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Part: 2927
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Description:
Company: Allegro Micro Systems, Inc.
Datasheet: Download 2927 datasheet File size : 343 kB
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2927 DUAL FULL-BRIDGE PWM MOTOR DRIVER
PRELIMINARY INFORMATION (Subject to change without notice) September 16, 1997
2927
DUAL FULL-BRIDGE PWM MOTOR DRIVER
The A2927SEB motor driver is designed to drive both windings of a bipolar stepper motor or bidirectionally control two dc motors. Both bridges are capable of sustaining 50 V and include internal pulse-width modulation (PWM) control of the output current to 1.5 A.
39 GND
Data Sheet 29319.23
SENSE 1
PHASE 1
VREF 1
ENABLE 1
43
42
41
RC1
E
44
GND
EN1
VCC
1
40
6
5
4
3
2
1
LOGIC SUPPLY
OUT 1A
OUT 1B
I10
I11
1
7 8 9 10 11 12 13 14 15 16 17
VBB
PWM 1
38 37
1
36 35 34 33
For PWM current control, the maximum output current is determined by the user's selection of a reference voltage and sensing resistor. Two logic-level inputs select output current limits of 0, 33%, 67%, or 100% of the maximum level. A PHASE input to each bridge determines load current direction. Active-low ENABLE inputs control the four drivers in each bridge. Internally generated delays prevent cross-over currents when switching current direction. Special power-up sequencing is not required. Thermal protection circuitry disables the outputs if the chip temperature exceeds safe operating limits. The A2927SEB is supplied in a 44-lead power PLCC for surfacemount applications. Its batwing construction provides for maximum package power dissipation in the smallest possible construction.
2
32 31
GND
ABSOLUTE MAXIMUM RATINGS at TJ +150°C
Motor Supply Voltage, VBB .......... 50 V Output Current, IOUT ....... ±1.5 A Logic Supply Voltage, VCC .......... 7.0 V Logic Input Voltage Range, VIN ....... -0.3 V to +7.0 V Output Emitter Voltage, VE ......... 1.0 V Package Power Dissipation, PD ....... See Graph Operating Temperature Range, TA ......... -20°C to +85°C Storage Temperature Range, TS ....... -55°C to +150°C
Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified peak current rating or a junction temperature of +150°C.
O RO PE DC EN UE IN ER TF NE OR CR IS FO D --
30 PWM 2 29 GND
U D
T C
LOAD SUPPLY 22
OUT 2B 21
OUT 2A 18
SENSE 2 20
V REF 2 25
I20 23
I21 24
PHASE 2
ENABLE
RC 2
E2
Y L N
2
26
27
EN 2
19
2
28
Dwg. PP-021
FEATURES
s 1.5 A Output Current
s 50 V Output Sustaining Voltage s Internal Flyback Diodes s Undervoltage Lockout
s Digital Control of Output Current
s Internal Thermal Shutdown Circuitry
Always order by complete part number: A2927SEB .
2927 DUAL FULL-BRIDGE PWM MOTOR DRIVER
PWM CURRENT-CONTROL CIRCUITRY
CHANNEL 1 PIN NUMBERS SHOWN. OUT A
6
VBB
22
OUT
3
B
V REF 44 20 k ÷10 40 k 10 k I0 2 I1 1 RS
5
E SENSE
4
+
ONE SHOT
41 RC
SOURCE DISABLE
RC C C R T
C
T
Dwg. EP-007-4
TRUTH TABLE
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
12.5
R J
Enable L L H
T
Phase H L X
OutA H L Z
OutB L H Z
=6
10
/W °C
7.5
X = Don't care Z = High impedance
5.0
2.5
R
JA
= 35
°C/W
0 25 50 75 100 TEMPERATURE IN °C 125 150
Dwg. GP-020-1
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1997 Allegro MicroSystems, Inc.
2927 DUAL FULL-BRIDGE PWM MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TA = +25°C, VBB = 50 V, VCC = 5.0 V, VREF = 5.0 V (unless otherwise noted).
Limits Characteristic Output Drivers (OUTA or OUTB) Motor Supply Range Output Leakage Current VBB ICEX IOUT = ±1.5 A, L = 15 mH VOUT = VBB VOUT = 0 Output Saturation Voltage VCE(SAT) Sink Driver, IOUT = +1.0 A* Sink Driver, IOUT = +1.5 A* Source Driver, IOUT = -1.0 A* Source Driver, IOUT = -1.5 A* Flyback Diode Forward Volt. Driver Supply Current VF IBB(ON) IBB(OFF) Control Logic Input Voltage VIN(1) VIN(0) Input Current IIN(1) IIN(0) Reference Voltage Range Current Limit Threshold (at trip point) VREF VREF/ VSENSE All Inputs All Inputs VIN = 2.4 V VIN = 0.8 V Operating I0 = I1 = 0.8 V I0 = 2.4 V, I1= 0.8 V I0 = 0.8 V, I1 = 2.4 V Thermal Shutdown Temp. Total Logic Supply Current TJ ICC(ON) ICC(OFF) I0 = I1 = VEN = 0.8 V, No Load I0 = I1 = 2.4 V, No Load 2.4 -- -- -- 1.5 9.5 13.5 25.5 -- -- -- -- -- <1.0 -3.0 -- 10 15 30 170 90 10 -- 0.8 20 -200 7.5 10.5 16.5 34.5 -- 105 12 V V µA µA V -- -- -- °C mA mA IF = 1.5 A Both Bridges ON, No Load Both Bridges OFF 10 -- -- -- -- -- -- -- -- -- -- <1.0 <-1.0 0.5 0.8 1.8 1.9 1.6 6.5 4.0 50 5.0 -5.0 0.7 0.9 1.9 2.0 2.0 9.0 4.0 V µA µA V V V V V mA mA Symbol Test Conditions Min. Typ. Max. Units
Negative current is defined as coming out of (sourcing) the specified device pin. Typical Data is for design information only. * Pulse test (<10 ms).
