IC-PI datasheet(31/49 Pages) ICHAUS

31 / 49 page

preliminary

iC-PI PROGRAMMABLE 12-BIT

Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

Rev B1, Page 31/48

SIGNAL LEVEL CONTROL and SIGNAL MONITORING

iC-PI’s signal level controller can keep the input signals

for the sine-to-digital converter constant, regardless

of temperature and aging effects, when using control

output ACO to track the sensor supply.

ACOR(1:0) presets the output current range of pin

ACO, the control’s highside current source output, and

ACOT(1:0) defines its control mode.

The resulting internal signal amplitude and the control’s

operating range are both monitored and thus can be

used for error messaging.

ACOR

Addr. 0x15, bit 7:6

Code

Current range

5 mA

10 mA

25 mA

50 mA

Table 38: ACO Output Current Range (applies for con-

trol modes and constant current source)

ACOT

Addr. 0x16, bit 1:0

Code

Operating mode

Sine/cosine square control

Sum control

Constant current source

Not permitted (device test only)

Table 39: ACO Output Control Mode

The modes square control and sum control feature an

adjustable deadband, meaning that a deviation of the

input signal levels is balanced only if the configured

control deadband is exceeded (refer to ACOHYS). Due

to this, the control’s influence on the sensor’s signal

quality (regarding THD) can be significantly reduced.

The deadband is disabled when configuring a zero hys-

teresis, so that any deviation of the input levels will be

balanced immediately over the ACO output.

ACOHYS

Addr. 0x16, bit 6:4

Code

Hysteresis to setpoint (ACOT = 00)

000

2.5 %

001

5 %

010

7.5 %

011

10 %

1xx

None (continuous control)

Note

This function is available with square control and

sum control modes.

Table 40: Control Deadband

Square Control Mode

The standard control mode is square control which

uses (sine2 + cosine2) to adjust the ACO output current.

ACOS(4:0) determines the internal signal amplitudes

within the closed-loop control and, simultaneously, the

amplitude monitoring thresholds. The ideal setting is

when the sin/cos test signals available in operating

mode Test 5 are at 3 Vpp.

ACOS

Addr. 0x15, bit 5:1

Code

Square control (ACOT = 00)

0x00

Vpp() ≈ 1800 mV (60 %)

0x01

Vpp() ≈ 1830 mV (61 %)

...

≈

1800 mV

77−(1.25∗Code)

0x19

Vpp() ≈ 3000 mV (98 %)

...

0x1F

Vpp() ≈ 3600 mV (120 %)

Table 41: Square Control Setting (internal sin/cos sig-

nal amplitude)

Figure 16: Signal monitoring and test signals in

Test 5 mode (example for ACOS(4:0) =

0x19).

The signal monitoring thresholds are tracked according

to ACOS (4:0) and fit for square control mode. When

using sum control mode a different operating point can

be required for which the monitoring thresholds may

not be suitable. In this case signal monitoring should

be disabled via the error mask (see EMASKA etc.).

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