Figure 4-5. Potentiometer Position for Creating 14.3-kΩ ADJ Resistance
4.1.2.1 Using the Potentiometer to Estimate the Magnetic Flux Density Sensed by the TMAG5328
Similar to sweeping the DAC output voltage to find the sensed magnetic flux density, an estimate of the sensed
magnetic flux density can also be found by sweeping the potentiometer resistance by adjusting its position. In
this approach, the potentiometer is placed to create the maximum resistance (
). If the TMAG5328's
output is not asserted high (LED is OFF) for this potentiometer position, replace R2 with a 5kΩ resistor. If the
output is still not asserted high after replacing R2, then the sensed magnetic flux density is greater than the
15mT maximum magnetic flux density that can be sensed by the TMAG5328.
If the TMAG5328's output does in fact get asserted high when the maximum resistance is applied to the ADJ pin,
slowly turn the potentiometer clockwise until the output of the TMAG5328 first gets asserted low (LED is ON).
As soon as the output gets asserted low, stop turning the potentiometer. The resistance between the ADJ pin
and GND pin can then be measured and entered into the equation above to determine the TMAG5328's sensed
magnetic flux density. If the potentiometer has been fully turned clockwise (
not get asserted low, replace R2 with a 2kΩ resistor. If the output is still not asserted low after replacing R2, then
the sensed magnetic flux density is less than the 2mT minimum magnetic flux density that is able to be sensed
by the TMAG5328.
Since the potentiometer isn't affected by power resets, the potentiometer ensures that the same B
OP
is used
after a power reset, assuming that its position is not moved. As a result, the potentiometer option can be used
regardless if the SCB board is connected to it or not. If the potentiometer's position is accidentally changed,
however, the B
OP
will change. To ensure that the B
OP
doesn't change, one option is to measure the resistance
between the ADJ pin and GND pin and then use this resistor with the
fixed-resistor threshold adjustment option.
When making these resistance measurements, please make sure to do the resistance measurement when the
system is not powered.
4.1.3 Adjusting Threshold With Fixed Resistor
Another option for setting B
OP
is to place a resistor on footprint R7 (see
). The R7 resistance is the
resistance seen between the ADJ and GND pin of the TMAG5328. You must select a resistance within the 2-kΩ
to 15-kΩ range.
If you select the fixed resistor option for setting B
OP
, remove the jumper on J3 so that the DAC, potentiometer or
anything else that is not connected to the ADJ pin.
4.2 Power Supply Options and Jumper Settings
The TMAG5328 in this EVM can be powered from either the main power rail on the board, which is labeled
as VCC on the board, or it can be powered from an external power supply that is independent of the board's
main power rail. To power the TMAG5328 from the VCC rail, add a jumper on pins 1 and 2 of header J2. By
adding the jumper to J2, the TMAG5328 is powered from the same power supply as the DAC43701. If the SCB
Hardware
SBAU376 – DECEMBER 2021
TMAG5328 Evaluation Module
9
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