ALLEGRO A3938 User Manual
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A3938EQ, 32-pin PLCC
A3938LQ, 36-pin QSOP
A3938
Three-Phase Power MOSFET Controller
The A3938 is a three-phase, brushless dc motor controller. The A3938
high-current gate drive capability 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 fi xed 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 fi xed off-time pulse duration. For added fl exibility, 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 rectifi cation 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.
26301.104B
Data Sheet
A3938LD, 38-pin TSSOP
AB SO LUTE MAX I MUM RAT INGS
Load Supply Voltage, VBB...................................50 V
VREG (Transient)...............................................15 V
Logic Input Voltage Range, V
Sense Voltage, V
Pins: SA, SB, SC................................... –5 V to 50 V
Pins: GHA, GHB, GHC.................. –5 V to V
Pins: CA, CB, CC ...........................SA/SB/SC + 17 V
Operating Temperature Range
Ambient Temperature, T
Junction Temperature, T
Storage Temperature, TS..........–55°C to +150°C
Thermal Impedance (Typical), at T
measured on a JEDEC-standard "High-K" PCB
A3938EQ, R
A3938LD, R
A3938LQ, R
SENSE
........................................37°C/W
θJA
........................................38°C/W
θJA
........................................44°C/W
θJA
...–0.3 V to V
IN
........................... –5 V to 1.5 V
.............–20°C to +85°C
A
............................+150°C
J
= +25ºC;
A
LCAP
+0.3 V
+ 17 V
BB
The A3938 provides commutation logic for Hall sensors confi gured for
120-degree spacing. The Hall input pins are pulled-up to an internallygenerated 5 V reference. Power MOSFET protection features include:
bootstrap capacitor charging current monitor, regulator undervoltage
monitor, motor lead short-to-ground, and thermal shutdown.
The LD package is available in a lead-free version (100% matte tin
plated leadframe).
FEATURES
Drives wide range of N-channel MOSFETs
Low-side synchronous rectifi cation
Power MOSFET protection
Adjustable dead time for cross-con-
duction protection
Selectable coast or dynamic brake on
power-down or RESET input
Fast/slow current decay modes
Use the following complete part numbers when ordering:
Part Number Pins Package
A3938SEQ 32 PLCC
A3938SLQ 36 QSOP
A3938SLD 38 TSSOP
A3938SLD-T 38 TSSOP, Lead-free
Internal PWM current control
Motor lead short-to-ground
protection
Internal 5 V regulator
Fault diagnostic output
Thermal shutdown
Undervoltage protection
A3938
Three-Phase Power MOSFET Controller
Functional Block Diagram
(This diagram shows only one of the three outputs)
26301.104B
Data Sheet
Short to GND
Logic
TSD
Invalid Hall
VREG Undervoltage
High-Side
Protection
Logic
Low-Side
Protection
Logic
Regulator
Charge Pump
Turn-On
Delay
Turn-On
Delay
VREG
High-Side
Driver
Low-Side
Driver
FAULT
LCAP
+
0.1 uF
H1
H2
H3
PWM
DIR
RESET
BRAKE
MODE
RC
C
T
R
T
O.D.
Control
RC Blanking
Fixed Off-Time
VBB
VREG
CA
GHA
SA
GLA
SENSE
A
C
BOOT
0.1 uF
+
0.1 uF
+
10 uF
To Phase C
To Phase B
REF
DEAD
AGND
VREG
Dead-Time
Adjust
A
For 12 V applications, VBB must be shorted to VREG. For this condition, the absolute
V
REG
RESET
UVLO
Power Loss
Brake
PGND
BRKCAP
BRKSEL
maximum rating of 15 V on VREG must be maintained to prevent damage to the A3938.
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
R
S
+
4.7uF
2
A3938
Three-Phase Power MOSFET Controller
26301.104B
Data Sheet
ELECTRICAL CHARACTERISTICS
C
= 10 µF, PWM = 22.5 kHz, square wave, two phases active
VREG
1,2
Unless otherwise noted: T
Characteristics Symbol Test Conditions Min. Typ.
