Datasheet

Supply
Load
R 10W
FILTER
R 10W
FILTER
0.1 Fto1 Fm m
CeramicCapcitor
Current
Shunt
Supply
Voltage
V
IN+
V
IN-
V
S
3.3VSupply
CriticalOutput
OverlimitOutput
WarningOutput
Data(SDA)
Alert
Clock(SCL)
Critical
DAC+
Critical
DAC -
´
CMP
CMP
Filter
Watchdog
PowerRegister
CurrentRegister
I C
2
Interface
VoltageRegister
Convert
ADC
GND
GPIO
INA209
SMBus Alert Response
INA209
SBOS403B – JUNE 2007 – REVISED MARCH 2009 ......................................................................................................................................................... www.ti.com
Figure 22. INA209 with Input Filtering
Overload conditions are another consideration for the available. Testing has demonstrated that the addition
INA209 inputs. The INA209 inputs are specified to of 10 Ω resistors in series with each input of the
tolerate 26V across the inputs. A large differential INA209 sufficiently protects the inputs against dV/dt
scenario might be a short to ground on the load side failure up to the 26V rating of the INA209. These
of the shunt. This type of event can result in full resistors have no significant effect on accuracy.
power-supply voltage across the shunt (as long the
power supply or energy storage capacitors support it).
It must be remembered that removing a short to
The ALERT interrupt pin is set whenever Warning,
ground can result in inductive kickbacks that could
Over-Limit, Critical faults, or Conversion Ready states
exceed the 26V differential and common-mode rating
(in triggered modes) occur. The ALERT interrupt
of the INA209. Inductive kickback voltages are best
output signal is latched and can be cleared only by
dealt with by zener-type transient-absorbing devices
either reading the Status Register or by successfully
(commonly called transzorbs) combined with
responding to an alert response address. If the fault
sufficient energy storage capacitance.
is still present, the ALERT pin re-asserts. Asserting
In applications that do not have large energy storage
the ALERT pin does not halt automatic conversions
electrolytics on one or both sides of the shunt, an
that are already in progress. The ALERT output pin is
input overstress condition may result from an
open-drain, allowing multiple devices to share a
excessive dV/dt of the voltage applied to the input. A
common interrupt line. The ALERT output can be
hard physical short is the most likely cause of this
disabled via the SMBus Alert Mask/Enable Control
event, particularly in applications with no large
Register using the SMAEN bit. When disabled, the
electrolytics present. This problem occurs because an
ALERT pin goes to a high state.
excessive dV/dt can activate the ESD protection in
The INA209 responds to the SMBus alert response
the INA209 in systems where large currents are
address, an interrupt pointer return-address feature.
The SMBus alert response interrupt pointer provides
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