Data Sheet 29319.8* 3953 FULL-BRIDGE PWM MOTOR DRIVER 16 LOAD SUPPLY 2 15 OUTB RC 3 14 MODE GROUND 4 13 GROUND 12 GROUND 11 SENSE 10 OUTA 9 LOAD SUPPLY BRAKE 1 REF VBB LOGIC GROUND 5 LOGIC SUPPLY 6 PHASE 7 ENABLE 8 VCC VBB Dwg. PP-056 Note the A3953SB (DIP) and the A3953SLB (SOIC) are electrically identical and share a common terminal number assignment. ABSOLUTE MAXIMUM RATINGS Load Supply Voltage, VBB . . . . . . . . . . 50 V Output Current, IOUT (Continuous) . . . . . . . . . . . . . . ±1.3 A* Logic Supply Voltage, VCC . . . . . . . . . 7.0 V Logic/Reference Input Voltage Range, VIN . . . . . . . . . . . -0.3 V to VCC + 0.3 V Sense Voltage, VSENSE (VCC = 5.0 V) . . . . . . . . . . . . . . . . 1.0 V (VCC = 3.3 V) . . . . . . . . . . . . . . . . 0.4 V Package Power Dissipation, PD . . . . . . . . . . . . . . . . . . . . See Graph Operating Temperature Range, TA . . . . . . . . . . . . . . . . . -20˚C to +85˚C Junction Temperature, TJ . . . . . . . +150˚C† Storage Temperature Range, TS . . . . . . . . . . . . . . . . -55˚C to +150˚C Designed for bidirectional pulse-width modulated (PWM) current control of inductive loads, the A3953S— is capable of continuous output currents to ±1.3 A and operating voltages to 50 V. Internal fixed off-time PWM currentcontrol circuitry can be used to regulate the maximum load current to a desired value. The peak load current limit is set by the user’s selection of an input reference voltage and external sensing resistor. The fixed off-time pulse duration is set by a user- selected external RC timing network. Internal circuit protection includes thermal shutdown with hysteresis, transient-suppression diodes, and crossover current protection. Special power-up sequencing is not required. With the ENABLE input held low, the PHASE input controls load current polarity by selecting the appropriate source and sink driver pair. The MODE input determines whether the PWM current-control circuitry operates in a slow current-decay mode (only the selected source driver switching) or in a fast current-decay mode (selected source and sink switching). A userselectable blanking window prevents false triggering of the PWM currentcontrol circuitry. With the ENABLE input held high, all output drivers are disabled. A sleep mode is provided to reduce power consumption. When a logic low is applied to the BRAKE input, the braking function is enabled. This overrides ENABLE and PHASE to turn off both source drivers and turn on both sink drivers. The brake function can be used to dynamically brake brush dc motors. The A3953S— is supplied in a choice of two power packages; a 16-pin dual-in-line plastic package with copper heat-sink tabs, and a 16-lead plastic SOIC with copper heat-sink tabs. For both package styles, the power tab is at ground potential and needs no electrical isolation. FEATURES ■ ■ ■ ■ ■ ■ ■ ±1.3 A Continuous Output Current 50 V Output Voltage Rating 3 V to 5.5 V Logic Supply Voltage Internal PWM Current Control Saturated Sink Drivers (Below 1 A) Fast and Slow Current-Decay Modes Automotive Capable ■ Sleep (Low Current Consumption) Mode ■ Internal TransientSuppression Diodes ■ Internal ThermalShutdown Circuitry ■ Crossover-Current and UVLO Protection * Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current rating or a junction temperature of 150˚C. † Fault conditions that produce excessive junction temperature will activate the device’s thermal shutdown circuitry. These conditions can be tolerated but should be avoided. Always order by complete part number: Part Number A3953SB A3953SLB Package 16-Pin DIP 16-Lead SOIC RθJA 43°C/W 67°C/W RθJT 6°C/W 6°C/W 3953 FULL-BRIDGE PWM MOTOR DRIVER 6 VCC 10 15 LOAD SUPPLY OUTA 9 OUTB LOGIC SUPPLY LOAD SUPPLY FUNCTIONAL BLOCK DIAGRAM 16 SLEEP & STANDBY MODES MODE 14 VBB 7 BRAKE 1 INPUT LOGIC 8 PWM LATCH R 11 – ENABLE UVLO & TSD + PHASE SENSE Q S BLANKING GROUND VCC 4 RS RC 3 5 12 + – 2 REF RT CT 13 GROUND VTH Dwg. FP-036-2A TRUTH TABLE BRAKE ENABLE PHASE MODE OUTA OUTB DESCRIPTION H H X H Off Off Sleep Mode H H X L Off Off Standby H L H H H L Forward, Fast Current-Decay Mode H L H L H L Forward, Slow Current-Decay Mode H L L H L H Reverse, Fast Current-Decay Mode H L L L L H Reverse, Slow Current-Decay Mode L X X H L L Brake, Fast Current-Decay Mode L X X L L L Brake, No Current Control X = Irrelevant 2 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1995, 2000 Allegro MicroSystems, Inc. ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS 3953 FULL-BRIDGE PWM MOTOR DRIVER 5 RθJT = 6.0°C/W 4 3 SUFFIX 'B', R θJA = 43°C/W 2 1 SUFFIX 'LB', R θJA = 63°C/W 0 25 50 75 100 TEMPERATURE IN °C 125 150 Dwg. GP-049-2A ELECTRICAL CHARACTERISTICS at TJ = 25˚C, VBB = 5 V to 50 V, VCC = 3.0 V to 5.5 V (unless otherwise noted.) Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units VCC — 50 V Power Outputs Load Supply Voltage Range VBB Operating, IOUT = ±1.3 A, L = 3 mH Output Leakage Current ICEX VOUT = VBB — <1.0 50 µA VOUT = 0 V — <-1.0 -50 µA ISO ISENSE - IOUT1, IOUT = 850 mA, VSENSE = 0 V, VCC = 5 V 22 33 38 mA VCE(SAT) VSENSE = 0.4 V, VCC = 3.0 V: Sense Current Offset Output Saturation Voltage BRAKE = H Source Driver, IOUT = -0.85 A — 1.0 1.1 V (Forward/Reverse Mode) Source Driver, IOUT = -1.3 A — 1.7 1.9 V Sink Driver, IOUT = 0.85 A — 0.4 0.5 V Sink Driver, IOUT = 1.3 A — 1.1 1.3 V Output Saturation Voltage VCE(SAT) VSENSE = 0.4 V, VCC = 3.0 V: BRAKE = L Sink Driver, IOUT = 0.85 A — 1.0 1.2 V (Brake Mode) Sink Driver, IOUT = 1.3 A — 1.3 1.5 V IF = 0.85 A — 1.2 1.4 V IF = 1.3 A — 1.4 1.6 V Clamp Diode Forward Voltage (Sink or Source) VF Continued next page… www.allegromicro.com 3 3953 FULL-BRIDGE PWM MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TJ = 25˚C, VBB = 5 V to 50 V, VCC = 3.0 V to 5.5 V (unless otherwise noted.) Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units CT = 680 pF, RT= 30 kΩ, VCC = 3.3 V 18.3 20.4 22.5 µs Comparator Trip to Source Off, IOUT = 25 mA Comparator Trip to Source Off, IOUT = 1.3 A — 1.0 1.5 µs — 1.8 2.6 µs IRC Charge On to Source On, IOUT = 25 mA IRC Charge On to Source On, IOUT = 1.3 A — 0.4 0.7 µs — 0.55 0.85 µs VCC = 3.3 V, RT ≥ 12 kΩ, CT = 680 pF 0.8 1.4 1.9 µs VCC = 5.0 V, RT ≥ 12 kΩ, CT = 470 pF 0.8 1.6 2.0 µs ENABLE On to Source On — 1.0 — µs ENABLE Off to Source Off — 1.0 — µs ENABLE On to Sink On — 1.0 — µs ENABLE Off to Sink Off (MODE = L) — 0.8 — µs PHASE Change to Sink On — 2.4 — µs PHASE Change to Sink Off — 0.8 — µs PHASE Change to Source On — 2.0 — µs PHASE Change to Source Off — 1.7 — µs 1 kΩ Load to 25 V, VBB = 50 V 0.3 1.5 3.0 µs IOUT = 1.3 A 70 — — kHz AC Timing PWM RC Fixed Off-time PWM Turn-Off Time PWM Turn-On Time PWM Minimum On Time Propagation Delay Times Crossover Dead Time Maximum PWM Frequency tOFF RC tPWM(OFF) tPWM(ON) tON(min) tpd tCODT fPWM(max) IOUT = ±1.3 A, 50% to 90%: Continued next page… 4 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3953 FULL-BRIDGE PWM MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TJ = 25˚C, VBB = 5 V to 50 V, VCC = 3.0 V to 5.5 V (unless otherwise noted. ) Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units TJ — 165 — °C ∆TJ — 8.0 — °C UVLO Enable Threshold 2.5 2.75 3.0 V UVLO Hysteresis 0.12 0.17 0.25 V Control Circuitry Thermal Shutdown Temp. Thermal Shutdown Hysteresis Logic Supply Current ICC(ON) VENABLE = 0.8 V, VBRAKE = 2.0 V — 42 50 mA ICC(OFF) VENABLE = 2.0 V, VMODE = 0.8 V — 12 15 mA ICC(Brake) VBRAKE = 0.8 V — 42 50 mA ICC(Sleep) VENABLE = VMODE = VBRAKE = 2.0 V — 500 800 µA Motor Supply Current IBB(ON) VENABLE = 0.8 V — 2.5 4.0 mA (No Load) IBB(OFF) VENABLE = 2.0 V, VMODE = 0.8 V — 1.0 50 µA IBB(Brake) VBRAKE = 0.8 V — 1.0 50 µA IBB(Sleep) VENABLE = VMODE = 2.0 V — 1.0 50 µA Operating 3.0 5.0 5.5 V Logic Supply Voltage Range VCC Logic Input Voltage VIN(1) 2.0 — — V VIN(0) — — 0.8 V Logic Input Current VSENSE Voltage Range IIN(1) VIN = 2.0 V — <1.0 20 µA IIN(0) VIN = 0.8 V — <-2.0 -200 µA VSENSE(3.3) VCC = 3.0 V to 3.6 V 0 — 0.4 V VSENSE(5.0) VCC = 4.5 V to 5.5 V 0 — 1.0 V Reference Input Current IREF VREF = 0 V to 1 V — — ±5.0 µA Comparator Input Offset Volt. VIO VREF = 0 V — ±2.0 ±5.0 mV www.allegromicro.com 5 3953 FULL-BRIDGE PWM MOTOR DRIVER FUNCTIONAL DESCRIPTION Internal PWM Current Control During Forward and Reverse Operation. The A3953S— contains a fixed offtime pulse-width modulated (PWM) current-control circuit that can be used to limit the load current to a desired value. The peak value of the current limiting (ITRIP) is set by the selection of an external current sensing resistor (RS) and reference input voltage (VREF). The internal circuitry compares the voltage across the external sense resistor to the voltage on the reference input terminal (REF) resulting in a transconductance function approximated by: VREF ITRIP ≈ – ISO RS The user selects an external resistor (RT) and capacitor (CT) to determine the time period (tOFF = RT x CT) during which the drivers remain disabled (see “RC Fixed Off-Time” below). At the end of the RC interval, the drivers are enabled allowing the load current to increase again. The PWM cycle repeats, maintaining the peak load current at the desired value (see figure 2). Figure 2 Fast and Slow Current-Decay Waveforms ENABLE MODE where ISO is the offset due to base drive current. I TRIP RC In forward or reverse mode the current-control circuitry limits the load current as follows: when the load current reaches ITRIP, the comparator resets a latch that turns off the selected source driver or selected sink and source driver pair depending on whether the device is operating in slow or fast current-decay mode, respectively. In slow current-decay mode, the selected source driver is disabled; the load inductance causes the current to recirculate through the sink driver and ground clamp diode. In fast current-decay mode, the selected sink and source driver pair are disabled; the load inductance causes the current to flow from ground to the load supply via the ground clamp and flyback diodes. Figure 1 — Load-Current Paths V BB DRIVE CURRENT LOAD CURRENT RC Dwg. WP-015-1 INTERNAL PWM CURRENT CONTROL DURING BRAKE-MODE OPERATION Brake Operation - MODE Input High. The brake circuit turns off both source drivers and turns on both sink drivers. For dc motor applications, this has the effect of shorting the motor’s back-EMF voltage resulting in current flow that dynamically brakes the motor. If the back-EMF voltage is large, and there is no PWM current limiting, the load current can increase to a value that approaches that of a locked rotor condition. To limit the current, when the ITRIP level is reached, the PWM circuit disables the conducting sink drivers. The energy stored in the motor’s inductance is discharged into the load supply causing the motor current to decay. RECIRCULATION (SLOW-DECAY MODE) RECIRCULATION (FAST-DECAY MODE) RS As in the case of forward/reverse operation, the drivers are enabled after a time given by tOFF = RT x CT (see “RC Fixed Off-Time” below). Depending on the back-EMF voltage (proportional to the motor’s decreasing speed), the load current again may increase to ITRIP. If so, the PWM cycle will repeat, limiting the peak load current to the desired value. Dwg. EP-006-13A 6 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3953 FULL-BRIDGE PWM MOTOR DRIVER During braking, when the MODE input is high, the peak current limit can be approximated by: ITRIP BRAKE MH ≈ VREF RS CAUTION: Because the kinetic energy stored in the motor and load inertia is being converted into current, which charges the VBB supply bulk capacitance (power supply output and decoupling capacitance), care must be taken to ensure the capacitance is sufficient to absorb the energy without exceeding the voltage rating of any devices connected to the motor supply. Brake Operation - MODE Input Low. During braking, with the MODE input low, the