Document
A4975
Full-Bridge PWM Microstepping Motor Driver
FEATURES AND BENEFITS
▪ ±1.5 A continuous output current ▪ 50 V output voltage rating ▪ Internal PWM current control ▪ 3-bit nonlinear DAC ▪ Fast, mixed fast/slow, and slow current decay modes ▪ Internal thermal shutdown circuitry ▪ Crossover-current and UVLO protection
PACKAGES:
Package B, 16-pin DIP with exposed tabs
Package LB, 16-pin SOIC with internally fused pins
Not to scale
DESCRIPTION
The A4975 is designed to drive one winding of a bipolar stepper motor in a microstepping mode. The outputs are rated for continuous output currents to ±1.5 A and operating voltages to 50 V. Internal pulse-width-modulated (PWM) current control combined with an internal three-bit nonlinear digitalto-analog converter allows the motor current to be controlled in full-, half-, quarter-, or eighth-step (microstepping) modes. Nonlinear increments minimize the number of control lines necessary for microstepping. Microstepping provides increased step resolution and reduces torque variations and resonance problems at low speed.
Internal circuitry determines whether the PWM current control circuitry operates in a slow (recirculating) current decay mode, fast (regenerative) current decay mode, or in a mixed current decay mode in which the off-time is divided into a period of fast current decay and with the remainder of the fixed off-time spent in slow current decay. The combination of user-selectable current-sensing resistor and reference voltage, digitally selected output current ratio, and slow, fast, or mixed current decay modes provides users with a broad, variable range of motor control.
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Functional Block Diagram
LOGIC SUPPLY OUTA OUTB LOAD SUPPLY
PHASE 7
6 VCC
10 15
16
VBB
GROUND 4 5
12 13
UVLO & TSD
PFD 1
MIXED-DECAY COMPARATOR
+ –
BLANKING
VCC
PWM LATCH
R Q
S
BLANKING GATE
CURRENT-SENSE COMPARATOR
+ –
÷5
D/A
+–
RC 3
V TH
VCC VCC VCC
CT RT
2 8 9 14
47 kΩ (typ) 47 kΩ (typ) 47 kΩ (typ)
SENSE 11
DISABLE RS
REF D2 D1 D0
4975-DS, Rev. 7 MCO-0000193
January 31, 2022
A4975
Full-Bridge PWM Microstepping Motor Driver
DESCRIPTION (CONTINUED)
Internal circuit protection includes thermal shutdown with hysteresis, an undervoltage monitor, and crossover-current protection. Special power-up sequencing is not required. The A4975 is supplied in a choice of two power packages: a 16-pin dual in-line plastic package with copper heat-sink tabs (suffix ‘B’), and a 16-lead plastic SOIC with internally fused pins (suffix ‘LB’).
For both package styles, the thermally enhanced pins are at ground potential and need no electrical isolation. Both packages are lead (Pb) free, with 100% matte tin leadframe plating.
SELECTION GUIDE Part Number A4975SB-T * A4975SLBTR-T
Packing 16-pin DIP with exposed thermal tabs 16-pin SOICW with internally fused pins
Package 25 per tube 1000 per reel
* A4975SB-T is no longer in production. The device should not be purchased for new design applications. Samples are no longer available. Date of status change: July 2, 2018. For existing customer transition, and for new customers or new applications, use A4975SLBTR-T.
ABSOLUTE MAXIMUM RATINGS Characteristic
Load Supply Voltage Logic Supply Voltage Logic/Reference Input Voltage Range Sense Voltage
Symbol VBB VCC VIN VS
Output Current, Continuous
IOUT
Package Power Dissipation Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
PD TA
TJ(max)
Tstg
Notes
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.
Range S Fault conditions that produce excessive junction temperature will activate the device’s thermal shutdown circuitry. These conditions can be tolerated but should be avoided.
Rating 50 6
–0.3 to 6 0.5
±1.5
See graph (p. 3) –20 to 85
150
–55 to 150
Units V V V V
A
W °C
°C
°C
2
Allegro MicroSystems 955 Perimeter Road Manchester, NH 03103-3353 U.S.A. www.allegromicro.com
A4975
Full-Bridge PWM Microstepping Motor Driver
THERMAL CHARACTERISTICS Characteristic
Package Thermal Resistance, Junction to Ambient
Symbol RθJA
Test Conditions* B Package, single-layer PCB, 1 in2. 2-oz. exposed copper LB Package, 2-layer PCB, 0.3 in2. 2-oz. exposed copper each side
Package Thermal Resistance, Junction to Tab
RθJT
*Additional thermal information available on Allegro website.
Value 43 67 6
Units °C/W °C/W °C/W
ALLOWABLE PACKAGE POWER DISSIPATION (W)
4 R θJT = 6.0°C/W
3
SUFFIX 'B', RθJA = 43°C/W 2
1 SUFFIX 'LB', R θJA = 67°C/W
0
25
50
75
100
125
150
TEMPERATURE IN °C
3
Allegro MicroSystems 955 Perimeter Road Manchester, NH 03103-3353 U.S.A. www.allegromicro.com
A4975
Full-Bridge PWM Microstepping Motor Driver
ELECTRICAL CHARACTERISTICS: Valid at TA = 25°C, VCC = 4.5 to 5.5 V,unless otherwise noted
Characteris.