The TMAG6181-Q1 AMR angle sensor can be used in either in single-ended output mode or differential output mode. TMAG6181-Q1 has the drive capability to either drive differential-ended or single-ended SAR or Sigma Delta ADCs. Typically, an external microcontroller processes the AMR output signals to extract the angular position.

The differential-ended output mode is helpful to eliminate any common mode disturbances in the system. Figure 7-2 shows a typical application circuit where the differential output signals SIN_P, SIN_N, COS_P, and COS_N are all connected to the four single-ended ADCs in the external microcontroller. If differential ADCs are available, then they are typically recommended. The load capacitors and resistors must match each other to typically achieve high accuracy. During sleep mode or when a fault is detected, the outputs are placed in high-impedance state. To ensure that external microcontroller can detect this case, TI recommends using pulldown or pullup resistors.

The TMAG6181-Q1 can drive capacitive loads up to 10nF directly on the AMR output pins and, for a cable with capacitances of 100pF/m, the device can drive up to 100m capacitive loads. With the ability to source and sink currents up to 1mA, the device can drive resistive loads.

Figure 7-2 Application Diagram for TMAG6181-Q1 in Differential-Ended Output Mode

If the number of ADC ports in the microcontroller are limited, or if the number of wires from the sensor to the microcontroller must be kept to a minimum, Figure 7-4 shows a typical application circuit where only the positive output channels (SIN_P and COS_P) are connected to single-ended ADCs. The unused output signals (SIN_N and COS_N) can be either left floating or connected to ground through a high resistance. In single-ended output mode, the dynamic range (SNR) and noise immunity is typically reduced compared to the differential output mode. To reduce noise on the outputs and for filtering EMC disturbances, an external low-pass filter such as a first order RC network can be used. The bandwidth of the external filter must be designed based on the rotation speed of the magnetic field to be detected. TI recommends adding pullup or pulldown resistors to ground on the single-ended outputs (SIN_P and COS_P) so the outputs are defined when the outputs are in high-impedance state. The supply voltage of the sensor is used as the reference for the ADCs in the microcontroller.

Figure 7-3 Application Diagram for TMAG6181-Q1 in Single-Ended Output Mode