INA203_15 Datasheet, PDF (22/37 Pages) Texas Instruments – INA20x Unidirectional Measurement Current-Shunt Monitor With Dual Comparators

INA203, INA204, INA205
SBOS393E – MARCH 2007 – REVISED NOVEMBER 2015
9 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The INA203, INA204, and INA205 series is designed to enable easy configuration for detecting overcurrent
conditions and current monitoring in an application. This device is also incorporate two open-drain comparators
with internal 0.6-V references. On 14-pin versions, the comparator references can be overridden by external
inputs. Comparator 1 includes a latching capability, and Comparator 2 has a user-programmable delay. 14-pin
versions also provide a 1.2-V reference output. This device can also be paired with minimum additional devices
to create more sophisticated monitoring functional blocks.
9.2 Typical Application
Raychem
Polyswitch
< 18V
Battery
V_S+
OUT
CMP1 IN-
CMP1 IN+
CMP2 IN+
CMP2 IN-
C_BYPASS ^GND
0.01mF
INA203
x20
1.2V REF
V_IN+
V_IN-
1.2V REF OUT
CMP1 OUT
CMP2 OUT
CMP2 DELAY
CMP1 RESET
Reset
3.3kW
Pull-Up
Resistors
Load
+5V Supply
Overlimit⁽¹⁾
Warning⁽¹⁾
Latch
Optional
C_DELAY
0.01mF
NOTE: (1) Warning at half current (with optional delay). Overlimit latches when Polyswitch opens.
Figure 38. Polyswitch Warning and Fault Detection Circuit
9.2.1 Design Requirements
The device measures current through a resistive shunt with current flowing in one direction, thus enabling
detection of an overlimit or warning event only when the differential input voltage exceeds the corresponding
threshold limits. When the current reaches the warning limit of 0.6 V, the output of CMP2 will transition high
indicating a warning condition. When the current futher increases to or past the overlimit limit of 1.2 V, the output
of CMP1 will transition high indicating an overlimit condition. Optional C_DELAY can be sized to add delay to CMP1.
9.2.2 Detailed Design Procedure
Figure 38 shows the basic connections of the device. The input terminals, IN+ and IN–, should be connected as
closely as possible to the current-sensing resistor or polymeric switch to minimize any resistance in series with
the shunt resistance. Additional resistance between the current-sensing resistor and input terminals can result in
errors in the measurement. When input current flows through this external input resistance, the voltage
developed across the shunt resistor can differ from the voltage reaching the input terminals.
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