8925

8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS 8925 Data Sheet 26301.30 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS LOGIC GROUND LOGIC SUPPLY POWER GROUND 7 8 9 39 38 37 36 35 34 33 32 31 POWER GROUND SUB V BB POWER GROUND ABSOLUTE MAXIMUM RATINGS AT TA = +25°C Load Supply Voltage, VBB ..................... 14 V Output Current, IOUT .......................... ±4.0 A Logic Supply Voltage, VCC ..................... 14 V Logic Input Voltage Range, VIN ................................ -0.3 V to +6.0 V Package Power Dissipation, PD ......................................... See Graph Operating Temperature Range, TA ..................................... 0 °C to +70°C Junction Temperature, TJ ............... +150°C† Storage Temperature Range, TS ................................ -55°C to +150°C † Fault conditions that produce excessive junction temperature will activate device thermal shutdown circuitry. These conditions can be tolerated, but should be avoided. Output current rating may be restricted to a value determined by system concerns and factors. These include: system duty cycle and timing, ambient temperature, and use of any heatsinking and/or forced cooling. For reliable operation, the specified maximum junction temperature should not be exceeded. T C UY DL ON RO PE DC EN UE IN ER TF NE OR CR IS O DF — 10 11 12 13 14 15 16 17 CHARGE PUMPS AND CONTROL SEQUENCING CIRCUITRY The A8925CEB is a DMOS three-phase brushless dc motor controller/driver designed for use in Winchester disk drives and other data storage applications. The power output stages are capable of ±4 A output currents and have DMOS power outputs with less than 0.25 Ω rDS(on) for low power dissipation. Intrinsic ground clamp and flyback diodes protect the output drivers when switching inductive loads. Thermal shutdown circuitry is provided to protect the device from excessive junction temperature. A transconductance amplifier is used to linearly regulate the load current and control motor speed. Internal current-sensing circuitry eliminates the need for external sense resistors. Analog and digital control circuitry provide complete sequencing of the output drivers as well as providing brake, disable, and tachometer functions. A FAULT output flag indicates the presence of an under-voltage condition on the 12 V supply, excessive junction temperature, or an invalid Hall input combination. The A8925CEB’s commutation logic is compatible with motors that have digital Hall-effect sensors with 120° of electrical separation. Internal charge pump circuitry is provided to drive the Nchannel DMOS source drivers to their required gate voltages. The A8925CEB is provided in a 44-lead PLCC power package for surface-mount applications. The copper batwing provides for maximum allowable package power dissipation in the smallest possible construction. ENABLE V CC 40 FAULT 43 TACH 4 OUT C 44 POLE 1 OUTB 42 OUT A NC 41 NC 6 5 3 2 30 + 29 POWER GROUND SUB 25 26 27 19 20 18 21 22 23 COMP. 1 24 NC 2 ERROR AMP REFERENCE LOAD SUPPLY VSENSE BRAKE NC H H H 3 28 Dwg. PP-034 FEATURES s s s s s s s s s DMOS Outputs Low r DS(on) - 0.25 Ω Maximum Linear Current Control Internal Commutation Circuitry Internal Current Sensing Thermal Shutdown Circuitry Under Voltage Detection Circuitry Fault Output Flag Power Surface-Mount Package Always order by complete part number: A8925CEB . 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS 12.5 R θJ T /W °C =6 10 7.5 5.0 2.5 R θJA = 3 0°C /W 0 25 50 75 100 TEMPERATURE IN °C 125 150 Dwg. GP-020B ELECTRICAL CHARACTERISTICS AT TA = +25°C, VCC = VBB = 12 V Limits Characteristic Logic Supply Voltage Load Supply Voltage Supply Current Thermal Shutdown Symbol VCC V BB ICC TJ IOUT = ±4.0 A, Pulse Test IOUT = 4.0 A, L = 2 mH IF = ±4.0 A VOUT = 14 V VOUT = 0 V Test Conditions Operating Operating Operating VENABLE = 0 V Min. 10 10 — — — Typ. 12 12 30 2.0 165 Max. 14 14 50 4.0 — Units V V mA mA °C Ω V V µA µA Output Drivers Output ON Resistance Output Sustaining Voltage Clamp Diode Forward Voltage Output Leakage Current rDS(on) VDS(sus) VF IDSX — 14 — — — 0.20 — 1.5 10 -10 0.25 — 2.0 300 -300 Control Logic Logic Input Voltage VIN(0) VIN(1) Logic Input Voltage VIN(0) VIN(1) Logic Input Current IIN(0) IIN(1) VIN = 0.8 V VIN = 2.4 V BRAKE ENABLE, POLE — 2.4 — 3.0 — — — — — — — — 0.8 — 0.8 — -1.0 1.0 V V V V µA µA NOTE: Negative current is defined as coming out of (sourcing) the specified device terminal. Continued next page... 