A3946 Half-Bridge Power MOSFET Controller Features and Benefits Description On-chip charge pump for 7 V minimum input supply voltage High-current gate drive for driving a wide range of N-channel MOSFETs Bootstrapped gate drive with top-off charge pump for 100% duty cycle Overtemperature protection Undervoltage protection -40C to 135C ambient operation The A3946 is designed specifically for applications that require high power unidirectional DC motors, three-phase brushless DC motors, or other inductive loads. The A3946 provides two high-current gate drive outputs that are capable of driving a wide range of power N-channel MOSFETs. The high-side gate driver switches an N-channel MOSFET that controls current to the load, while the low-side gate driver switches an N-channel MOSFET as a synchronous rectifier. Package: 16-pin TSSOP with exposed thermal pad (Suffix LP) A bootstrap capacitor provides the above-battery supply voltage required for N-channel MOSFETs. An internal top-off charge pump for the high side allows DC (100% duty cycle) operation of the half-bridge. The A3946 is available in a power package: a 16-lead TSSOP with exposed thermal pad (suffix LP). It is lead (Pb) free, with 100% matte tin plated leadframe (suffix -T). Approximate Scale 1:1 Typical Application VBAT BOOT VBB ~FAULT ECU IN1 IN2 RESET DT 29319.150i GH A3946 PAD S GL CP1 CP2 VREF VREG LGND PGND M A3946 Half-Bridge Power MOSFET Controller Selection Guide Part Number A3946KLPTR-T Packing 4000 pieces/reel Package 16-pin TSSOP with exposed thermal pad Absolute Maximum Ratings Characteristic Symbol Notes Rating Units V Load Supply Voltage VBB 60 Logic Inputs Voltage VIN -0.3 to 6.5 V Pin S Voltage VS -4 to 60 V VGH -4 to 75 V VBOOT -0.6 to 75 V Pin GH Voltage Pin BOOT Voltage Pin DT Voltage VDT VREF V Pin VREG Voltage VREG -0.6 to 15 V -40 to 135 C 150 C Operating Ambient Temperature TA Maximum Junction Temperature TJ(max) Storage Temperature Range K Tstg -55 to 150 C ESD Rating, Human Body Model AEC-Q100-002, all pins 2000 V ESD Rating, Charged Device Model AEC-Q100-011, all pins 1050 V THERMAL CHARACTERISTICS Characteristic Symbol Test Conditions* Value Units Mounted on a 2-layer PCB with 3.8 in . 2-oz copper both sides 43 C/W Mounted on a 4-layer PCB based on JEDEC standard 34 C/W 2 Package Thermal Resistance RJA *Additional thermal information available on Allegro Web site. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 A3946 Half-Bridge Power MOSFET Controller Functional Block Diagram +VBAT C1 0.47 uF, X7R V rated to VBAT C2 0.47 uF, X7R V rated to VBAT P VBB CP2 VREF 10 k7 L VREG Charge Pump +5 Vref 0.1 uF X7R 10 V CP1 L CREG ILIM P P Top-Off Charge Pump BOOT ~FAULT Protection VREG Undervoltage Overtemperature UVLOBOOT Bootstrap UVLO CBOOT L VREF DT RDEAD Turn-On Delay IN1 P Control Logic L RGATE GH High Side Driver S VREG L IN2 RGATE GL Low Side Driver PGND L P RESET LGND L L P PAD Control Logic Table IN1 IN2 X X 0 0 0 1 1 1 DT Pin RESET GH GL Function X 0 Z Z Sleep mode RDEAD - LGND 1 L H Low-side FET ON following dead time RDEAD - LGND 1 L L All OFF 0 RDEAD - LGND 1 L L All OFF 1 RDEAD - LGND 1 H L High-side FET ON following dead time 0 0 VREF 1 L L All OFF 0 1 VREF 1 L H Low-side FET ON 1 0 VREF 1 H L High-side FET ON 1 1 VREF 1 H H CAUTION: High-side and low-side FETs ON Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 A3946 Half-Bridge Power MOSFET Controller ELECTRICAL CHARACTERISTICS at TA = -40 to +135C, VBB = 7 to 60 V (unless otherwise noted) Characteristics Symbol Test Conditions Limits Min. Typ. Max. Units - - 3 6 mA - 10 A VBB > 7.75 V, Ireg = 0 mA to 15 mA 12.0 13 13.5 V VBB = 7 V to 7.75 V, Ireg = 0 mA to 15 mA 11.0 - 13.5 V - 62.5 - kHz RESET = High, Outputs Low VBB Quiescent Current IVBB VREG Output Voltage VREG Charge Pump Frequency FCP CP1, CP2 VREF Output Voltage VREF IREF 4 mA, CREF = 0.1 F 4.5 - 5.5 V Top-Off Charge Pump Current ITO VBOOT - VS = 8.5 V 20 - - A Turn On Time trise CLOAD = 3300 pF, 20% to 80% 60 100 ns Turn Off Time tfall