PX3511D ® Data Sheet February 26, 2007 Advanced Synchronous Rectified Buck MOSFET Driver with Protection Features The PX3511D is high frequency MOSFET driver specifically designed to drive upper and lower power N-Channel MOSFETs in a synchronous rectified buck converter topology. This driver combined with the PX3511D Digital Multi-Phase Buck PWM controller and N-Channel MOSFETs forms a complete core-voltage regulator solution for advanced microprocessors. The PX3511D drives both upper and lower gates over a range of 4.5V to 13.2V. This drive-voltage provides the flexibility necessary to optimize applications involving tradeoffs between gate charge and conduction losses. An advanced adaptive zero shoot-through protection is integrated to prevent both the upper and lower MOSFETs from conducting simultaneously and to minimize the dead time. The PX3511D includes an overvoltage protection feature operational before VCC exceeds its turn-on threshold, at which the PHASE node is connected to the gate of the low side MOSFET (LGATE). The output voltage of the converter is then limited by the threshold of the low side MOSFET, which provides some protection to the microprocessor if the upper MOSFET(s) is shorted. The PX3511D also features an input that recognizes a highimpedance state, working together with Intersil multi-phase PWM controllers to prevent negative transients on the controlled output voltage when operation is suspended. This feature eliminates the need for the schottky diode that may be utilized in a power system to protect the load from negative output voltage damage. Ordering Information PART NUMBER PART (Note) MARKING PX3511DDDG-RA 11DD TEMP. RANGE (°C) Features • Dual MOSFET Drives for Synchronous Rectified Bridge • Pin-to-pin Compatible with ISL6596 • Advanced Adaptive Zero Shoot-Through Protection - Body Diode Detection - Auto-zero of rDS(ON) Conduction Offset Effect • Adjustable Gate Voltage for Optimal Efficiency • 36V Internal Bootstrap Schottky Diode • Bootstrap Capacitor Overcharging Prevention • Supports High Switching Frequency (up to 2MHz) - 3A Sinking Current Capability - Fast Rise/Fall Times and Low Propagation Delays • Optimized for 3.3V PWM Input • Three-State PWM Input for Output Stage Shutdown • Three-State PWM Input Hysteresis for Applications With Power Sequencing Requirement • Pre-POR Overvoltage Protection • VCC Undervoltage Protection • Expandable Bottom Copper Pad for Enhanced Heat Sinking • Dual Flat No-Lead (DFN) Package - Near Chip-Scale Package Footprint; Improves PCB Efficiency and Thinner in Profile • Pb-Free Plus Anneal Available (RoHS Compliant) Applications • Optimized for POL DC/DC Converters for IBA Systems • Core Regulators for Intel® and AMD® Microprocessors PACKAGE (Pb-free) PKG. DWG. # 0 to +85 10 Ld 3x3 DFN L10.3X3 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 FN6463.0 • High Current DC/DC Converters • High Frequency and High Efficiency VRM and VRD Related Literature Technical Brief TB363 “Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices (SMDs)” Technical Brief TB389 “PCB Land Pattern Design and Surface Mount Guidelines for QFN (MLFP) Packages” 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. All Rights Reserved All other trademarks mentioned are the property of their respective owners. PX3511D Pinouts PX3511D (10 LD 3x3 DFN) TOP VIEW 1 UGATE BOOT 2 N/C 3 PWM 4 GND 5 10 PHASE 9 PVCC GND 8 N/C 7 VCC 6 LGATE Block Diagram PX3511D UVCC BOOT VCC UGATE Pre-POR OVP FEATURES +5V 13.6K POR/ PWM SHOOTTHROUGH PROTECTION PHASE (LVCC) PVCC UVCC = PVCC FOR PX3511D CONTROL 6.4K LOGIC LGATE GND PAD 2 FOR DFN DEVICES, THE PAD ON