A3938
Three-Phase Power MOSFET Controller
Features and Benefits
▪
Drives a wide range of N-channel MOSFETs
▪
Low-side synchronous rectification
▪
Power MOSFET protection
▪
Adjustable dead time for cross-conduction protection
▪
Selectable coast or dynamic brake on power-down or
RESET input
▪
Fast/slow current decay modes
▪
Internal PWM current control
▪
Motor lead short-to-ground protection
▪
Internal 5 V regulator
▪
Fault diagnostic output
▪
Thermal shutdown
▪
Undervoltage protection
Description
The A3938 is a three-phase, brushless DC motor controller.
It has a high-current gate drive capability that allows driving
of a wide range of power MOSFETs and can support motor
supply voltages to 50 V. The A3938 integrates a bootstrapped
high-side driver to minimize the external component count
required to drive N-channel MOSFET drivers.
Internal fixed off-time, PWM current-control circuitry can be
used to regulate the maximum load current to a desired value.
The peak load current limit is set by the user’s selection of an
input reference voltage and external sensing resistor. A user-
selected external RC timing network sets the fixed off-time
pulse duration. For added flexibility, the PWM input can provide
speed/torque control where the internal current control circuit
sets a limit on the maximum current.
The A3938 includes a synchronous rectification feature. This
shorts out the current path through the power MOSFET reverse
body diodes during PWM off-cycle current decay. This can
minimize power dissipation in the MOSFETs, eliminate the
need for external power clamp diodes, and potentially allow a
more economical choice for the MOSFET drivers.
The A3938 provides commutation logic for Hall sensors
configured for 120-degree spacing. The H-all input pins are
pulled-up to an internally-generated 5 V reference. Power
MOSFET protection features include: bootstrap capacitor
charging current monitor, regulator undervoltage monitor,
motor lead short-to-ground, and thermal shutdown.
Package 38-pin TSSOP (suffix LD):
Approximate Scale 1:1
The LD package is lead (Pb) free, with 100% matte tin plated
leadframe.
RESET 1
GLC 2
SC 3
N/C 4
N/C 5
GHC 6
CC 7
GLB 8
SB 9
GHB 10
CB 11
GLA 12
SA 13
GHA 14
CA 15
VREG 16
LCAP 17
N/C 18
FAULT 19
Fault
38 N/C
37 N/C
36 PGND
35 AGND
34 DEAD
33 REF
32 SENSE
31 RC
30 PWM
29 BRKSEL
Control
Logic
28 BRKCAP
27 BRAKE
26 DIR
25 H2
24 H3
23 N/C
22 H1
21 VBB
20 MODE
26301.104H
A3938
Three-Phase Power MOSFET Controller
Selection Guide
Part Number
A3938SLDTR-T
Packing
4000 per reel
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
VREG Pin, Transient
Logic Input Voltage Range
Sense Voltage Range
Output Voltage Range
SA, SB, SC Pins
GHA, GHB, GHC Pins
CA, CB, CC Pins
Operating Ambient Temperature
Junction Temperature
Storage Temperature
T
A
T
J
T
stg
Range S
–5 to 50
–5 to V
BB
+ 17
V
Sx
+ 17
–20 to 85
150
–55 to 150
Symbol
V
BB
V
REG
V
IN
V
SENSE
Notes
Rating
50
15
–0.3 to V
LCAP
+ 0.3
–5 to 1.5
Units
V
V
V
V
V
V
V
V
ºC
ºC
ºC
Thermal Characteristics
(may require derating at maximum conditions)
Characteristic
Package Thermal Resistance
Symbol
R
θJA
Test Conditions
LD package, 4 layer PCB based on JEDEC standard
Min. Units
51
ºC/W
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A3938
Three-Phase Power MOSFET Controller
Functional Block Diagram
(This diagram shows only one of the three outputs)
FAULT
O.D.
