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6953 FULL-BRIDGE PWM MOTOR DRIVER
PRELIMINARY INFORMATION
(Subject to change without notice) October 5, 1998
NO (INTERNAL) CONNECTION
6953
FULL-BRIDGE PWM MOTOR DRIVER
Designed for bidirectional pulse-width modulated (PWM) current control of inductive loads, the A6953SEB is capable of continuous output currents to 1.5 A and operating voltages to 50 V. Internal fixed off-time PWM current-control 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 userselected 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 user-selectable blanking window prevents false triggering of the PWM current-control 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 A6953SEB is supplied in a surface-mount, 28-lead plastic leaded chip carrier. The power tab is at ground potential and needs no electrical isolation.
Data Sheet 29319.9
LOAD SUPPLY
BRAKE
RC
REF
MODE 27
OUTB
28
26
4
3
2
1
GROUND
5 6 7 8 9 10 VBB LOGIC
25 24 23 22 21 20 19 VCC
GROUND
GROUND
11
GROUND
13
14
16
12
15
17 SENSE
EMITTERS
LOGIC SUPPLY
LOAD SUPPLY
ENABLE
PHASE
OUTA
18
Dwg. PP-057
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, VBB . . . . . . . . . . 50 V Output Current, IOUT (Continuous) . . . . . . . . . . . . . . 1.5 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 (at TA = 25C), PD . . . . . . . . . . . . . . . . . . . . . . . 3.47 W Operating Temperature Range, TA . . . . . . . . . . . . . . . . . -20C to +85C Junction Temperature, TJ . . . . . . . +150C Storage Temperature Range, TS . . . . . . . . . . . . . . . . -55C to +150C
* 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 150C. Fault conditions that produce excessive junction temperature will activate the device's thermal shutdown circuitry. These conditions can be tolerated but should be avoided.
FEATURES
s s s s s s s s 1.5 A Continuous Output Current s Internal TransientSuppression Diodes 50 V Output Voltage Rating s Internal Thermal3 V to 5.5 V Logic Supply Voltage Shutdown Circuitry Internal PWM Current Control s Crossover-Current Saturated Sink Drivers (Below 1 A) and UVLO Protection Fast and Slow Current-Decay Modes Automotive Capable Sleep (Low Current Consumption) Mode
Always order by complete part number:
Part Number A6953SEB Package 28-Lead SOIC RJA 36C/W RJT 6C/W
6953 FULL-BRIDGE PWM MOTOR DRIVER
FUNCTIONAL BLOCK DIAGRAM
LOAD SUPPLY LOAD SUPPLY
1 18 EMITTERS - Q
BLANKING
OUTA
LOGIC 12 VCC SUPPLY
SLEEP & STANDBY MODES
15
16
28
MODE 27 VBB PHASE 13 UVLO & TSD
ENABLE 14
BRAKE
2
INPUT LOGIC
R S RC 4 CT +-
VCC GROUND 19-25 RT
VTH
Dwg. FP-036-5
TRUTH TABLE
BRAKE H H H H H H L L ENABLE H H L L L L X X PHASE X X H H L L X X MODE H L H L H L H L OUT A Off Off H H L L L L OUT B Off Off L L H H L L Sleep Mode Standby Forward, Fast Current-Decay Mode Forward, Slow Current-Decay Mode Reverse, Fast Current-Decay Mode Reverse, Slow Current-Decay Mode Brake, Fast Current-Decay Mode Brake, No Current Control DESCRIPTION
X = Irrelevant
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 1998 Allegro MicroSystems, Inc.
