A3980KLP View Datasheet(PDF) - Allegro MicroSystems
Part Name
Description
MFG CO.
'A3980KLP' PDF : 18 Pages View PDF
A3980
Automotive DMOS Microstepping Driver
with Translator
Application Information
The A3980 is a power circuit, therefore careful consider-
ation must be given to power dissipation and the effects
of high currents on interconnect and supply wiring.
+
Power Dissipation. A first order approximation of
the power dissipation in the A3980 can be determined
by examining the power dissipation in each of the
two full-bridges during each of the operation modes.
When synchronous rectification is used, current flow
M
most of the time through the DMOS FETs that are
switched on. When synchronous rectification is not
used, the current flows through the body diode of
the DMOS FETs during the decay phase. The use of
fast or slow decay also affects the dissipation. All the
above combinations can be calculated from five basic
DMOS output states, shown in the following illustrations.
Synchronous Slow Decay
+
+
Both low-side DMOS output
transistors are on. Current circu-
lates through both transistors and
the load.
M
M
Dissipation is I2R losses in the
DMOS transistors:
× PSS = I2 (2 RDSONL)
Synchronous Fast Decay
+
+
Diagonally opposite DMOS output
transistors are on. Current flows
from ground through load to posi-
tive supply.
Dissipation is I2R losses in the
M
M
DMOS transistors:
PSF = I2 (RDSONH + RDSONL)
Drive Current Ramp
Diagonally opposite DMOS
output transistors are on. Cur-
rent flows from positive supply
through load to ground. Used in
all combinations.
Dissipation is I2R losses in the
DMOS transistors:
PD = I2 (RDSONH + RDSONL)
Non-Synchronous Slow Decay
One low-side DMOS output tran-
sistor and one body diode conduct-
ing. Current circulates through the
diode, the transistor, and the load.
Dissipation is I2R losses in the
DMOS transistors plus IV loss in
the diode:
× × PNS = (I2 RDSONL) + (I VF)
Non-Synchronous Fast Decay
Diagonally opposite body diodes
conducting. Current flows from
ground through load to positive
supply.
Dissipation is IV losses in the
diodes:
PNF = I (VFH + VFl)
Allegro MicroSystems, Inc.
14
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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