LM27222 LM27222 High-Speed 4.5A Synchronous MOSFET Driver Literature Number: SNVS306A LM27222 High-Speed 4.5A Synchronous MOSFET Driver General Description Features The LM27222 is a dual N-channel MOSFET driver designed to drive MOSFETs in push-pull configurations as typically used in synchronous buck regulators. The LM27222 takes the PWM output from a controller and provides the proper timing and drive levels to the power stage MOSFETs. Adaptive shoot-through protection prevents damaging and efficiency reducing shoot-through currents, thus ensuring a robust design capable of being used with nearly any MOSFET. The adaptive shoot-through protection circuitry also reduces the dead time down to as low as 10ns, ensuring the highest operating efficiency. The peak sourcing and sinking current for each driver of the LM27222 is about 3A and 4.5Amps respectively with a Vgs of 5V. System performance is also enhanced by keeping propagation delays down to 8ns. Efficiency is once again improved at all load currents by supporting synchronous, non-synchronous, and diode emulation modes through the LEN pin. The minimum output pulse width realized at the output of the MOSFETs is as low as 30ns. This enables high operating frequencies at very high conversion ratios in buck regulator designs. To support low power states in notebook systems, the LM27222 draws only 5A from the 5V rail when the IN and LEN inputs are low or floating. n n n n n n n n n n n Adaptive shoot-through protection 10ns dead time 8ns propagation delay 30ns minimum on-time 0.4 pull-down and 0.9 pull-up drivers 4.5A peak driving current MOSFET tolerant design 5A quiescent current 30V maximum input voltage in buck configuration 4V to 6.85V operating voltage SO-8 and LLP packages Applications n n n n High Current Buck And Boost Voltage Converters Fast Transient DC/DC Power Supplies Single Ended Forward Output Rectification CPU And GPU Core Voltage Regulators Typical Application 20117902 FIGURE 1. (c) 2006 National Semiconductor Corporation DS201179 www.national.com LM27222 High-Speed 4.5A Synchronous MOSFET Driver March 2006 LM27222 Connection Diagram 20117901 Top View SO-8 (NS Package # M08A) JA = 172C/W or LLP-8 (NS Package # SDC08A) JA = 39C/W Ordering Information Order Number Size NSC Drawing # LM27222M SO-8 M08A LM27222MX LM27222SD LLP-8 SDC08A LM27222SDX Package Type Supplied As Rail 95 Units/Rail Tape and Reel 2500 Units/Reel Tape and Reel 1000 Units/Reel Tape and Reel 4500 Units/Reel Pin Descriptions Pin # Pin Name Pin Function 1 SW High-side driver return. Should be connected to the common node of high and low-side MOSFETs. 2 HG High-side gate drive output. Should be connected to the high-side MOSFET gate. Pulled down internally to SW with a 10K resistor to prevent spurious turn on of the high-side MOSFET when the driver is off. 3 CB Bootstrap. Accepts a bootstrap voltage for powering the high-side driver. 4 IN Accepts a PWM signal from a controller. Active High. Pulled down internally to GND with a 150K resistor to prevent spurious turn on of the high-side MOSFET when the controller is inactive. 5 LEN Low-side gate enable. Active High. Pulled down internally to GND with a 150K resistor to prevent spurious turn-on of the low-side MOSFET when the controller is inactive. 6 VCC Connect to +5V supply. 7 LG Low-side gate drive output. Should be connected to low-side MOSFET gate. Pulled down internally to GND with a 10K resistor to prevent spurious turn on of the low-side MOSFET when the driver is off. 8 GND www.national.com Ground. 2 LM27222 Block Diagram 20117903 3 www.national.com LM27222 Absolute Maximum Ratings (Note 1) Power Dissipation (Note 3) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Storage Temperature VCC to GND -0.3V to 7V CB to GND -0.3V to 36V CB to SW -0.3V to 7V SW to GND (Note 2) -2V to 36V LEN, IN, LG to GND -0.3V to VCC + 0.3V 7V HG to GND -65 to 150C ESD Susceptibility Human Body Model 2kV Operating Ratings (Note 1) VCC 4V to 6.85V Junction Temperature Range -40 to 125C CB (max) -0.3V to 36V Junction Temperature 720mW 33V +150C Electrical Characteristics (Note 4) VCC = CB = 5V, SW = GND = 0V, unless otherwise specified. Typicals and limits appearing in plain type apply for TA = TJ = +25C. Limits appearing in boldface type apply over the entire operating temperature range (-40C TJ 125C). Symbol Parameter Conditions Min Typ Max Units 5 15 A POWER SUPPLY Iq_op Operating Quiescent Current IN = 0V, LEN = 0V 30 IN = 0V, LEN = 5V 500 540 650 A 825 HIGH-SIDE DRIVER Peak Pull-up Current 3 A 2.5 1.5 RH-pu Pull-up Rds_on RH-pd Pull-down Rds_on ISW = IHG = 0.3A 0.4 t4 Rise Time Timing Diagram, CLOAD = 3.3nF 17 t6 Fall Time Timing Diagram, CLOAD = 3.3nF 12 ns t3 Pull-up Dead Time Timing Diagram 9.5 ns t5 Pull-down Delay Timing Diagram 16.5 ns 30 ns 3.2 A ICB = IHG = 0.3A 0.9 Peak Pull-down Current ton_min 4.5 Minimum Positive Output Pulse Width A ns LOW-SIDE DRIVER Peak Pull-up Current RL-pu Pull-up Rds_on IVCC = ILG = 0.3A 0.9 Peak Pull-down Current RL-pd 2.5 1.5 4.5 A Pull-down Rds_on IGND = ILG = 0.3A 0.4 t8 Rise Time Timing Diagram, CLOAD = 3.3nF 17 t2 Fall Time Timing Diagram, CLOAD = 3.3nF 14 ns t7 Pull-up Dead