MLX90821

Relative Pressure Sensor IC

Page 20 of 40

REV 004 – 4 MAR 2021

3901090821

ADC

The 16 bit differential ADC has a range from –VDDA/2 to +VDDA/2.

There are 7 different ADC channels. Channel 0 is not used. Table 13 below describes all the channels.

ADC

Signal

Remarks

SIN[2:0]

0

-

Nothing connected

1

P

Pressure

2

Tint

Internal Temperature

3

Vsup

External Supply

4

InP/InN

Multiplexing between Positive/Negative Sensor

Output

5

Vdig

Digital Regulator

6

Tntc

NTC Output

7

Text

External Temperature

Table 13: ADC channels

The different channels are converted in a constantly repeating sequence. A new ADC conversion is done every

50us following the sequence shown below in Figure 10. This is resulting in an updated pressure output value

every 200us.

P

Tint

P

Text

P

Tntc

P

Vsup

P

...

Tint

P

Text

P

Tntc

P

InP/InN

P

Tint

P

Figure 10: ADC sequence

Digital

The digital is built around a 16-bit microcontroller. It contains besides the processor also ROM, RAM and EEPROM

and a set of user and system IO registers.

Temperature compensation of the pressure signal and pressure linearization is handled by the microcontroller.

For the pressure compensation there are EEPROM parameters allocated to be able to cover a large variety of

calibration approaches.

Both for gain and offset of the pressure signal, there is a separate temperature dependency programmable

ranging from a temperature independence to a first order, second order and finally a third order compensation.

This is reflected in EEPROM parameters for the offset (O0, O1, O2 and O3) and for the gain (G0, G1, G2 and G3).

If required, the linearity of the pressure signal can also be compensated without a temperature dependency or

with a first order temperature dependency through EEPROM parameters L0 and L1.

Linearization of the NTC temperature is also covered partially by the microcontroller. More information in this

topic can be found in chapter 16.