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A3968SLBTR-T

P1-P3P4-P6P7-P8
Dual Full-Bridge PWM Motor Driver with Brake
A3968
4
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Load Supply Voltage Range V
BB
Operating, I
OUT
= ±650 mA, L = 3 mH V
CC
—30 V
Output Leakage Current I
CEX
V
OUT
= 30 V — <1.0 50 μA
V
OUT
= 0 V — <-1.0 -50 μA
Output Saturation Voltage V
CE(SAT)
Source Driver, I
OUT
= -400 mA — 1.7 2.0 V
Source Driver, I
OUT
= -650 mA — 1.8 2.1 V
Sink Driver, I
OUT
= +400 mA, V
S
= 0.5 V — 0.3 0.5 V
Sink Driver, I
OUT
= +650 mA, V
S
= 0.5 V — 0.7 1.3 V
Clamp Diode Forward Voltage V
F
I
F
= 400 mA — 1.1 1.4 V
I
F
= 650 mA — 1.4 1.6 V
Motor Supply Current I
BB(ON)
Both bridges ON (forward or reverse) — 3.0 5.0 mA
(No Load)
I
BB(OFF)
All INPUTs = 2.4 V — <1.0 200 μA
ELECTRICAL CHARACTERISTICS at T
A
= +25°C, V
BB
= 30 V, V
CC
= 4.75 V to 5.5 V, V
REF
= 2 V,
V
S
= 0 V, 56 kΩ & 680 pF RC to Ground (unless noted otherwise)
Limits
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Output Drivers
Logic Supply Voltage Range V
CC
Operating 4.75 — 5.50 V
Logic Input Voltage V
IN(1)
2.4 — — V
V
IN(0)
——0.8V
Logic Input Current I
IN(1)
V
IN
= 2.4 V — <1.0 20 μA
I
IN(0)
V
IN
= 0.8 V — <-20 -200 μA
Reference Input Volt. Range V
REF
Operating 0.1 – 2.0 V
Reference Input Current I
REF
-2.5 0 1.0 μA
Reference Divider Ratio V
REF
/V
TRIP
3.8 4.0 4.2 —
Current-Sense Comparator V
IO
V
REF
= 0.1 V -6.0 0 6.0 mV
Input Offset Voltage
Current-Sense Comparator V
S
Operating -0.3 — 1.0 V
Input Voltage Range
Sense-Current Offset I
SO
I
S
– I
OUT
, 50 mA ≤ I
OUT
≤ 650 mA 12 18 24 mA
Control Logic
NOTES:1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device terminal.
Dual Full-Bridge PWM Motor Driver with Brake
A3968
5
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Limits
Characteristic Symbol Test Conditions Min. Typ. Max. Units
ELECTRICAL CHARACTERISTICS at T
A
= +25°C, V
BB
= 30 V, V
CC
= 4.75 V to 5.5 V, V
REF
= 2 V,
V
S
= 0 V, 56 kΩ & 680 pF RC to Ground (unless noted otherwise) (cont.)
Control Logic (continued)
NOTES:1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device terminal.
PWM RC Frequency f
osc
C
T
= 680 pF, R
T
= 56 kΩ 22.9 25.4 27.9 kHz
PWM Propagation Delay Time t
PWM
Comparator Trip to Source OFF — 1.0 1.4 μs
Cycle Reset to Source ON — 0.8 1.2 μs
Cross-Over Dead Time t
codt
1 kΩ Load to 25 V 0.2 1.8 3.0 μs
Propagation Delay Times t
pd
I
OUT
= ±650 mA, 50% to 90%:
Disable OFF to Source ON — 100 — ns
Disable ON to Source OFF — 500 — ns
Disable OFF to Sink ON — 200 — ns
Disable ON to Sink OFF — 200 — ns
Brake Enable to Sink ON — 2200 — ns
Brake Enable to Source OFF — 200 — ns
Thermal Shutdown Temp. T
J
—165— °C
Thermal Shutdown Hysteresis ΔT
J
—15—°C
UVLO Enable Threshold V
T(UVLO)+
Increasing V
CC
—4.14.6 V
UVLO Hysteresis V
T(UVLO)hys
0.1 0.6 — V
Logic Supply Current I
CC(ON)
Both bridges ON (forward or reverse) — — 50 mA
I
CC(OFF)
All INPUTs
= 2.4 V — — 9.0 mA
I
CC(BRAKE)
All INPUTs
= 0.8 V — — 95 mA
Typical output saturation voltages showing
Satlington sink-driver operation.
200 007004
300
OUTPUT CURRENT IN MILLIAMPERES
