MIC24085CYMLTR

MIC24085 18V, 3A, 1MHz, High-Performance, Integrated FET Buck Regulator in Tiny 3mm × 3mm QFN General Description Micrel’s MIC24085 is a constant-frequency, current-mode PWM buck regulator with integrated switchers. The MIC24085 is targeted for cost-sensitive and highperformance applications. The MIC24085 operates over a supply range of 4.5V to 18V at a fixed 1MHz switching frequency and can be used to provide up to 3A of output current. The output voltage is adjustable down to 0.9V. The MIC24085 provides the features of low standby current at 10µA, device enable, input undervoltage lockout, and output voltage monitoring. The part also provides fault protections of overcurrent and overtemperature. The MIC24085 is available in a 16-pin 3mm × 3mm QFN package with a junction operating range from –40°C to +125°C. Datasheets and support documentation are available on Micrel’s web site at: www.micrel.com. Features • • • • • • • • • • • • • • • Input voltage range 4.5V to 18V 3A output current 1MHz switching frequency 0.9V reference voltage with ±1.5% accuracy Fixed output voltages are available at: 1.5V/1.8V/2.5V/3.3V/5V Peak current-mode PWM with internal compensation PFM mode for light load efficiency 10µA typical shutdown current 4ms internal soft start Cycle-by-cycle current limit with frequency foldback Output overvoltage protection Enable input/power-good (PG) output Thermal-shutdown protection –40°C to +125°C junction temperature range Available in 16-pin 3mm × 3mm QFN package Applications • Camera, set-top box, gateways, and routers • Networking/telecom infrastructure • Printers, scanners, graphic cards, and video cards Typical Applications Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com October 22, 2013 Revision 1.1 Micrel, Inc. MIC24085 Ordering Information Part Number Output Voltage MIC24085AYML ADJ MIC24085BYML 1.5V MIC24085CYML 1.8V MIC24085DYML 2.5V MIC24085EYML 3.3V MIC24085FYML 5V Junction Temperature Range Package Lead Finish –40°C to +125°C 16-Pin 3mm x 3mm QFN Pb-Free Pin Configuration 16-Pin 3mm × 3mm QFN (ML) (Top View) Pin Description Pin Number Pin Name 1, 12, 13, 16 SW Switch Node (Output): Power stage output. Connect an inductor to this pin. 2, 3, 11 VCC Supply Voltage (for control circuit and power stage): A ceramic input capacitor between VCC and the power ground (PGND) is required. 4 GND Analog Ground: GND is the ground path of the control circuitry. 5 FB Feedback (Input): Input to the error amplifier of the PWM controller. The FB pin is regulated to 0.9V. A resistor divider connecting the feedback to the output is used to adjust the desired output voltage. 6, 7 NC No connection. 8 PG Power Good (Output): Open drain output, which needs a pull-up. The PG pin turns logic high when the converter output voltage is regulated in the range from 93% to 103% of the setting. 9 EN Enable (Input): An accurate Enable with hysteresis is provided. High = enable, Low = shutdown. Enable has an internal pull-up to ensure a stable state if this pin is not connected. 10 BST Boost (Output): Bootstrapped voltage to the high-side N-channel MOSFET. A boost capacitor of 0.1μF is connected between the BST pin and the SW pin. 14,15 PGND Power Ground: PGND is the ground path for the power stage. EP ePAD Exposed Pad. It must be connected to PGND on the PCB. October 22, 2013 Pin Function 2 Revision 1.1 Micrel, Inc. MIC24085 Absolute Maximum Ratings(1) Operating Ratings(2) VVCC to PGND................................................ −0.3V to +20V VSW to PGND ................................................. −0.3V to +20V VEN, VFB, VPG, to GND ..................................... −0.3V to + 6V VBST to VSW ..................................................... −0.3V to + 6V VBST to PGND ................................................ −0.3V to +26V PGND to GND ............................................. −0.3V to + 0.3V Junction Temperature .............................................. +150°C Storage Temperature (TS) ......................... −65°C to +150°C Lead Temperature (soldering, 10sec) ........................ 260°C (3) ESD Rating .................................................................. 2kV Supply Voltage (VVCC) ....................................... 4.5V to 18V Output Current ................................................................ 