Circuitry
13
SBOU241A – April 2020 – Revised June 2020
Copyright © 2020, Texas Instruments Incorporated
INA228, INA229, INA237, INA238, and INA239 EVM User’s Guide
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 – TP11. Note that there is one extra
test point 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 J2 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.
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 PAMB Controller. 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 PAMB Controller), or when stacking the EVMs. Currently the PAMB Controller
and GUI are setup to only use 1 EVM at a time, with SW0 and SW1 both set to GND.
R8 is used as a pullup resistor for the ALERT pin, which is routed to 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 PAMB Controller.
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 J3. This can be useful when using the
EVM with a custom controller (other than the PAMB Controller), or when stacking the EVMs. Currently the
PAMB Controller and GUI are setup to only use one EVM at a time, with SW1 set to CS3.
R6 is used as a pullup resistor for the ALERT pin, which is routed to J3. LED D2 and current limiting
resistor R5 are used to indicate when the ALERT has triggered.
