The TMAG5328 B_OP is set by connecting a resistor or a voltage source to the “ADJ” pin. Figure 8-1 shows how to use resistor R1 to set the B_OP. Figure 8-2 shows hows to use a DAC as a voltage source for setting the B_OP. Using the DAC allows the user to dynamically change the B_OP with software. To use a DAC, the output of the DAC must settle within 4 µs after the 80-µA current source of the “ADJ” pin is turned ON.

Figure 8-1 Setting B_OP of One TMAG5328 Device Using a Resistor

Figure 8-2 Setting B_OP of One TMAG5328 Device Using a DAC

As a DAC alternative, Figure 8-3 shows how a voltage divider may be used as a voltage source. In Figure 8-3, an operational amplifier is placed between the voltage divider and the “ADJ” pin so that the voltage fed to the “ADJ” pin is not impacted by the internal current source of the TMAG5328 when the current source is turned ON. To use an op amp, the output of the op amp must settle within 4 µs after the 80-µA current source of the “ADJ” pin is turned ON.

Figure 8-3 Setting B_OP of One TMAG5328 Device Using a Voltage Divider

A potentiometer or rheostat may be integrated into a voltage divider, and the user can adjust this potentiometer to dynamically update the B_OP. Figure 8-4 shows how to use a potentiometer in a voltage divider to set the B_OP of the TMAG5328. The maximum output voltage, which determines the maximum B_OP, is set based on the values of resistors R1 and R3. The minimum output voltage, which determines the minimum B_OP, is set based on the values of the maximum potentiometer resistance, R1’s resistance, and R3’s resistance. The user should select a minimum output voltage greater than 0.16 V and a maximum output voltage less than 1.2 V.

Figure 8-4 Setting B_OP of One TMAG5328 Device Using a Voltage Divider and Potentiometer

Figure 8-5 shows how the TMAG5328’s internal current source can drive a apotentiometer or rheostat instead of a voltage divider. In this implementation, resistor R2 should be at least 2 kΩ to ensure that the “ADJ” resistance is always above its minimum 2 kΩ. The sum of the maximum potentiometer resistance and the resistance of R1 must also be less than 15 kΩ.

Figure 8-5 Setting B_OP of One TMAG5328 Device Using a Potentiometer and the TMAG5328’s Internal Current Source

Multiple TMAG5328 devices may be used in the same system. When setting the B_OP using a resistor, TI recommends that each TMAG5328 has its own “ADJ” resistor, even if multiple TMAG5328 devices have the same “ADJ” resistor value. Figure 8-6 shows an example implementation that has three TMAG5328 devices. If each device is set to the same B_OP, then the resistances of R1, R2, and R3 are equal.

Figure 8-6 Setting B_OP of Three TMAG5328 Devices Using Three Resistors

When setting the B_OP using a DAC, one DAC can be used to set the “ADJ” pin voltage of multiple devices only if the DAC’s output could sink the current from all of the TMAG5328 devices. Figure 8-7 shows an example of a DAC driving the “ADJ” pin of three TMAG5328 devices. A DAC can only work reliably in this specific scenario if the DAC’s output can settle within 4 µs after being exposed to the three “ADJ” current sources. Each current source is 80 µA, therefore the DAC can only reliably work if the DAC's output can settle within 4 µs after being exposed to 80 x 3 = 240 µA of current.

Figure 8-7 Setting B_OP of Three TMAG5328 Devices Using a DAC