THE BOTTOM SIDE OF THE PACKAGE MUST BE SOLDERED TO THE CIRCUIT’S GROUND. FN6463.0 February 26, 2007 Typical Application - 4 Channel Converter Using ISL6595 and PX3511D Gate Drivers +12V PX3511D +5V 1 UGATE PHASE 8 2 BOOT PVCC 7 3 PWM VCC 6 4 GND LGATE 5 3 +3.3V VDD V12_SEN 1 UGATE PHASE 8 OUT1 2 BOOT PVCC 7 VID4 OUT2 3 PWM VCC 6 VID3 ISEN1 4 GND LGATE 5 VID2 OUT3 ISL6595 VID1 OUT4 VID0 ISEN2 VID5 OUT5 LL0 OUT6 LL1 ISEN3 OUTEN OUT7 OUT8 TO µP VCC_PWRGD Vout PX3511D 1 UGATE PHASE 8 2 BOOT PVCC 7 3 PWM VCC 6 4 GND LGATE 5 RTN ISEN4 OUT9 RESET_N OUT10 PX3511D ISEN5 1 UGATE PHASE 8 PVCC 7 FAULT FAULT1 OUT11 2 BOOT OUTPUTS FAULT2 OUT12 3 PWM VCC 6 ISEN6 4 GND LGATE 5 FN6463.0 February 26, 2007 I2C I/F BUS SDA TEMP_SEN SCL CAL_CUR_EN RTHERM SADDR CAL_CUR_SEN VSENP VSENN PX3511D FROM µP PX3511D GND PX3511D Absolute Maximum Ratings Thermal Information Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15V Supply Voltage (PVCC) . . . . . . . . . . . . . . . . . . . . . . . . . VCC + 0.3V BOOT Voltage (VBOOT-GND). . . . . . . . . . . . . . . . . . . . . . . . . . . .36V Input Voltage (VPWM) . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to 7V UGATE. . . . . . . . . . . . . . . . . . . VPHASE - 0.3VDC to VBOOT + 0.3V VPHASE - 3.5V (<100ns Pulse Width, 2µJ) to VBOOT + 0.3V LGATE . . . . . . . . . . . . . . . . . . . . . . GND - 0.3VDC to VPVCC + 0.3V GND - 5V (<100ns Pulse Width, 2µJ) to VPVCC + 0.3V PHASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3VDC to 15VDC GND - 8V (<400ns, 20µJ) to 30V (<200ns, VBOOT-GND<36V)) ESD Rating Human Body Model . . . . . . . . . . . . . . . . . . . . Class I JEDEC STD Thermal Resistance θJA (°C/W) θJC (°C/W) SOIC Package (Note 1) . . . . . . . . . . . . 100 N/A DFN Package (Notes 2, 3) . . . . . . . . . . 48 7 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 Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . 0°C to +85°C Maximum Operating Junction Temperature . . . . . . . . . . . . . +125°C Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8V to 13.2V Supply Voltage Range, PVCC . . . . . . . . . . . . . . . . 5V to 12V ±10% 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. NOTES: 1. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. 2. 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. 3. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside. Electrical Specifications Recommended Operating Conditions, Unless Otherwise Noted. PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS IVCC PX3511D, fPWM = 300kHz, VVCC = 12V - 4.5 - mA IVCC PX3511D, fPWM = 1MHz, VVCC = 12V - 5 - mA IPVCC PX3511D, fPWM = 300kHz, VPVCC = 12V - 7.5 - mA IPVCC PX3511D, fPWM = 1MHz, VPVCC = 12V - 8.5 - mA VCC Rising Threshold 6.1 6.4 6.7 V VCC Falling Threshold 4.7 5.0 5.3 V VPWM = 3.3V - 400 - µA VPWM = 0V - -350 - µA PWM Rising Threshold (Note 4) VCC = 12V - 1.70 - V PWM Falling Threshold (Note 4) VCC = 12V - 1.30 - V Typical Three-State Shutdown Window VCC = 12V 1.23 - 1.82 V Three-State Lower Gate Falling Threshold VCC = 12V - 1.18 - V Three-State Lower Gate Rising Threshold VCC = 12V - 0.76 - V Three-State Upper Gate Rising Threshold VCC = 12V - 2.36 - V Three-State Upper Gate Falling Threshold VCC = 12V - 1.96 - V - 245 - ns VCC SUPPLY CURRENT Bias Supply Current Gate Drive Bias Current POWER-ON RESET AND ENABLE PWM INPUT (See Timing Diagram on Page 6) Input Current IPWM Shutdown Holdoff Time tTSSHD UGATE Rise Time (Note 4) tRU VPVCC = 12V, 3nF Load, 10% to 90% - 26 - ns LGATE Rise Time (Note 4) tRL VPVCC = 12V, 3nF Load, 10% to 90% - 18 - ns 4 FN6463.0 February 26, 2007 PX3511D Electrical Specifications Recommended Operating Conditions, Unless