+
NO (INTERNAL) 26 CONNECTION
PWM LATCH
OUTB
17 SENSE RS GROUND 5-11
3 REF
6953 FULL-BRIDGE PWM MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TJ = 25C, 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
Power Outputs
Load Supply Voltage Range Output Leakage Current V BB ICEX Operating, IOUT = 1.5 A, L = 3 mH VOUT = VBB VOUT = 0 V Sense Current Offset Output Saturation Voltage BRAKE = H (Forward/Reverse Mode) ISO VCE(SAT) ISENSE - I OUT1, IOUT = 850 mA, VSENSE = 0 V, VCC = 5 V VSENSE = 0.4 V, V CC = 3.0 V: Source Driver, IOUT = -0.85 A Source Driver, IOUT = -1.5 A Sink Driver, IOUT = 0.85 A Sink Driver, IOUT = 1.5 A Output Saturation Voltage BRAKE = L (Brake Mode) Clamp Diode Forward Voltage (Sink or Source) VF VCE(SAT) VSENSE = 0.4 V, V CC = 3.0 V: Sink Driver, IOUT = 0.85 A Sink Driver, IOUT = 1.5 A IF = 0.85 A IF = 1.5 A -- -- -- -- 1.0 1.3 1.2 1.4 1.2 1.5 1.4 1.7 V V V V -- -- -- -- 1.0 1.3 0.5 1.3 1.2 1.5 0.8 1.5 V V V V VCC -- -- 20 -- <1.0 <-1.0 30 50 50 -50 40 V A A mA
Continued next page...
6953 FULL-BRIDGE PWM MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TJ = 25C, 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
AC Timing
PWM RC Fixed Off-time PWM Turn-Off Time tOFF RC tPWM(OFF) CT = 680 pF, R T= 30 k, VCC = 3.3 V Comparator Trip to Source OFF, IOUT = 25 mA Comparator Trip to Source OFF, IOUT = 1.5 A IRC Charge ON to Source ON, IOUT = 25 mA IRC Charge ON to Source ON, IOUT = 1.5 A VCC = 3.3 V, R T 12 k, C T = 680 pF VCC = 5.0 V, R T 12 k, C T = 470 pF Propagation Delay Times tpd IOUT = 1.5 A, 50% to 90%: ENABLE ON to Source ON ENABLE OFF to Source OFF ENABLE ON to Sink ON ENABLE OFF to Sink OFF (MODE = L) PHASE Change to Sink ON PHASE Change to Sink OFF PHASE Change to Source ON PHASE Change to Source OFF Crossover Dead Time Maximum PWM Frequency tCODT fPWM(max) 1 k Load to 25 V, V BB = 50 V IOUT = 1.5 A -- -- -- -- -- -- -- -- 0.3 70 1.0 1.0 1.0 0.8 2.4 0.8 2.0 1.7 1.5 -- -- -- -- -- -- -- -- -- 3.0 -- s s s s s s s s s kHz 18.3 -- -- -- -- 0.8 0.8 20.4 1.0 1.8 0.4 0.55 1.4 1.6 22.5 1.5 2.6 0.7 0.85 1.9 2.0 s s s s s s s
PWM Turn-On Time
tPWM(ON)
PWM Minimum On Time
tON(min)
Continued next page...