internal current-control circuitry is disabled. Therefore, care should be taken to ensure that the motor’s current does not exceed the ratings of the device. The braking current can be measured by using an oscilloscope with a current probe connected to one of the motor’s leads, or if the back-EMF voltage of the motor is known, approximated by: IPEAK BRAKE ML ≈ VBEMF – 1V RLOAD RC Fixed Off-Time. The internal PWM current-control circuitry uses a one shot to control the time the driver(s) remain(s) off. The one-shot time, tOFF (fixed off-time), is determined by the selection of an external resistor (RT) and capacitor (CT) connected in parallel from the RC timing terminal to ground. The fixed off-time, over a range of values of CT = 470 pF to 1500 pF and RT = 12 kΩ to 100 kΩ, is approximated by: tOFF ≈ RT x CT The operation of the circuit is as follows: when the PWM latch is reset by the current comparator, the voltage on the RC terminal will begin to decay from approximately 0.60VCC. When the voltage on the RC terminal reaches approximately 0.22VCC, the PWM latch is set, thereby enabling the driver(s). www.allegromicro.com RC Blanking. In addition to determining the fixed off-time of the PWM control circuit, the CT component sets the comparator blanking time. This function blanks the output of the comparator when the outputs are switched by the internal current-control circuitry (or by the PHASE, BRAKE, or ENABLE inputs). The comparator output is blanked to prevent false over-current detections due to reverse recovery currents of the clamp diodes, and/or switching transients related to distributed capacitance in the load. During internal PWM operation, at the end of the tOFF time, the comparator’s output is blanked and CT begins to be charged from approximately 0.22VCC by an internal current source of approximately 1 mA. The comparator output remains blanked until the voltage on CT reaches approximately 0.60VCC. When a transition of the PHASE input occurs, CT is discharged to near ground during the crossover delay time (the crossover delay time is present to prevent simultaneous conduction of the source and sink drivers). After the crossover delay, CT is charged by an internal current source of approximately 1 mA. The comparator output remains blanked until the voltage on CT reaches approximately 0.60VCC. When the device is disabled, via the ENABLE input, CT is discharged to near ground. When the device is reenabled, CT is charged by an internal current source of approximately 1 mA. The comparator output remains blanked until the voltage on CT reaches approximately 0.60VCC. For 3.3 V operation, the minimum recommended value for CT is 680 pF ± 5 %. For 5.0 V operation, the minimum recommended value for CT is 470 pF ± 5%. These values ensure that the blanking time is sufficient to avoid false trips of the comparator under normal operating conditions. For optimal regulation of the load current, the above values for CT are recommended and the value of RT can be sized to determine tOFF. For more information regarding load current regulation, see below. 7 3953 FULL-BRIDGE PWM MOTOR DRIVER LOAD CURRENT REGULATION WITH INTERNAL PWM CURRENT-CONTROL CIRCUITRY When the device is operating in slow current-decay mode, there is a limit to the lowest level that the PWM current-control circuitry can regulate load current. The limitation is the minimum duty cycle, which is a function of the user-selected value of tOFF and the minimum on-time pulse tON(min) max that occurs each time the PWM latch is reset. If the motor is not rotating (as in the case of a stepper motor in hold/detent mode, a brush dc motor when stalled, or at startup), the worst case value of current regulation can be approximated by: PWM of the PHASE and ENABLE Inputs. The PHASE and ENABLE inputs can be pulse-width modulated to regulate load current. Typical propagation delays from the PHASE and ENABLE inputs to transitions of the power outputs are specified in the electrical characteristics table. If the internal PWM current control is used, the comparator blanking function is active during phase and enable transitions. This eliminates false tripping of the over-current comparator caused by switching transients (see “RC Blanking” above). Enable PWM. With the MODE input low, toggling the ENABLE input turns on and off the selected source and sink drivers. The corresponding pair of flyback and ground-clamp diodes conduct after the drivers are [(VBB – VSAT(source+sink)) x tON(min)max] – (1.05(VSAT(sink) + VF) x tOFF) disabled, resulting in fast current decay. When IAVE ≈ the device is enabled the internal current-control 1.05 x (tON(min)max + tOFF) x RLOAD circuitry will be active and can be used to limit the where tOFF = RT x CT, RLOAD is the series resistance of the load current in a slow current-decay mode. load, VBB is the motor supply voltage and t ON(min)max is For applications that PWM the ENABLE input and specified in the electrical characteristics table. When the desire the internal current-limiting circuit to function in the motor is rotating, the back EMF generated will influence fast decay mode, the ENABLE input signal should be the above relationship. For brush dc motor applications, inverted and connected to the MODE input. This prevents the current regulation is improved. For stepper motor the device from being switched into sleep mode when the applications, when the motor is rotating, the effect is more ENABLE input is low. complex. A discussion of this subject is included in the section on stepper motors below. Phase PWM. Toggling the PHASE terminal selects which sink/source pair is enabled, producing a load current that The following procedure can be used to evaluate the varies with the duty cycle and remains continuous at all worst-case slow current-decay internal PWM load current times. This can have added benefits in bidirectional brush regulation in the system: dc servo motor applications as the transfer function Set VREF to 0 volts. With the load connected and the between the duty cycle on the PHASE input and the PWM current control operating in slow current-decay average voltage applied to the motor is more linear than in mode, use an oscilloscope to measure the time the output the case of ENABLE PWM control (which produces a is low (sink on) for the output that is chopping. This is the discontinuous current at low current levels). For more typical minimum on time (tON(min) typ) for the device. The information see “DC Motor Applications” below. CT then should be increased until the measured value of Synchronous Fixed-Frequency PWM. The internal tON(min) is equal to tON(min) max as specified in the electrical PWM current-control circuitry of multiple A3953S— characteristics table. When the new value of CT has been devices can be synchronized by using the simple circuit set, the value of RT should be decreased so the value for shown in figure 3. A 555 IC can be used to generate the tOFF = RT x CT (with the artificially increased value of CT) is reset pulse/blanking signal (t1) for the device and the equal to the nominal design value. The worst-case loadperiod of the PWM cycle (t2). The value of t1 should be a current regulation then can be measured in the system minimum of 1.5 ms. When used in this configuration, the under operating conditions. RT and CT components should be omitted. The PHASE and ENABLE inputs should not be PWM with this circuit configuration due to the absence of a blanking function synchronous with their transitions. 