Quiescent Current I
LCAP Regulator V
VREG =VBB Supply Voltage Range V
VBB
LCAP
REG
RESET = 1, Coast mode, stopped – – 8.0 mA
I
lcap
VREG = VBB, observe maximum rating = 15 V 10.8 – 13.2 V
VBB = 13.2 V to 18 V, I
VREG Output Voltage V
VREG Load Regulation V
VREG Line Regulation V
REG
REGLOADIvreg
REGLIN
VBB = 18 V to 50 V, I
I
vreg
Control Logic
Logic Input Voltage
Logic Input Current
V
IN(1)
V
IN(0)
I
IN(1)
I
IN(0)
Minimum high level for logical 1 2.0 – – V
Maximum low level for logical 0 – – 0.8 V
VIN = 2.0 V –30 – –90 µA
VIN = 0.8 V –50 – –130 µA
= 25°C, V
A
= 18 V to 50 V, C
BB
= 0.1 µF, C
LCAP
1
= 0.1 µF,
BOOT
Max. Units
= –3.0 mA 4.75 5 5.25 V
= –10 mA – VBB – 2.5 – V
vreg
= –10 mA 12.4 13 13.6 V
vreg
= –1 mA to –30 mA, Coast mode – 25 – mV
= –10 mA, Coast mode – 40 – mV
Gate Drive
Low-Side Drive, Output High V
High-Side Drive, Output High V
Pull-Up Switch Resistance R
Pull-Down Switch Resistance R
Low-Side Switching, 10/90 Rise Time tr
Low-Side Switching, 10/90 Fall Time tf
High-Side Switching, 10/90 Rise Time tr
High-Side Switching, 10/90 Fall Time tf
Propagation Delay; GHx,GLx Rising T
Propagation Delay; GHx,GLx Falling T
Dead Time, Maximum t
Dead Time, Minimum t
Continued on next page...
HGL
HGH
DS(ON)
DS(ON)
GL
GL
GH
GH
pr
pf
DEAD
DEAD
Igx = 0 V
– 0.8 V
REG
– 0.5 – V
REG
Igx = 0 10.4 11.6 12.8 V
Igx = –50 mA – 14 – Ω
Igx = 50 mA – 4 – Ω
C
= 3300 pF – 120 – ns
load
C
= 3300 pF – 60 – ns
load
C
= 3300 pF – 120 – ns
load
C
= 3300 pF – 60 – ns
load
PWM to gate drive out, C
PWM to gate drive out, C
V
= 0, GHx to GLx, C
dead
I
= 780 µA, GLx to GHx, C
DEAD
= 3300 pF – 220 – ns
load
= 3300 pF – 110 – ns
load
= 0 3.5 5.6 7.6 µs
load
= 0 50 100 150 ns
load
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
3
A3938
Three-Phase Power MOSFET Controller
26301.104B
Data Sheet
ELECTRICAL CHARACTERISTICS
C
= 0.1 µF, C
BOOT
Characteristics Symbol Test Conditions Min. Typ.
Bootstrap Capacitor
Bootstrap Capacitor Voltage V
Bootstrap R
OUT
Charge Current (Source) I
Current Limit Circuitry
Input Offset Voltage V
Input Current , Sense pin I
Input Current , Reference pin I
Blank Time t
RC Charge Current I
RC Voltage Threshold
= 10 µF, PWM = 22.5 kHz, square wave, two phases active
VREG
1,2
(continued) Unless otherwise noted: T
R
BLANK
V
V
CX
RC
RCL
RCH
Icx = 0, Vsx = 0, V
CX
Icx = –50 mA – 9 12 Ω
CX
0 V < V
IO
B
B
cmr
0 V < Vcm, V
0 V < Vcm, V
R = 56 kΩ, C = 470 pF – 0.91 – µs
= 13 V 10.4 11.6 12.8 V
reg
< 1.5 V – – ± 5 mV
< 1.5 V – –25 – µA
diff
< 1.5 V – 0 – µA
diff
= 25°C, V
A
= 18 V to 50 V, C
BB
1
= 0.1 µF,
LCAP
Max. Units
100 – – mA
–0.9 –1 –1.1 mA
1.0 1.1 1.2 V
2.7 3.0 3.3 V
Protection Circuitry
Bootstrap Charge Threshold I
Short to Ground, Drain-Source Monitor V
VREG Undervoltage Threshold
Fault Output Voltage
Brake Capacitor Supply Current I
Low Side Gate Voltage V
cx
dsh
UVLO
V
OUT
BRAKE
GLBH
Thermal Shutdown Temperature T
Thermal Shutdown Hysteresis ∆T
1
Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for
individual units, within the specifi ed maximum and minimum limits.
2
Negative current is defi ned as conventional current coming out of (sourced from) the specifi ed device terminal.
GHx turns on, and GLx turns off, at I
V
– VSX, high side on 1.3 2.0 2.7 V
BB
V
increasing 9.2 9.7 10.2 V
REG
decreasing 8.6 9.1 9.6 V
V
REG
cx
– –9 – mA
IOL = 1 mA – – 0.5 V
VBB = 8 V, BRKSEL = 1 – 30 – µA
VBB=0, BRKCAP = 8V – 6.6 – V
J
J
– 165 – °C
–10– °C
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
4
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