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AD8417WBRMZ

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P17
AD8417 Data Sheet
EXTERNAL REFERENCED OUTPUT
Tying both pins together and to a reference produces an output
equal to the reference voltage when there is no differential input
(see Figure 29). The output decreases the reference voltage when
the input is negative, relative to the −IN pin, and increases when
the input is positive, relative to the −IN pin.
–
+
R1
OUT
GND
V
S
V
REF
1
V
REF
2
AD8417
R2
R3
R4
–IN
+IN
2.5V
11882-027
Figure 29. External Referenced Output
SPLITTING THE SUPPLY
By tying one reference pin to V
S
and the other to the ground pin,
the output is set at half of the supply when there is no differential
input (see Figure 30). The benefit of this configuration is that
an external reference is not required to offset the output for
bidirectional current measurement. Tying one reference pin
to V
S
and the other to the ground pin creates a midscale offset
that is ratiometric to the supply, which means that if the supply
increases or decreases, the output remains at half the supply. For
example, if the supply is 5.0 V, the output is at half scale or 2.5 V.
If the supply increases by 10% (to 5.5 V), the output increases
to 2.75 V.
–
+
R1
OUT
GND
V
S
V
REF
1
V
REF
2
AD8417
R2
R3
R4
–IN
+IN
11882-028
Figure 30. Split Supply
SPLITTING AN EXTERNAL REFERENCE
Use the internal reference resistors to divide an external reference
by 2 with an accuracy of approximately 0.5%. Split an external
reference by connecting one V
REF
x pin to ground and the other
V
REF
x pin to the reference (see Figure 31).
–
+
R1
OUT
GND
V
S
V
REF
1
V
REF
2
AD8417
R2
R3
R4
–IN
+IN
5V
11882-029
Figure 31. Split External Reference
Rev. B | Page 12 of 16
Data Sheet AD8417
Rev. B | Page 13 of 16
APPLICATIONS INFORMATION
MOTOR CONTROL
3-Phase Motor Control
The AD8417 is ideally suited for monitoring current in 3-phase
motor applications.
The 250 kHz typical bandwidth of the AD8417 provides
instantaneous current monitoring. Additionally, the typical
low offset drift of 0.1 μV/°C means that the measurement error
between the two motor phases is at a minimum over temperature.
The AD8417 rejects PWM input common-mode voltages in the
−2 V to +70 V (with a 5 V supply) range. Monitoring the current
on the motor phase allows sampling of the current at any point
and provides diagnostic information, such as a short to GND
and battery. Refer to Figure 33 for the typical phase current
measurement setup with the AD8417.
H-Bridge Motor Control
Another typical application for the AD8417 is to form part of
the control loop in H-bridge motor control. In this case, place
the shunt resistor in the middle of the H-bridge to accurately
measure current in both directions by using the shunt available
at the motor (see Figure 32). Using an amplifier and shunt in
this location is a better solution than a ground referenced op
amp because ground is not typically a stable reference voltage in
this type of application. The instability of the ground reference
causes inaccuracies in the measurements that can be made with
a simple ground referenced op amp. The AD8417 measures current
in both directions as the H-bridge switches and the motor changes
direction. The output of the AD8417 is configured in an external
referenced bidirectional mode (see the Bidirectional Operation
section).
AD8417
+IN
SHUNT
MOTOR
V
REF
1
V
S
OUT
–IN GND
5V
CONTROLLER
V
REF
2NC
5V
2.5V
11882-030
Figure 32. H-Bridge Motor Control
AD8417
BIDIRECTIONAL CURRENT MEASUREMENT
REJECTION OF HIGH PWM COMMON-MODE VOLTAGE (–2V TO +70V)