3A Junction Temperature (TJ) ........................ −40°C to +125°C Junction Thermal Resistance MLF-16 (θJA) ..................................................... 68°C/W MLF-16 (θJC) .................................................... 7.5°C/W Electrical Characteristics(4) VVCC = 12V; TA = 25°C, unless noted. Bold values indicate −40°C ≤ TJ ≤ +125°C. Parameter Condition Min. Typ. Max. Units 18 V Power Supply Input 4.5 VCC Input Voltage Range Quiescent Supply Current No Switching, VFB = 1.5V Shutdown Supply Current VEN = 0V 2.3 mA 5 10 µA VCC UVLO Threshold 4.3 4.5 V VCC UVLO Hysteresis 650 mV Reference (MIC24085AYML) Feedback Reference Voltage -40°C ≤ TJ ≤ +125°C (±1.5%) FB Bias Current VFB = 0.6V 0.886 Soft-Start Time 0.9 0.914 V 50 500 nA 4 ms Load Regulation IOUT = 100mA to 3A 0.5 % Line Regulation VVCC = 4.5V to 18V 0.5 % Enable Control 2.2 EN Logic Level High V 0.8 EN Logic Level Low EN Hysteresis EN Bias Current 480 VEN = 5V 3.5 VEN = 0V -1.5 V mV µA PWM 0.9 1.0 1.1 Switching Frequency VFB = 0.9V MHz Foldback Switching Frequency VFB < 60% × 0.9V 250 kHz Maximum Duty Cycle VFB = 0V, 1MHz 97 % Minimum Duty Cycle VFB = 1V 0 % Notes: 1. Exceeding the absolute maximum ratings may damage the device. 2. The device is not guaranteed to function outside its operating ratings. 3. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF. 4. Specification for packaged product only. October 22, 2013 3 Revision 1.1 Micrel, Inc. MIC24085 Electrical Characteristics(4) (Continued) VVCC = 12V; TA = 25°C, unless noted. Bold values indicate −40°C ≤ TJ ≤ +125°C. Parameter Condition Min. Typ. Max. Units Internal MOSFET High Side On-Resistance ISW = 1A 135 mΩ Low Side On-Resistance ISW = 1A 90 mΩ Overcurrent Protection VFB = 0.9V 3.4 3.8 4.4 A Power Good Threshold Voltage Sweep VFB from Low-to-High 91 93 95 %VOUT Power Good Hysteresis Sweep VFB from High-to-Low 1.5 Power Good Low Voltage VFB < 90% x VNOM, IPG = -0.3mA 50 100 mV Power Good Recovery Hold Time PG recovery after power restoration 11 12 ms Current-Limit Threshold Power Good 9 %VOUT Thermal Protection Overtemperature Shutdown TJ Rising Overtemperature Shutdown Hysteresis October 22, 2013 4 170 °C 10 °C Revision 1.1 Micrel, Inc. MIC24085 Typical Characteristics TJ = −40°C to +125°C, VCC = 12V (unless otherwise noted). October 22, 2013 5 Revision 1.1 Micrel, Inc. MIC24085 Typical Characteristics (Continued) TJ = −40°C to +125°C, VCC = 12V (unless otherwise noted). October 22, 2013 6 Revision 1.1 Micrel, Inc. MIC24085 Functional Characteristics TJ = −40°C to +125°C, VCC = 12V (unless otherwise noted). October 22, 2013 7 Revision 1.1 Micrel, Inc. MIC24085 Functional Diagram October 22, 2013 8 Revision 1.1 Micrel, Inc. MIC24085 Power Good (PG) Power good (PG) is an open drain output pin. A 10kΩ resistor to VOUT is required for pull-up. The PG pin turns low if the output voltage is below 93% of the reference voltage (0.9V). After VOUT fault and recovery, PG is held low for a typical duration of 11ms. See the Electrical Characteristics table for additional information. Functional Description Micrel’s MIC24085 is an 18V, 3A, 1MHz buck regulator with integrated MOSFETSs for low-cost highperformance applications. The MIC24085 provides basic features including enable, power good, internal soft-start, current-limit, and overtemperature protections. VCC Supply Voltage and UVLO The MIC24085 is held in the off state until VCC reaches the UVLO threshold, which has a 650mV hysteresis. A ceramic capacitor from VCC to PGND is recommended for clean operation. Enable and Soft-Start When the MIC24085 is enabled, the reference voltage is controlled to ramp-up from 0V to 0.9V in approximately 4ms. During the soft-start, the current limit is enabled to protect the device in case of a short circuit present at the output. Peak Current-Mode PWM To achieve fast transient response, the peak currentmode PWM control is employed in the MIC24085. As illustrated in the Functional Diagram, the high-side MOSFET current (ISW) is sensed and summed with a slope-compensating ramp. Then it is compared with the error amplifier output to generate a PWM signal. Channel 1: VOUT, Channel 2: PG, Hold Time: 11ms Output Voltage Protection The MIC24085 turns both high-side and low-side MOSFETs off to shut down the buck regulator output voltage when the output voltage exceeds 103% of the regulated voltage. After