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1990, 1995 Allegro MicroSystems, Inc. 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS ELECTRICAL CHARACTERISTICS CONTINUED Limits Characteristic Logic Output Voltage (FAULT, TACH) Symbol VOUT(0) VOUT(1) Test Conditions IOUT = 3 mA IOUT = -50 µA Min. — 2.0 Typ. — — Max. 0.8 — Units V V Error Amplifier Input Bias Current Input Offset Voltage Input Common-Mode Voltage Range Error Voltage Gain Unity Gain Bandwidth Common-Mode Rejection Ratio Power Supply Rejection Ratio IIB VOS VIC AVD BW CMRR PSRR VS OUT / V S IN , V CM = 1.0 V VCM = 0.01 V VCM = 1.0 V — — 0.01 — — — — 5.0 3.0 — 80 1.0 80 50 10 5.0 6.0 — — — — µA mV V dB MHz dB dB Miscellaneous Current Sense Gain Current-Sense Matching Under-Voltage Trip Point Hall Input Current AiCS — VCC IIN(0) IIN(1) Hall Input Threshold Hall Input Pull-Up Resistance VIN RPU VIN = 0 V VIN = 5.0 V IOUT = -1.0 A IOUT = -1.0 A 1/1k — 8.0 — — — — 1/1.2k ±3.0 — -500 -250 3.8 25 1/1.4k ±5.0 9.5 -1000 -500 — — — % V µA µA V kΩ NOTE: Negative current is defined as coming out of (sourcing) the specified device terminal. COMMUTATION TRUTH TABLE Hall Sensor Inputs H1 High High High Low Low Low High Low X X H2 Low Low High High High Low High Low X X H3 High Low Low Low High High High Low X X ENABLE BRAKE FAULT High High High High High High High High Low X High High High High High High High High High Low High High High High High High Low Low X X OUT A High High Z Low Low Z Z Z Z Low Outputs OUT B Low Z High High Z Low Z Z Z Low OUT C Z Low Low Z High High Z Z Z Low X = Irrelevant Z = High Impedance 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS TERMINAL FUNCTIONS Term. 1 2 3 4 6 7–17 18 19 20 21 22 23 24 26 28 29–39 40 42 43 44 Terminal Name OUTB LOGIC SUPPLY LOGIC GROUND OUT C ENABLE POWER GROUND VSENSE COMP. REFERENCE ERROR AMP. LOAD SUPPLY BRAKE H1 H2 H3 POWER GROUND FAULT OUTA TACH POLE Function Power DMOS output. VCC; low-current 12 V supply for the logic. Low-level logic ground. Power DMOS output. Active high chip enable. Power ground and thermal heat sink. External precision resistor for sense-FET current. Compensation; error amplifier output. VREF ; voltage input that sets the power output current. Input that controls the current in the load. VBB; high-current 12 V supply for the voice-coil motor. A logic low turns OFF all source drivers and turns ON all sink drivers (shorts the windings to ground). High-level input from a Hall sensor. High-level input from a Hall sensor. High-level input from a Hall sensor. Power ground and thermal heat sink. A logic low at this output indicates a thermal shutdown, under -voltage fault, or an invalid Hall input combination. Power DMOS output. Speed reference output; the H1 Hall input divided by the number of motor poles. Designates four- or eight-pole motor; Low = 4 pole, High = 8 pole. FUNCTIONAL DESCRIPTION V BB CHARGE PUMP SENSE AMPLIFIER I OUT . VSENSE 1200 SEQUENTIAL LOGIC OUT R3 R1 RS C1 Power Outputs (OUT A, OUTB, and OUTC). The power outputs of the A8925CEB are DMOS transistors with a maximum rDS(on) of 0.25 Ω. Intrinsic ground clamp and flyback diodes clamp transient voltage spikes when switching inductive loads. Internal charge pump circuitry is used to drive the gates of the N-channel source drivers to their required gate voltages. Current Control. Current in the load is monitored by an internal sense amplifier that produces an output current that is approximately one twelve hundredth that of the load current (see Figure). This current is output to the VSENSE terminal and develops a voltage Continued next page... C2 OUT _ R2 VREF V COMP. SUB + + ERROR AMPLIFIER Dwg. EP-040 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS across RS that equals RS • ILOAD /1200. This sense voltage (VSENSE) is compared to a reference voltage (VREF ) and an error voltage is developed that is gated in by the sequential control logic to drive the gate of the appropriate output sink transistor. A transconductance control function is thus realized where IOUT = V REF • 1200/R S. External components C1, C2, R1, R2, and R3 are compensation components used to obtain