CLOAD = 3300 pF, 80% to 20% - - - - - - 40 80 ns 4 - 6 8 2 - 3 4 VREG - 1.5 - - V VREG - 0.2 - - 200 350 500 ns Rdead = 100 k 5 6 7 s Logic input to unloaded GH, GL. DT = VREF - - 150 ns RESET = Low Gate Output Drive Pullup On Resistance Pulldown On Resistance RDSUP RDSDOWN GH Output Voltage VGH GL Output Voltage VGL Tj = 25C Tj = 135C Tj = 25C Tj = 135C tpw < 10 s, Bootstrap Capacitor fully charged - V Timing Dead Time (Delay from Turn Off to Turn On) Propagation Delay tDEAD tPD Rdead = 5 k Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 A3946 Half-Bridge Power MOSFET Controller ELECTRICAL CHARACTERISTICS at TA = -40 to +135C, VBB = 7 to 60 V (unless otherwise noted) Limits Characteristics Symbol Test Conditions Min. Typ. Max. Units 7.8 8.3 8.8 V Protection VREGOFF VREG decreasing VREGON VREG increasing 8.6 9.1 9.6 V VBSOFF VBOOT decreasing 7.25 7.8 8.3 V VBSON VBOOT increasing 8 8.75 9.5 V Thermal Shutdown Temperature TJTSD Temperature increasing 170 TJ Recovery = TJTSD - TJ 15 - - C Thermal Shutdown Hysteresis - - IIN(1) IN1 VIN / IN2 VIN = 2.0 V 40 100 A IIN(0) IN1 VIN / IN2 VIN = 0.8 V - - - 16 40 A - - - - - - - 1 A - - V 0.8 V 300 mV 400 mV 1 A VREG Undervoltage BOOT Undervoltage C Logic Input Current RESET pin only Logic Input Voltage VIN(1) VIN(0) Logic Input Hysteresis Fault Output IN1 / IN2 logic high 2.0 RESET logic high 2.2 Logic low - All digital inputs Vol I = 1 mA, fault asserted Voh V=5V - 100 - - V Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 A3946 Half-Bridge Power MOSFET Controller Functional Description VREG. A 13 V output from the on-chip charge pump, used to power the low-side gate drive circuit directly, provides the current to charge the bootstrap capacitors for the high-side gate drive. possible UVBOOT), FAULT = 0; also the fault latch is cleared immediately, and remains cleared. If the power is restored (no UVREG or UVREF), and if no OVERTEMP fault exists, then the latched fault remains cleared when the RESET line returns to high. However, FAULT = 1 may still occur because a UVBOOT fault condition may still exist. The VREG capacitor, CREG, must supply the instantaneous current to the gate of the low-side MOSFET. A 10 F, 25 V capacitor should be adequate. This capacitor can be either electrolytic Charge Pump. The A3946 is designed to accommodate a or ceramic (X7R). wide range of power supply voltages. The charge pump output, VREG, is regulated to 13 V nominal. Diagnostics and Protection. The fault output pin, ~FAULT, goes low (i.e., FAULT = 1) when the RESET line is In all modes, this regulator is current-limited. When VBB < 8 V, high and any of the following conditions are present: the charge pump operates as a voltage doubler. When 8 V < * Undervoltage on VREG (UVREG). Note that the outputs become active as soon as VREG comes out of undervoltage, even though the ~FAULT pin is latched until reset. * Undervoltage on VREF (UVREF). Note that this condition does NOT latch a fault. * A junction temperature > 170C (OVERTEMP). This condition sets a latched fault. * An undervoltage on the stored charge of the BOOT capacitor (UVBOOT). This condition does NOT set a latched fault. An overtemperature event signals a latched fault, but does not disable any output drivers, regulators, or logic inputs. The user must turn off the A3946 (e.g., force the RESET line low) to prevent damage. The power FETs are protected from inadequate gate drive voltage by undervoltage detectors. Either of the regulator undervoltage faults (UVREG or UVREF) disable both output drivers until both voltages have been restored. The high-side driver is also disabled during a UVBOOT fault condition. Under many operating conditions, both the high-side (GH) and low-side (GL) drivers may be off, allowing the BOOT capacitor to discharge (or never become charged) and create a UVBOOT fault condition, which in turn inhibits the high-side driver and creates a FAULT = 1. This fault is NOT latched. To remove this fault, momentarily turn on GL to charge the