5 Circuitry
This section summarizes the EVM subsystems and their components.
5.1 Current Sensing IC
This section describes the main INA device and supporting components.
U1 is the main INA current-sensing device (either the INA228, INA229, INA237, INA238, or INA239). C1 and C2
are bypass capacitors that are placed near the sensor to help mitigate power supply noise and provide current
quickly to the device when needed. LED D1 with current limiting resistor R4 are used to indicate when the EVM
is powered on.
The device pins can be monitored directly through the test points TP1 – TP12. Note that there are two extra test
points on GND for convenience.
5.2 Input Signal Path
This section describes the circuitry of the input signal path.
J1 is the main connection terminal. Pin 1 of J1 is used to tie the system ground to the EVM ground. Pin 2 of J1
is used for the VBUS measurement within the sensor. Pins 3 and 4 are tied to IN–, and Pins 5 and 6 are tied to
IN+. There are two pins each for IN– and IN+ for convenience.
R1 can be used for an optional onboard shunt resistor with a 2512 footprint. Alternatively, a shunt can be placed
across the IN+ and IN– terminals of J1. If desired, a differential voltage can be applied directly for measurement
tests.
C3, R2, and R3 combine to make an optional input filter. R2 and R3 are populated with 0-Ω resistors by default.
When using input filtering, take into account the input bias current of the device. C3 can also be used without R2
and R3 to reduce noise. See the data sheet for more info on input filtering.
5.3 Digital Circuitry
This section describes the digital circuitry around the device.
5.3.1 I2C (INA228, INA237, INA238)
J2 and J3 are the main header pins that connect the digital and power pins to the SCB Controller or other EVMs.
J3 connects to the EVM/SCB on the right, while J2 connects to more EVMs on the left. R5 and R6 are used as
pullup resistors for the main digital IO pins.
SW0 and SW1 set the I2C address of the device. This can be useful when using the EVM with a custom
controller (other than the SCB Controller), or when connecting multiple EVMs together. Currently the SCB
Controller and GUI are set up to use four EVMs at a time.
R8 is used as a pullup resistor for the ALERT pin, which is routed to both J2 and J3. LED D2 and current limiting
resistor R7 are used to indicate when the ALERT has triggered.
5.3.2 SPI (INA229, INA239)
J2 and J3 are the main header pins that connect the digital and power pins to the SCB Controller or other EVMs.
J3 connects to the EVM/SCB on the right, while J2 connects to more EVMs on the left. R7–R10 are 0-Ω resistors
in series with the main digital IO pins. Optionally, these resistor spaces can be used to provide inline filtering on
the digital lines, or the resistors can be removed to disconnect the digital pins from the header pins.
SW1 is used to redirect the control signal line (CS) to 1 of 4 pins on J2 and J3. This can be useful when using
the EVM with a custom controller (other than the SCB Controller), or when connecting multiple EVMs together.
Currently the SCB Controller and GUI are set up to use four EVM at a time. (Note, if using the PAMB Controller
and the SENS064A EVM, you can only use one EVM at a time, with SW1 on the EVM set to CS3, and the GUI
switch setting set to CS1.)
R6 is used as a pullup resistor for the ALERT pin, which is routed to J2 and J3. LED D2 and current limiting
resistor R5 are used to indicate when the ALERT has triggered.
Circuitry
SBOU241C – APRIL 2020 – REVISED JULY 2021
INA228, INA229, INA237, INA238, and INA239 EVM User’s Guide
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