MIC3385 8MHz Inductorless Buck Regulator with LDO Standby Mode General Description The Micrel MIC3385 is a high-efficiency inductorless buck ® regulator that features a LOWQ LDO standby mode that draws only 18µA of quiescent current. The MIC3385 requires no external inductor enabling an ultra-low noise, small size, and high efficiency solution for portable power applications. In PWM mode, the MIC3385 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 MIC3385 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 MIC3385 is available in the 14-pin 3mm x 3.5mm ® 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. LOWQ® Features • 2.7 to 5.5V supply voltage ® • Light load LOWQ LDO mode – 18µA 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 • Ultra-fast transient response • No external inductor required • Enables sub 1mm profile solution • Fully integrated MOSFET switches • Micropower shutdown • Thermal shutdown and current limit protection ® • Pb-free 14-pin 3x3.5x0.9mm MLF package • –40°C to +125°C junction temperature range Applications • • • • • • Slim digital cameras MP3 players Portable power applications Cellular phones PDAs USB peripherals 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 September 22, 2015 Revision 3.0 Micrel, Inc. MIC3385 Typical Application 2.5V OUT Efficiency 100 90 80 70 60 50 40 30 20 10 0 0 ® Adjustable Output Buck Regulator with LOWQ Mode V IN =3.2V VIN =3.6V VIN =4.2V 100 200 300 400 500 600 OUTPUT CURRENT (mA) Ordering Information Part Number Voltage Temperature Range Package Lead Finish MIC3385YHL Adj. –40° to +125°C 14-Pin 3mm x 3.5mm MLF ® MIC3385-1.5YHL 1.5V –40° to +125°C 14-Pin 3mm x 3.5mm MLF ® Pb-free Pb-free Notes: 1. MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. 2. Other voltage options available. Please contact Micrel for details. September 22, 2015 2 Revision 3.0 Micrel, Inc. MIC3385 Pin Configuration FB 1 14 BIAS VIN 2 13 LDO LOWQ 3 12 AVIN EN 4 11 GND OUT 5 10 SW OUT 6 9 SW OUT 7 8 SW ® 14- Pin 3mm x 3.5mm MLF (HL) Pin Description Pin Number Pin Name 1 FB Feedback. Input to the error amplifier. Connect to the external resistor divider network to set the output voltage. 2 VIN Supply Voltage (Input): Supply voltage for the internal switches and drivers. 3 LOWQ 4 EN 5,6,7 OUT Switch Output after inductor. 8,9,10 11 SW GND Power Ground. Requires input capacitor to GND. 12 AVIN Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND. 13 LDO LDO Output (Output): Connect to VOUT for LDO mode operation. 14 BIAS Internal circuit bias supply. Must be de-coupled to signal ground with a 0.1µF capacitor and should not be loaded. September 22, 2015 Pin Function 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. Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 5µA. Switch (Output): Internal power MOSFET output switches before Inductor 3 Revision 3.0 Micrel, Inc. MIC3385 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 (3) EDS Rating .................................................................. 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 3x3.5 MLF-14 (θJA) ........................................... 55°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. 2.7 Supply Voltage Range Under-Voltage Lockout Threshold Typ. (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) 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) 1 1.01 1.02 V V 0.99 0.98 FB pin input current 1 0.75 1 nA 1.85 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 % Output Voltage Load Regulation, LDO Mode 100µA < ILOAD < 50mA VLOWQ = 0V 0.1 % Maximum Duty Cycle VFB ≤ 0.4V PWM Switch ON-Resistance ISW = 50mA VFB = 0.7VFB_NOM (High Side Switch) ISW = -50mA VFB = 1.1VFB_NOM (Low Side Switch) 100 A % 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 0.5 Enable Threshold Enable Input Current LDO Dropout Voltage September 22, 2015 IOUT = 50mA, Note 5 110 4 mV Revision 3.0 Micrel, Inc. MIC3385 Electrical Characteristics(4) (Continued) 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. 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 0.47 µH 60 Internal Inductor 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. September 22, 2015 5 Revision 3.0 Micrel, Inc. MIC3385 Typical Characteristics ― PWM Mode 2.5V OUT Efficiency 1.8V OUT Efficiency 100 100 90 90 80 80 70 60 50 V IN =3.2V VIN =3.6V VIN =4.2V 70 60 40 30 20 10 0 0 20 10 100 200 300 400 500 600 OUTPUT CURRENT (mA) 0 0 1.2V OUT Efficiency 100 90 V IN =3.2V 80 70 60 50 VIN =3.6V VIN =4.2V 40 30 20 10 0 0 1100 100 90 V IN =3.2V 80 V IN =3.2V VIN =3.6V VIN =4.2V 70 60 50 40 30 50 40 30 100 200 300 400 500 600 OUTPUT CURRENT (mA) Quiescent Current vs. Input Voltage 1000 20 10 0 0 1.0V OUT Efficiency 100 90 V IN =3.2V 80 70 VIN =3.6V 60 50 0 0 9.0 VIN =3.6V VIN =4.2V 100 200 300 400 500 600 OUTPUT CURRENT (mA) Load Regulation 1.018 1.014 1.010 1.006 VIN =4.2V 1.002 40 30 20 10 100 200 300 400 500 600 OUTPUT CURRENT (mA) 1.5V OUT Efficiency 0.998 VIN =3.6V /LowQ=V IN 0.994 100 200 300 400 500 600 OUTPUT CURRENT (mA) 0.990 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) Frequency vs. Input Voltage 8.5 900 8.0 800 700 600 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) September 22, 2015 7.5 7.