AD7291BCPZ データシートの表示（PDF） - Analog Devices

部品番号

コンポーネント説明

メーカー

AD7291BCPZ

8-Channel, I2C, 12-Bit SAR ADC with Temperature Sensor

Analog Devices 

AD7291

MODES OF OPERATION

When supplies are first applied to the AD7291, the ADC

powers up in partial power-down mode and normally remains

in this partial power-down state while not converting. Once

the master addresses the AD7291, it exits partial power-down.

There are two methods of initiating a conversion on the

AD7291: command mode and autocycle mode.

COMMAND MODE

In command mode, the AD7291 converts on demand on either

a single channel or a sequence of channels. Writing in the

command register puts the device into command mode. This is

the default mode of operation and allows a conversion to be

automatically selected any time a write operation occurs to the

command register. To enter this mode, the required combina-

tion of channels is written into the command register (Register

0x00). Following the write operation, the AD7291 must be

addressed again to indicate that a read operation is required.

The read then takes place from the voltage or temperature

conversion result register. For the first conversion to occur,

the address pointer written to the AD7291 must point to the

voltage conversion result register or TSENSE conversion result

register. The conversion is completed while the first four channel

address bits are read. The next conversion in the sequence takes

place once the next read from the result register is initiated.

Data Sheet

When operating the device in fast mode, the acquisition and

conversion times combined take approximately 4.45 µs (1.25 µs

acquisition time plus 3.2 µs conversion time). When in command

mode, the device cycles through the selected channels from the

lowest selected channel in the sequence to the next lowest until

all the channels in the sequence are converted.

To exit the command mode, the master must not acknowledge

the final byte of data. This stops the AD7291 transmitting,

allowing the master to assert a stop condition on the bus. On

the receipt of a stop condition, the AD7291 stops converting

and enters partial power-down mode, but the content of the

command register is preserved. Once the device is readdressed

and a read is initiated from the voltage conversion register, the

AD7291 begins converting on the previously selected sequence

of channels. The conversion sequence starts converting the

first selected channel in the sequence; that is, if Channel 1,

Channel 2, and Channel 3 are selected and a stop condition

occurs after the Channel 1 result is read, on resumption of

conversions, Channel 1 is reconverted and the conversion

sequence continues.

Rev. C | Page 24 of 28

Share Link: