LX7176A 4A Step-Down-Regulator Production Datasheet Description Features The LX7176A is a 4A step-down regulator with integrated MOSFETs packaged in a space saving QFN12 2mm x 2mm for today's mobile devices. It uses an ultra fast, constant frequency hysteretic control method to minimize external filter components while maintaining excellent regulation. The LX7176A reference voltage is 0.6V. 0-4A Step-down Regulator The LX7176A operates from 3V to 5.5V rails and outputs 0.6V to 100% of the input voltage. Automatically switches to DCM switching under light loads to improve efficiency Cycle-by-cycle current limiting protects against overcurrent conditions. Hiccup mode provides protection for heavy over-load or short-circuit faults. Thermal protection shuts down the regulator under overtemperature conditions. Over voltage conditions will immediately shut off the output to protect against permanent damage. The LX7176A automatically restarts when all fault conditions are cleared. Internal soft start circuitry limits start up inrush currents. 100% Duty Ratio Operation Operational Input Supply Voltage Range: 3V-5.5V (short durations to 6.5V.) Hysteretic control offers best transient response CCM switching at a constant 1.65MHz Input under voltage and over voltage protection Enable and Power Good Function Internal soft-start Cycle-by-Cycle Over Current Protection Hiccup Mode protects against short circuit faults RoHS Compliant Applications Figure 1: Typical Application Diagram Copyright (c) 2013 Rev. 1.1a 1/28/2014 * High Performance HDD * LCD TV * Notebook/Netbook * Server and Workstations * Video Cards * PoE Powered Devices Smart Phone Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 1 LX7176A 4A Step-Down-Regulator Production Datasheet Pin Configuration and Pinout * 76A YWWL * Pin 1 Indicator, YWWL = Year/Week/Lot Code RoHS / Pb-free Matte Tin Pin Finish Figure 2: Pinout Ordering Information Ambient Temperature Type Package Part Number 0C to 85C RoHS compliant, Pb-free QFN 2x2mm 12L LX7176ACLQ LX7176ACLQ-TR Packaging Type Bulk Tape and Reel Thermal Properties Thermal Resistance(JA) QFN 2x2mm 12L Typ 30 Units C/W Note: The JA number assumes no forced airflow. Junction Temperature is calculated using TJ = TA + (PD x JA). In particular, JA is a function of the PCB construction. The stated number above is for a four-layer board in accordance with JESD-51 (JEDEC). Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 2 LX7176A 4A Step-Down-Regulator Production Datasheet Pin Description Pin Number Pin Designator 1, 10 PVIN 2, 11 3, 12 4 SW PGND AGND 5 NC 6 OUT 7 FB 8 EN 9 PG Copyright (c) 2013 Rev. 1.1a 1/28/2014 Description Supply Voltage. Bypass PVIN to ground plane as close as possible to the IC. Switch Output. Drives the external L-C filter. Power Ground. Connect to ground plane. Analog Ground. Connect to ground plane. No connect pin. Leave floating. Serves as SCL when accessing the serial port. Output Voltage Sense Pin - This pin monitors the output voltage. Serves as SDA when accessing the serial port. Digital signals at this pin will be capacitively coupled onto FB and disturb the output voltage. Feedback - Analog input, monitors the output voltage either directly or through a resistor divider. Enable - Digital input. Force high to enable the IC. Power Good - Open drain digital output. Pulls low to indicate a fault condition. Requires an external pull up resistor. Also used to monitor selected internal signals. Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 3 LX7176A 4A Step-Down-Regulator Production Datasheet Block Diagram Figure 3: Block Diagram Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 4 LX7176A 4A Step-Down-Regulator Production Datasheet Absolute Maximum Ratings Performance is not necessarily guaranteed over this entire range. These are maximum stress ratings only. Exceeding these ratings, even momentarily, can cause immediate damage, or negatively impact long-term operating reliability. Parameter PVIN, EN, PG, OUT, FB, SW to PGND AGND to PGND SW to PGND (Shorter than 50ns) Junction Temperature Range Storage Temperature Range Peak Lead Soldering Temperature (40s, reflow) Min -0.3 -0.3 -2 0 -65 Max 7 0.3 7 150 150 260 (+0, -5) Units V V V C C C Operating Ratings Performance is generally guaranteed over this range as further detailed below under Electrical Characteristics. Parameter Input Voltage Output Voltage Output Current (VIN = 3V to 5V) Ambient Temperature Min 3.0 0.6 0 0 Max 5.5 5.5 4 85 Units V V A C Note: Corresponding Max Junction Temperature is 125C Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 5 LX7176A 4A Step-Down-Regulator Production Datasheet Electrical Characteristics Unless otherwise specified, the following specifications apply over the operating ambient temperature of 0C TA 85C with the following test conditions: PVIN = 5V. Typical parameters refers to TJ = 25C. VOUT = 0.9V. VOUT is disconnected from FB for open loop tests. Iload = 0,. EN=high, GBD specifications are guaranteed by design and/or characterization and are not tested on a production basis. Symbol PVIN IQPSM ISLEEP UVLORISING UVLOHYST OVPR OVPF VREF VREF TSS THICCUP VOUT VOUT Parameter PSM Bias Current Input Current at Shutdown Under Voltage Rising Threshold UVLO Hysteresis Over Voltage Rising Threshold Over Voltage Falling Threshold FBIL FBUV RDISC SW RDSON_H Copyright (c) 2013 Rev. 1.1a 1/28/2014 Min VOUT Accuracy Load Regulation FB Input Current FB Under Voltage Threshold Output Discharge Resistance Typ Enable PSM 280 EN = low, TJ = 25C 0.1 PVIN rising PVIN falling PVIN rising. Will also trigger on DV/DT > 1V/s PVIN falling 5.5 Reference Voltage VREF Slew Rate Hiccup Time Line Regulation VOUTLR Conditions VOUT is set to 0.9V with 0.1% feedback resistors. PVIN = 5V, , 0C to 85C. ILOAD = 0.1A VIN from 3V to 5V, (in DCM) VOUT = 0.9V. Note ILOAD = 2.5A 1 (in CCM) VOUT = 0.9V, IOUT = 0A to 4A . Note 1 0.891 High Side On Resistance Units A 3 A 2.8 V 0.2 V 6.1 V 5.85 V 0.6 3.75 1.2 V mV/s ms 0.9 0.909 V 0.01 %/V 0.06 -0.06 %/A 1 VOUT below this threshold will initiate a hiccup sequence. EN = low Max 80 80 314 46 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 A %VREF 500 m Page 6 LX7176A 4A Step-Down-Regulator Production Datasheet Symbol IRATED Parameter Low Side On Resistance Rated Output Current ICL Current Limit RDSON_L TSH TH Thermal Shutdown Threshold Thermal Shutdown Hysteresis FSW PWM Switching Frequency EN VIH VIL IIN PG Input High Input Low Input Current VPG90 VPG110 VPGHY PGRDSON PGILEAK PGOOD VOUT Lower Threshold PGOOD VOUT Upper Threshold Hysteresis PGOOD Pull-down Resistance PGOOD Leakage Current Conditions Min Typ Max 21 PVIN = 3V to 5V. Note 1 Peak inductor current. PVIN = 3V to 5V . Note 1 m 4 6.3 Units A 7.4 9 A Note 1 150 C Note 1 20 C VOUT / VIN 35%, T=25C, Note 1 1.55 0.4 1.65 0.01 1.75 MHz 1.2 V V A 1 VOUT rising, percentage of VREF 90 % VOUT falling, percentage of VREF 110 % 5 % Percentage of VREF TJ = 25C 13 50 0 1 A Note 1: These parameters are not tested, but guaranteed by design and characterization. Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 7 LX7176A 4A Step-Down-Regulator Production Datasheet Typical Performance Curves (Efficiency) 100% 90% Efficiency 80% 70% 60% 50% VOUT = 0.9V VOUT = 1.8V VOUT = 3.3V 40% 30% 1 10 100 Load Current (mA) 1000 Figure 4: LX7176A Efficiency with VIN = 5V, L = 0.47H, COUT = 22F Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 8 LX7176A 4A Step-Down-Regulator Production Datasheet Step Response(Load Current = 1.5A to 4A, L = 0.47H, COUT = 22F) Typical Performance Curves Figure 5. Step Load Figure 6. Step Load Rising Edge Figure 7. Step Load Falling Edge Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 9 LX7176A 4A Step-Down-Regulator Production Datasheet Theory of Operation Basic Operation The LX7176A compares the FB voltage to an internal reference, VREF. When FB is lower than Vref, the upper switch turns on and the lower LX7166 switch turns off. When FB is higher than VREF, the upper switch turns off and the lower switch turns on. An internal ramp and a frequency control loop keep the switching frequency constant when in constant conduction mode (CCM) over a wide range of output capacitor values and parasitic components (i.e. ESR, ESL). At light loads, the converter automatically reduces the switching frequency to optimize conversion efficiency. a hiccup sequence will be initiated where both output switches are shut off for 1.2ms before initiating another soft start. This protects against a crowbar short circuit. FB under voltage detection is not active during startup. Setting the Output Voltage The reference voltage is 0.6V R VOUT = 1 + 1 VREF R2 (1) Where R1 is high side feedback divider resistor, R2 is low side feedback divider resistor, VREF is 0.6V. Startup The LX7176A is enabled when EN is high and PVIN rises above the UVLO threshold. At start up, after all the internal bias voltages and currents stabilize, VREF ramps up from 0V to the target voltage at the defined slew rate. While VREF ramps, PGOOD is held low. At the end of the ramp time, PGOOD is allowed to go high if the FB has reached the PGOOD rising threshold. Over Current Protection The LX7176A protects against all types of short circuit conditions. Cycle by cycle over current protection turns off the upper switch when the current exceeds the ICL threshold. When this occurs, the upper switch is kept off for about 360ns before being allowed to turn on again. After startup, if FB drops below the FBUV threshold, Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 10 LX7176A 4A Step-Down-Regulator Production Datasheet Recommended Output Filter Components The following tables show recommended feedback component values (RHIGH, RLOW, Cff) for different input/output voltages, power inductor (L), and output capacitance (C) values that result in optimum closed loop response of the regulator in each case. The estimated crossover frequency is also shown in the table in each case. If the L*C factor exceeds a certain number the regulator would run with low phase margin, or become unstable. The L and C range provided in the table provides 30, or higher of phase margin. Therefore, it is not recommended to increase L*C factor beyond what is given in the table. It is a good practice to determine L such that the peak-to-peak inductor ripple current in continuous conduction mode operation is roughly equal to 30% of converter's rated output current. In general, increasing the inductance slows down the closed loop response of the regulator. Hence, for applications that require fast line/load transient response, lower inductance values should be preferred over larger ones. Output capacitance can be determined based on desired output ripple voltage staying within the limits provided in the table depending on the inductance value. VIN (V) VOUT (V) L (H) COUT (F) RHIGH (k) RLOW (k) 4x22 2.2 47 3x22 1x22 12 150 73 27 3x22 0.9 12 120 1x22 200 5x22 92 22 3x22 60 120 2x22 110 130 12 170 1x22 300 5x22 140 10 4x22 0.47 84 100 4x22 5.0 83 100 