Datasheet

V
OUT
IN-
IN+
GND
R
SHUNT
INA216
Load
V
CM
R
P
R
P
V
OUT
IN-
IN+
GND
R
SHUNT
INA216
Load
V = 1.8 V
to 5.5V
CM
V
OUT
IN-
IN+
GND
R
SHUNT
INA216
Load
V
CM
R
P
R
P
INA216
www.ti.com SBOS503C –JUNE 2010– REVISED NOVEMBER 2011
APPLICATION INFORMATION
Basic Connections
Figure 18 shows the basic connections of the
INA216. The input pins, IN+ and IN–, should be
connected as closely as possible to the shunt resistor
to minimize any resistance in series with the shunt
resistance.
Figure 20. Shunt Resistance Measurement Using
a Kelvin Connection
Power Supply
The INA216 does not have a dedicated power-supply
pin. Instead, an internal connection to the IN+ pin
serves as the power supply for this device. Because
Figure 18. Typical Application
the INA216 is powered from the IN+ pin, the
common-mode input range is limited on the low end
Figure 19 illustrates the INA216 connected to a shunt
to 1.8V. Therefore, the INA216 cannot be used as a
resistor with additional trace resistance in series with
low-side current shunt monitor.
the shunt placed between where the current shunt
monitors the input pins. With the typically low shunt
Selecting R
S
resistor values commonly used in these applications,
even small amounts of additional impedance in series
The selection of the value of the shunt resistor (R
S
) to
with the shunt resistor can significantly affect the
use with the INA216 is based on the specific
differential voltage present at the INA216 input pins.
operating conditions and requirements of the
application. The starting point for selecting the
resistor is to first determine the desired full-scale
output from the INA216. The INA216 is available in
four gain options: 25, 50, 100, and 200. By dividing
the desired full-scale output by each of the gain
options, there are then four available differential input
voltages that can achieve the desired full-scale output
voltage, given that the appropriate gain device is
used. With four values for the total voltage that is to
be dropped across the shunt, the decision on how
much of a drop is allowed in the application must be
made. Most applications have a maximum drop
allowed to ensure that the load receives the required
voltage necessary to operate. Assuming that there
Figure 19. Shunt Resistance Measurement
are now multiple shunt voltages that are acceptable
Including Trace Resistance, R
P
(based on the design criteria), the choice of what
value shunt resistor to use can be made based on
Figure 20 shows a proper Kelvin, or four-wire,
accuracy. As a result of the INA216 auto-zero
connection of the shunt resistor to the INA216 input
architecture, the input offset voltage is extremely low.
pins. This connection helps ensure that the only
However, even the 100μV maximum input offset
impedance between the current monitor input pins is
voltage specification plays a role in the decision of
the shunt resistor.
which shunt resistor value to choose. With a larger
shunt voltage present at the current shunt monitor
input, less error is introduced by the input offset
voltage.
Copyright © 2010–2011, Texas Instruments Incorporated Submit Documentation Feedback 9
Product Folder Link(s): INA216