AD7785 Analog Devices, AD7785 Datasheet - Page 24

• Manufacturer Part Number: AD7785
• Description: 3-Channel, Low Noise, Low Power, 20-Bit ?-? ADC with On-Chip In-Amp and Reference
• Manufacturer: Analog Devices

Specifications of AD7785

• Resolution (bits): 20bit
• # Chan: 3
• Sample Rate: n/a
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: ± (Vref/Gain)
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

AD7785
Continuous Read
Rather than write to the communications register to access
the data each time a conversion is complete, the AD7785
can be configured so that the conversions are placed on the
DOUT/ RDY line automatically. By writing 01011100 to the
communications register, the user needs only to apply the 24
SCLK cycles to the ADC, and the 20-bit result followed by four
1s is automatically placed on the DOUT/ RDY line when a
conversion is complete. The ADC should be configured for
continuous conversion mode.
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 is placed on the DOUT/ RDY line. When
the conversion is read, DOUT/ RDY returns high until the next
conversion is available. In this mode, the data can be read only
once. In addition, the user must ensure that the data-word is
DOUT/RDY
SCLK
DIN
CS
0x5C
Figure 19. Continuous Read
Rev. 0 | Page 24 of 32
DATA
read 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
AD7785 to read the word, the serial output register is reset
when the next conversion is completed, and the new conversion
is placed in the output serial register.
To exit the continuous read mode, the instruction 01011000
must be written to the communications register while the
DOUT/ RDY pin is low. While in the continuous read mode,
the ADC monitors activity on the DIN line so that it can receive
the instruction to exit the continuous read mode. Additionally,
a reset occurs if 32 consecutive 1s are seen on DIN. Therefore,
DIN should be held low in continuous read mode until an
instruction is written to the device.
DATA
DATA