Otherwise Noted. (Continued) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS UGATE Fall Time (Note 4) tFU VPVCC = 12V, 3nF Load, 90% to 10% - 18 - ns LGATE Fall Time (Note 4) tFL VPVCC = 12V, 3nF Load, 90% to 10% - 12 - ns UGATE Turn-On Propagation Delay (Note 4) tPDHU VPVCC = 12V, 3nF Load, Adaptive - 10 - ns LGATE Turn-On Propagation Delay (Note 4) tPDHL VPVCC = 12V, 3nF Load, Adaptive - 10 - ns UGATE Turn-Off Propagation Delay (Note 4) tPDLU VPVCC = 12V, 3nF Load - 10 - ns LGATE Turn-Off Propagation Delay (Note 4) tPDLL VPVCC = 12V, 3nF Load - 10 - ns LG/UG Three-State Propagation Delay (Note 4) tPDTS VPVCC = 12V, 3nF Load - 10 - ns Upper Drive Source Current IU_SOURCE VPVCC = 12V, 3nF Load - 1.25 - A Upper Drive Source Impedance RU_SOURCE 150mA Source Current 1.4 2.0 3.0 Ω - 2 - A 0.9 1.65 3.0 Ω - 2 - A 0.85 1.3 2.2 Ω - 3 - A 0.60 0.94 1.35 Ω OUTPUT (Note 4) Upper Drive Sink Current IU_SINK VPVCC = 12V, 3nF Load Upper Drive Sink Impedance RU_SINK 150mA Sink Current Lower Drive Source Current IL_SOURCE Lower Drive Source Impedance RL_SOURCE 150mA Source Current VPVCC = 12V, 3nF Load Lower Drive Sink Current IL_SINK VPVCC = 12V, 3nF Load Lower Drive Sink Impedance RL_SINK 150mA Sink Current NOTE: 4. Guaranteed by Characterization. Not 100% tested in production. Functional Pin Description PACKAGE PIN # SOIC DFN PIN SYMBOL 1 1 UGATE Upper gate drive output. Connect to gate of high-side power N-Channel MOSFET. 2 2 BOOT Floating bootstrap supply pin for the upper gate drive. Connect the bootstrap capacitor between this pin and the PHASE pin. The bootstrap capacitor provides the charge to turn on the upper MOSFET. See the Internal Bootstrap Device section under Description for guidance in choosing the capacitor value. - 3, 8 N/C 3 4 PWM The PWM signal is the control input for the driver. The PWM signal can enter three distinct states during operation, see the three-state PWM Input section under Description for further details. Connect this pin to the PWM output of the controller. 4 5 GND Bias and reference ground. All signals are referenced to this node. It is also the power ground return of the driver. 5 6 LGATE 6 7 VCC 7 9 PVCC This pin supplies power to both upper and lower gate drives. Its operating range is +4.5V to 13.2V. Place a high quality low ESR ceramic capacitor from this pin to GND. 8 10 PHASE Connect this pin to the SOURCE of the upper MOSFET and the DRAIN of the lower MOSFET. This pin provides a return path for the upper gate drive. 9 11 PAD FUNCTION No Connection. Lower gate drive output. Connect to gate of the low-side power N-Channel MOSFET. Its operating range is +6.8V to 13.2V. Place a high quality low ESR ceramic capacitor from this pin to GND. Connect this pad to the power ground plane (GND) via thermally enhanced connection. 5 FN6463.0 February 26, 2007 PX3511D Description 1.18V<PWM<2.36V 0.76V<PWM<1.96V PWM tPDLU tPDHU tTSSHD tPDTS tPDTS UGATE tFU tRU LGATE tFL tRL tTSSHD tPDLL tPDHL FIGURE 1. TIMING DIAGRAM Operation Designed for versatility and speed, the PX3511D MOSFET driver control both high-side and low-side N-Channel FETs of a half-bridge power train from one externally provided PWM signal. Prior to VCC exceeding its POR level, the Pre-POR overvoltage protection function is activated during initial startup; the upper gate (UGATE) is held low and the lower gate (LGATE), controlled by the Pre-POR overvoltage protection circuits, is connected to the PHASE. Once the VCC voltage surpasses the VCC Rising Threshold (See Electrical Specifications), the PWM signal takes control of gate transitions. A rising edge on PWM initiates the turn-off of the