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 6 Revision 3.0 Micrel, Inc. MIC3385 Typical Characteristics ― LDO Mode September 22, 2015 7 Revision 3.0 Micrel, Inc. MIC3385 Typical Characteristics ― LDO Mode (cont.) September 22, 2015 8 Revision 3.0 Micrel, Inc. MIC3385 Functional Characteristics Load Transient LDO Mode Load (25mA/div) Load (100mA/div) Output Voltag e AC Coupled (50mV/div) Output Voltag e AC Coupled (50mV/div) Load Transient PWM Mode COUT = 10µF Time (100µs/div ) Time (100µs/div ) Enable Transient LDO Mode Enable (2V/div) Enable (2V/div) Output Voltag e (1.5V/div) Output Voltag e (1.5V/div) Enable Transient PWM Mode COUT = 10µF COUT = 10µF Time (40µs/div ) Time (40µs/div ) September 22, 2015 COUT = 10µF 9 Revision 3.0 Micrel, Inc. MIC3385 Functional Diagram MIC3385 Block Diagram September 22, 2015 10 Revision 3.0 Micrel, Inc. MIC3385 BIAS The BIAS pin supplies the power to the internal power to the control and reference circuitry. The bias is powered from input voltage through an RC lowpass filter. The RC lowpass filter frequency is: 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 to ground (GND) pin for bypassing. Please refer to layout recommendations. ≥ AVIN Analog VIN (AVIN) provides power to the LDO subsection and the bias through an internal 6Ω resistor. AVIN and VIN must be tied together. Careful layout should be considered to ensure that high frequency switching noise caused by VIN is reduced before reaching AVIN. 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: R1 VOUT = VREF × + 1 R2 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. 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: 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 = 1 2π × R1× 160kHz For fixed options a feedforward capacitor from the output to the FB pin is required. Typically a 100pF small ceramic capacitor is recommended 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. September 22, 2015 1 2π (20 )Ω(100nF ) 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. GND Combines PGND and SGND Power ground (PGND) is the ground path for the high current PWM mode. Signal ground (SGND) is the ground path for the biasing and control circuitry. 11 Revision 3.0 Micrel, Inc. MIC3385 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. Application Information The MIC3385 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. It is 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 MIC3385 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. September 22, 2015 Output Capacitor The MIC3385 is optimized for a 10µF output capacitor. A larger value can be used to improve transient response The MIC3385 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 10µF, 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. 12 Revision 3.0 Micrel, Inc. MIC3385 Layout Recommendations Top Layer Bottom Layer Note: The above figures demonstrate the recommended layout for the MIC3385 adjustable option. September 22, 2015 13 Revision 3.0 Micrel, Inc. MIC3385 U1 MIC3385YHL Vin 2 J1 Vin 5.5 Max C1 10µF/6.3V OUT VIN 12 AVin SW 1 R4 10K JP1 1X2 2 J4 EN LDO 4 J3 LOWQ Vin 8, 9, 10 R1 Option FB LOWQ C4 10µF/3.6V 13 EN 3 J5 OUT 5, 6, 7 C3 82pF/50V 1 R2 Option R3 14 R5 10K BIAS GND 11 C2 0.1µF/6.3V J2 GND J6 GND MIC3385 Adjustable Output Schematic Bill of Materials Item C1, C4 C2 C3 Part Number Manufacturer C1608X5R0J106K TDK JMK107BJ106MA-T Taiyo Yuden GRM188R60J106M Murata Qty. (2) 10µF Ceramic Capacitor X5R, 6.3V 2 (3) 10µF Ceramic Capacitor X7R, 6.3V 2 1µF Ceramic Capacitor X5R, 6.3V 1 1µF Ceramic Capacitor X7R, 6.3V 1 82pF Ceramic Capacitor COG, 50V 1 (1) C1005X5R0J104M TDK 04026D104MAT2A AVX VJ0402Y104KXQPW1BC Vishay C1005COG1H820J Description (1) (4) (5) (1) TDK (5) 82pF Ceramic Capacitor COG, 10V 1 (5) 100K, 1% 0402, 1/16W (Optional) 1 (5) 124K, 1% 0402, 1/16W (Optional) 1 (5) 20Ω, 1% 0603, 1/16W 1 (5) 10K, 1% 0603, 1/16W 1 8MHz Power System Module w/LDO Standby Mode 1 VJ0402A80KXQPW1BC Vishay R1 CRCW04021003FKEYE3 Vishay R2 CRCW04021243FKEYE3 Vishay R3 CRCW060320R0FKEYE3 Vishay R4, R5 CRCW06031002FKEYE3 Vishay U1 MIC3385YHL Micrel, Inc. (6) Notes: 1. TDK: www.tdk.com. 2. Taiyo Yuden, Inc.: www.t-yuden.com. 3. Murata: www.murata.com. 4. AVX: www.avxcorp.com. 5. Vishay: www.website.com. 6. Micrel, Inc.: www.micrel.com. September 22, 2015 14 Revision 3.0 Micrel, Inc. MIC3385 Package Information 14-Pin 3mm x 3.5mm MLF (HL) 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. © 2006 Micrel, Incorporated. September 22, 2015 15 Revision 3.0