2.5A Synchronous Buck Regulator

® ISL8502 Data Sheet January 17, 2007 FN6389.0 2.5A Synchronous Buck Regulator with Integrated MOSFETs The ISL8502 is a synchronous buck controller with internal MOSFETs packaged in a small 4mmx4mm QFN package. The ISL8502 can support a continuous load of 2.5A and has a very wide input voltage range. With the switching MOSFETs integrated into the IC, the complete regulator footprint can be very small and provide a much more efficient solution than a linear regulator. The ISL8502 is capable of stand alone operation or it can be used in a master slave combination for multiple outputs that are derived from the same input rail. Multiple slave channels (up to six) can be synchronized. This method minimizes the EMI and beat frequencies effect with multi-channel operation. The switching PWM controller drives two internal N-Channel MOSFETs in a synchronous-rectified buck converter topology. The synchronous buck converter uses voltagemode control with fast transient response. The switching regulator provides a maximum static regulation tolerance of ±1% over line, load, and temperature ranges. The output is user-adjustable by means of external resistors down to 0.6V. The output is monitored for undervoltage events. The switching regulator also has overcurrent protection. Thermal shutdown is integrated. The ISL8502 features a bidirectional Enable pin that allows the part to pull the enable pin low during fault detection. Features • Over 2.5A Continuous Output Current • Integrated MOSFETs for Small Regulator Footprint • Adjustable Switching Frequency, 500kHz - 1.2MHz • Tight Output Voltage Regulation, ±1% Over Temperature • Wide Input Voltage Range, 5V ±10% or 5.5V to 14V • Wide Output Voltage Range, from 0.6V • Simple Single-Loop Voltage-Mode PWM Control Design • Input Voltage Feed-Forward for Constant Modulator Gain • Fast PWM Converter Transient Response • Lossless rDS(ON) High Side and Low Side Overcurrent Protection • Undervoltage Detection • Integrated Thermal Shutdown Protection • Power Good Indication • Adjustable Soft-Start • Pb-Free Plus Anneal Available (RoHS Compliant) Applications • Point of Load Applications • Graphics Cards - GPU and Memory Supplies • ASIC Power Supplies • Embedded Processor and I/O supplies • DSP Supplies Pinout ISL8502 (24 LD QFN) TOP VIEW BOOT PVCC Ordering Information VCC VIN VIN VIN 24 PGOOD SGND EN SYNCH M/S FS 1 2 3 4 5 6 7 COMP 8 FB 9 SS 10 PGND 11 PGND 12 PGND GND 25 23 22 21 20 19 18 VIN 17 PHASE 16 PHASE 15 PHASE 14 PHASE 13 PGND PART NUMBER ISL8502IRZ* (Note) PART TEMP. MARKING RANGE (°C) 85 02IRZ -40 to +85 PACKAGE PKG. DWG. # 24 Ld 4x4 QFN L24.4x4D (Pb-free) *Add “-T” suffix for tape and reel. NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. 1 b CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2006, 2007. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Block Diagram PVCC VCC SS PGOOD VIN (x4) VIN PVCC SERIES REGULATOR POR MONITOR 30μA OC MONITOR 2 SGND EN SYNCH M/S FS FN6389.0 January 17, 2007 BIAS PVCC BOOT FAULT MONITORING ISL8502 VOLTAGE MONITOR GATE DRIVE AND ADAPTIVE SHOOT THRU PROTECTION PHASE (x4) CLOCK AND OSCILLATOR GENERATOR 0.6V REFERENCE OC MONITOR FB COMP PGND (x4) ISL8502 Typical Application Schematic POWER GOOD ENABLE PGOOD EN SYNCH M/S VCC PVCC SS BOOT VIN VIN 5.5V to 14V + ISL8502 PHASE + PGND VOUT FS FB SGND COMP STAND ALONE REGULATOR: VIN 5.5V TO 14V Typical Application Schematic VIN 4.5V TO 5.5V POWER GOOD ENABLE PGOOD EN PVCC VCC SS BOOT VIN + ISL8502 PHASE + VOUT SYNCH M/S FS FB SGND COMP PGND STAND ALONE REGULATOR: VIN 4.5V TO 5.5V 3 FN6389.0 January 17, 2007 ISL8502 ISL8502 With Multiple Slaved Channels VIN MASTER M/S SS PVCC VIN VOUT1 PHASE + FS SYNCH RT EN GND ISL8502 ENABLE M/S 5K RT FS VOUT2 SYNCH EN ISL8502 SLAVE PHASE + VIN GND M/S 5K RT FS VIN VOUTN SYNCH EN PHASE + GND ISL8502 SLAVE 4 FN6389.0 January 17, 2007 ISL8502 Absolute Maximum Ratings VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to +16.5V VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to +6.0V Absolute Boot Voltage, VBOOT . . . . . . . . . . . . . . . . . . . . . . . +22.0V Upper Driver Supply Voltage, VBOOT - VPHASE . . . . . . . . . . . +6.0V All other Pins . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to VCC + 0.3V Thermal Information Thermal Resistance θJA (°C/W) θJC (°C/W) QFN Package (Notes 1, 2) . . . . . . . . . 