MIC2285AYMT-TR

MIC2285A 8MHz PWM Synchronous Buck Regulator with LDO Standby Mode General Description Features The Micrel MIC2285A is a high efficiency 8MHz PWM synchronous buck (step-down) regulator that features a LOWQ® LDO standby mode that draws only 20µA of quiescent current. The MIC2285A allows an ultra-low noise, small size, and high efficiency solution for portable power applications. In PWM mode, the MIC2285A operates with a constant frequency 8MHz 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 MIC2285A 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 MIC2285A is available in the 10-pin 2mm x 2mm Thin MLF® 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/input voltage • Light load LOWQ® LDO mode – 20µA quiescent current – Low noise, 75µVrms • 8MHz PWM mode – Output current to 600mA – >90% efficiency – 100% maximum duty cycle • Adjustable output voltage option down to 1V – Fixed output voltage options available • Ultra-fast transient response • Requires only a 0.47µH inductor • Enables sub 0.55mm profile solution • Fully integrated MOSFET switches • Micropower shutdown • Thermal shutdown and current limit protection • 10-pin 2mm x 2mm x 0.55mm MLF® package • –40°C to +125°C junction temperature range Applications • Cellular phones • PDAs • USB peripherals ____________________________________________________________________________________________________ Typical Application 2.5VOUT Efficiency 100 90 80 70 60 50 V IN =3.2V VIN =3.6V VIN =4.2V 40 30 20 Adjustable Output Buck Regulator with LOWQ® Mode 10 0 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) LOWQ is a registered trademark of Micrel, Inc MLF and MicroLeadFrame are registered trademarks of 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 August 2007 M9999-083107-B Micrel, Inc. MIC2285A Ordering Information Part Number MIC2285AYMT Marking Output Voltage* Junction Temperature Range Package Lead Finish WPA Adj. –40° to +125°C 10-Pin 2x2 Thin MLF® Pb-free Note * For other voltage options available, please contact Micrel Marketing for details. MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. Pin Configuration AGND 1 10 PGND LDO 2 9 SW BIAS 3 8 VIN AVIN 4 7 LOWQ FB 5 6 EN 10-Pin 2mm x 2mm Thin MLF® (MT) Pin Description Pin Number 1 2 3 Pin Name AGND LDO BIAS 4 AVIN 5 FB 6 EN 7 _____ LOWQ 8 9 10 VIN SW PGND August 2007 Pin Function Analog (signal) Ground. LDO Output (Output): Connect to VOUT for LDO mode operation. Internal circuit bias supply. Must be decoupled to signal ground with a 0.1µF capacitor and should not be loaded. Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND. 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. Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 5µA. 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. Supply Voltage (Input): Supply voltage for the internal switches and drivers. Switch (Output): Internal power MOSFET output switches. Power Ground. 2 M9999-083107-B Micrel, Inc. MIC2285A 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 2x2 MLF-10L (θJA) ................................... 60°C/W Electrical Characteristics(4) VIN = VEN = VLOWQ =3.6V; L = 0.47µH; COUT = 10µF; TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C Parameter Condition Min Supply Voltage Range Under-Voltage Lockout Threshold Typ 2.7 (turn-on) 2.45 UVLO Hysteresis 2.55 Max Units 5.5 V 2.65 V 100 mV Quiescent Current, PWM mode VFB = 0.9 * VNOM (not switching) 790 900 µA Quiescent Current, LDO mode VLOWQ = 0V;IOUT = 0mA 20 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 V [Fixed Output] Voltages Nominal VOUT tolerance –1 –2 +1 +2 % % FB pin input current 1 Current Limit in PWM Mode 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 0.8 % Output Voltage Load Regulation, LDO Mode 100µA < ILOAD < 50mA VLOWQ = 0V 0.5 1 % 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 1.85 A % % 100 0.4 0.4 Ω Ω Oscillator Frequency 7.2 8 8.8 MHz LOWQ Threshold Voltage 0.5 0.85 1.3 V 0.1 2 µA 0.85 1.3 V 0.1 2 µA LOWQ Input Current Enable Threshold 0.5 Enable Input Current LDO