output through a 40mΩ P-Channel MOSFET. AGND Signal ground (AGND) 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. 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 and bypass switch are placed in a "tristated" condition, where both the high side P-channel Mosfet and the low-side N-channel are in an off or nonconducting state. Do not drive the enable pin above the supply voltage. September 2006 10 M9999-091106 Micrel, Inc. MIC2224 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 1µF, 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. Application Information The MIC2224 is a 600mA PWM power supply that utilizes a dynamically adjustable output voltage for powering RF power amplifiers. By dynamically adjusting the output power as necessary, battery life can be dramatically improved in battery powered RF applications. For instances where high power is required, the MIC2224 also has a bypass mode. Bypass mode is enabled by driving the DAC pin above 1.2V. This bypasses the input supply directly to the output through a highly efficient, short circuit protected, 40mΩ P channel MOSFET. Inductor Selection The MIC2224 is designed for use with a 4.7µH 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 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. Output Capacitor The MIC2224 is optimized for a 1µF ceramic output capacitor. The MIC2224 utilizes type III internal compensation and utilizes internal high frequency zeros to compensate for the double pole roll off of the LC filter. For this reason, larger output capacitors can create September 2006 IPK = IOUT 11 ⎛ V VOUT ⎜⎜1 − OUT VIN ⎝ + 2× f ×L ⎞ ⎟⎟ ⎠ M9999-091106 Micrel, Inc. MIC2224 Bill of Materials VIN 2.7V to 5.5V 2, 3 5 C1 1µF 4 DAC 6 MIC2224 VIN SW AVIN Item C1, C2 L1 Part Number 06036D105MAT2 AVX PGND 10 GND Description Qty. 1µF Ceramic Capacitor X5R, 6.3V 0603 2 4.7µH 3.2mm x 2.5mm x 1.55mm 1 (2) C1608X5R0J105K TDK GRM185R60J105KE21D Murata(3) LQH32CN4R7M53K Murata(3) CDRH2D14-4R7 U1 (1) C2 1µF DAC 7 Manufacturer VOUT 8, 9 ENABLE AGND GND VOUT 1 L1 4.7µH Sumida (4) (2) GLF201208T4R7M* TDK MIC2224YML Micrel 4.7µH Inductor 94mΩ 3.2mm x 3.2mm x 1.55mm 4.7µH Inductor 660mΩ (5) Micrel Data Sheet Title Here 1 Notes: 1. AVX Tel: 843-448-9411 2. TDK. Tel: 714-508-8800 3. Murata Tel: 949-916-4000 4. Sumida Tel: 408-982-9660 5. Micrel Semiconductor Tel: 408-944-0800 * For maximum load currents less than 200mA September 2006 12 M9999-091106 Micrel, Inc. MIC2224 Package Information ® 10-Pin 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. © 2005 Micrel, Incorporated. September 2006 13 M9999-091106