2x22 1.0 70 33 4x22 1.5 F crossover (kHz) 2x22 5x22 3x22 0 1x22 5x22 280 575 180 6.8 4x22 3x22 220 280 2x22 1x22 170 220 2x22 0.33 Copyright (c) 2013 Rev. 1.1a 1/28/2014 Cff (pF) 7.5 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 15 0 400 625 Page 11 LX7176A 4A Step-Down-Regulator Production Datasheet Recommended Output Filter Components - Continued VIN (V) VOUT (V) L (H) 2.2 1.5 COUT (F) RHIGH (k) RLOW (k) Cff (pF) 2x22 33 76 1x22 12 110 3x22 27 74 2x22 12 1x22 5x22 3.0 0.9 22 0.47 60 120 3x22 2x22 1x22 5x22 4x22 0.33 6.8 49 2x22 70 58 4x22 68 1.5 2x22 190 1x22 6.8 240 1.8 1.0 84 200 77 6.8 4x22 5.0 85 120 120 5x22 120 180 6.8 3x22 3x22 92 120 325 2x22 130 1x22 260 150 5x22 110 2x22 240 130 0 4x22 0.47 475 130 0 3x22 2x22 1x22 120 180 190 60 475 5x22 4x22 0.33 150 240 120 190 0 3x22 2x22 60 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 260 220 30 1x22 Copyright (c) 2013 Rev. 1.1a 1/28/2014 57 5x22 190 0 F crossover (kHz) 12 4x22 2.2 78 3x22 1x22 Cff (pF) 150 150 0 RLOW (k) 5x22 100 10 RHIGH (k) 1x22 120 12 COUT (F) 3x22 2x22 4x22 L (H) 140 93 5x22 VOUT (V) 90 3x22 1x22 VIN (V) 68 4x22 1.0 F crossover (kHz) 500 Page 12 LX7176A 4A Step-Down-Regulator Production Datasheet Recommended Output Filter Components - Continued VIN (V) VOUT (V) L (H) COUT (F) RHIGH (k) RLOW (k) Cff (pF) 5x22 12 4x22 2.2 3x22 6.8 1x22 1.8V 1.0 Copyright (c) 2013 Rev. 1.1a 1/28/2014 60 3x22 110 100 1x22 2.2 55 64 22 5x22 1.5 60 5x22 87 3x22 100 2x22 140 540 120 240 5x22 100 4x22 3.3 1.0 75 4x22 1x22 5.0 170 120 33 3x22 140 79 2x22 190 87 1x22 325 150 5x22 170 5x22 76 4x22 4x22 89 1x22 0.33 81 140 2x22 0.47 F crossover (kHz) 2x22 1x22 120 Cff (pF) 67 79 240 RLOW (k) 4x22 2x22 6.8 RHIGH (k) 42 49 6.8 COUT (F) 58 4x22 3x22 L (H) 5x22 42 3x22 VOUT (V) 36 5x22 4x22 3.0 VIN (V) 50 2x22 1.5 F crossover (kHz) 0 0 0.47 3x22 110 2x22 2x22 160 1x22 1x22 350 5x22 5x22 97 4x22 120 3x22 3x22 0 150 2x22 240 1x22 525 4x22 0.33 33 3x22 240 350 225 50 0 450 220 540 120 22 135 30 0 2x22 1x22 200 260 325 475 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 525 Page 13 LX7176A 4A Step-Down-Regulator Production Datasheet Package Dimensions QFN 2x2mm 12L Package MILLIMETERS MIN MAX 0.80 1.00 0.20 REF 0.20 0.30 INCHES MIN MAX 0.031 .039 0.008 REF 0.008 0.012 D 1.90 0.075 D2 E e 0.50BSC 1.90 2.10 0.50 BSC 0.02BSC 0.075 0.083 0.020 REF 0.30 0.012 Dim A A3 B L 2.10 0.45 0.083 0.018 Note: 1. Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm (.006") on any side. Lead dimension shall not include solder coverage. 2. Dimensions are in millimeters, inches for reference only. Recommended Footprint Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 14 LX7176A 4A Step-Down-Regulator Production Datasheet Disclaimer: This PCB land pattern recommendation is based on information available to Microsemi by its suppliers. The actual land pattern to be used could be different depending on the materials and processes used in the PCB assembly, end user must account for this in their final layout. Microsemi makes no warranty or representation of performance based on this recommended land pattern PRODUCTION DATA - Information contained in this document is pre-production data and is proprietary to Microsemi. It may not be modified in any way without the express written consent of Microsemi. Product referred to herein is offered in pre-production form only and may not have completed Microsemi's Quality Assurance process for Release to Production. Microsemi reserves the right to change or discontinue this proposed product at any time. Copyright (c) 2013 Rev. 1.1a 1/28/2014 Microsemi Analog Mixed Signal Group One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996 Page 15