Dropout Voltage August 2007 IOUT = 50mA Note 5 110 3 mV M9999-083107-B Micrel, Inc. MIC2285A Parameter Condition Min Output Voltage Noise LOWQ = 0V; COUT = 10µF, 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. August 2007 4 M9999-083107-B Micrel, Inc. MIC2285A Typical Characteristics – PWM Mode 2.5VOUT Efficiency 1.8VOUT Efficiency 100 90 80 70 60 100 V IN=3.2V 90 V IN=3.2V VIN=3.6V VIN=4.2V 80 70 60 100 90 V IN=3.2V 80 VIN=3.6V 70 VIN=4.2V 60 VIN=3.6V VIN=4.2V 50 40 50 40 50 40 30 30 20 10 20 10 30 20 100 200 300 400 500 600 OUTPUT CURRENT (mA) 0 0 1.2VOUT Efficiency 70 60 VIN=3.6V VIN=4.2V 50 40 30 30 20 10 20 10 0 0 1100 100 200 300 400 500 600 OUTPUT CURRENT (mA) Quiescent Current vs. Input Voltage 0 0 9.0 1000 1.018 1.014 VIN=3.6V 0.998 VIN=3.6V LowQ=VIN 0.994 0.990 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) Frequency vs. Input Voltage 8.0 800 1.5 1.006 1.002 900 7.5 600 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 1.010 VIN=4.2V 8.5 700 100 200 300 400 500 600 OUTPUT CURRENT (mA) Load Regulation 100 90 V IN=3.2V 80 80 50 40 100 200 300 400 500 600 OUTPUT CURRENT (mA) 1.0VOUT Efficiency 100 90 V IN=3.2V 70 60 10 0 0 1200 CURRENT LIMIT (mA) 0 0 ENABLE THRESHOLD (V) 1.5VOUT Efficiency 7.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 100 200 300 400 500 600 OUTPUT CURRENT (mA) Peak Current Limit vs. Supply Voltage 1000 800 600 400 200 LowQ = VIN 0 2.7 3.4 4.1 4.8 SUPPLY VOLTAGE (V) 5.5 Enable Threshold vs. Supply Voltage 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 LowQ = V IN 0.5 2.7 3.4 4.1 4.8 SUPPLY VOLTAGE (V) August 2007 5.5 5 M9999-083107-B Micrel, Inc. MIC2285A Typical Characteristics - LDO Mode 80 60 40 20 50 40 30 20 10 VOUT = 3.3V IOUT = 25mA LowQ = 0V 40 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) 60 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) DROPOUT VOLTAGE (mV) 100 Dropout Voltage vs. Temperature 70 160 120 0 2.7 80 Current Limit vs. Supply Voltage LowQ = 0V 3.4 4.1 4.8 SUPPLY VOLTAGE (V) 120 100 80 60 40 20 Dropout Voltage vs. Temperature 9 30 25 20 15 10 VOUT = 3.3V IOUT = 10mA LowQ = 0V 5 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) VOUT = 3.3V IOUT = 50mA LowQ = 0V 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 5.5 35 Dropout Voltage vs. Temperature 140 DROPOUT VOLTAGE (mV) CURRENT LIMIT (mA) 140 Dropout Voltage vs. Temperature 8 7 6 5 4 3 2 1 VOUT = 3.3V IOUT = 1mA LowQ = 0V 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Enable Threshold Voltage vs. Supply Voltage ENABLE THRESHOLD (V) 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 2.7 August 2007 LowQ = 0V 3.4 4.1 4.8 SUPPLY VOLTAGE (V) 6 5.5 M9999-083107-B Micrel, Inc. MIC2285A Typical Characteristics – LDO Mode (cont.) Quiescent Current vs. Output Current 24 23 22 21 20 19 18 17 16 15 0 VIN = 3.6V LowQ = 0V 20 40 60 80 100 OUTPUT CURRENT (mA) August 2007 Output Voltage vs. Output Current 1.836 OUTPUT VOLTAGE (V) QUIESCENT CURRENT (µA) 25 1.827 1.818 1.809 1.8 1.791 1.782 1.773 1.764 0 VIN = 3.6V VOUT =1.8V LowQ = 0V 20 40 60 80 100 OUTPUT CURRENT (mA) 7 M9999-083107-B Micrel, Inc. MIC2285A Functional Diagram MIC2285A Block Diagram August 2007 8 M9999-083107-B Micrel, Inc. MIC2285A Functional Characteristics Load Transient LDO Mode Output Current (20mA/div) Output Current (100mA/div) Output Voltage AC Coupled (50mV/div) Output Voltage AC Coupled (50mV/div) Load Transient PWM Mode 10mA 10mA COUT = 4.7µF COUT = 4.7µF Time (20µs/div) Time (20µs/div) Enable Transient LDO Mode Output Voltage (1V/div) 0V Enable (2V/div) 0V Enable (2V/div) Output Voltage (1V/div) Enable Transient PWM Mode 0V 0V COUT = 4.7µF COUT = 4.7µF Time (40µs/div) Time (40µs/div) August 2007 9 M9999-083107-B Micrel, Inc. MIC2285A 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. 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. Typically, an 82pF small ceramic capacitor is recommended. LDO The LDO pin is the output of the linear regulator and should be connected to the output. In LOWQ mode (LOWQ1.5V), 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