A3908EEETR-T Allegro Microsystems Inc, A3908EEETR-T Datasheet - Page 5

• Manufacturer Part Number: A3908EEETR-T
• Description: IC MOTOR DRIVER DC LV 500MA 8DFN
• Manufacturer: Allegro Microsystems Inc

Specifications of A3908EEETR-T

• Applications: DC Motor Driver
• Number Of Outputs: 1
• Current - Output: 500mA
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-UFDFN
• Motor Type: DC
• No. Of Outputs: 1
• Output Current: 500mA
• Output Voltage: 4.8V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: DFN
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Load: -
• Lead Free Status / Rohs Status: Compliant
• Other names: 620-1282-2

A3908
Voltage Regulation
across the motor coil. The voltage across the OUTA
and OUTB terminal is sensed and compared to an
internal threshold voltage. The high-side switch will
be driven in linear mode to keep the applied voltage
maintained at the calculated level, as follows:
where V
Then, for forward mode:
and for reverse mode:
The alternative method is to provide a tightly regu-
lated voltage to the motor supply pin and run the
source and sink drivers as switches. The voltage drop
across these switches will vary linearly with tempera-
ture and current, therefore the voltage across the motor
coil also will vary. The A3908 will eliminate these
sources of error for a system where controlling the
motor voltage is the optimum means of control.
Thermal Shutdown
puts if the junction temperature, T
There is 15°C of hysteresis, so when the junction
temperature drops below 150°C, the device will begin
to operate normally.
V
V
V
OUT
OUT
OUT
REF
= 4 × V
= V
= V
(VBG) is 1.285 V typical.
OUTA
OUTB
REF
The A3908 regulates the voltage
– V
The A3908 will disable the out-
– V
(R
OUTB
OUTA
Control Logic Table
2
/ [R
IN1
,
0
0
1
1
1
.
+R
J
2
, reaches 165°C.
]) ,
IN2
Functional Description
0
1
0
1
Settings
OUTA
V
High
Low
Off
REG
Dropout Mode
total R
motor supply voltage, V
to the regulated value, the IC enters dropout mode. In
this case, the voltage across the motor coil will be:
Brake Mode
goes into high-side brake mode (turns on both source
drivers). There is no protection during braking, so care
must be taken to ensure that the peak current does not
exceed the absolute maximum current, I
Standby Mode
mode will turn off all of the circuitry and draw typi-
cally less than 100 nA from the VDD line. There will
be a very short delay, approximately 2 μs, before
enabling the output drivers after release of standby
mode.
Power Dissipation
based on the below three components:
P
OUTB
Low Voltage DC Motor Driver
V
High
Low
P
V
Off
D(sink)
REG
D(src)
DS(on)
MOTOR
P
bias
= I
= I
= V
of approximately 1.2 Ω total. When the
When both inputs are high, the A3908
Resulting Mode
= V
LOAD
LOAD
DD
The source and sink drivers have a
To minimize battery drain, standby
Reverse
Standby
Forward
DD
Brake
× I
. Power can be approximated
(V
× R
– I
DD
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
DD
LOAD
DD
DS(sink)
.
–V
, drops too low compared
REG
(R
DS(sink)
, and
) ,
+ R
OUT
DS(src)
.
)
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