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Data Sheet
AD7739
Rev. A | Page 19 of 32
CHANNEL CONVERSION TIME REGISTERS
8 Bits, Read/Write Registers, Address 0x30 to
Address 0x37, Default Value 0x91
The conversion time registers enable or disable chopping and
configure the digital filter for a particular channel (see
Table 25an
d Table 26). This register value affects the conversion time,
frequency response, and noise performance of the ADC.
MODE REGISTER
8 Bits, Read/Write Register, Address 0x38 to
Address 0x3F, Default Value 0x00
The mode register configures the part and determines its operating
mode register clears the ADC status register, sets the RDY pin
to a logic high level, exits all current operations, and starts the
mode specified by the mode bits.
The
AD7739 contains only one mode register. The two LSBs of
the address are used for writing to the mode register to specify
the channel selected for the operation determined by the MD2
to MD0 bits. Only the address 0x38 must be used for reading
from the mode register.
Table 25. Channel Conversion Time Registers Bits
Bit
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Mnemonic
Chop
FW (7-bit filter word)
Default
1
0x11
Table 26. Channel Conversion Time Registers Bit Descriptions
Bit
Mnemonic
Description
7
Chop
Chopping enable bit. Set to 1 to apply chopping mode for a particular channel.
6 to 0
FW
Chop = 1, single conversion or continuous conversion with one channel enabled.
Conversion Time (s) = (FW × 128 + 262)/MCLK Frequency (MHz), the FW range is 2 to 127.
Chop = 1, continuous conversion with two or more channels enabled.
Conversion Time (s) = (FW × 128 + 263)/MCLK Frequency (MHz), the FW range is 2 to 127.
Chop = 0, single conversion or continuous conversion with one channel enabled.
Conversion Time (s) = (FW × 64 + 213)/MCLK Frequency (MHz), the FW range is 3 to 127.
Chop = 0, continuous conversion with two or more channels enabled.
Conversion Time (s) = (FW × 64 + 214)/MCLK Frequency (MHz), the FW range is 3 to 127.
Table 27. Mode Register Bits
Bit
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Mnemonic
MD2
MD1
MD0
CLKDIS
Dump
Cont RD
24/16 BIT
Clamp
Default
0
Table 28. Mode Register Bit Descriptions
Bit
Mnemonic
Description
7 to 5
MD2 to MD0
Mode bits. These three bits determine th
e AD7739 operation mode. Writing a new value to the mode bits exit
the part from the mode in which it has been operating and place it in the newly requested mode immediately.
The function of the mode bits follows.
MD2
MD1
MD0
Mode
Address Used for Mode Register Write
Specifies
0
Idle
0
1
Continuous conversion
First channel to start converting
0
1
0
Single conversion
Channel to convert
0
1
Power-down (standby)
1
0
ADC zero-scale self-calibration
Conversion time for calibration
1
0
1
ADC full-scale self-calibration (for 2.5 V)
Conversion time for calibration
1
0
Channel zero-scale system calibration
Channel to calibrate
1
Channel full-scale system calibration
Channel to calibrate