ADIS16006

Rev. 0 | Page 11 of 16

THEORY OF OPERATION

The ADIS16006 is a low cost, low power, complete dual-axis

accelerometer with an integrated serial peripheral interface

(SPI) and an integrated temperature sensor whose output is

also available on the SPI interface. The ADIS16006 is capable

of measuring acceleration with a full-scale range of ±5 g

(minimum). The ADIS16006 can measure both dynamic

acceleration (that is, vibration) and static acceleration (that is,

gravity).

SELF-TEST

The ST pin controls the self-test feature. When this pin is set to

ometer. The resulting movement of the beam allows the user to

test if the accelerometer is functional. The typical change in

This pin may be left open-circuit or connected to common in

normal use. The ST pin should never be exposed to voltage

condition cannot be guaranteed (that is, multiple supply voltages

recommended.

SERIAL INTERFACE

The serial interface on the ADIS16006 consists of five wires: CS,

TCS, SCLK, DIN, and DOUT. Both accelerometer axes and the

temperature sensor data are available on the serial interface.

The CS and TCS are used to select the accelerometer or tem-

perature sensor outputs, respectively. CS and TCS cannot be

active at the same time.

The SCLK input provides access to data from the internal data

registers.

ACCELEROMETER SERIAL INTERFACE

Figure 3 shows the detailed timing diagram for serial interfacing to

the accelerometer in the ADIS16006. The serial clock provides

the conversion clock. CS initiates the conversion process and

data transfer and also frames the serial data transfer for the

accelerometer output. The accelerometer output is sampled on

the second rising edge of the SCLK input after the falling edge

of the CS. The conversion requires 16 SCLK cycles to complete.

The rising edge of CS puts the bus back into three-state. If CS

remains low, the next digital conversion is initiated. The details

for the control register bit functions are shown in Table 6.

Accelerometer Control Register

MSB

LSB

DONTC

ZERO

ZERO

ZERO

ZERO

ONE

ZERO

PM0

Table 6. Accelerometer Control Register Bit Functions

Bit

Mnemonic

Comments

7

DONTC

Don’t care. Can be 1 or 0.

6, 5, 4

ZERO

These bits should be held low.

3

ADD0

This address bit selects the X-axis or Y-axis

outputs. A 0 selects the X-axis; a 1 selects

the Y-axis.

2

ONE

This bit should be held high.

1

ZERO

This bit should be held low.

0

PM0

This bit selects the operation mode for

the accelerometer; set to 0 for normal

operation and 1 for power-down mode.

Power-Down

By setting PM0 to 1 when updating the accelerometer control

register, the ADIS16006 is put into a shutdown mode. The

information stored in the control register is maintained during

shutdown. The ADIS16006 changes modes as soon as the control

register is updated. Therefore, if the part is in shutdown mode

and PM0 is changed to 0, the part powers up on the 16th SCLK

rising edge.

ADD0

By setting ADD0 to 0 when updating the accelerometer control

register, the X-axis output is selected. By setting ADD0 to 1, the

Y-axis output is selected.

ZERO

ZERO is defined as the logic low level.

ONE

ONE is defined as the logic high level.

DONTC

DONTC is defined as don’t care and can be a low or high logic

level.

Accelerometer Conversion Details

Every time the accelerometer is sampled, the sampling function

of their initial values (assuming no additional external filtering

capacitors have been added). The recovery time for the filter

capacitor to recharge is approximately 10 μs. Thus, sampling the

accelerometer at a rate of 10 kSPS or less does not induce a

sampling error. However, as sampling frequencies increase

above 10 kSPS, one can expect sampling errors to attenuate the

actual acceleration levels.