lower MOSFET (see Timing Diagram). After a short propagation delay [tPDLL], the lower gate begins to fall. Typical fall times [tFL] are provided in the Electrical Specifications section. Adaptive shoot-through circuitry monitors the LGATE voltage and determines the upper gate delay time [tPDHU]. This prevents both the lower and upper MOSFETs from conducting simultaneously. Once this delay period is complete, the upper gate drive begins to rise [tRU] and the upper MOSFET turns on. A falling transition on PWM results in the turn-off of the upper MOSFET and the turn-on of the lower MOSFET. A short propagation delay [tPDLU] is encountered before the upper gate begins to fall [tFU]. Again, the adaptive shootthrough circuitry determines the lower gate delay time, tPDHL. The PHASE voltage and the UGATE voltage are monitored, and the lower gate is allowed to rise after PHASE drops below a level or the voltage of UGATE to PHASE reaches a level depending upon the current direction (See next section for details). The lower gate then rises [tRL], turning on the lower MOSFET. 6 Advanced Adaptive Zero Shoot-Through Deadtime Control (Patent Pending) The PX3511D driver incorporates a unique adaptive deadtime control technique to minimize deadtime, resulting in high efficiency from the reduced freewheeling time of the lower MOSFETs’ body-diode conduction, and to prevent the upper and lower MOSFETs from conducting simultaneously. This is accomplished by ensuring either rising gate turns on its MOSFET with minimum and sufficient delay after the other has turned off. During turn-off of the lower MOSFET, the PHASE voltage is monitored until it reaches a -0.2V/+0.8V trip point within 15ns for a forward/reverse current, at which time the UGATE turns on after 10ns propagation delay. An auto-zero comparator is used to correct the rDS(ON) drop in the phase voltage preventing from false detection of the -0.2V phase level during rDS(ON conduction period. In the case of zero current and/or 15ns phase detect expired, the UGATE turns on after 10ns propagation delay. During the phase detection, the disturbance of LGATE’s falling transition on the PHASE node is blanked out to prevent falsely tripping. Once the PHASE is high, the advanced adaptive shoot-through circuitry monitors the PHASE and UGATE voltages during a PWM falling edge and the subsequent UGATE turn-off. If either the UGATE falls to less than 1.75V above the PHASE or the PHASE falls to less than +0.8V, the LGATE is released to turn on after 10ns propagation delay. Three-State PWM Input A unique feature of these drivers and other Intersil drivers is the addition of a shutdown window to the PWM input. If the PWM signal enters and remains within the shutdown window for a set holdoff time, the driver outputs are disabled and both MOSFET gates are pulled and held low. The shutdown state is removed when the PWM signal moves outside the shutdown window. Otherwise, the PWM rising and falling FN6463.0 February 26, 2007 PX3511D thresholds outlined in the Electrical Specifications determine when the lower and upper gates are enabled. This feature helps prevent a negative transient on the output voltage when the output is shut down, eliminating the Schottky diode that is used in some systems for protecting the load from reversed output voltage events. As an example, suppose two IRLR7821 FETs are chosen as the upper MOSFETs. The gate charge, QG , from the data sheet is 10nC at 4.5V (VGS) gate-source voltage. Then the QGATE is calculated to be 53nC for PVCC = 12V. We will assume a 200mV droop in drive voltage over the PWM cycle. We find that a bootstrap capacitance