BOOT capacitor. Latched faults may be cleared by a low pulse, 1 to 10 s wide, on the RESET line. Throughout that pulse (despite a VBB< 15 V, the charge pump operates as a voltage doubler/ PWM, current-controlled, voltage regulator. When VBB>15 V, the charge pump operates as a PWM, current-controlled, voltage regulator. Efficiency shifts, from 80% at VBB= 7 V, to 20% at VBB = 50 V. CAUTION. Although simple paralleling of VREG supplies from several A3946s may appear to work correctly, such a configuration is NOT recommended. There is no assurance that one of the regulators will not dominate, taking on all of the load and back-biasing the other regulators. (For example, this could occur if a particular regulator has an internal reference voltage that is higher that those of the other regulators, which would force it to regulate at the highest voltage.) Sleep Mode/Power Up. In Sleep Mode, all circuits are disabled in order to draw minimum current from VBB. When powering up and leaving Sleep Mode (the RESET line is high), the gate drive outputs stay disabled and a fault remains asserted until VREF and VREG pass their undervoltage thresholds. When powering up, before starting the first bootstrap charge cycle, wait until t = CREG 4 (where CREG is in F, and t is in ns) to allow the charge pump to stabilize. When powered-up (not in Sleep Mode), if the RESET line is low for > 10 s, the A3946 may start to enter Sleep Mode (VREF < 4 V). In that case, ~FAULT = 1 as long as the RESET line remains low. If the RESET line is open, the A3946 should go into Sleep Mode. However, to ensure that this occurs, the RESET line must be grounded. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 A3946 Half-Bridge Power MOSFET Controller Dead Time. The analog input pin DT sets the delay to turn on the high- or low-side gate outputs. When instructed to turn off, the gate outputs change after an short internal propagation delay (90 ns typical). The dead time controls the time between this turn-off and the turn-on of the appropriate gate. The duration, tDEAD, can be adjusted within the range 350 ns to 6000 ns using the following formula: tDEAD = 50 + (RDEAD 16.7 ) where tDEAD is in ns, and RDEAD is in , and should be in the range 5 k < RDEAD < 100 k. Do not ground the DT pin. If the DT pin is left open, dead time defaults to 12 s. Control Logic. Two different methods of control are possible with the A3946. When a resistor is connected from DT to ground, a single-pin PWM scheme is utilized by shorting IN1 with IN2. If a very slow turn-on is required (greater than 6 s), the two input pins can be hooked-up individually to allow the dead times to be as long as needed. The dead time circuit can be disabled by tying the DT pin to VREF. This disables the turn-on delay and allows direct control of each MOSFET gate via two control lines. This is shown in the Control Logic table, on page 2. Top-Off Charge Pump. An internal charge pump allows 100% duty cycle operation of the high-side MOSFET. This is a low-current trickle charge pump, and is only operated after a high-side has been signaled to turn on. A small amount of bias current is drawn from the BOOT pin to operate the floating high-side circuit. The top-off charge pump simply provides enough drive to ensure that the gate voltage does not droop due to this bias supply current. The charge required for initial turn-on of the high-side gate must be supplied by bootstrap capacitor charge cycles. This is described in the section Application Information. VREF. VREF is used for the internal logic circuitry and is not intended as an external power supply. However, the VREF pin can source up to 4 mA of current. A 0.1 F capacitor is needed for decoupling. Fault Response Table Fault Mode No Fault BOOT Capacitor Undervoltage Thermal Shutdown Sleep 5 3 ~FAULT VREG VREF GH1 GL1 1 1 ON ON (IL) (IL) 1 0 ON ON 0 (IL) 3 1 0 ON ON 0 0 4 1 0 OFF ON 0 0 1 0 ON ON (IL) (IL) 0 1 OFF OFF High Z High Z VREG Undervoltage VREF Undervoltage RESET 2 (IL) indicates that the state is determined by the input logic. 