AMPLIFICATION
HIGH OUTPUT DRIVE
AD8214
INTERFACE
CIRCUIT
V
+
I
U
I
V
I
W
V–
OPTIONAL
DEVICE FOR
OVERCURRENT
PROTECTION AND
FAST (DIRECT)
SHUTDOWN OF
POWER STAGE
AD8417
CONTROLLER
5V 5V
M
11882-031
Figure 33. 3-Phase Motor Control
AD8417 Data Sheet
Rev. B | Page 14 of 16
SOLENOID CONTROL
High-Side Current Sense with a Low-Side Switch
In the case of a high-side current sense with a low-side switch,
the PWM control switch is ground referenced. Tie an inductive
load (solenoid) to a power supply and place a resistive shunt
between the switch and the load (see Figure 34). An advantage
of placing the shunt on the high side is that the entire current,
including the recirculation current, is measurable because the
shunt remains in the loop when the switch is off. In addition,
diagnostics are enhanced because shorts to ground are detected
with the shunt on the high side.
In this circuit configuration, when the switch is closed, the
common-mode voltage decreases to near the negative rail.
When the switch is open, the voltage reversal across the inductive
load causes the common-mode voltage to be held one diode
drop above the battery by the clamp diode.
–IN
1
GND
2
V
REF
2
3
NC
4
+IN
8
V
REF
1
7
V
S
6
OUT
OUTPUT
5
V
INDUCTIVE
LOAD
CLAMP
DIODE
BATTERY
SWITCH
SHUNT
NC = NO CONNECT.
+
–
5
AD8417
11882-032
Figure 34. Low-Side Switch
High-Side Current Sense with a High-Side Switch
The high-side current sense with a high-side switch configuration
minimizes the possibility of unexpected solenoid activation and
excessive corrosion (see Figure 35). In this case, both the switch
and the shunt are on the high side. When the switch is off, the
battery is removed from the load, which prevents damage from
potential shorts to ground while still allowing the recirculating
current to be measured and to provide diagnostics. Removing the
power supply from the load for the majority of the time that the
switch is open minimizes the corrosive effects that can be caused
by the differential voltage between the load and ground.
When using a high-side switch, the battery voltage is connected
to the load when the switch is closed, causing the common-mode
voltage to increase to the battery voltage. In this case, when the
switch is open, the voltage reversal across the inductive load
causes the common-mode voltage to be held one diode drop
below ground by the clamp diode.
–IN
1
GND
2
V
REF
2
3
NC
4
+IN
8
V
REF
1
7
V
S
6
OUT
OUTPUT
5
V
INDUCTIVE
LOAD
SHUNT
CLAMP
DIODE
BATTERY
SWITCH
NC = NO CONNECT.
+
–
5
AD8417
11882-033
Figure 35. High-Side Switch
High Rail Current Sensing
In the high rail, current sensing configuration, the shunt resistor is
referenced to the battery. High voltage is present at the inputs of
the current sense amplifier. When the shunt is battery referenced,
the AD8417 produces a linear ground referenced analog output.
Additionally, the AD8214 provides an overcurrent detection
signal in as little as 100 ns (see Figure 36). This feature is useful
in high current systems where fast shutdown in overcurrent
conditions is essential.
V
S
1
+IN
2
V
REG
3
NC
4
–IN
8
NC
7
GND
6
OUT
OUTPUT
OVERCURRENT
DETECTION (<100ns)
5V
SHUNT
INDUCTIVE
LOAD
SWITCH
CLAMP
DIODE
BATTERY
+
–
5
AD8214
NC = NO CONNECT.
–IN
1
GND
2
V
REF
2
3
NC
4
+IN
8
V
REF
1
7
V
S
6
OUT
5
AD8417
TOP VIEW
(Not to Scale)
11882-034
Figure 36. High Rail Current Sensing
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P17

AD8417WBRMZ

Mfr. #:
Buy AD8417WBRMZ
Manufacturer:
Analog Devices Inc.
Description:
Current Sense Amplifiers DMOS CSAmp G=60 80V BiDir 0 Drift
Lifecycle:
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