Data Sheet

ADA4571

Rev. 0 | Page 19 of 21

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DIAGNOSTICS

Radius Calculation

value. These outputs have a fixed 90° phase relationship and

therefore the calculated radius value remains in a predictable,

predetermined range that varies with the temperature of the

device independent of the current magnetic field direction. This

in the ECU. When the calculated radius is no longer within the

acceptable bounds, a fault may occur in the system. To calculate

radius, use the following formula:

2

2

)

2

(

)

2

(

DD

COS

DD

SIN

RAD

V

V

V

V

V

−

+

−

=

It is important to perform offset calibration before calculating

the radius.

Figure 32 shows the allowable radius values when GC mode is

enabled and Figure 33 shows the allowable radius values when

specified in the Specifications section. This range is represented

by the shaded region in Figure 32 and Figure 33.

indicated as well.

Figure 32. GC On Radius Values

Figure 33. GC Off Radius Values

Monitoring of the VTEMP pin can allow an even tighter range

for radius length at the known temperature. See the

Specifications section and the Typical Performance

Characteristics section for exact values and output amplitude

specifications at each temperature.

Broken Bond Wire Detection

The ADA4571 includes circuitry to detect broken bond wire

conditions between the AMR sensor and the instrumentation

amplifier. The detection circuitry consists of current sources

and window comparators placed on the signal connections

between the AMR sensor and the ASIC. The purpose of the

current sources is to pull the signal node outside of the normal

operating region in the event of an open bond wire between the

AMR sensor and the ASIC. The purpose of the window

comparators is to detect when the signal from the AMR sensor

is outside of the normal operating region. When the comparators

detect that the signal nodes are outside the normal operating

region, the circuit pulls the VSIN and/or VCOS node to ground

to indicate the fault to the host controller.

In addition to the active circuitry, there are applications

recommendations, such as the utilization of pull-up and pull-

down resistors, which detect broken bond wires by pulling

nodes outside of the defined operating regions. A broken bond

wire at VTEMP, VCOS, and VSIN interrupts the corresponding

outputs. To ensure that the output enters into a known state if

there is a broken bond wire on these pins, connect a 200 kΩ

pull-down resistor at these pins. Pulling these nodes outside of

the normal operating region signals a fault to the host

controller.

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

0

5

GC ON

–40°C

+25°C

+125°C

+150°C

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

0

5

GC OFF

–40°C

+25°C

+125°C

+150°C