AD7791 Analog Devices, AD7791 Datasheet - Page 17

• Manufacturer Part Number: AD7791
• Description: 24-Bit, Single-Channel, Ultra Low Power, Sigma Delta A/D Converter
• Manufacturer: Analog Devices

Specifications of AD7791

• Resolution (bits): 24bit
• # Chan: 1
• Sample Rate: n/a
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

Continuous Read Mode
Rather than write to the communications register each time a
conversion is complete to access the data, the AD7791 can be
placed in continuous read mode. By writing 001111XX to the
communications register, the user needs only to apply the
appropriate number of SCLK cycles to the ADC and the 24-bit
word will automatically be placed on the DOUT/ RDY line
when a conversion is complete.
When DOUT/ RDY goes low to indicate the end of a conver-
sion, sufficient SCLK cycles must be applied to the ADC and the
data conversion will be placed on the DOUT/ RDY line. When
the conversion is read, DOUT/ RDY will return high until the
next conversion is available. In this mode, the data can be read
only once. Also, the user must ensure that the data-word is read
DOUT/RDY
SCLK
DIN
CS
0x3C
Figure 15. Continuous Read
Rev. 0 | Page 17 of 20
DATA
before the next conversion is complete. If the user has not read
the conversion before the completion of the next conversion or
if insufficient serial clocks are applied to the AD7791 to read the
word, the serial output register is reset when the next conver-
sion is complete and the new conversion is placed in the output
serial register.
To exit the continuous read mode, the instruction 001110XX
must be written to the communications register while the RDY
pin is low. While in the continuous read mode, the ADC moni-
tors activity on the DIN line so that it can receive the
instruction to exit the continuous read mode. Additionally, a
reset will occur if 32 consecutive 1s are seen on DIN. Therefore,
DIN should be held low in continuous read mode until an in-
struction is to be written to the device.
DATA
DATA
AD7791
04227-0-008