8 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3953 FULL-BRIDGE PWM MOTOR DRIVER Figure 3 Synchronous Fixed-Frequency Control Circuit To minimize current-sensing inaccuracies caused by ground trace I x R drops, the current-sensing resistor should have a separate return to the ground terminal of the device. For low-value sense resistors, the I x R drops in the printed wiring board can be significant and should be taken into account. The use of sockets should be avoided as their contact resistance can cause variations in the effective value of RS. 20 kΩ t 100 kΩ V CC 2 RC 1 1N4001 2N2222 t RC N 1 Dwg. EP-060 Miscellaneous Information. A logic high applied to both the ENABLE and MODE terminals puts the device into a sleep mode to minimize current consumption when not in use. An internally generated dead time prevents crossover currents that can occur when switching phase or braking. Thermal protection circuitry turns off all drivers should the junction temperature reach 165°C (typical). This is intended only to protect the device from failures due to excessive junction temperatures and should not imply that output short circuits are permitted. The hysteresis of the thermal shutdown circuit is approximately 15°C. APPLICATION NOTES Current Sensing. The actual peak load current (IPEAK) will be above the calculated value of ITRIP due to delays in the turn off of the drivers. The amount of overshoot can be approximated by: IOS ≈ (VBB – [(ITRIP x RLOAD) + VBEMF]) x tPWM(OFF) LLOAD where VBB is the motor supply voltage, VBEMF is the backEMF voltage of the load, RLOAD and LLOAD are the resistance and inductance of the load respectively, and tPWM(OFF) is specified in the electrical characteristics table. The reference terminal has a maximum input bias current of ±5 µA. This current should be taken into account when determining the impedance of the external circuit that sets the reference voltage value. www.allegromicro.com Generally, larger values of RS reduce the aforementioned effects but can result in excessive heating and power loss in the sense resistor. The selected value of RS should not cause the absolute maximum voltage rating of 1.0 V (0.4 V for VCC = 3.3 V operation), for the SENSE terminal, to be exceeded. The current-sensing comparator functions down to ground allowing the device to be used in microstepping, sinusoidal, and other varying current-profile applications. Thermal Considerations. For reliable operation it is recommended that the maximum junction temperature be kept below 110°C to 125°C. The junction temperature can be measured best by attaching a thermocouple to the power tab/batwing of the device and measuring the tab temperature, TTAB. The junction temperature can then be approximated by using the formula: TJ ≈ TTAB + (ILOAD x 2 x VF x RθJT) where VF may be chosen from the electrical specification table for the given level of ILOAD. The value for RθJT is given in the package thermal resistance table for the appropriate package. The power dissipation of the batwing packages can be improved by 20% to 30% by adding a section of printed circuit board copper (typically 6 to 18 square centimeters) connected to the batwing terminals of the device. The thermal performance in applications that run at high load currents and/or high duty cycles can be improved by adding external diodes in parallel with the internal diodes. In internal PWM slow-decay applications, only the two ground clamp diodes need be added. For internal fast-decay PWM, or external PHASE or ENABLE input PWM applications, all four external diodes should be added for maximum junction temperature reduction. PCB Layout. The load supply terminal, VBB, should be decoupled with an electrolytic capacitor (>47 µF is recom- 9 3953 FULL-BRIDGE PWM MOTOR DRIVER mended) placed as close to the device as is physically practical. To minimize the effect of system ground I x R drops on the logic and reference input signals, the system ground should have a low-resistance return to the motor supply voltage. See also “Current Sensing” and “Thermal Considerations” above. Fixed Off-Time Selection. With increasing values of tOFF, switching losses will decrease, low-level load-current regulation will improve, EMI will be reduced, the PWM frequency will decrease, and ripple current will