LM2720 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 n n n n n n n n n n n n 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 n Servers and workstations n High current, ultra-fast transient microprocessors Pin Configuration 24-Pin Plastic SOIC DS101322-1 Top View See NS Package Number M24B © 2000 National Semiconductor Corporation DS101322 www.national.com LM2720 5-Bit Programmable, High Frequency Multi-phase PWM Controller February 2000 LM2720 Absolute Maximum Ratings (Note 1) Storage Temperature If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Susceptibility (Note 8) VCC5V (VCC 5V + 0.2V) VCC12V 20V Junction Temperature 10 sec., 300˚C Operating Ratings (Note 1) 125˚C Power Dissipation (Note 2) 2 kV Soldering Time, Temperature 7V PWRGD −65˚C to +150˚C VCC 5V 4.5V to 5.5V VCC 12V 10V to 18V Junction Temperature Range 0˚C to 70˚C 1.6W 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 Parameter VDACOUT 5-bit DAC Output Voltage ICC12V Quiescent VCC12V Current ICC5V Operating VCC5V Current VREF Rref Pin Voltage VINL Vid0:4, Clksel, Divsel, and Enable Pins Logic Threshold VINH Vid0:4 and Enable Pins Internal Pullup Current IINL Clksel, Divsel Pins Internal Pullup Current Conditions (Note 3) Enable = 5V, VID = 00001, DRV Outputs Floating VOUT = 2.00V Min Typ Max N−1.5% N N+1.5% V 1 2 mA 4.3 8 mA 1.225 Logic Low (Note 4) Logic High (Note 5) The Corresponding Pin = 0V Gate Driver Resistance When Sinking Current ISINK = 50 µA, VCC12V = 14V VDRV DRV0:3 Output Voltage IDRV = 10 mA, VCC12V = 14V 1.8 Units V 1.5 3.5 2.8 60 100 140 −10 0 10 V V µA 12 Ω VCC12V − 1.5V VCC12V −1.0V V 7 ns 40 60 mA 90 160 tfall DRV0:3 Fall Time (Note 6) ISRC DRV0:3 Source Current ISINK DRV0:3 Sink Current DRV0:3 = 0V, VCC12V = 14V DRV0:3 = 5V, VCC12V = 14V VBgOUT BgOUT Voltage Current Limit Not Activated 4 0 IBgOUT BgOUT Sink Current Current Limit Activated BgOUT = 1V IFB FB Pin Bias Current FB = 2V FOSC Oscillator Frequency 7.0 ∆D DRV0:3 Duty Cycle Match 8.02kΩ from Rref Pin to Ground Duty Cycle = 50% −1 +1 % ∆ph DRV0:3 Phase Accuracy Duty Cycle = 50%, Fclock = 8 MHz −1 +1 Deg Toff PWM Off time Power Good Detection Window, ∆VOUT VPWRGD 8.0 Divide by 4 22 Divide by 3 22 1.3V ≤ VOUT ≤ 1.9V ± 100 2V ≤ VOUT ≤ 3.5V ± 150 50 Hysteresis www.national.com 2.4 50 2 mA V 5 30 Hysteresis Power Good Detection Window, ∆VOUT 1.0 250 mA nA 8.7 MHz % mV (Continued) 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 Parameter IPWRGD Power Good Sink Current VOCC_CM Over-current Comparator Common Mode Range IB_OC+ OC+ Input Bias Current IB_OC− OC− Input Bias Current VOS_OCC Over-current Comparator Input Offset Voltage Conditions VPWRGD = 0.4V Min Typ 0.8 1 3 VIN = 5V, OC+ = 5V, OC− = 4V VIN = 5V, OC+ = 6V, OC− = 5V VIN = 5V Max Units mA 12 V 100 145 200 µA 85 120 165 µA 2 16 42 VIN = 12V FB = 0V 21 mV 78 % 1.36 mmho 2 V DMAX Maximun Duty Cycle gm Error Amplifier Transconductance Vramp Ramp Signal Peak-to-Peak Amplitude Icomp COMP Pin Source Current 250 360 550 µA Icomp COMP Pin Sink Current 160 260 400 µA Vcomp_hi COMP Pin High Clamp Vcomp_lo COMP Pin Low Clamp VPOR Power On Reset Trip Point tSS 2.9 V 0.19 V Vcc5V Pin Voltage Rising 4.0 Vcc5V Pin Voltage Falling 3.6 Vcc12V Minimum Working Voltage (Note 7) 3.8 V Soft Start Delay FOSC = 8MHz 1.6 ms V 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-to-ambient 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 www.national.com LM2720 Electrical Characteristics LM2720 Electrical Characteristics (Continued) 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 4 Units 1.30 V 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 VID4:0 = 11100 VID4:0 = 11011 2.3 VID4:0 = 11010 VID4:0 = 11001 VID4:0 = 11000 2.5 VID4:0 = 10111 VID4:0 = 10110 VID4:0 = 10101 www.national.com Typical 2.4 2.6 2.7 2.8 2.9 3.0 VID4:0 = 10100 VID4:0 = 10011 VID4:0 = 10010 3.1 VID4:0 = 10001 VID4:0 = 10000 3.4 3.2 3.3 3.5 LM2720 Pin Description Pin Pin Name Pin Function 1 Vcc5V Supply Voltage Input (5V nominal) 2 Divsel 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. 3 Clksel 4 Extclk 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. 5 Rref 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. 6 Vid0 5-Bit DAC Input (LSB). 7 Vid1 5-Bit DAC Input. 8 Vid2 5-Bit DAC Input. 9 Vid3 5-Bit DAC Input. 10 Vid4 5-Bit DAC Input (MSB) 11 OC+ Over-current Comparator. Non-inverting input. 12 OC− Over-current Comparator. Inverting input. 13 COMP Compensation Pin. This is the output of the internal transconductance amplifier. Compensation network should be connected between this pin and feedback ground FBG. 14 FB Feedback Input. Normally Kelvin connected to supply output. 15 Bgout 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. 16 FBG Feedback Ground. This pin should be connected to the ground at the supply output. 17 ENABLE Output Enable Pin. Tie to logic high to enable and logic low to disable. 18 GND Power Ground Pin. 19 DRV2 Phase 2 Output. 20 DRV0 Phase 0 Output. 21 Vcc12V Supply Voltage for FET Drivers DRV0:3. 22 DRV1 Phase 1 Output. 23 DRV3 Phase 3 Output. 24 PWRGD 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 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 www.national.com DS101322-2 LM2720 Block Diagram www.national.com 6 LM2720 DS101322-3 Typical Application 7 www.national.com LM2720 5-Bit Programmable, High Frequency Multi-phase PWM Controller Physical Dimensions inches (millimeters) unless otherwise noted 24-Lead Small Outline Package Order Number LM2720M NS Package Number M24B LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.