MIC2224 High Efficiency 2MHz PWM Buck Converter with DAC Input and 40mΩ Bypass Switch Preliminary 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 • 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: –40°C to +125°C and is available in a 3mm x 3mm MLFTM-10L package. • Cellular phones • PDAs ____________________________________________________________________________________________________ Typical Application 2, 3 5 4 C1 1µF DAC 6 SW VIN AVIN VOUT 1 VOUT 8, 9 C2 1µF ENABLE DAC AGND GND L1 4.7µH MIC2224 VIN 2.6V to 5.5V 7 PGND 10 GND 2MHz PWM Converter with DAC input and 40mΩ Bypass Switch Micrel, Inc. • 2180 Fortune Drive • San Jose, Ca 95131 • USA • tel +1 (408) 944-0800 • fax +1 (408) 474-1000 • http://www.micrel.com 2005January 2005 M9999-012705 [email protected] Micrel MIC2224 Ordering Information Part Number Output Voltage(1) Junction Temp. Range Package Lead Finish MIC2224YML Adj. –40° to +125°C 3x3 MLF-10L 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 3mm x 3mm MLF-10L (ML) Pin Description Pin Pin Name Pin Function 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 5uA ( typ 1uA ) 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 January 2005 Connect to ground. 2 M9999-012705 www.micrel.com Micrel MIC2224 Absolute Maximum Rating (Note 1) 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 Operating Ratings 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 Range (TJ) .. -40°C to +125°C Thermal Resistance θJA MLF .................................................... 60°C/W Electrical Characteristics (4) VIN = VEN = 3.6V;VDAC=0.6V; L = 4.7µH; COUT = 1µF; TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C Parameter Condition Min 2.7 Supply Voltage Range Total Quiescent Current Shutdown Current Typ VDAC = 0.6V VOUT = 2.4V (regulator on, not switching) VEN = 0V (regulator off) Max 5.5 V 360 450 µA 1 5 µA 100 Maximum Duty Cycle Units % 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 0.55 0.75 ISW = 100mA , Low-Side Switch 0.6 0.85 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) Ω 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 85 V mV DAC Input DAC Input Current Output Voltage/DAC Voltage January 2005 0.15 (internally set) 2 3 3 M9999-012705 www.micrel.com µA V/V Micrel Parameter MIC2224 Condition Min DAC Voltage required to enable bypass mode 1.176 Typ Max Units Bypass Switch Bypass Switch Threshold Bypass Switch Hysteresis 1.2 1.224 V 35 mV Delay from VDAC = 1.2V to VOUT = 0.90VIN 10 µs Bypass Switch On-Resistance VIN = 3.0V, IBYPASS = 100mA 40 Bypass Switch Leakage VDAC < 1.2V Bypass Transition Time 1 Bypass Over-Current Limit 1.4 mΩ 5 µA 2.5 A 32 µs 12.5 % Shutdown Temperature 160 °C Over Temperature Shutdown Hysteresis 20 °C Current Limit Retry Time Current Limit Retry Duty Cycle Over Temperature Shutdown 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. January 2005 4 M9999-012705 www.micrel.com Micrel MIC2224 Typical Characteristics January 2005 5 M9999-012705 www.micrel.com Micrel MIC2224 Typical Characteristics (cont.) January 2005 6 M9999-012705 www.micrel.com Micrel MIC2224 Function 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 10 s Output Voltage (2V/div) Time 10 s 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 January 2005 Time 10µs 7 M9999-012705 www.micrel.com Micrel 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 January 2005 8 M9999-012705 www.micrel.com Micrel MIC2224 Functional Block Diagram VOUT VIN 1.2V AVIN SW DRIVER DAC EN 80k 40k AGND PGND MIC2224 Block Diagram January 2005 9 M9999-012705 www.micrel.com Micrel MIC2224 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. 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. Applications 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, 40mOhm P channel MOSFET. 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. 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 40mOhm P-Channel MOSFET. 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. 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 "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. 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 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. 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 (40mOhm typical) P-Channel MOSFET switch. The feedback signal provides the control path to set the output at 3X the DAC voltage. 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. 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. 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 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. January 2005 10 M9999-012705 www.micrel.com Micrel MIC2224 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: IPK = IOUT ⎛ V VOUT ⎜⎜1 − OUT VIN ⎝ + 2× f ×L January 2005 ⎞ ⎟ ⎟ ⎠ 11 M9999-012705 www.micrel.com Micrel MIC2224 Bill of Materials 2, 3 5 4 C1 1µF DAC 6 SW VIN AVIN C1,C2 06036D105MAT2 C1608X5R0J105K L1 VOUT 8, 9 C2 1µF 7 PGND 10 GND Description Manufacturer 1uF Ceramic Capacitor X5R, 6.3V 0603 AVX 1uF Ceramic Capacitor X5R, 6.3V 0603 TDK GRM185R60J105KE21D 1uF Ceramic Capacitor X5R, 6.3V 0603 Murata LQH32CN4R7M53K 4.7uH 3.2mmx2.5mmx1.55mm Murata 4.7uH Inductor 94mOhm 3.2mmx3.2mmx1.55mm Sumida CDRH2D14-4R7 GLF201208T4R7M U1 1 DAC AGND Part Number VOUT ENABLE GND Ref L1 4.7µH MIC2224 VIN 2.7V to 5.5V MIC2224YML (1) 4.7uH Inductor 660mOhm (1) 2MHz Dynamically Controlled PWM Regulator TDK Qty 2 1 (1) (1) 1 Micrel Semiconductor 1 Notes: 1. For maximum load currents less than 200mA January 2005 12 M9999-012705 www.micrel.com Micrel MIC2224 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. © 2005 Micrel, Incorporated. January 2005 13 M9999-012705 www.micrel.com