39 2.5 Maximum Junction Temperature (Plastic Package) . . . . . . +150°C Maximum Storage Temperature Range . . . . . . . . . -65°C to +150°C Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . +300°C (SOIC - Lead Tips Only) Recommended Operating Conditions Supply Voltage on VIN . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5V to 14V Ambient Temperature Range . . . . . . . . . . . . . . . . . . -40°C to +85°C Junction Temperature Range. . . . . . . . . . . . . . . . . -40°C to +125°C CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. 150°C max junction temperature is intended for short periods of time to prevent shortening the lifetime. Operation close to 150°C junction may trigger the shutdown of the device even before 150°C, since this number is specified as typical. NOTE: 1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech Brief TB379. 2. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside. 3. Not production tested. 4. Minimum VIN can operate below 5.5V as long as VCC is greater than 4.5V. 5. Maximum VIN can be higher than 14V voltage stress across the upper and lower do not exceed 15.5V in all conditions. 6. Circuit requires 100ns minimum on time to detect over current condition. Electrical Specifications Refer to Block and Simplified Power System Diagrams and Typical Application Schematics. Operating Conditions Unless Otherwise Noted: Vin = 12V, or VCC = 5V ±10%, TA = -40°C to +85°C. Typical are at TA = +25°C. SYMBOL TEST CONDITIONS MIN TYP MAX UNITS PARAMETER VIN SUPPLY Input Voltage Range VIN VIN tied to VCC 5.54 4.5 145 5.5 7 1.25 2 V V mA mA Input Operating Supply Current Input Standby Supply Current SERIES REGULATOR VCC Voltage Maximum Output Current VCC Current Limit POWER-ON RESET Rising VCC POR Threshold Falling VCC POR Threshold ENABLE Rising Enable Threshold Voltage Falling Enable Threshold Voltage Enable Sinking Current OSCILLATOR PWM Frequency IQ IQ_SBY VFB = 1.0V EN tied to GND, VIN = 14V VPVCC IPVCC VIN > 5.6V VIN = 12V VIN = 12V, VCC shorted to PGND. Note 3 4.5 50 5.0 5.5 V mA 300 mA 4.2 3.85 4.4 4.0 4.49 4.10 V V VEN_Rising VEN_Fall IEN 2.7 2.3 500 V V μA fOSC RT = 96kΩ RT = 40kΩ FS pin tied to VCC 400 960 500 1200 800 1.0 600 1440 kHz kHz kHz V Ramp Amplitude ΔVOSC VIN = 14V 5 FN6389.0 January 17, 2007 ISL8502 Electrical Specifications Refer to Block and Simplified Power System Diagrams and Typical Application Schematics. Operating Conditions Unless Otherwise Noted: Vin = 12V, or VCC = 5V ±10%, TA = -40°C to +85°C. Typical are at TA = +25°C. (Continued) SYMBOL ΔVOSC VVIN/ΔVOSC DMAX DMAX VIN = 5V By Design fOSC = 500kHz fOSC = 1.2MHz 88 76 TEST CONDITIONS MIN TYP 0.470 8 MAX UNITS V % % PARAMETER Ramp Amplitude Modulator Gain Maximum Duty Cycle Maximum Duty Cycle REFERENCE VOLTAGE Reference Voltage System Accuracy FB Pin Bias Current SOFT-START Soft-Start Current Enable Soft-Start Threshold Enable Soft-Start Threshold Hysteresis Enable Soft-Start Voltage High ERROR AMPLIFIER DC Gain Gain-Bandwidth Product Maximum Output Voltage Slew Rate INTERNAL MOSFETS Upper MOSFET rDS(ON) Lower MOSFET rDS(ON) PGOOD PGOOD Threshold VREF -1.0 0.600 +1.0 ±80 ±200 V % nA ISS 20 0.8 30 1.0 12 40 1.2 μA V mV 2.8 3.2 3.8 V Note 3 GBWP Note 3 3.9 SR 88 15 4.4 5 dB MHz V V/μs rDS_Upper rDS_Lower VCC = 5V VCC = 5V 180 90 mΩ mΩ VFB/VREF Rising Edge Hysteresis 1% Falling Edge Hysteresis 1% 107 86 111 90 250 115 93 % % ms PGOOD Rising Delay PGOOD Leakage Current PGOOD Low Voltage PGOOD Sinking Current PROTECTION Positive Current Limit Negative Current Limit Undervoltage Level Thermal Shutdown Setpoint Thermal Recovery Setpoint tPGOOD_DELAY fOSC = 500kHz VPGOOD = 5.5V 5 0.10 0.5 μA V mA VPGOOD IPGOOD Note 3 Note 3 IPOC INOC VFB/VREF TSD TSR VCC = 5V, IOC from PHASE to PGND. Notes 3, 6 VCC = 5V, IOC from VIN to PHASE. Notes 3, 6 2.8 2.2 76 3.5 3.0 80 150 130 4.0 3.5 84 A A % °C °C Note 3 Note 3 6 FN6389.0 January 17, 2007 ISL8502 Typical Performance Curves 80 70 60 EFFICIENCY (%) EFFICIENCY (%) 50 40 30 20 10 0 0 1 OUTPUT LOAD (A) 2 5VIN 9VIN 14VIN VIN = 12V, VOUT = 2.5V, IO = 2A, fs = 500kHz, L = 4.7µH, CIN = 20µF, COUT = 100µF+22µF, TA = +25° C, unless otherwise noted. 90 80 70 60 50 40 30 20 10 0 0 1 OUTPUT LOAD (A) 2 5VIN 9VIN 14VIN FIGURE 1. EFFICIENCY vs LOAD (VOUT = 0.6V 500kHz) FIGURE 2. EFFICIENCY vs LOAD (VOUT = 1.2V 500kHz) 90 80 70 EFFICIENCY (%) 14VIN EFF