MIC2285YML-TR

MIC2285 8MHz PWM Synchronous Buck Regulator with LDO Standby Mode General Description Features The Micrel MIC2285 is a high efficiency 8MHz pulse width modulated (PWM) synchronous buck (stepdown) regulator that features a LOWQ™ LDO standby mode that draws only 18µA of quiescent current. The MIC2285 allows an ultra-low noise, small size, and high efficiency solution for portable power applications. • 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 500mA >90% efficiency 100% maximum duty cycle • Adjustable output voltage option down to 1V Fixed output voltage options available • Ultra-fast transient response • Uses a tiny 0.47µH inductor • Enables sub 1mm profile solution • Fully integrated MOSFET switches • Micropower shutdown • Thermal shutdown and current limit protection • Pb-free 10-pin 3mm x 3mm MLF package • –40°C to +125°C junction temperature range In PWM mode, the MIC2285 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 MIC2285 operates from a 2.7V to 5.5V input voltage and features internal power MOSFETs that can supply up to 500mA output current in PWM mode. It can operate with a maximum duty cycle of 100% for use in low-dropout conditions. The MIC2285 is available in the 10-pin 3mm x 3mm 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. Applications • Cellular phones • PDAs • USB peripherals ____________________________________________________________________________________________________ Typical Application 1.8VOUT Efficiency 100 90 VIN =3.2V 80 70 60 50 VIN =3.6V VIN=4.2V 40 30 20 Adjustable Output Buck Regulator with LOWQ™ Mode 10 0 0 100 200 300 400 500 OUTPUT CURRENT (mA) Patent Pending LOWQ is a trademark of Micrel, Inc MLF and MicroLeadFrame are 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 January 2006 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 Ordering Information Part Number Output Voltage* Junction Temperature Range Package Lead Finish MIC2285YML Adj. –40° to +125°C 10-Pin 3x3 MLF™ Pb-free Note: * Other Voltage options available. Contact Micrel for details. Pin Configuration 10 PGND AGND 1 LDO 2 9 SW BIAS 3 8 VIN AVIN 4 7 LOWQ FB 5 EP 6 EN 10-Pin 3mm x 3mm MLF (ML) Pin Description Pin Number Pin Name 1 AGND Pin Function Analog (signal) Ground. 2 LDO LDO Output (Output): Connect to VOUT for LDO mode operation. 3 BIAS Internal circuit bias supply. Must be filtered from input voltage through an RC lowpass filter with a cutoff frequency ≥ 1 . 2π(20.5Ω )(100nF ) Analog Supply/Input Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND. 4 AVIN 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/Input Voltage (Input): Supply voltage for the internal switches and drivers. 9 SW Switch (Output): Internal power MOSFET output switches. 10 PGND EP GND January 2006 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 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 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 = 0.47µH; COUT = 10µF; 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) 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 ± 2% (over temperature) 1 1.02 V 0.98 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) 0.675 1 nA 1.85 A % % 100 0.4 Ω 0.4 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 January 2006 IOUT = 50mA Note 5 110 3 mV M9999-012406 www.micrel.com Micrel, Inc. MIC2285 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. January 2006 4 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 Typical Characteristics – PWM Mode 2.5VOUT Efficiency 1.8VOUT Efficiency 100 100 60 100 90 V IN=3.2V 90 80 70 V IN=3.2V VIN=3.6V VIN=4.2V 80 70 60 90 V IN=3.2V 80 VIN=3.6V 70 VIN=3.6V VIN=4.2V 60 50 50 50 40 40 40 30 20 30 20 30 20 10 0 0 10 100 200 300 400 500 OUTPUT CURRENT (mA) 0 0 1.2VOUT Efficiency 0 0 90 50 50 80 70 60 VIN=4.2V 1.018 VIN=3.2V 1.014 VIN=3.6V 1.010 VIN=4.2V 1.006 40 1.002 30 20 30 20 0.998 10 10 0 0 1100 100 200 300 400 500 OUTPUT CURRENT (mA) Quiescent Current vs. Input Voltage 0 0 9.0 1000 Frequency vs. Input Voltage 900 8.0 800 7.5 600 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 1.5 0.990 0 100 200 300 400 500 OUTPUT CURRENT (mA) 8.5 700 VIN=3.6V LowQ=VIN 0.994 1200 CURRENT LIMIT (mA) 40 100 200 300 400 500 OUTPUT CURRENT (mA) Load Regulation 100 90 V IN=3.2V 80 70 VIN=3.6V 60 VIN=4.2V 10 100 200 300 400 500 OUTPUT CURRENT (mA) 1.0VOUT Efficiency 100 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 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) January 2006 5.5 5 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 Typical Characteristics - LDO Mode 80 60 40 20 60 50 40 30 20 10 VOUT = 3.3V IOUT = 25mA LowQ = 0V 40 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) Dropout Voltage vs. Temperature 70 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) DROPOUT VOLTAGE (mV) 100 0 2.7 80 160 120 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 Current Limit vs. Supply Voltage 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 January 2006 LowQ = 0V 3.4 4.1 4.8 SUPPLY VOLTAGE (V) 6 5.5 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 Typical Characteristics – LDO Mode (cont.) Quiescent Current vs. Output Current 1.836 24 23 22 21 20 19 18 17 16 15 0 VIN = 3.6V LowQ = 0V 20 40 60 80 100 OUTPUT CURRENT (mA) January 2006 OUTPUT VOLTAGE (V) QUIESCENT CURRENT (µA) 25 Output Voltage vs. Output Current 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 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 Functional Diagram MIC2285 Block Diagram January 2006 8 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 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) January 2006 9 M9999-012406 www.micrel.com Micrel, Inc. MIC2285 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