increase. The value of tOFF can be chosen for optimization of these parameters. For applications where audible noise is a concern, typical values of tOFF are chosen to be in the range of 15 ms to 35 ms. Stepper Motor Applications. The MODE terminal can be used to optimize the performance of the device in microstepping/sinusoidal stepper-motor drive applications. When the load current is increasing, slow decay mode is used to limit the switching losses in the device and iron losses in the motor. This also improves the maximum rate at which the load current can increase (as compared to fast decay) due to the slow rate of decay during tOFF. When the load current is decreasing, fast-decay mode is used to regulate the load current to the desired level. This prevents tailing of the current profile caused by the backEMF voltage of the stepper motor. In stepper-motor applications applying a constant current to the load, slow-decay mode PWM is typically used to limit the switching losses in the device and iron losses in the motor. the motor is more linear than in the case of ENABLE PWM control (which produces a discontinuous current at low current levels). With bidirectional dc servo motors, the PHASE terminal can be used for mechanical direction control. Similar to when braking the motor dynamically, abrupt changes in the direction of a rotating motor produces a current generated by the back-EMF. The current generated will depend on the mode of operation. If the internal current control circuitry is not being used, then the maximum load current generated can be approximated by ILOAD = (VBEMF + VBB)/RLOAD where VBEMF is proportional to the motor’s speed. If the internal slow current-decay control circuitry is used, then the maximum load current generated can be approximated by ILOAD = VBEMF/RLOAD. For both cases care must be taken to ensure that the maximum ratings of the device are not exceeded. If the internal fast current-decay control circuitry is used, then the load current will regulate to a value given by: ILOAD = VREF/RS. CAUTION: In fast current-decay mode, when the direction of the motor is changed abruptly, the kinetic energy stored in the motor and load inertia will be converted into current that charges the VBB supply bulk capacitance (power supply output and decoupling capacitance). Care must be taken to ensure that the capacitance is sufficient to absorb the energy without exceeding the voltage rating of any devices connected to the motor supply. See also “Brake Operation” above. Figure 4 — Typical Application In dc servo applications, which require accurate positioning at low or zero speed, PWM of the PHASE input is selected typically. This simplifies the servo control loop because the transfer function between the duty cycle on the PHASE input and the average voltage applied to 10 V +5 V BB REF 2 15 3 14 VBB 4 6 ENABLE 47 µF MODE 13 LOGIC 12 5 PHASE 16 11 VCC 10 7 8 0.5 Ω 30 kΩ 1 470 pF BRAKE + DC Motor Applications. In closed-loop systems, the speed of a dc motor can be controlled by PWM of the PHASE or ENABLE inputs, or by varying the reference input voltage (REF). In digital systems (microprocessor controlled), PWM of the PHASE or ENABLE input is used typically thus avoiding the need to generate a variable analog voltage reference. In this case, a dc voltage on the REF input is used typically to limit the maximum load current. VBB 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 9 Dwg. EP-047-2A 3953 FULL-BRIDGE PWM MOTOR DRIVER A3953SB Dimensions in Inches (controlling dimensions) 16 0.020 0.008 9 NOTE 4 0.430 MAX 0.280 0.240 0.300 BSC 1 0.070 0.045 0.100 0.775 0.735 8 0.005 BSC MIN 0.210 MAX 0.015 0.150 0.115 MIN 0.022 0.014 Dwg. MA-001-17A in Dimensions in Millimeters (for reference only) 16 0.508 0.204 9 NOTE 4 10.92 MAX 7.11 6.10 7.62 BSC 1 1.77 1.15 2.54 19.68 18.67 BSC 8 0.13 MIN 5.33 MAX 0.39 3.81 2.93 MIN 0.558 0.356 NOTES: 1. 2. 3. 4. 