of at least 0.267µF is required. In addition, more than 400mV hysteresis also incorporates into the three-state shutdown window to eliminate PWM input oscillations due to the capacitive load seen by the PWM input through the body diode of the controller’s PWM output when the power-up and/or power-down sequence of bias supplies of the driver and PWM controller are required. During initial startup, the VCC voltage rise is monitored. Once the rising VCC voltage exceeds 6.4V (typically), operation of the driver is enabled and the PWM input signal takes control of the gate drives. If VCC drops below the falling threshold of 5.0V (typically), operation of the driver is disabled. Pre-POR Overvoltage Protection Prior to VCC exceeding its POR level, the upper gate is held low and the lower gate is controlled by the overvoltage protection circuits. The PHASE is connected to the gate of the low side MOSFET (LGATE), which provides some protection to the microprocessor if the upper MOSFET(s) is shorted during startup, normal, or shutdown conditions. For complete protection, the low side MOSFET should have a gate threshold well below the maximum voltage rating of the load/microprocessor. Internal Bootstrap Device Both drivers feature an internal bootstrap Schottky diode. Simply adding an external capacitor across the BOOT and PHASE pins completes the bootstrap circuit. The bootstrap function is also designed to prevent the bootstrap capacitor from overcharging due to the large negative swing at the trailing-edge of the PHASE node. This reduces voltage stress on the boot to phase pins. The bootstrap capacitor must have a maximum voltage rating above PVCC + 5V and its capacitance value can be chosen from the following equation: Q GATE C BOOT_CAP ≥ -------------------------------------ΔV BOOT_CAP (EQ. 1) Q G1 • PVCC Q GATE = ------------------------------------ • N Q1 V GS1 where QG1 is the amount of gate charge per upper MOSFET at VGS1 gate-source voltage and NQ1 is the number of control MOSFETs. The DVBOOT_CAP term is defined as the allowable droop in the rail of the upper gate drive. 7 1.4 1.2 CBOOT_CAP (µF) Power-On Reset (POR) Function 1.6 1. 0.8 0.6 QGATE = 100nC 0.4 50nC 0.2 20nC 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 ΔVBOOT_CAP (V) FIGURE 2. BOOTSTRAP CAPACITANCE vs BOOT RIPPLE VOLTAGE Gate Drive Voltage Versatility The PX3511D provides the user flexibility in choosing the gate drive voltage for efficiency optimization. The PX3511D ties the upper and lower drive rails together. Simply applying a voltage from +4.5V up to 13.2V on PVCC sets both gate drive rail voltages simultaneously, while VCC’s operating range is from +6.8V up to 13.2V. For 5V operation, ISL6596/ISL6609 is recommended. Power Dissipation Package power dissipation is mainly a function of the switching frequency (FSW), the output drive impedance, the external gate resistance, and the selected MOSFET’s internal gate resistance and total gate charge. Calculating the power dissipation in the driver for a desired application is critical to ensure safe operation. Exceeding the maximum allowable power dissipation level will push the IC beyond the maximum recommended operating junction temperature of 125°C. The maximum allowable IC power dissipation for the SO8 package is approximately 800mW at room temperature, while the power dissipation capacity in the DFN package, with an exposed heat escape pad, is more than 1.5W. The DFN package is more suitable for high frequency applications. See Layout Considerations paragraph for thermal transfer improvement suggestions. When designing the driver into an application, it is