A3979SLPTR-T Allegro Microsystems Inc, A3979SLPTR-T Datasheet - Page 9

• Manufacturer Part Number: A3979SLPTR-T
• Description: IC DRIVER MICROSTEPPING 28-TSSOP
• Manufacturer: Allegro Microsystems Inc

Specifications of A3979SLPTR-T

• Applications: Stepper Motor Driver
• Number Of Outputs: 1
• Current - Output: ±2.5A
• 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: 28-TSSOP Exposed Pad, 28-eTSSOP, 28-HTSSOP
• Motor Type: DMOS
• No. Of Outputs: 2
• Output Current: 2.5A
• Output Voltage: 35V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: TSSOP
• No. Of Pins: 28
• Operating Temperature Range: -20°C To +85°C
• Operating Current: 8mA
• Operating Temperature Classification: Commercial
• Package Type: TSSOP EP
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 620-1148-2; A3979SLPTR-T

A3979
Synchronous Rectification.
cycle is triggered by an internal fixed–off-time cycle, load
current recirculates according to the decay mode selected
by the control logic. The A3979 synchronous rectification
feature turns on the appropriate MOSFETs during the decay
of the current, and effectively shorts out the body diodes
with the low R
significantly and eliminates the need for external Schottky
diodes for most applications. The synchronous rectification
can be set to either Active mode or Disabled mode:
Layout.
mounted should have a heavy ground plane. For optimum
electrical and thermal performance, the A3979 should be
soldered directly onto the board.
The load supply terminals, VBBx, should be decoupled with
an electrolytic capacitor (>47 μF is recommended), placed
as close to the device as possible.
To avoid problems due to capacitive coupling of the high
dv / dt switching transients, route the bridge-output traces
away from the sensitive logic-input traces.
Always drive the logic inputs with a low source impedance
to increase noise immunity.
Grounding.
PGND (power ground) terminal must be connected together
externally.
All ground lines should be connected together and be as
short as possible. A star ground system, centered under the
device, is an optimum design.
The copper ground plane located under the exposed thermal
pad is typically used as the star ground.
The printed circuit board on which the device is
DS(On)
The AGND (analog ground) terminal and the
driver. This reduces power dissipation
When a PWM off-
DMOS Microstepping Driver with Translator
Applications Information
Current Sensing.
ground-trace IR drops in sensing the output current level,
the current-sense resistors, R
ground return to the star ground of the device. This path
should be as short as possible.
For low-value sense resistors, the IR drops in the printed cir-
cuit board sense resistor traces can be significant and should
be taken into account.
The use of sockets should be avoided as they can introduce
variation in R
Allegro MicroSystems recommends a value of R
Thermal Protection.
all drivers when the junction temperature reaches 165°C,
typical. It is intended only to protect the device from failures
due to excessive junction temperatures and should not imply
that output short circuits are permitted. Thermal shutdown
has a hysteresis of approximately 15°C.
• Active Mode. When the SR input is logic low, Active
• Disabled Mode. When the SR input is logic high, syn-
mode is enabled and synchronous rectification can occur.
This mode prevents reversal of the load current by turning
off synchronous rectification when a zero current level is
detected. This prevents the motor winding from conduct-
ing in the reverse direction.
chronous rectification is disabled. This mode is typi-
cally used when external diodes are required to transfer
power dissipation from the A3979 package to the external
diodes.
Sx
due to their contact resistance.
R
S
To minimize inaccuracies caused by
= 0.5/I
This internal circuitry turns off
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
Sx
, should have an independent
TRIP
max
S
given by
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