2 This fault occurs whenever there is an undervoltage on the BOOT capacitor. This fault is not latched. 3 These faults are latched. Clear by pulsing RESET = 0. Note that outputs become active as soon as VREG comes out of undervoltage, even though ~FAULT = 0. 4 Unspecified VREF undervoltage threshold < 4 V. 5 During power supply undervoltage conditions, GH and GL are instructed to be 0 (low). However, with VREG < 4 V, the outputs start to become high impedance (High Z). Refer to the section Sleep Mode/Power Up. 1 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 A3946 Half-Bridge Power MOSFET Controller Application Information Bootstrap Capacitor Selection. CBOOT must be correctly selected to ensure proper operation of the device. If too large, time is wasted charging the capacitor, with the result being a limit on the maximum duty cycle and PWM frequency. If the capacitor is too small, the voltage drop can be too large at the time the charge is transferred from the CBOOT to the MOSFET gate. To keep the voltage drop small: At power-up and when the drivers have been disabled for a long time, the bootstrap capacitor can be completely discharged. In this case, Delta_v can be considered to be the full high-side drive voltage, 12 V. Otherwise, Delta_v is the amount of voltage dropped during the charge transfer, which should be 400 mV or less. The capacitor is charged whenever the S pin is pulled low, via a GL PWM cycle, and current flows from VREG through the internal bootstrap diode circuit to CBOOT. QBOOT >> QGATE where a factor in the range of 10 to 20 is reasonable. Using 20 as the factor: and QBOOT = CBOOT x VBOOT = QGATE x 20 CBOOT = QGATE x 20 / VBOOT The voltage drop on the BOOT pin, as the MOSFET is being turned on, can be approximated by: Delta_v = QGATE / CBOOT For example, given a gate charge, QGATE, of 160 nC, and the typical BOOT pin voltage of 12 V, the value of the Boot capacitor, CBOOT, can be determined by: CBOOT = (160 nC x 20) / 12 V 0.266 F Power Dissipation. For high ambient temperature applications, there may be little margin for on-chip power consumption. Careful attention should be paid to ensure that the operating conditions allow the A3946 to remain in a safe range of junction temperature. The power consumed by the A3946 can be estimated as: P_total = Pd_bias + Pd_cpump + Pd_switching_loss where: Pd_bias = VBB x IVBB , typically 3 mA, and Pd_cpump = (2VBB - VREG) IAVE, for VBB < 15 V, or Pd_cpump = (VBB - VREG) IAVE, for VBB > 15 V, Therefore, a 0.22 F ceramic (X7R) capacitor can be chosen for the Boot capacitor. in either case, where In that case, the voltage drop on the BOOT pin, when the high-side MOSFET is turned on, is: and Delta_v = 160 nC / 0.22 F = 0.73 V Bootstrap Charging. It is good practice to ensure that the high-side bootstrap capacitor is completely charged before a high-side PWM cycle is requested. IAVE = QGATE x 2 x fPWM Pd_switching_loss = QGATE x VREG x 2 x fPWM Ratio, where Ratio = 10 / (RGATE + 10 ). The time required to charge the capacitor can be approximated by: tCHARGE = CBOOT (Delta_v / 100 mA) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 A3946 Half-Bridge Power MOSFET Controller Application Block Diagrams +VBAT C1 0.47 F C2 10 F P VBB VREF CP2 VREF 0.1 uF ILIM L L VREG Charge Pump +5 Vref 10 k7 CP1 P P Top-Off Charge Pump BOOT ~FAULT Protection VREG Undervoltage Overtemperature UVLOBOOT Bootstrap UVLO CBOOT 0.47 F IRF2807 L DT RDEAD 15.8 k7 GH High Side Driver Turn-On Delay RGATE IN1 Control Logic S VREG Forward IRF2807 L IN P 33 7 470 k7 L IN CREG 10 F IN2 GL Low Side Driver Brake RGATE 33 7 PGND External +5 V L RESET M LGND P L L DC Motor P Diagram A. Dependent drivers. Unidirectional motor control with braking and dead time. TDEAD = 1 s; QTOTAL = 160 nC. