ZSC31150 Datasheet

© 2016 Integrated Device Technology, Inc.

11

December 6, 2016

2.3 Analog Front End (AFE)

The analog front end (AFE) consists of the programmable gain amplifier (PGA), the multiplexer (MUX), and the analog-to-digital converter

(ADC).

2.3.1 Programmable Gain Amplifier (PGA)

Table 2.1 shows the adjustable gains, the sensor signal spans, and the allowed common mode range.

Table 2.1 Adjustable Gains, Resulting Sensor Signal Spans, and Common Mode Ranges

No.

Overall Gain

Max. Span

[mV/V] [a]

Gain

Amp1

Gain

Amp2

Gain

Amp3

Input Common Mode Range

XZC = Off

XZC = On

1

420

1.8

30

7

2

29 to 65

45 to 55

2

280

2.7

30

4.66

2

29 to 65

45 to 55

3

210

3.6

15

7

2

29 to 65

45 to 55

4

140

5.4

15

4.66

2

29 to 65

45 to 55

5

105

7.1

7.5

7

2

29 to 65

45 to 55

6

70

10.7

7.5

4.66

2

29 to 65

45 to 55

7

52.5

14.3

3.75

7

2

29 to 65

45 to 55

8

35

21.4

3.75

4.66

2

29 to 65

45 to 55

9

26.3

28.5

3.75

3.5

2

29 to 65

45 to 55

10

14

53.75

1

7

2

29 to 65

45 to 55

11

9.3

80

1

4.66

2

29 to 65

45 to 55

12

7

107

1

3.5

2

29 to 65

45 to 55

13

2.8

267

1

1.4

2

32 to 57

not applicable

[a] Recommended internal signal range maximum is 80% of the VDDA voltage. Span is calculated by the following formula:

Span = 80% / gain.

[b] Bridge in Voltage Mode with maximum input signal (with XZC = +300% Offset), 14-bit accuracy. Refer to the ZSC31150 Functional

Description for usable input signal/common mode range at bridge in current mode. See section 2.3.2 for an explanation of the extended

analog zero compensation (XZC).

2.3.2 Offset Compensation

The ZSC31150 supports two methods of sensor offset compensation (zero shift):



Digital offset correction



XZC: analog compensation for large offset values (up to a maximum of approximately 300% of the span, depending on the gain

adjustment)

The digital sensor offset correction will be processed during the digital signal correction/conditioning by the calibration microcontroller (CMC).

Analog sensor offset pre-compensation is needed for compensation of large offset values, which would overdrive the analog signal path by

uncompensated gaining. For analog sensor offset pre-compensation, a compensation voltage is added in the analog pre-gaining signal path

(coarse offset removal). The analog offset compensation in the AFE can be adjusted by 6 EEPROM bits (refer to the ZSC31150 Functional

Description for details).