Datasheet

Supply
Load
R 10W
FILTER
R 10W
FILTER
0.1 Fto1 Fm m
CeramicCapacitor
Current
Shunt
Data(SDA)
3.3VSupply
Clock(SCL)
´
PowerRegister
CurrentRegister
Two-Wire
Interface
VoltageRegister
V
IN+
ADC
INA220
GND
A0
A1
SupplyVoltage
V
IN-
V
S
V
BUS
INA220
www.ti.com SBOS459D –JUNE 2009–REVISED SEPTEMBER 2010
sampling rate (>1MHz). Filter using the lowest available. Testing has demonstrated that the addition
possible series resistance and ceramic capacitor. of 10Ω resistors in series with each input of the
Recommended values are 0.1mF to 1.0mF. Figure 19 INA220 sufficiently protects the inputs against dV/dt
shows the INA220 with an additonal filter added at failure up to the 26V rating of the INA220. These
the input. resistors have no significant effect on accuracy.
Overload conditions are another consideration for the
Simple Current Shunt Monitor Usage
INA220 inputs. The INA220 inputs are specified to
(No Programming Necessary)
tolerate 26V across the inputs. A large differential
The INA220 can be used without any programming if
scenario might be a short to ground on the load side
it is only necessary to read a shunt voltage drop and
of the shunt. This type of event can result in full
bus voltage with the default 12-bit resolution, 320mV
power-supply voltage across the shunt (as long the
shunt full-scale range (PGA=÷8), 32V bus full-scale
power supply or energy storage capacitors support it).
range, and continuous conversion of shunt and bus
It must be remembered that removing a short to
voltage.
ground can result in inductive kickbacks that could
exceed the 26V differential and common-mode rating
Without programming, current is measured by
of the INA220. Inductive kickback voltages are best
reading the shunt voltage. The Current Register and
dealt with by zener-type transient-absorbing devices
Power Register are only available if the Calibration
(commonly called transzorbs) combined with
Register contains a programmed value.
sufficient energy storage capacitance.
Programming the INA220
In applications that do not have large energy storage
electrolytics on one or both sides of the shunt, an
The default power-up states of the registers are
input overstress condition may result from an
shown in the INA220 register descriptions section of
excessive dV/dt of the voltage applied to the input. A
this data sheet. These registers are volatile, and if
hard physical short is the most likely cause of this
programmed to other than default values, must be
event, particularly in applications with no large
re-programmed at every device power-up. Detailed
electrolytics present. This problem occurs because an
information on programming the Calibration Register
excessive dV/dt can activate the ESD protection in
specifically is given in the section, Programming the
the INA220 in systems where large currents are
INA220 Power Measurement Engine.
Figure 19. INA220 with Input Filtering
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