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 A3946 Half-Bridge Power MOSFET Controller +VBAT P C1 0.47 F C2 10 F VBB VREF CP2 VREF CP1 0.1 uF 10 k7 L L VREG Charge Pump +5 Vref P CREG P 10 F ILIM P Top-Off Charge Pump BOOT ~FAULT M Protection VREG Undervoltage Overtemperature UVLOBOOT Bootstrap UVLO CBOOT IRF2807 L VREF DT GH RGATE High Side Driver Turn-On Delay 33 7 470 k7 DC Motor #1 IN1 Forward Control Logic Slow Decay DC Motor #2 Forward S VREG L IRF2807 IN2 RGATE GL Slow Decay External +5 V DC Motor #2 0.47 F Low Side Driver 33 7 PGND L RESET LGND P L L 470 k7 M DC Motor #1 P Diagram B. Independent drivers. One high-side drive and one low-side drive. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 A3946 Half-Bridge Power MOSFET Controller +VBAT C1 0.47 F C2 10 F P P VBB VREF CP2 VREF CP1 0.1 uF 10 k7 ILIM L L VREG Charge Pump +5 Vref P P Top-Off Charge Pump DC Motor #1 Bootstrap UVLO DT High Side Driver Turn-On Delay RGATE GH 33 7 470 k7 DC Motor #1 IN1 Forward Control Logic Slow Decay S P VREG DC Motor #2 Forward IRF2807 L IN2 RGATE GL Low Side Driver Slow Decay 33 7 470 k7 PGND External +5 V DC Motor #2 IRF2807 L VREF M M BOOT ~FAULT Protection VREG Undervoltage Overtemperature UVLOBOOT CREG 10 F L P RESET LGND L L P PAD Diagram C. Independent drivers. Two low-side drives. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 A3946 Half-Bridge Power MOSFET Controller Pin-out Diagram LP package VREG 1 16 VBB CP2 2 15 VREF CP1 3 14 DT PGND 4 13 LGND GL 5 12 RESET S 6 11 IN2 GH 7 10 IN1 BOOT 8 9 ~FAULT PAD Terminal List Table Name Number Description VREG 1 Gate drive supply. CP2 2 Charge pump capacitor, positive side. When not using the charge pump, leave this pin open. CP1 3 Charge pump capacitor, negative side. When not using the charge pump, leave this pin open. PGND* 4 External ground. Internally connected to the power ground. GL 5 Low-side gate drive output for external MOSFET driver. External series gate resistor can be used to control slew rate seen at the power driver gate, thereby controlling the di/dt and dv/dt of the S pin output. S 6 Directly connected to the load terminal. The pin is also connected to the negative side of the bootstrap capacitor and negative supply connection for the floating high-side drive. GH 7 High-side gate drive output for N-channel MOSFET driver. External series gate resistor can be used to control slew rate seen at the power driver gate, thereby controlling the di/dt and dv/dt of the S pin output. BOOT 8 High-side connection for bootstrap capacitor, positive supply for the high-side gate drive. ~FAULT 9 Diagnostic output, open drain. Low during a fault condition. IN1 10 Logic control. IN2 11 Logic control. RESET 12 Logic control input. When RESET = 0, the chip is in a very low power sleep mode. LGND* 13 External ground. Internally connected to the logic ground. DT 14 Dead Time. Connecting a resistor to GND sets the turn-on delay to prevent shoot-through. Forcing this input high disables the dead time circuit and changes the logic truth table. VREF 15 5 V internal reference decoupling terminal. VBB 16 Supply Input. PAD - Exposed thermal pad. Not connected to any pin, but should be externally connected to ground, to reduce noise pickup by the pad. The PGND pin (4) and LGND pin (13) grounds are NOT internally connected, and both must be connected to ground externally. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 A3946 Half-Bridge Power MOSFET Controller LP Package TSSOP with Exposed Thermal Pad 0.45 5.00 0.10 4 4 16 +0.05 0.15 -0.06 0.65 16 1.70 B 4.40 0.10 3.00 6.40 0.20 0.60 0.15 A 1 6.10 (1.00) 2 3.00 16X 0.25 SEATING PLANE 0.10 C +0.05 0.25 -0.06 3.00 0.65 C SEATING PLANE GAUGE PLANE 1 2 3.00 C PCB Layout Reference View 1.20 MAX 0.15 MAX For Reference Only (reference JEDEC MO-153 ABT) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area B Exposed thermal pad (bottom surface) C Reference land pattern layout (reference IPC7351 SOP65P640X110-17M); All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13 A3946 Half-Bridge Power MOSFET Controller Copyright (c)2003-2010 Allegro MicroSystems, Inc. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14