5 Dwg. MA-001-17A mm Exact body and lead configuration at vendor’s option within limits shown. Lead spacing tolerance is non-cumulative. Lead thickness is measured at seating plane or below. Webbed lead frame. Leads 4, 5, 12, and 13 are internally one piece. Supplied in standard sticks/tubes of 25 devices. www.allegromicro.com 11 3953 FULL-BRIDGE PWM MOTOR DRIVER A3953SLB Dimensions in Inches (for reference only) 16 9 0.0125 0.0091 0.419 0.394 0.2992 0.2914 0.050 0.016 0.020 0.013 1 2 0.050 3 0° TO 8° BSC 0.4133 0.3977 0.0926 0.1043 0.0040 MIN. Dwg. MA-008-17A in Dimensions in Millimeters (controlling dimensions) 16 9 0.32 0.23 10.65 10.00 7.60 7.40 1.27 0.40 0.51 0.33 1 2 1.27 3 10.50 10.10 BSC 0° TO 8° 2.65 2.35 0.10 MIN. NOTES: 1. 2. 3. 4. 12 Dwg. MA-008-17A mm Exact body and lead configuration at vendor’s option within limits shown. Lead spacing tolerance is non-cumulative. Webbed lead frame. Leads 4, 5, 12, and 13 are internally one piece. Supplied in standard sticks/tubes of 47 devices or add “TR” to part number for tape and reel. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3953 FULL-BRIDGE PWM MOTOR DRIVER The products described here are manufactured under one or more U.S. patents or U.S. patents pending. 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 products are not authorized for use as critical components in life-support devices or systems without express written approval. 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. www.allegromicro.com 13 3953 FULL-BRIDGE PWM MOTOR DRIVER MOTOR DRIVERS Output Ratings* Part Number† INTEGRATED CIRCUITS FOR BRUSHLESS DC MOTORS 3-Phase Power MOSFET Controller — 28 V 3933 3-Phase Power MOSFET Controller — 50 V 3932 3-Phase Power MOSFET Controller — 50 V 7600 2-Phase Hall-Effect Sensor/Driver 400 mA 26 V 3626 Bidirectional 3-Phase Back-EMF Controller/Driver ±600 mA 14 V 8906 2-Phase Hall-Effect Sensor/Driver 900 mA 14 V 3625 3-Phase Back-EMF Controller/Driver ±900 mA 14 V 8902–A 3-Phase Controller/Drivers ±2.0 A 45 V 2936 & 2936-120 INTEGRATED BRIDGE DRIVERS FOR DC AND BIPOLAR STEPPER MOTORS Dual Full Bridge with Protection & Diagnostics ±500 mA 30 V 3976 PWM Current-Controlled Dual Full Bridge ±650 mA 30 V 3966 PWM Current-Controlled Dual Full Bridge ±650 mA 30 V 3968 PWM Current-Controlled Dual Full Bridge ±750 mA 45 V 2916 PWM Current-Controlled Dual Full Bridge ±750 mA 45 V 2919 PWM Current-Controlled Dual Full Bridge ±750 mA 45 V 6219 PWM Current-Controlled Dual Full Bridge ±800 mA 33 V 3964 PWM Current-Controlled Full Bridge ±1.3 A 50 V 3953 PWM Current-Controlled Dual Full Bridge ±1.5 A 45 V 2917 PWM Current-Controlled Microstepping Full Bridge ±1.5 A 50 V 3955 PWM Current-Controlled Microstepping Full Bridge ±1.5 A 50 V 3957 PWM Current-Controlled Dual DMOS Full Bridge ±1.5 A 50 V 3972 Dual Full-Bridge Driver ±2.0 A 50 V 2998 PWM Current-Controlled Full Bridge ±2.0 A 50 V 3952 DMOS Full Bridge PWM Driver ±2.0 A 50 V 3958 Dual DMOS Full Bridge ±2.5 A 50 V 3971 UNIPOLAR STEPPER MOTOR & OTHER DRIVERS Voice-Coil Motor Driver ±500 mA 6V 8932–A Voice-Coil Motor Driver ±800 mA 16 V 8958 Unipolar Stepper-Motor Quad Drivers 1A 46 V 7024 & 7029 Unipolar Microstepper-Motor Quad Driver 1.2 A 46 V 7042 Unipolar Stepper-Motor Translator/Driver 1.25 A 50 V 5804 Unipolar Stepper-Motor Quad Driver 1.8 A 50 V 2540 Unipolar Stepper-Motor Quad Driver 1.8 A 50 V 2544 Unipolar Stepper-Motor Quad Driver 3A 46 V 7026 Unipolar Microstepper-Motor Quad Driver 3A 46 V 7044 Function * Current is maximum specified test condition, voltage is maximum rating. See specification for sustaining voltage limits or over-current protection voltage limits. Negative current is defined as coming out of (sourcing) the output. † Complete part number includes additional characters to indicate operating temperature range and package style. Also, see 3175, 3177, 3235, and 3275 Hall-effect sensors for use with brushless dc motors. 14 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000