Time Timing Diagram 11.5 ns t1 Pull-down Delay Timing Diagram 7.7 ns HG-SW Pull-down Resistance 10k LG-GND Pull-down Resistance 10k LEN-GND Pull-down Resistance 150K IN-GND Pull-down Resistance 150K IN = 0V, Source Current 50 nA IN = 5V, Sink Current 33 A ns PULL-DOWN RESISTANCES LEAKAGE CURRENTS Ileak_IN IN pin Leakage Current www.national.com 4 (Continued) VCC = CB = 5V, SW = GND = 0V, unless otherwise specified. Typicals and limits appearing in plain type apply for TA = TJ = +25C. Limits appearing in boldface type apply over the entire operating temperature range (-40C TJ 125C). Symbol Ileak_LEN Parameter LEN pin Leakage Current Conditions Min Typ Max Units LEN = 0V, Source Current 200 nA LEN = 5V, Sink Current 33 A LOGIC VIH_LEN LEN Low to High Threshold VIL_LEN Low to High Transition LEN High to Low Threshold High to Low Transition VIH_IN IN Low to High Threshold Low to High Transition VIL_IN IN High to Low Threshold High to Low Transition Threshold Hysteresis 65 % of VCC 65 % of VCC 30 % of VCC 30 % of VCC 0.7 V Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating ratings are conditions under which the device operates correctly. Operating Ratings do not imply guaranteed performance limits. Note 2: The SW pin can have -2V to -0.5 volts applied for a maximum duty cycle of 10% with a maximum period of 1 second. There is no duty cycle or maximum period limitation for a SW pin voltage range of -0.5V to 30 Volts. Note 3: Maximum allowable power dissipation is a function of the maximum junction temperature, TJMAX, the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PMAX = (TJMAX-TA) / JA. The junction-toambient thermal resistance, JA, for the LM27222M, it is 165C/W. For a TJMAX of 150C and TA of 25C, the maximum allowable power dissipation is 0.76W. The JA for the LM27222SD is 42C/W. For a TJMAX of 150C and TA of 25C, the maximum allowable power dissipation is 3W. Note 4: Min and Max limits are 100% production tested at 25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. Limits are used to calculate National's Average Outgoing Quality Level (AOQL). Timing Diagram 20117904 5 www.national.com LM27222 Electrical Characteristics (Note 4) LM27222 Typical Waveforms 20117908 20117907 FIGURE 3. PWM High-to-Low Transition at IN Input FIGURE 2. PWM Low-to-High Transition at IN Input 20117909 FIGURE 4. LEN Operation The typical waveforms are from a circuit similar to Figure 1 with: Q1: 2 x Si7390DP Q2: 2 x Si7356DP L1: 0.4 H VIN: 12V www.national.com 6 LM27222 Application Information GENERAL The LM27222 is designed for high speed and high operating reliability. The driver can handle very narrow, down to zero, PWM pulses in a guaranteed, deterministic way. Therefore, the HG and LG outputs are always in predictable states. No latches are used in the HG and LG control logic so the drivers cannot get "stuck" in the wrong state. The driver design allows for powering up with a pre-biasing voltage being present at the regulator output. To reduce conduction losses in DC-DC converters with low duty factors the LM27222 driver can be powered from a 6.5V 5% power rail. It is recommended to use the same power rail for both the controller and driver. If two different power rails are used, never allow the PWM pulse magnitude at the IN input or the control voltage at the LEN input to be above the driver VCC voltage or unpredictable HG and LG outputs pulse widths may result. 20117906 MINIMUM PULSE WIDTH As the input pulse width to the IN pin is decreased, the pulse width of the high-side gate drive (HG-SW) also decreases. However, for input pulse widths 60ns and smaller, the HG-SW remains constant at 30ns. Thus the minimum pulse width of the driver output is 30ns. Figure 5 shows an input pulse at the IN pin 20ns wide, and the output of the driver, as measured between the nodes HG and SW is a 30ns wide pulse. Figure 6 shows the variation of the SW node pulse width vs IN pulse width. At the IN pin, if a falling edge is followed by a rising edge within 5ns, the HG may ignore the rising edge and remain low until the IN pin toggles again. If a rising edge is followed by a falling edge within 5ns, the pulse may be completely ignored. FIGURE 6. ADAPTIVE SHOOT-THROUGH PROTECTION The LM27222 prevents shoot-through power loss by ensuring that both the high- and low-side MOSFETs are not conducting at the same time. When the IN signal rises, LG is first pulled down. The adaptive shoot-through protection circuit waits for LG to reach 0.9V before turning on HG. Similarly, when IN goes low, HG is pulled down first, and the circuit turns LG on only after the voltage difference between the high-side gate and the switch node, i.e. HG-SW, has fallen to 0.9V. It is possible in some applications that at power-up the driver's SW pin is above 3V in either buck or boost comverter applications. For instance, in a buck configuration a pre-biasing voltage can be either a voltage from anothert power rail connected to the load, or a leakage voltage through the load, or it can be an output capacitor precharged above 3V while no significant load is present. In a boost application it can be an input voltage rail above 3V. In the case of insufficient initial CB-SW voltage (less than 2V) such as when the output rail is pre-biased, the shootthrough protection circuit holds LG low for about 170ns, beginning from the instant when IN goes high. After the 170ns delay, the status of LG is dictated by LEN and IN. Once LG goes high and SW goes low, the bootstrap capacitor will be charged up (assuming SW is grounded for long enough time). As a result, CB-SW will be close to 5V and the LM27222 will now fully support synchronous operation. The dead-time between the high- and low-side pulses is kept as small as possible to minimize conduction through the body diode of the low-side MOSFET(s). 