optimal response and settling of the current control loop. Information on how to select these components is available. FAULT. The FAULT terminal when low indicates the presence of one of three fault conditions: A) An under-voltage condition on the logic supply. The trip point for this function is between 8 and 9.5 volts. An invalid Hall input combination … all inputs High or all inputs Low. An excessive device junction temperature. The thermal shutdown circuitry disables the output drivers in addition to forcing the FAULT output signal low. HALL INPUTS (H1, H2, H3). The A8925CEB is configured for use with open-collector Hall-effect devices. Internal 25 kΩ pull up resistors to 10 volts are connected to these inputs. ENABLE. The ENABLE terminal when Low puts the device in a low current consumption, power-down mode. When ENABLE is High the device is active. BRAKE. When the BRAKE input goes Low the output source drivers are disabled and the gates of the sink drivers are pulled high and left floating. This achieves optimum passive braking performance since the sink power DMOS output drivers are ON until the motor has fully completed braking. The braking control circuitry operates off the load supply (VBB) to allow it to remain operational during power loss by using the back-EMF voltage of the motor as it’s supply. LOAD SUPPLY (VBB ). This terminal is the power supply connection for the power output drivers and braking control circuitry. This terminal should be decoupled with a large-value capacitor to absorb load currents dumped back into the supply during the de-energization of motor windings. These currents can cause the supply voltage to exceed the maximum voltage rating of the device if not properly decoupled. The intrinsic ground clamp and flyback diodes will rectify the motor’s back-EMF voltage during power loss. In applications were use of the motor’s back-EMF voltage is desired a series diode should be used to isolate this terminal from the logic supply (VCC ). This is to avoid dumping the charge back into the supply and therefor clamping the voltage available from rectification of the motor’s back-EMF voltage. LOGIC SUPPLY (VCC). This is the 12 volt supply terminal for the A8925CEB and powers all circuitry except the power outputs and brake control circuitry. LOGIC GROUND. This must be connected to the power ground terminals in systems that do not use separate power and logic grounds. POWER GROUND. Terminals 7 through 17 and 29 through 39 are webbed together and attach to the die mounting area to form a low thermal resistance path to allow heat to be conducted out of the device. The power dissipation of the package can be further enhanced by soldering these terminals to a large area of copper foil on the printed wiring board. B) C) TACH and POLE. In order to develop a low-jitter tachometer signal (TACH) for use in controlling motor speed, the A8925CEB divides the frequency of the H1 input by the number of poles in the motor. This eliminates the jitter caused by variations in Halleffect device placement , sensitivity, and magnet strengths by always changing state when looking at the same magnet/sensor pair. The resulting TACH signal changes state every mechanical revolution of the motor. The POLE input sets the TACH signal for fourpole motors when Low or eight-pole motors when High. 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS DIMENSIONS IN INCHES (for reference only) 28 18 29 0.319 0.291 0.021 0.013 0.695 0.685 0.656 0.650 0.319 0.291 0.050 BSC INDEX AREA 17 0.032 0.026 39 7 40 0.020 MIN 44 1 2 6 0.656 0.650 0.695 0.685 Dwg. MA-005-44A in 0.180 0.165 DIMENSIONS IN MILLIMETERS (controlling dimensions) 28 18 29 8.10 7.39 0.533 0.331 17.65 17.40 16.662 16.510 INDEX AREA 17 0.812 0.661 8.10 7.39 1.27 BSC 39 7 40 0.51 MIN 44 1 2 6 4.57 4.20 16.662 16.510 17.65 17.40 Dwg. MA-005-44A mm NOTES: 1. Webbed lead frame. Leads 7 through 17 and 29 through 39 are internally one piece. 2. Exact body and lead configuration at vendor’s option within limits shown. 3. Lead spacing tolerance is non-cumulative. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS 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 design of its products. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use. 8925 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000