A4985SESTR-T Allegro Microsystems Inc, A4985SESTR-T Datasheet - Page 12

• Manufacturer Part Number: A4985SESTR-T
• Description: IC STEPPER MOTOR DRIVER 24QFN
• Manufacturer: Allegro Microsystems Inc

Specifications of A4985SESTR-T

• Applications: Stepper Motor Driver, 2 Phase
• Number Of Outputs: 1
• Current - Output: *
• Voltage - Load: 8 V ~ 35 V
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-WFQFN Exposed Pad
• Motor Type: Stepper
• No. Of Outputs: 2
• Output Current: 1A
• Output Voltage: 35V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: QFN
• No. Of Pins: 24
• Operating Temperature Range: -20°C To +85°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 620-1374 - Board Eval Motor Control A4985
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

A4985
Layout. The printed circuit board should use a heavy ground-
plane. For optimum electrical and thermal performance, the
A4985 must be soldered directly onto the board. On the under-
side of the A4985 package is an exposed pad, which provides a
path for enhanced thermal dissipation. The thermal pad should be
soldered directly to an exposed surface on the PCB. Thermal vias
are used to transfer heat to other layers of the PCB.
In order to minimize the effects of ground bounce and offset
issues, it is important to have a low impedance single-point
ground, known as a star ground, located very close to the device.
By making the connection between the pad and the ground plane
directly under the A4985, that area becomes an ideal location for
a star ground point. A low impedance ground will prevent ground
bounce during high current operation and ensure that the supply
voltage remains stable at the input terminal.
GND
R4
OUT2B
C3
C4
C7
C6
OUT2A OUT1A
GND
ROSC
VDD
U1
C1
VBB
OUT1B
R5
CAPACITANCE
DMOS Microstepping Driver with Translator
BULK
GND
ES package configuration shown
Application Layout
GND
C2
The two input capacitors should be placed in parallel, and as
close to the device supply pins as possible. The ceramic capaci-
tor (CIN1) should be closer to the pins than the bulk capacitor
(CIN2). This is necessary because the ceramic capacitor will be
responsible for delivering the high frequency current components.
The sense resistors, RSx , should have a very low impedance
path to ground, because they must carry a large current while
supporting very accurate voltage measurements by the current
sense comparators. Long ground traces will cause additional
voltage drops, adversely affecting the ability of the comparators
to accurately measure the current in the windings. The SENSEx
pins have very short traces to the RSx resistors and very thick,
low impedance traces directly to the star ground underneath the
device. If possible, there should be no other components on the
sense circuits.
OUT2B
And Overcurrent Protection
C4
C3
Thermal Vias
PCB
C7
OUT2B
ENABLE
GND
CP1
CP2
VCP
C6
R4
OUT2A
A4985
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
A4985
ROSC
PAD
OUT1A
R5
OUT1B
STEP
GND
VDD
REF
DIR
Solder
Trace (2 oz.)
Signal (1 oz.)
Ground (1 oz.)
Thermal (2 oz.)
V
DD
OUT1B
C1
V
BB
C2
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