20117905 FIGURE 5. Min On Time 7 www.national.com LM27222 Application Information 4. The high-current loop between the high-side and lowside MOSFETs and the input capacitors should be as small as possible. 5. There should be enough copper area near the MOSFETs and the inductor for heat dissipation. Vias may also be added to carry the heat to other layers. (Continued) POWER DISSIPATION The power dissipated in the driver IC when switching synchronously can be calculated as follows: TYPICAL APPLICATION CIRCUIT DESCRIPITON The Application Example on the following page shows the LM27222 being used with National's LM27212, a 2-phase hysteretic current mode controller. Although this circuit is capable of operating from 5V to 28V, the components are optimized for an input voltage range of 9V to 28V. The high-side FET is selected for low gate charge to reduce switching losses. For low duty cycles, the average current through the high-side FET is relatively small and thus we trade off higher conduction losses for lower switching losses. The low-side FET is selected solely on RDS_ON to minimize conduction losses. If the input voltage range were 4V to 6V, the MOSFET selection should be changed. First, much lower voltage FETs can be used, and secondly, high-side FET RDS_ON becomes a larger loss factor than the switching losses. Of course with a lower input voltage, the input capacitor voltage rating can be reduced and the inductor value can be reduced as well. For a 4V to 6V application, the inductor can be reduced to 200nH to 300nH. The switching frequency of the LM27212 is determined by the allowed ripple current in the inductor. This circuit is set for approximately 300kHz. At lower input voltages, higher frequencies are possible without suffering a significant efficiency loss. Although the LM27222 can support operating frequencies up to 2MHz in many applications, the LM27212 should be limited to about 1MHz. The control architecture of the LM27212 and the low propagation times of the LM27222 potentially gives this solution the fastest transient response in the industry. where fSW = switching frequency VCC = voltage at the VCC pin, QG_H = total gate charge of the (parallel combination of the) high-side MOSFET(s) QG_L = total gate charge of the (parallel combination of the) low-side MOSFET(s) RG_H = gate resistance of the (parallel combination of the) high-side MOSFET(s) RG_L = gate resistance of the (parallel combination of the) low-side MOSFET(S) RH_pu = pull-up RDS_ON of the high-side driver RH_pd = pull-down RDS_ON of the high-side driver RL_pu = pull-up RDS_ON of the low-side driver RL_pd = pull-down RDS_ON of the low-side driver PC BOARD LAYOUT GUIDELINES 1. Place the driver as close to the MOSFETs as possible. 2. HG, SW, LG, GND: Run short, thick traces between the driver and the MOSFETs. To minimize parasitics, the traces for HG and SW should run parallel and close to each other. The same is true for LG and GND. 3. Driver VCC: Place the decoupling capacitor close to the VCC and GND pins. www.national.com 8 * Q1, Q3: 2 x Si7390DP ** Q2, Q4: 2 x Si7356DP Application Example 20117920 LM27222 9 www.national.com LM27222 Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead Small Outline Package Order Number: LM27222M, LM27222MX NS Package Number M08A 8-Lead LLP Package Order Number: LM27222SD, LM27222SDX NS Package Number SDC08A www.national.com 10 LM27222 High-Speed 4.5A Synchronous MOSFET Driver Notes 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. For the most current product information visit us at www.national.com. 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. 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. BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ``Banned Substances'' as defined in CSP-9-111S2. Leadfree products are RoHS compliant. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Communications and Telecom www.ti.com/communications Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps DLP(R) Products www.dlp.com Energy and Lighting www.ti.com/energy DSP dsp.ti.com Industrial www.ti.com/industrial Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical Interface interface.ti.com Security www.ti.com/security Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive Microcontrollers microcontroller.ti.com Video and Imaging RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page www.ti.com/video e2e.ti.com Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2011, Texas Instruments Incorporated