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AD8210YRZ-AD8210YRZ-REEL7
High-Side Bi-Directional Current Shunt Monitor
High-Side
Bi-directional
Current Shunt Monitor
Rev. PrA
FEATURES
High common-mode voltage range
−2 V to +65 V operating
−5 V to +68 V survival
Gain = 20
Wide operating temperature range
Die: −40°C to +150°C
8-lead SOIC: −40°C to +125°C
Adjustable offset
Available in SOIC and die form
EXCELLENT AC AND DC PERFORMANCE
5 µV/°C offset drift
30 ppm/°C gain drift
80 dB CMRR dc to 10 kHz
APPLICATIONS
42V DC/DC Converter Current Sensing
High Side Current Sensing
Motor controls
Transmission controls
Diesel injection controls
Engine management
Suspension controls
Vehicle dynamic controls
FUNCTIONAL BLOCK DIAGRAM Figure 1: Typical Operating Circuit
GENERAL DESCRIPTION The AD8210 is a high-side, single-supply, bi-directional current
shunt monitor featuring a wide input common mode voltage
range of -2V to 65V, high bandwidth, set gain of 20, and a typi-
cal supply voltage of 5V.
The AD8210 is offered in die and packaged form. The operat-
ing temperature range for the die is 25°C higher (up to 150°C)
than that of the packaged part to enable the user to apply the
AD8210 in high temperature applications.
Excellent AC and DC performance over temperature keeps
errors in the measurement loop to a minimum. Offset drift is
typically below 5uV/ °C, and the Gain drift is typically below
30ppm/°C.
Bi-directional current measurement is achieved by offsetting
the output between 0.05V and 4.8V with a 5V supply. With the
VREF 2 pin connected to the V+ pin, and VREF1 pin connected to
GND pin, the output is set at half scale. Attaching both VREF
pins to GND causes the output to be unipolar, starting near
ground. Attaching both VREF pins to V+ cause the output to be
Vsupply
VOUT-+ -
unipolar starting near V+. Other offsets can be obtained by
applying an external voltage to VREF1 and VREF2 pins.
Specifications TA= Operating Temperature Range, Vs=5V, unless otherwise
noted
ABSOLUTE MAXIMUM RATINGS
Table 1. Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features pro-
prietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electro-
static discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or
loss of functionality.
OUTPUT OFFSET ADJUSTMENT The output of the AD8210 can be adjusted for unidirectional or
bidirectional operation.
UNIDIRECTIONAL OPERATION Unidirectional operation allows the AD8210 to measure cur-
rents through a resistive shunt in one direction. The basic
modes for unidirectional operation are ground referenced
output mode and V+ referenced output mode.
In the case of unidirectional operation, the output could be set
at the negative rail (near ground) or at the positive rail (near
V+) when the differential input is 0 V. The output moves to the
opposite rail when a correct polarity differential input voltage is
applied. In this case, full scale is approximately 250 mV. The
required polarity of the differential input depends on the output
voltage setting. If the output is set at the positive rail, the input
polarity needs to be negative to move the output down. If the
output is set at ground, the polarity is positive to move the
output up.
GROUND REFERENCED OUTPUT When using the AD8210 in this mode, both reference inputs are
tied to ground, which causes the output to sit at the negative rail
when there are zero differential volts at the input (see Figure 2).
Figure 2. Ground Referenced Output
Table 2. V+ = 5 V
V+ REFERENCED OUTPUT This mode is set when both reference pins are tied to the posi-
tive supply. It is typically used when the diagnostic scheme
requires detection of the amplifier and the wiring before power
is applied to the load (see Figure 3).
Figure 3. V+ Referenced Output
Table 3. V+ = 5 V
BIDIRECTIONAL OPERATION Bidirectional operation allows the AD8210 to measure currents
through a resistive shunt in two directions.
In this case, the output is set anywhere within the output range.
Typically, it is set at half-scale for equal range in both directions.
In some cases, however, it is set at a voltage other than half-scale
when the bidirectional current is nonsymmetrical.
Table 4. V+ = 5 V, VO = 2.5 with VIN = 0 V Adjusting the output is accomplished by applying voltage(s) to
the reference inputs.
VREF1 and VREF2 are tied to internal resistors that connect to an
internal offset node. There is no operational difference between
the pins
EXTERNAL REFERENCE OUTPUT Tying both pins together and to a reference produces an output
at the reference voltage when there is no differential input (see
Figure 4). The output moves down from the reference voltage
when the input is negative relative to the −IN pin and up when
the input is positive relative to the −IN pin.
Figure 4. External Reference Output
SPLITTING AN EXTERNAL REFERENCE In this case, an external reference is divided by 2 with an
accuracy of approximately 0.5% by connecting one VREF pin to
ground and the other VREF pin to the reference (see Figure 17).
Figure 5: Split External Reference
SPLITTING THE SUPPLY By tying one reference pin to V+ and the other to the ground
pin, the output is set at half of the supply when there is no
differential input (see Figure 6). The benefit is that no external
reference is required to offset the output for bidirectional
current measurement. This 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 goes to 2.75 V.
Figure 6: Split Supply
V Out
V Out
5V
2.5V
Rs
APPLICATIONS A typical application for the AD8210 is high-side measurement
of a current through a solenoid for PWM control of the sole-
noid opening. Typical applications include hydraulic transmis-
sion control and diesel injection control.
Two typical circuit configurations are used for this type of
application.
HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE
SWITCH In this case, the PWM control switch is ground referenced. An
inductive load (solenoid) is tied to a power supply. A resistive
shunt is placed between the switch and the load (see Figure 7).
An advantage of placing the shunt on the high side is that the
entire current, including the re-circulation current, can be
measured since the shunt remains in the loop when the switch
is off. In addition, diagnostics can be enhanced because shorts
to ground can be detected with the shunt on the high side.
In this circuit configuration, when the switch is closed, the
common-mode voltage moves down to near the negative rail.
When the switch is opened, 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.
Figure 7. Low-Side Switch
HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE
SWITCH This configuration minimizes the possibility of unexpected
solenoid activation and excessive corrosion (see Figure 8). In
this case, both the switch and the shunt are on the high side.
When the switch is off, this removes the battery from the load,
which prevents damage from potential shorts to ground, while
still allowing the recirculation current to be measured and pro-
viding for diagnostics. Removing the power supply from the
load for the majority of the time minimizes the corrosive effects
that could be caused by the differential voltage between the load
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 opened, the voltage reversal across the
inductive load causes the common-mode voltage to be held one
diode drop below ground by the clamp diode.
Figure 8. High-Side Switch
Another typical application for the AD8210 is as part of the
control loop in H-bridge motor control. In this case, the
AD8210 is placed in the middle of the H-bridge (see Figure 9)
so that it can accurately measure current in both directions by
using the shunt available at the motor. This is a better solution
than a ground referenced op amp because ground is not typi-
cally a stable reference voltage in this type of application. This
instability in the ground reference causes the measurements
that could be made with a simple ground referenced op amp to
be inaccurate.
The AD8210 measures current in both directions as the
H-bridge switches and the motor changes direction. The output
of the AD8206 is configured in an external reference bidirec-
tional mode, see the Output Offset Adjustment section.
Figure 9. Motor Control Application
INDUCTIVE
LOAD
42V BATTERY
NC = NO CONNECT
42V
BATTERY
NC = NO CONNECT
SHUNT
NC = NO CONNECT
MOTOR
5V