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
6953 FULL-BRIDGE PWM MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TJ = 25C, 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
Control Circuitry
Thermal Shutdown Temp. Thermal Shutdown Hysteresis UVLO Enable Threshold UVLO Hysteresis Logic Supply Current ICC(ON) ICC(OFF) ICC(Brake) ICC(Sleep) Motor Supply Current (No Load) IBB(ON) IBB(OFF) IBB(Brake) IBB(Sleep) Logic Supply Voltage Range Logic Input Voltage VCC VIN(1) VIN(0) Logic Input Current IIN(1) IIN(0) VSENSE Voltage Range VSENSE(3.3) VSENSE(5.0) Reference Input Current Comparator Input Offset Volt. IREF VIO VIN = 2.0 V VIN = 0.8 V VCC = 3.0 V to 3.6 V VCC = 4.5 V to 5.5 V VREF = 0 V to 1 V VREF = 0 V VENABLE = 0.8 V, VBRAKE = 2.0 V VENABLE = 2.0 V, VMODE = 0.8 V VBRAKE = 0.8 V VENABLE = VMODE = VBRAKE = 2.0 V VENABLE = 0.8 V VENABLE = 2.0 V, VMODE = 0.8 V VBRAKE = 0.8 V VENABLE = VMODE = 2.0 V Operating TJ TJ -- -- 2.5 225 -- -- -- -- -- -- -- -- 3.0 2.0 -- -- -- 0 0 -- -- 165 8.0 2.75 275 42 12 47 500 2.5 1.0 1.0 1.0 5.0 -- -- <1.0 <-2.0 -- -- -- 2.0 -- -- 3.0 325 50 15 55 800 4.0 50 50 50 5.5 -- 0.8 20 -200 0.4 1.0 0.5 5.0 C C V mV mA mA mA A mA A A A V V V A A V V A mV
6953 FULL-BRIDGE PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION
Internal PWM Current Control During Forward and Reverse Operation. The A6953SEB 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 where ISO is the offset due to base drive current. 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
The user selects an external resistor (RT) and capacitor (CT) to determine the time period (t OFF = RT*CT) during which the drivers remain disabled (see "RC Fixed Offtime" 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
I TRIP RC 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. As in the case of forward/reverse operation, the drivers are enabled after a time given by tOFF = RT*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.
DRIVE CURRENT RECIRCULATION (SLOW-DECAY MODE) RECIRCULATION (FAST-DECAY MODE)
RS
Dwg. EP-006-13A
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
6953 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 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 0.22 VCC by an internal current source of approximately 1 mA. The comparator output remains blanked until the voltage on CT reaches approximately 0.60 VCC. 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 0.60 VCC. 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 0.60 VCC . 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 C T are recommended and the value of RT can be sized to determine t OFF. For more information regarding load current regulation, see below.
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 k to 100 k, is approximated by: tOFF RT * 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 0.60 VCC . When the voltage on the RC terminal reaches approximately 0.22 VCC, the PWM latch is set, thereby enabling the driver(s).
6953 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)) * tON(min)max] - (1.05(VSAT(sink) + VF) * t OFF) disabled, resulting in fast current decay. When IAVE the device is enabled the internal current-control 1.05 * (tON(min)max + tOFF) * R LOAD circuitry will be active and can be used to limit the where tOFF = RT * 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 discontinuous current at low current levels). For more the typical minimum ON time (tON(min) typ) for the device. information see "DC Motor Applications" below. The CT then should be increased until the measured value Synchronous Fixed-Frequency PWM. The internal of tON(min) is equal to tON(min) max as specified in the PWM current-control circuitry of multiple A6953SEB electrical characteristics table. When the new value of CT devices can be synchronized by using the simple circuit has been set, the value of RT should be decreased so the shown in figure 3. A 555 IC can be used to generate the value for tOFF = RT * C T (with the artificially increased value reset pulse/blanking signal (t1) for the device and the of CT) is equal to the nominal design value. The worstperiod of the PWM cycle (t2). The value of t1 should be a case load-current regulation then can be measured in the minimum of 1.5 ms. When used in this configuration, the system 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.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
6953 FULL-BRIDGE PWM MOTOR DRIVER
Figure 3 Synchronous Fixed-Frequency Control Circuit
V CC
t2
To minimize current-sensing inaccuracies caused by ground trace I * 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 * 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.
RC 1
100 k
20 k
1N4001 2N2222 t
1
Dwg. EP-060
RC N
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 165C (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 15C.
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 R S 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 110C to 125C. 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: T J TTAB + (ILOAD * 2 * VF * RJT) where VF may be chosen from the electrical specification table for the given level of ILOAD. The value for RJT 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.
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 * RLOAD ) + VBEMF]) * t PWM(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 0.5 A. This current should be taken into account when determining the impedance of the external circuit that sets the reference voltage value.
