LM2720M

LM2720 5-Bit Programmable, High Frequency Multi-phase PWM Controller OBSOLETE LM2720 February 3, 2000 5-Bit Programmable, High Frequency Multi-phase PWM Controller General Description The LM2720 provides an attractive solution for power supplies of high power microprocessors exhibiting ultra fast load transients. Compared to a conventional single-phase supply, an LM2720 based multi-phase supply distributes the thermal and electrical loading among components in multiple phases and greatly reduces the corresponding stress in each component. The LM2720 can be programmed to control either a 3-phase converter or a 4-phase converter. Phase shift among the phases is 120° in the case of three phase and 90° with four-phase. Because the power channels are out of phase, there can be significant ripple cancellation for both the input and output current, resulting in reduced input and output capacitor size. Due to the nominal operating frequency of 2 MHz per phase, the size of the output inductors can be greatly reduced which results in a much faster load transient response and a dramatically shrunk output capacitor bank. Microprocessor power supplies with all surface mount components can be easily built. The internal high speed transconductance amplifier guarantees good dynamic performance. The internal master clock frequency of up to 8 MHz is set by an external reference resistor. An external clock of 10 MHz can also be used to drive the chip to achieve frequency control and multi-chip operation. The LM2720 also provides input under-voltage lock-out with hysteresis, input over-current protection and output voltage power good detection. Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Ultra fast load transient response Enables all surface-mount-design Selectable 2, 3, 4 phase operation Clock frequency from 40 kHz to 10 MHz Precision load current sharing 5-bit programmable from 3.5V to 1.3V VID code compatible to VRM 8.X specification Output voltage is 2.0V for VID code 11111 Selectable internal or external clock Digital 16-step soft start Input under-voltage lock-out, over-current protection Open-drain power good signal output Applications ■ Servers and workstations ■ High current, ultra-fast transient microprocessors Pin Configuration 24-Pin Plastic SOIC 10132201 Top View See NS Package Number M24B © 2009 National Semiconductor Corporation 101322 Print Date/Time: 2009/03/26 20:37:33 www.national.com 101322 Version 3 Revision 1 LM2720 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VCC5V PWRGD VCC12V Junction Temperature Power Dissipation (Note 2) 7V (VCC 5V + 0.2V) 20V 125°C 1.6W Storage Temperature ESD Susceptibility (Note 8) Soldering Time, Temperature −65°C to +150°C 2 kV 10 sec., 300°C (Note 1) 4.5V to 5.5V 10V to 18V 0°C to 70°C Operating Ratings VCC 5V VCC 12V Junction Temperature Range Electrical Characteristics VCC5V = 5V, VCC12V = 12V unless otherwise specified. Typicals and limits appearing in plain type apply for TA = TJ = +25°C. Limits appearing in boldface type apply over the entire operating temperature range. Symbol VDACOUT ICC12V ICC5V VREF VINL VINH Parameter 5-bit DAC Output Voltage Quiescent VCC12V Current Operating VCC5V Current Rref Pin Voltage Vid0:4, Clksel, Divsel, and Enable Logic Low (Note 4) Pins Logic Threshold Logic High (Note 5) Vid0:4 and Enable Pins Internal Pullup Current IINL Clksel, Divsel Pins Internal Pullup Current Gate Driver Resistance When Sinking Current VDRV tfall ISRC ISINK VBgOUT IBgOUT IFB FOSC ΔD Δph Toff DRV0:3 Output Voltage DRV0:3 Fall Time DRV0:3 Source Current DRV0:3 Sink Current BgOUT Voltage BgOUT Sink Current FB Pin Bias Current Oscillator Frequency DRV0:3 Duty Cycle Match DRV0:3 Phase Accuracy PWM Off time Power Good Detection Window, ΔVOUT 3.5 60 The Corresponding Pin = 0V −10 (Note 3) Enable = 5V, VID = 00001, DRV Outputs Floating VOUT = 2.00V Conditions Min N−1.5% Typ N 1 4.3 1.225 1.8 2.8 100 0 12 VCC12V − 1.5V 40 90 VCC12V −1.0V 7 60 160 4 0 1.0 7.0 −1 −1 22 22 ±100 2.4 30 8.0 8.7 +1 +1 5 250 140 10 µA 1.5 Max N+1.5% 2 8 Units V mA mA V V V ISINK = 50 µA, VCC12V = 14V IDRV = 10 mA, VCC12V = 14V (Note 6) DRV0:3 = 0V, VCC12V = 14V DRV0:3 = 5V, VCC12V = 14V Current Limit Not Activated Current Limit Activated BgOUT = 1V FB = 2V 8.02kΩ from Rref Pin to Ground Duty Cycle = 50% Duty Cycle = 50%, Fclock = 8 MHz Divide by 4 Divide by 3 1.3V ≤ VOUT ≤ 1.9V Ω V ns mA mA V mA nA MHz % Deg % mV VPWRGD www.national.com 101322 Version 3 Revision 1 2 Print Date/Time: 2009/03/26 20:37:33 LM2720 Symbol Hysteresis Parameter Power Good Detection Window, ΔVOUT Hysteresis Conditions 2V ≤ VOUT ≤ 3.5V Min Typ 50 ±150 50 Max Units IPWRGD VOCC_CM IB_OC+ IB_OC− VOS_OCC DMAX gm Vramp Icomp Icomp Vcomp_hi Vcomp_lo VPOR Power Good Sink Current Over-current Comparator Common Mode Range OC+ Input Bias Current OC− Input Bias Current Over-current Comparator Input Offset Voltage Maximun Duty Cycle Error Amplifier Transconductance Ramp Signal Peak-to-Peak Amplitude COMP Pin Source Current COMP Pin Sink Current COMP Pin High Clamp COMP Pin Low Clamp Power On Reset Trip Point VPWRGD = 0.4V 0.8 3 1 12 145 120 16 21 78 1.36 2 200 165 42 mA V µA µA mV % mmho V 550 400 µA µA V V V V ms VIN = 5V, OC+ = 5V, OC− = 4V VIN = 5V, OC+ = 6V, OC− = 5V VIN = 5V VIN = 12V FB = 0V 100 85 2 250 160 360 260 2.9 0.19 Vcc5V Pin Voltage Rising Vcc5V Pin Voltage Falling 4.0 3.6 3.8 1.6 Vcc12V Minimum Working Voltage (Note 7) tSS Soft Start Delay FOSC = 8MHz Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating ratings do not imply guaranteed performance limits. Note 2: Maximum allowable power dissipation is a function of the maximum junction temperature, TJMAX, the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PMAX = (TJMAX − TA)/θJA. The junction-toambient thermal resistance, θJA, for LM2720 is 78°C/W. For a TJMAX of 150°C and TA of 25°C, the maximum allowable power dissipation is 1.6W. Note 3: The letter N stands for the typical output voltages appearing in italic boldface type in Table 1. Note 4: Max value of logic low means any voltage below this value is guaranteed to be taken as logic low whereas a voltage higher than this value is not guaranteed to be taken as a logic low. Note 5: Min value of logic high means any voltage above this value is guaranteed to be taken as logic high whereas a voltage lower than this value is not guaranteed to be taken as a logic high. Note 6: When driving bipolar FET drivers in the typical application circuit. Note 7: When Vcc12V pin goes below this voltage, all DRV pins go to 0V. Note 8: ESD ratings is based on the human body model, 100pF discharged through 1.5kΩ. 3 101322 Version 3 Revision 1 Print Date/Time: 2009/03/26 20:37:33 www.national.com LM2720 TABLE 1. 5-Bit DAC Output Voltage Table Symbol VDACOUT Parameter 5-Bit DAC Output Voltages for Different VID Codes Conditions VID4:0 = 01111 VID4:0 = 01110 VID4:0 = 01101 VID4:0 = 01100 VID4:0 = 01011 VID4:0 = 01010 VID4:0 = 01001 VID4:0 = 01000 VID4:0 = 00111 VID4:0 = 00110 VID4:0 = 00101 VID4:0 = 00100 VID4:0 = 00011 VID4:0 = 00010 VID4:0 = 00001 VID4:0 = 00000 VID4:0 = 11111 VID4:0 = 11110 VID4:0 = 11101 VID4:0 = 11100 VID4:0 = 11011 VID4:0 = 11010 VID4:0 = 11001 VID4:0 = 11000 VID4:0 = 10111 VID4:0 = 10110 VID4:0 = 10101 VID4:0 = 10100 VID4:0 = 10011 VID4:0 = 10010 VID4:0 = 10001 VID4:0 = 10000 Typical 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 Units V www.national.com 101322 Version 3 Revision 1 4 Print Date/Time: 2009/03/26 20:37:33 LM2720 Pin Description Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Pin Name Vcc5V Divsel Clksel Extclk Rref Vid0 Vid1 Vid2 Vid3 Vid4 OC+ OC− COMP FB Bgout FBG ENABLE GND DRV2 DRV0 Vcc12V DRV1 DRV3 PWRGD Supply Voltage Input (5V nominal) Selects Phase Mode. Logic low selects 4 phase. Logic high selects 3 phase. 