2.0
OUTPUT SATURATION VOLTAGE IN VOLTS
1.0
0
0.5
1.5
2.5
500
600
T
A
= +25°C
SOURCE DRIVER
SINK DRIVER
Dual Full-Bridge PWM Motor Driver with Brake
A3968
6
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Internal PWM Current Control. The A3968 dual
full-bridges bidirectionally control two DC motors. A
n
internal fi xed-frequency PWM control circuit controls the
the load current in each motor. The current-control circuitry
works as follows: when the outputs of the full-bridge are
turned on, current increases in the motor winding. The load
current is sensed by the current-control comparator via
an external sense resistor. R
S
. Load current continues to
increase until it reaches the predetermined value, set by the
selection of external current-sensing resistors and reference
input voltage (V
REF
) according to the equation:
I
TRIP
= I
OUT
+ I
SO
= V
REF
/(4 R
S
)
where I
SO
is the sense-current error (typically 18 mA) due
to the base-drive current of the sink driver transistor.
At the trip point, the comparator resets the source-en-
able latch, turning off the source driver of that full-bridge.
The source turn-off of one full-bridge is independent of
the other full-bridge. Load inductance causes the current to
recirculate through the sink driver and ground-clamp diode.
The current decreases until the internal clock oscillator sets
the source-enable latches of both Full-bridges, turning on
the source drivers of both bridges. Load current increases
again, and the cycle is repeated.
The frequency of the internal clock oscillator is set by
the external timing components R
T
C
T
. The frequency can
be approximately calculated as:
f
osc
= 1/(R
T
C
T
+ t
blank
)
where t
blank
is defi ned below.
The range of recommended values for R
T
and C
T
are
20 to 100 k and 470 to 1000 pF respectively. Nominal
values of 56 k and 680 pF result in a clock frequency of
25.4 kHz.
Current-Sense Comparator Blanking. When the
source driver is turned on, a current spike occurs due to the
reverse-recovery currents of the clamp diodes and switch-
ing transients related to distributed capacitance in the load.
To prevent this current spike from erroneously resetting the
source enable latch, the current-control comparator output
is blanked for a short period of time when the source driver
is turned on. The blanking time is set by the timing compo-
nent C
T
according to the equation:
t
blank
= 1900 C
T
(μs).
A nominal C
T
value of 680 pF will give a blanking time
of 1.3 μs.
The current-control comparator is also blanked when
the load current changes polarity (direction or phase
change). This internally generated blank time is approxi-
mately 1.8 μs.
FUNCTIONAL DESCRIPTION
+
–
0
Dwg. WM-003-2
V
PHASE
I
OUT
t
d
I
TRIP
t
blank
INTERNAL
OSCILLATOR
BRIDGE
ON
SOURCE
OFF
BRIDGE
ON
R C
T
T
ALL
OFF
Enlargement A
See Enlargement A
Dwg. EP-006-16
R
S
BB
V
BRIDGE ON
SOURCE OFF
ALL OFF
P1-P3P4-P6P7-P8

A3968SLBTR-T

Mfr. #:
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Manufacturer:
Description:
IC MOTOR DRVR 4.75V-5.5V 16SOIC
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