AD7739

Rev. 0 | Page 20 of 32

CHANNEL CONVERSION TIME REGISTERS

8 Bits, Read/Write Registers, Address 0x30–0x37h, Default Value 0x91

The conversion time registers enable or disable chopping and configure the digital filter for a particular channel. This register value affects

the conversion time, frequency response, and noise performance of the ADC.

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

Bit

Mnemonic

Description

7

CHOP

Chopping Enable Bit. Set to 1 to apply chopping mode for a particular channel.

6–0

FW

CHOP = 1, single conversion or continuous conversion with one channel enabled.

Conversion Time (µs) = (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 (µs) = (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 (µs) = (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 (µs) = (FW × 64 + 214)/MCLK Frequency (MHz), the FW range is 3 to 127.

MODE REGISTER

8 Bits, Read/Write Register, Address 0x38–0x3F, Default Value 0x00

The mode register configures the part and determines its operating mode. Writing to the 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.

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

0

0

0

0

0

0

0

Bit

Mnemonic

Description

7–5

MD2–MD0

Mode Bits. These three bits determine the AD7739 operation mode. Writing a new value to the mode bits will

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 is described in more detail below.

MD2

MD1

MD0

Mode

Address Used for Mode Register

Write Specifies:

0

0

0

Idle

0

0

1

Continuous Conversion

First Channel to Start Converting

0

1

0

Single Conversion

Channel to Convert

0

1

1

Power-Down (Standby)

1

0

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

1

0

Channel Zero-Scale System Calibration

Channel to Calibrate

1

1

1

Channel Full-Scale System Calibration

Channel to Calibrate