6953 FULL-BRIDGE PWM MOTOR DRIVER
PCB Layout. The load supply terminal, VBB, should be decoupled with an electrolytic capacitor (>47 F is recommended) placed as close to the device as is physically practical. To minimize the effect of system ground I * 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. 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.
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 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 currentdecay 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 = V REF/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.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
6953 FULL-BRIDGE PWM MOTOR DRIVER
Dimensions in Inches (controlling dimensions)
18 12
0.013 0.021 0.219 0.191
19
11
0.026 0.032 0.456 0.450 0.495 0.485
INDEX AREA
0.050
BSC
0.219 0.191
25
5
26 0.020
MIN
28
1
4
0.165 0.180
0.456 0.450 0.495 0.485
Dwg. MA-005-28A in
Dimensions in Millimeters (for reference only)
18 12
0.331 0.533 5.56 4.85
19
11
1.27
BSC
0.812 0.661 11.58 11.43 12.57 12.32
INDEX AREA
5.56 4.85
25
5
26 0.51
MIN
28
1
4
4.57 4.20
NOTES: 1. 2. 3. 4. 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 5 - 11 and 19 - 25 are internally one piece.
11.582 11.430 12.57 12.32
Dwg. MA-005-28A mm
6953 FULL-BRIDGE PWM MOTOR DRIVER
MOTOR DRIVERS SELECTION GUIDE
Function Output Ratings * 2.0 A 10 mA 20 mA 20 mA 900 mA 400 mA 300 mA 900 mA 4.0 A 1.0 A 750 mA 1.5 A 750 mA 2.0 A 2.0 A 1.3 A 1.5 A 800 mA 650 mA 750 mA 1.8 A 1.25 A 1A 1.2 A 500 mA 800 mA 350 mA Part Number INTEGRATED CIRCUITS FOR BRUSHLESS DC MOTORS 3-Phase Controller/Drivers Hall-Effect Latched Sensors 2-Phase Hall-Effect Sensor/Controller Hall-Effect Complementary-Output Sensor 2-Phase Hall-Effect Sensor/Driver 2-Phase Hall-Effect Sensor/Driver Hall-Effect Complementary-Output Sensor/Driver 3-Phase Back-EMF Controller/Driver 3-Phase Controller/DMOS Driver 3-Phase Back-EMF Controller/Driver PWM Current-Controlled Dual Full Bridge PWM Current-Controlled Dual Full Bridges PWM Current-Controlled Dual Full Bridge Dual Full-Bridge Driver PWM Current-Controlled Full Bridge PWM Current-Controlled Full Bridge PWM Current-Controlled Microstepping Full Bridges PWM Current-Controlled Dual Full Bridge PWM Current-Controlled Dual Full Bridge PWM Current-Controlled Dual Full Bridge Unipolar Stepper-Motor Quad Driver Unipolar Stepper-Motor Translator/Driver Unipolar Stepper-Motor Quad Drivers Unipolar Microstepper-Motor Quad Driver Voice-Coil Motor Driver Voice-Coil Motor Driver Voice-Coil (and Spindle) Motor Driver * 45 V 24 V 25 V 25 V 14 V 26 V 60 V 14 V 14 V 7V 45 V 45 V 45 V 50 V 50 V 50 V 50 V 33 V 30 V 45 V 50 V 50 V 46 V 46 V 6V 16 V 7V 2936 and 2936-120 3175 and 3177 3235 3275 3625 3626 5275 8902-A 8925 8984 2916 2917 and 2918 2919 2998 3952 3953 3955 and 3957 3964 3966 and 3968 6219 2544 5804 7024 and 7029 7042 8932-A 8958 8984
INTEGRATED BRIDGE DRIVERS FOR DC AND BIPOLAR STEPPER MOTORS
OTHER INTEGRATED CIRCUIT & PMCM MOTOR DRIVERS
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.
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.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

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