Short to GND
TSD
Invalid Hall
VREG Undervoltage
VBB
A
+
VREG
Regulator
+
10 uF
CA
C
BOOT
0.1 uF
0.1 uF
LCAP
+
0.1 uF
H1
Charge Pump
H2
H3
PWM
Control
Logic
High-Side
Protection
Logic
Turn-On
Delay
High-Side
Driver
GHA
To Phase C
DIR
RESET
SA
BRAKE
VREG
MODE
RC
C
T
R
T
Low-Side
Protection
Logic
RC Blanking
Fixed Off-Time
Turn-On
Delay
Low-Side
Driver
GLA
To Phase B
SENSE
R
S
REF
VREG
DEAD
Dead-Time
Adjust
BRKCAP
V
REG
UVLO
RESET
AGND
Power Loss
Brake
+
4.7uF
PGND
BRKSEL
A
For 12 V applications, VBB must be shorted to VREG. For this condition, the absolute
maximum rating of 15 V on VREG must be maintained to prevent damage to the A3938.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A3938
Three-Phase Power MOSFET Controller
ELECTRICAL CHARACTERISTICS
1,2
Unless otherwise noted: T
A
= 25°C, V
BB
= 18 V to 50 V, C
LCAP
= 0.1
μF,
C
BOOT
= 0.1
μF,
C
VREG
= 10
μF,
PWM = 22.5 kHz, square wave, two phases active
Characteristics
Quiescent Current
LCAP Regulator
VREG =VBB Supply Voltage Range
VREG Output Voltage
VREG Load Regulation
VREG Line Regulation
Control Logic
Logic Input Voltage
V
IN(1)
V
IN(0)
Logic Input Current
Gate Drive
Low-Side Drive, Output High
High-Side Drive, Output High
Pull-Up Switch Resistance
Pull-Down Switch Resistance
Low-Side Switching, 10/90 Rise Time
Low-Side Switching, 10/90 Fall Time
High-Side Switching, 10/90 Rise Time
High-Side Switching, 10/90 Fall Time
Propagation Delay; GHx,GLx Rising
Propagation Delay; GHx,GLx Falling
Dead Time, Maximum
Dead Time, Minimum
V
HGL
V
HGH
R
DS(ON)
R
DS(ON)
tr
GL
tf
GL
tr
GH
tf
GH
T
pr
T
pf
t
DEAD
t
DEAD
I
gx
= 0
I
gx
= 0
I
gx
= –50 mA
I
gx
= 50 mA
C
load
= 3300 pF
C
load
= 3300 pF
C
load
= 3300 pF
C
load
= 3300 pF
PWM to gate drive out, C
load
= 3300 pF
PWM to gate drive out, C
load
= 3300 pF
V
dead
= 0, GHx to GLx, C
load
= 0
I
DEAD
= 780
μA,
GLx to GHx, C
load
= 0
V
REG
– 0.8 V
REG
– 0.5
10.4
–
–
–
–
–
–
–
–
3.5
50
11.6
14
4
120
60
120
60
220
110
5.6
100
–
12.8
–
–
–
–
–
–
–
–
7.6
150
V
V
Ω
Ω
ns
ns
ns
ns
ns
ns
μs
ns
I
IN(1)
I
IN(0)
Minimum high level for logical 1
Maximum low level for logical 0
V
IN
= 2.0 V
V
IN
= 0.8 V
2.0
–
–30
–50
–
–
–
–
–
0.8
–90
–130
V
V
μA
μA
Symbol
I
VBB
V
LCAP
V
REG
V
REG
V
REGLOAD
V
REGLIN
Test Conditions
RESET = 1, Coast mode, stopped
I
lcap
= –3.0 mA
VREG = VBB, observe maximum rating = 15 V
V
BB
= 13.2 V to 18 V, I
vreg
= –10 mA
V
BB
= 18 V to 50 V, I
vreg
= –10 mA
I
vreg
= –1 mA to –30 mA, Coast mode
I
vreg
= –10 mA, Coast mode
Min.
–
4.75
10.8
–
12.4
–
–
Typ.
1
–
5
–
V
BB
– 2.5
13
25
40
Max.
8.0
5.25
13.2
–
13.6
–
–
Units
mA
V
V
V
V
mV
mV
Continued on next page...
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A3938
Three-Phase Power MOSFET Controller
ELECTRICAL CHARACTERISTICS
1,2
(continued)
Unless otherwise noted: T
A
= 25°C, V
BB
= 18 V to 50 V, C
LCAP
= 0.1
μF,
C
BOOT
= 0.1
μF,
C
VREG
= 10
μF,
PWM = 22.5 kHz, square wave, two phases active
Characteristics
Bootstrap Capacitor
Bootstrap Capacitor Voltage
Bootstrap R
OUT
Charge Current (Source)
Current Limit Circuitry
Input Offset Voltage
Input Current , Sense pin
Input Current , Reference pin
Blank Time
RC Charge Current
RC Voltage Threshold
Protection Circuitry
Bootstrap Charge Threshold
Short to Ground, Drain-Source Monitor
VREG Undervoltage Threshold
Fault Output Voltage
Brake Capacitor Supply Current
Low Side Gate Voltage
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
1
Symbol
Test Conditions
Min.
Typ.
1
Max.
Units
V
CX
R
CX
I
CX
I
cx
= 0, V
sx
= 0, V
reg
= 13 V
I
cx
= –50 mA
10.4
–
100
11.6
9
–
12.8
12
–
V
Ω
mA
V
IO
I
B
I
B
t
BLANK
I
RC
V
RCL
V
RCH
0 V < V
cmr
< 1.5 V
0 V < V
cm
, V
diff
< 1.5 V
0 V < V
cm
, V
diff
< 1.5 V
R = 56 kΩ, C = 470 pF
–
–
–
–
–0.9
1.0
2.7
–
–25
0
0.91
–1
1.1
3.0
±5
–
–
–
–1.1
1.2
3.3
mV
μA
μA
μs
mA
V
V
I
cx
V
dsh
UVLO
V
OUT
I
BRAKE
V
GLBH
T
J
ΔT
J
GHx turns on, and GLx turns off, at I
cx
V
BB
– V
SX
, high side on
V
REG
increasing
V
REG
decreasing
I
OL
= 1 mA
V
BB
= 8 V, BRKSEL = 1
V
BB
=0, BRKCAP = 8V
–
1.3
9.2
8.6
–
–
–
–
–
–9
2.0
9.7
9.1
–
30
6.6
165
10
–
2.7
10.2
9.6
0.5
–
–
–
–
mA
V
V
V
V
μA
V
°C
°C
Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for
individual units, within the specified maximum and minimum limits.
2
Negative current is defined as conventional current coming out of (sourced from) the specified device terminal.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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