recommended that the following calculation is used to ensure safe operation at the desired frequency for the selected MOSFETs. The total gate drive power losses due to the gate charge of MOSFETs and FN6463.0 February 26, 2007 PX3511D the driver’s internal circuitry and their corresponding average driver current can be estimated with Equations 2 and 3, respectively, BOOT PVCC D CGD P Qg_TOT = P Qg_Q1 + P Qg_Q2 + I Q • VCC RHI1 (EQ. 2) RLO1 Q G1 • PVCC 2 P Qg_Q1 = --------------------------------------- • F SW • N Q1 V GS1 G RG1 CDS RGI1 CGS Q1 S Q G2 • PVCC 2 P Qg_Q2 = --------------------------------------- • F SW • N Q2 V GS2 PHASE FIGURE 3. TYPICAL UPPER-GATE DRIVE TURN-ON PATH ⎛ Q G1 • PVCC • N Q1 Q G2 • PVCC • N Q2⎞ I DR = ⎜ ----------------------------------------------------- + -----------------------------------------------------⎟ • F SW + I Q V GS1 V GS2 ⎝ ⎠ PVCC (EQ. 3) D where the gate charge (QG1 and QG2) is defined at a particular gate to source voltage (VGS1and VGS2) in the corresponding MOSFET datasheet; IQ is the driver’s total quiescent current with no load at both drive outputs; NQ1 and NQ2 are number of upper and lower MOSFETs, respectively; PVCC is the drive voltage for both upper and lower FETs. The IQ*VCC product is the quiescent power of the driver without capacitive load and is typically 116mW at 300kHz and VCC = PVCC = 12V. The total gate drive power losses are dissipated among the resistive components along the transition path. The drive resistance dissipates a portion of the total gate drive power losses, the rest will be dissipated by the external gate resistors (RG1 and RG2) and the internal gate resistors (RGI1 and RGI2) of MOSFETs. Figures 3 and 4 show the typical upper and lower gate drives turn-on transition path. The power dissipation on the driver can be roughly estimated as: P DR = P DR_UP + P DR_LOW + I Q • VCC R LO2 R HI2 ⎛ ⎞ P Qg_Q2 P DR_LOW = ⎜ -------------------------------------- + ----------------------------------------⎟ • --------------------R + R R + R 2 ⎝ HI2 EXT2 LO2 EXT2⎠ Q1 RHI2 RLO2 G RG2 CDS RGI2 CGS Q2 S FIGURE 4. TYPICAL LOWER-GATE DRIVE TURN-ON PATH Application Information Layout Considerations The parasitic inductances of the PCB and of the power devices’ packaging (both upper and lower MOSFETs) can cause serious ringing, exceeding absolute maximum rating of the devices. Careful layout can help minimize such unwanted stress. The following advice is meant to lead to an optimized layout: (EQ. 4) R LO1 R HI1 ⎛ ⎞ P Qg_Q1 P DR_UP = ⎜ -------------------------------------- + ----------------------------------------⎟ • --------------------R + R R + R 2 ⎝ HI1 EXT1 LO1 EXT1⎠ R GI1 R EXT1 = R G1 + ------------N CGD R GI2 R EXT2 = R G2 + ------------N Q2 • Keep decoupling loops (PVCC-GND and BOOT-PHASE) as short as possible. • Minimize trace inductance, especially on low-impedance lines. All power traces (UGATE, PHASE, LGATE, GND, PVCC) should be short and wide, as much as possible. • Minimize the inductance of the PHASE node. Ideally, the source of the upper and the drain of the lower MOSFET should be as close as thermally allowable. • Minimize the current loop of the output and input power trains. Short the source connection of the lower MOSFET to ground as close to the transistor pin as feasible. Input capacitors (especially ceramic decoupling) should be placed as close to the drain of upper and source of lower MOSFETs as possible. In addition, for heat spreading, place copper underneath the IC whether it has an exposed pad or not. The copper area can be extended beyond the bottom area of the IC and/or connected to buried power ground