EVAL-ADA4571-2 User Guide

UG-1047

Rev. 0 | Page 7 of 9

Vsin vs Vcos

The Vsin vs Vcos graph is another way to visualize the electrical

angle from the ADA4571-2. However, there is more information

given in Figure 10, showing the radius of the output values which

can give further diagnostic information to system. As long as

the sensor is fully saturated, or the applied magnetic field strength

exceeds 25 kA/m, the radius value remains unchanged at a constant

temperature. As the AMR effect is smaller at high temperatures

the radius value changes with respect to temperature. See the

ADA4571-2 data sheet for the temperature coefficient values for

the output amplitude for the VSINx and VCOSx channels.

Figure 10. Vsin vs Vcos Graph

Digital Inputs

Four digital inputs on the ADA4571-2 can be toggled using the

Digital Inputs buttons.

The power-down button for each channel puts the devices into

a low power state by disabling the internal circuitry for that channel

and placing the outputs into a high impedance mode. See the

ADA4571-2 data sheet for the power-down current per channel

in the device. The power-down function of each channel can be

toggled separately.

The Gain Control 1 Disabled and Gain Control 2 Disabled

buttons put the device into the gain control mode (see Figure 11).

This mode alters bridge supply voltage based on the internal

temperature value of the device.

Through this mode, the output amplitude temperature coefficient

of the ADA4571-2 reduces. See the ADA4571-2 data sheet for

output amplitude vs. temperature with the gain control enabled

and disabled.

Figure 11. Digital Inputs Pane

Offset Calibration

An offset calibration is required to maximize the accuracy of

the ADA4571-2. The VSIN1, VCOS1, VSIN2, and VCOS2 channels have

inherent voltage offsets due to resistor mismatch within the

AMR sensor bridges. See the ADA4571-2 data sheet offset

voltage ranges for the outputs.

There are a few methods that can null the offsets for the outputs. To

run an offset calibration on Channel 1, click Run Cal CH1 (see

Figure 12). Once clicked, rotate the magnetic stimulus slowly

through an entire mechanical rotation. This ensures the maximum

and minimum output voltages are found for each channel.

Figure 12. Offset Calibration Pane