Data Sheet

ADA4570

APPLICATIONS INFORMATION

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Rev. 0 | 12 of 14

VTEMP OUTPUT PIN

An internal temperature sensor provides a voltage output at the

VTEMP pin that can be used to monitor the operating temperature

of the system and provide the reference for calibration. This output

voltage (VTEMP) is ratiometric to the ADA4570 supply voltage.

Using an ADC, the reference of which is supplied by the VDD of the

ADA4570, ensures that the digitized temperature measurement is

also ratiometric.

To achieve maximum accuracy from the VTEMP output voltage,

perform an initial calibration at a known and controlled temperature.

To calculate the temperature, use the following equation:

VDD −TCAL×TCO

TCO

(1)

where:

voltage.

temperature.

Specifications section for the exact value.

In Figure 18, an optional resistor is shown in the VTEMP signal

path to the ADC. When operating in a harsh environment, this

resistor increases device immunity to EMI.

POWER CONSUMPTION

The power consumption is dependent on the supply voltage and

temperature as shown in Figure 8.

The analog outputs are protected against short circuit to the VDD

pin or ground by a current limitation.

DIAGNOSTIC

Broken Bond Wire Detection

The ADA4570 includes the ability to detect broken bond wires

between the AMR sensor and the ASIC. When this circuitry detects

that the signal nodes are outside the normal operating region, the

device pulls the VSIN+, VSIN−, VCOS+, and VCOS− analog output

pins to ground. Monitor the voltage level of the analog signals

to verify that the output level does not fall within the short-circuit

diagnostic band shown in Figure 20. If the outputs fall within the

short-circuit diagnostic band shown in Figure 20, the user must take

the appropriate action.

Figure 20. Short-Circuit Diagnostic Band

Short-Circuit Diagnostic Bands

The output levels of the ADA4570 were designed to be within the

linear region shown in Figure 20 during normal operation. Validate

that the output levels are within the appropriate operating band. If

any, or all, of the VSIN+, VSIN−, VCOS+, and VCOS− outputs are

in the diagnostic bands, the outputs must be treated at the system

level because this is an indication of a potential fault.

Radius Calculation

The differential signal outputs, VSIN and VCOS, from the ADA4570

can be used to calculate a radius (VRAD) of the circle at any angle

of the applied magnetic field, as is shown in Figure 21.

Figure 21. Radius Values

VRAD is equal to the vector sum of the differential signal outputs,

VSIN and VCOS.

Due to the constant phase difference of 90° between the measure-

ments of the differential signal outputs, VSIN and VCOS, VRAD is

constant over an entire magnetic revolution for a constant tempera-

ture and supply.

It is important to perform an offset calibration before a radius

calculation is done.