plane(s) with thermal vias. This combination of vias for vertical heat escape, 8 FN6463.0 February 26, 2007 PX3511D PVCC Upper MOSFET Self Turn-On Effects At Start-up D CBOOT CGD PX3511D Should the driver have insufficient bias voltage applied, its outputs are floating. If the input bus is energized at a high dV/dt rate while the driver outputs are floating, because of self-coupling via the internal CGD of the MOSFET, the UGATE could momentarily rise up to a level greater than the threshold voltage of the MOSFET. This could potentially turn on the upper switch and result in damaging inrush energy. Therefore, if such a situation (when input bus powered up before the bias of the controller and driver is ready) could conceivably be encountered, it is a common practice to place a resistor (RUGPH) across the gate and source of the upper MOSFET to suppress the Miller coupling effect. The value of the resistor depends mainly on the input voltage’s rate of rise, the CGD/CGS ratio, as well as the gate-source threshold of the upper MOSFET. A higher dV/dt, a lower CDS/CGS ratio, and a lower gate-source threshold upper FET will require a smaller resistor to diminish the effect of the internal capacitive coupling. For most applications, a 5k to 10kΩ resistor is typically sufficient, not affecting normal performance and efficiency. VIN BOOT DU DL UGATE RUGPH extended copper plane, and buried planes for heat spreading allows the IC to achieve its full thermal potential. G CDS RGI CGS QUPPER S PHASE FIGURE 5. GATE TO SOURCE RESISTOR TO REDUCE UPPER MOSFET MILLER COUPLING The coupling effect can be roughly estimated with the following equations, which assume a fixed linear input ramp and neglect the clamping effect of the body diode of the upper drive and the bootstrap capacitor. Other parasitic components such as lead inductances and PCB capacitances are also not taken into account. These equations are provided for guidance purpose only. Therefore, the actual coupling effect should be examined using a very high impedance (10MΩ or greater) probe to ensure a safe design margin. –V DS ⎛ ----------------------------------⎞ dV ⎜ -----⋅ R ⋅ C iss⎟ dV ⎟ V GS_MILLER = ------- ⋅ R ⋅ C rss ⎜ 1 – e dt ⎜ ⎟ dt ⎜ ⎟ ⎝ ⎠ R = R UGPH + R GI C rss = C GD 9 (EQ. 5) C iss = C GD + C GS FN6463.0 February 26, 2007 PX3511D Dual Flat No-Lead Plastic Package (DFN) 2X 0.15 C A D A L10.3x3 10 LEAD DUAL FLAT NO-LEAD PLASTIC PACKAGE MILLIMETERS 2X 0.15 C B SYMBOL MIN 6 INDEX AREA 0.80 0.90 1.00 - - - 0.05 - 0.28 5,8 2.05 7,8 1.65 7,8 0.20 REF 0.18 D 1.95 E 0.10 C 0.08 C SIDE VIEW C SEATING PLANE 1 e 1.60 - 0.50 BSC - k 0.25 - - L 0.30 0.35 0.40 N 10 Nd 5 3 3. Nd refers to the number of terminals on D. 4. All dimensions are in millimeters. Angles are in degrees. 5. Dimension b applies to the metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. E2/2 6. The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 identifier may be either a mold or mark feature. NX L N-1 7. Dimensions D2 and E2 are for the exposed pads which provide improved electrical and thermal performance. NX b 5 (Nd-1)Xe REF. 8 2 2. N is the number of terminals. E2 e - 1. Dimensioning and tolerancing conform to ASME Y14.5-1994. NX k 8 1.55 NOTES: D2/2 2 N - Rev. 3 6/04 D2 (DATUM B) 2.00 8 7 6 INDEX AREA (DATUM A) A3 - 3.00 BSC E2 A 0.23 3.00 BSC D2 B NOTES A b TOP VIEW MAX A1 A3 E NOMINAL 0.10 M C A B 8. Nominal dimensions are provided to assist with PCB Land Pattern Design efforts, see Intersil Technical Brief TB389. BOTTOM VIEW C L 0.415 NX (b) (A1) 0.200 5 L NX L e SECTION "C-C" NX b C C C TERMINAL TIP FOR ODD TERMINAL/SIDE 10 FN6463.0 February 26, 2007