the output voltage drops back below the threshold, the MIC24085 runs to a soft-start. The loop compensation is designed internally in the MIC24085 to ensure loop stability, even with a low-ESR capacitor at the output, such as a ceramic output capacitor. PFM Mode at Light Load The MIC24085 runs in asynchronous buck mode at light load, where the bottom MOSFET is turned off when the inductor current drops to zero. This scheme prevents the output energy from being pumped back to the input, and improves the over-all efficiency. Thermal Shutdown The MIC24085 turns both high-side and low-side MOSFETs off to shut down the buck regulator output voltage when the internal temperature is over the setting threshold at around 170°C. After the temperature drops back below the threshold, the MIC24085 runs to a softstart. Current Limit and Frequency Foldback In the MIC24085 ISW is also used to determine overcurrent conditions. As the peak inductor current is limited, the output voltage of the buck converter drops as the load current increases. When the output voltage reaches 60% of regulated voltage (or feedback voltage reaches 60% of 0.9V), the switching frequency is forced to fold back, from 1MHz to 250kHz. This current-limit scheme reduces the average inductor current (even with the same peak inductor current), and improves the power consumption at the overload conditions. The current limit is always active when the regulator is enabled. Once the overcurrent condition is removed, the device runs to a soft-start and returns to a normal operation. October 22, 2013 9 Revision 1.1 Micrel, Inc. MIC24085 Transient Response and Control Loop Bandwidth MIC24085 with adjustable output voltage has been designed to work under a wide range of input and output voltages, supporting different values and types of output capacitance. By design, the MIC24085 has a lower control loop bandwidth. For designs with aggressive load step response requirements, using a fixed-output voltage version with a larger output capacitance is recommended. Adjustable Output Voltage: VIN = 12V, VOUT = 5V, Load Step = 0.5A to 2.5A at 50mA/µs with 1x470µF and 1x100µF output capacitance. Channel 1: VOUT, Channel 2: PG, Channel 3: Load Step October 22, 2013 10 Revision 1.1 Micrel, Inc. MIC24085 Evaluation Board Schematic Bill of Materials Item Part Number C1 GRM31CR61E106KA12 C2, C5 GRM188R71H104KA93D C3 C4 (Open) GRM31CF51A226ZE01L Manufacturer Murata Description (5) Qty. 10µF/25V Ceramic Capacitor, X5R, Size 1206 1 Murata 0.1µF/50V Ceramic Capacitor, X7R, Size 0603 2 Murata 22µF/10V Ceramic Capacitor, X5R, Size 1206 1 22µF/10V Ceramic Capacitor, X5R, Size 1206 1 40V Small Signal Schottky Diode, SOD123 1 3.3µH Inductor, 5A Sat. Current 1 3.32kΩ Resistor, Size 0603, 1% 1 Murata D1 (Open) SK33A L1 CIP0530LR3R3 R1, R4 CRCW06033K32FKEA R2, R8 CRCW060310K0FKEA Vishay Dale 10kΩ Resistor, Size 0603, 1% 2 R3 CRCW06034K99FKEA Vishay Dale 4.99kΩ Resistor, Size 0603, 1% 1 R5 CRCW06031K87FKEA Vishay Dale 1.87kΩ Resistor, Size 0603, 1% 1 R6 CRCW06031K24FKEA Vishay Dale 1.24kΩ Resistor, Size 0603, 1% 1 R7 CRCW0603732R0FKEA Vishay Dale 732Ω Resistor, Size 0603, 1% 1 18V, 3A, 1MHz Tiny Buck Regulator 1 U1 MIC24085AYML Diodes, Inc. (6) ABC Taiwan Electronics (7) Corporation Vishay Dale (8) (9) Micrel Inc. Notes: 5. Murata: www.murata.com. 6. Diodes, Inc.: www.diodes.com. 7. ABC Taiwan Electronics Corporation: www.atec-group.com. 8. Vishay: www.vishay.com. 9. Micrel, Inc.: www.micrel.com. October 22, 2013 11 Revision 1.1 Micrel, Inc. MIC24085 PCB Layout Recommendations Recommended Component Placement at Top Layer October 22, 2013 12 Revision 1.1 Micrel, Inc. MIC24085 PCB Layout Recommendations (Continued) Top Layer Mid-Layer 1 (Ground Plane) October 22, 2013 13 Revision 1.1 Micrel, Inc. MIC24085 PCB Layout Recommendations (Continued) Mid-Layer 2 (Ground Plane) Bottom Layer (Ground Plane) October 22, 2013 14 Revision 1.1 Micrel, Inc. MIC24085 Package Information(10) and Recommended Landing Pattern 16-Pin 3mm × 3mm QFN (ML) Note: 10. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com. October 22, 2013 15 Revision 1.1 Micrel, Inc. MIC24085 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 Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. 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. © 2013 Micrel, Incorporated. October 22, 2013 16 Revision 1.1