2927 DUAL FULL-BRIDGE PWM MOTOR DRIVER
APPLICATIONS INFORMATION
PWM CURRENT CONTROL: The UDN2927EB dual bridge is designed to drive both windings of a bipolar stepper motor. Output current is sensed and controlled independently in each bridge by an external sense resistor (RS ), internal comparator, and monostable multivibrator. When the bridge is turned ON, current increases in the motor winding and it is sensed by the external sense resistor until the sense voltage (VSENSE) reaches the level set at the comparator's input: ITRIP = VREF/10 RS The comparator then triggers the monostable which turns OFF the source driver of the bridge. The actual load current peak will be slightly higher than the trip point (especially for low-inductance loads) because of the internal logic and switching delays. This delay (td) is typically 2 µs. After turn-off, the motor current will normally decay, circulating through the external ground clamp diode and sink transistor. The source driver's OFF time (and therefore the magnitude of the current decrease) is determined by the monostable's external RC timing components, where toff = RTCT within the range of 20 k to 100 k and 200 pF to 500 pF. When the source driver is re-enabled, the winding current (the sense voltage) is again allowed to rise to the comparator's threshold. This cycle repeats itself, maintaining the average motor winding current at the desired level. Special circuitry has been included to prevent runaway current control when the fixed OFF time (toff) is set too short. This circuitry prevents the source driver from being re-enabled until the load current has decayed to below the ITRIP level.
RS
td t off
PWM OUTPUT CURRENT WAVEFORM
V PHASE
+ I
OUT
0
I TRIP
Dwg. WM-003-1A
LOAD CURRENT PATHS
V BB
BRIDGE ON SOURCE OFF ALL OFF
Dwg. EP-006-14
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
2927 DUAL FULL-BRIDGE PWM MOTOR DRIVER
CURRENT-CONTROL TRUTH TABLE
I0 L H L H I1 L L H H Output Current VRE F /10 RS = ITRIP VRE F /15 RS = 2/3 ITRIP VREF /30 RS = 1/3 ITRIP 0
GENERAL : Both bridges have internal flyback diodes (connected from the outputs to VBB) for protection against inductive transients. External ground-clamp diodes (connected from the outputs to ground) are required; Schottky ground-clamp diodes are recommended to minimize onchip power dissipation. To avoid excessive voltage spikes on the LOAD SUPPLY terminal (VBB), a large-value capacitor (47 µF) should be connected from VBB to ground as close as possible to the device. Under no circumstances should the voltage at LOAD SUPPLY exceed 50 V. A low-value (0.1 µF) ceramic capacitor at this terminal may be used for high-frequency noise suppression. The PHASE input to each bridge determines the direction motor winding current flows. An internally generated deadtime (approximately 3 µs) prevents crossover currents that can occur when switching the PHASE input. All four drivers in the bridge output can be turned OFF (VEN 2.4 V or I0 = I1 2.4 V), resulting in a fast current decay through the internal flyback and external groundclamp diodes. The fast current decay is desirable in halfstep and high-speed applications. All logic inputs float high; the ENABLE input must be tied low if it is not used. Varying the reference voltage (VREF) provides continuous control of the peak load current for micro-stepping applications, within the specified limits for VREF. Thermal protection circuitry turns OFF all drivers when the junction temperature reaches approximately +170° C. It is only intended to protect the device from failures due to excessive junction temperature and should not imply that output short circuits are permitted. The output drivers are reenabled when the junction temperature cools to approximately +160°C.
Loads with high distributed capacitances may result in high turn-ON current peaks. This peak (appearing across RS ) will attempt to trip the comparator, resulting in erroneous current control or high-frequency oscillations. An external RCCC low-pass filter may be needed to delay the action of the comparator. LOGIC CONTROL OF OUTPUT CURRENT: Two logic level inputs (I0 and I1) allow digital selection of the motor winding current at 100%, 67%, 33%, or 0% of the maximum level per the table. The 0% output current condition turns OFF all drivers in the bridge and can be used as an output enable function. These logic level inputs greatly enhance the implementation of µP-controlled drive formats. During half-step operations, the I0 and I1 inputs allow the µP to control the motor at a constant torque between all positions in an eight-step sequence. This is accomplished by digitally selecting 100% drive current when only one phase is ON and 67% drive current when two phases are ON. The logic control inputs can also be used to select a reduced current level (and reduced power dissipation) for `hold' conditions and/or increased current (and available torque) for start-up conditions.
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