2 phase operation is achieved by using 2 outputs in 4 phase mode. Clock Select: Logic high selects internal clock. Logic low selects external clock. External Clock Input. Output frequency = Clock Input / No. of Phases. Connect to Vcc5V to select internal clock. Connects to external reference resistor. Sets the operating frequency of the internal clock and the ramp time for the PWM. Reference voltage at this pin is 1.26V. 5-Bit DAC Input (LSB). 5-Bit DAC Input. 5-Bit DAC Input. 5-Bit DAC Input. 5-Bit DAC Input (MSB) Over-current Comparator. Non-inverting input. Over-current Comparator. Inverting input. Compensation Pin. This is the output of the internal transconductance amplifier. Compensation network should be connected between this pin and feedback ground FBG. Feedback Input. Normally Kelvin connected to supply output. Current Limit Flag. Goes to logic low when current limit is activated. When over-current condition is removed, this pin is weakly pulled up to Vcc5V. Feedback Ground. This pin should be connected to the ground at the supply output. Output Enable Pin. Tie to logic high to enable and logic low to disable. Power Ground Pin. Phase 2 Output. Phase 0 Output. Supply Voltage for FET Drivers DRV0:3. Phase 1 Output. Phase 3 Output. Power Good. This is an open-drain output that goes low (low impedance to ground) when the output voltage travels out of the threshold window, and resume to open-drain state when VOUT recovers into Pin Function the 50mV hysteresis window. The power good window threshold, i.e. ±100mV for 1.3V ≤ VOUT ≤ 1.9V or ±150mV for 2V ≤ VOUT ≤ 3.5V, is automatically set according to VID code. Connect a 1nF capacitor to ground to filter out the switching noise coupling from DRV3 to this pin. 5 101322 Version 3 Revision 1 Print Date/Time: 2009/03/26 20:37:33 www.national.com LM2720 Block Diagram 10132202 www.national.com 101322 Version 3 Revision 1 6 Print Date/Time: 2009/03/26 20:37:33 LM2720 Typical Application 10132203 7 101322 Version 3 Revision 1 Print Date/Time: 2009/03/26 20:37:33 FIGURE 1. www.national.com LM2720 Physical Dimensions inches (millimeters) unless otherwise noted 24-Lead Small Outline Package Order Number LM2720M NS Package Number M24B www.national.com 101322 Version 3 Revision 1 8 Print Date/Time: 2009/03/26 20:37:33 LM2720 Notes 9 101322 Version 3 Revision 1 Print Date/Time: 2009/03/26 20:37:33 www.national.com LM2720 5-Bit Programmable, High Frequency Multi-phase PWM Controller Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage Reference PowerWise® Solutions Serial Digital Interface (SDI) Temperature Sensors Wireless (PLL/VCO) www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise www.national.com/sdi www.national.com/tempsensors www.national.com/wireless WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/AU Quality and Reliability Feedback/Support Design Made Easy Solutions Mil/Aero SolarMagic™ Analog University® THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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Copyright© 2009 National Semiconductor Corporation For the most current product information visit us at www.national.com National Semiconductor Americas Technical Support Center Email: support@nsc.com www.national.com Tel: 1-800-272-9959 National Semiconductor Europe Technical Support Center Email: europe.support@nsc.com National Semiconductor Asia Pacific Technical Support Center Email: ap.support@nsc.com National Semiconductor Japan Technical Support Center Email: jpn.feedback@nsc.com 101322 Version 3 Revision 1 Print Date/Time: 2009/03/26 20:37:33