MLX90609

Angular Rate Sensor (Standard version)

390109060901

Page 12 of 22

Data Sheet

Rev 008

February/08

5.3 Usage of the ADC

The MLX90609 has the unique feature of simultaneously delivering an analog and a digital output

signal.

The MLX90609 includes an internal 11-bit successive-approximation-register ADC with a sample-

and-hold circuit and a programmable 2-channel analog multiplexer. The multiplexer connects the

OUTAR pin or the OUTTEMP pin to the sample-and-hold circuit.

After a power-up the ADC is in a sleep mode. Before usage of the sleeping ADC it's recommended

to use an initial dummy conversion. The result of this dummy conversion should be skipped but the

next conversions will be valid. After conversions the ADC can be put in the sleep mode again.

A conversion must be initiated by means of the SPI command ADCC. This command turns the

ADC on, sets a necessary channel and starts a conversion. To read a status of the conversion the

ADCR or STATR commands can be used. As soon as the conversion is completed, its result

should be read in the answer of the command ADCR (see tables 8, 9 and 10).

There are two conversion formulas below. The formulas reflect the typical ADC behavior and can

be used to evaluate the voltage on the OUTAR and OUTTEMP pins:

400

12

25

)

(

+

=

ADCcode

mV

V

OUTAR

300

16

25

)

(

+

=

ADCcode

mV

V

OUTTEMP

The ADCcode represents the 11-bit result of the conversion (see Table 10).

Table 6 gives a description of the bits that are mentioned in this section.

ADEN

The ADEN bit selects the power management mode of the ADC:

ADEN=0: ADC is switched to the sleep mode, no AD-conversion is allowed.

ADEN=1: AD-conversion is allowed.

This bit is set by the ADCC-command. After power-up bit ADEN is cleared.

BUSY

This bit will be set after a reset and will be toggled to zero after all initialization procedures inside

the MLX90609. While BUSY=1, only refusal answers will be sent.

CHAN

The CHAN bit is used to select the input source for the ADC.

CHAN=0: the angular rate channel.

CHAN=1: the temperature sensor channel.

This bit is set by the ADCC-command. After power-up bit CHAN is cleared.

EOC

End of AD-conversion bit. EOC bit indicates an ADC state.

EOC=0 : ADC in progress and can not be restarted.

EOC=1 : AD-conversion has been completed and can be restarted.

As a result, any attempt of the ADC starting will be rejected if EOC has a “0” state.

OPC

Unknown Operation Code. This bit is set when a received operation code was not recognized.

X

These bits are reserved or have an undefined state.

Table 6. SPI bits