ADA4841-X AD [Analog Devices], ADA4841-X Datasheet - Page 13

• Manufacturer Part Number: ADA4841-X
• Manufacturer: AD [Analog Devices]

Preliminary Technical Data
CONFIGURATION REGISTER, CFG
The AD7689 uses a 14-bit configuration register (CFG[13:0])
for configuring the inputs, channel to be converted, 1-pole filter
bandwidth, reference, and channel sequencer. The CFG is
latched MSB first with DIN synchronized to SCK rising edge. At
the end of conversion, the register is updated allowing the new
settings to be used. There is always a one deep conversion delay
regardless of when the CFG is written to; during or after
conversion. Note that at power up, the CFG is undefined and a
dummy conversion is required to update the register. To preload
the CFG with a factory setting, hold DIN high for 1 conversion.
Thus CFG[13:0] = 0x3FFF. This sets the AD7689 for:
• IN[7:0] unipolar referenced to GND, sequenced in order
• Full bandwidth for 1-pole filter
• Internal reference/temp sensor disabled, buffer enabled
• No read back of CFG
Table 9 Summarizes the configuration register bit details. Each
corresponding section, where necessary, highlights further
details of the bits used for the specific functions.
Table 9. Configuration Register Description
Bit
13
12:10
9:7
6
5:3
Name
CFG
INCC
INn
BW
REF
Description
0 – Keep current config settings
1 – Overwrite contents of register
Input Channel Configuration
Channel Selection in binary fashion
Selects BW for Low Pass Filter
0 – ¼ of BW
1 – Full BW
Reference/Buffer Selection
12
0
0
0
1
1
1
9
0
0
.
1
5
0
0
0
0
1
1
8
0
0
.
1
4
0
0
1
1
1
1
11
0
1
1
0
1
1
7
0
1
.
1
3
0
1
0
1
0
1
10
X
0
1
X
0
1
Function
IN0
IN1
IN7
Function
Internal ref, REF = 2.5V output
Internal ref, REF = 4.096V output
External ref, Temp enabled
External ref, internal Buffer,
Temp enabled
External ref, Temp disabled
External ref, internal Buf, Temp
disabled
Function
Bipolar differential pairs, IN-
referenced to V
Bipolar, IN0-IN7 referenced to
COM = V
Temperature sensor
Unipolar differential pairs, IN-
referenced to GND (±100mV)
Unipolar, IN0-IN7 referenced to
COM = GND (±100mV)
Unipolar, IN0-IN7 referenced to
GND (single ended)
REF
/2
REF
/2
Rev. PrC | Page 13 of 20
2:1
0
ANALOG INPUTS
Input Configurations
Figure 14 shows the different methods for configuring the
analog inputs with CFG[12:10].
The analog inputs can be configured as:
CH0+ (-)
CH0- (+)
CH1+ (-)
CH1- (+)
CH2+ (-)
CH2- (+)
CH3+ (-)
CH3- (+)
• Figure 14A, single ended referenced to system ground;
• Figure 14B, bipolar differential with a common reference
• Figure 14C, bipolar differential pairs with INx- referenced
CH3+
CH1+
CH2+
CH4+
CH5+
CH0+
CH6+
CH7+
CFG[12:10] = 111
point, COM, = V
Unipolar differential with COM connected to a ground
sense; CFG[12:10] = 110
to V
Unipolar differential pairs with INx- referenced to a
SEQ
RB
{
{
{
{
REF
Figure 14. Multiplexed Analog Input Configuraitons
/2; CFG[12:10] = 00X
A- 8 CHANNELS,
SINGLE ENDED
C - 4 CHANNELS,
DIFFERENTIAL
Channel Sequencer
Read back
0 – Read back current configuration at end of data
1- Do not read back contents of configuration
COM
COM
IN2
IN3
IN5
IN6
IN7
GND
IN2
IN3
IN5
IN6
IN7
GND
2
0
0
1
1
IN0
IN1
IN4
IN0
IN1
IN4
REF
1
0
1
0
1
2
.
/2; CFG[12:10] = 010
Function
Disable Sequencer
Update config during sequence
Scan IN0–INn (set in CFG[9:7])
then TEMP
Scan IN0–INn (set in CFG[9:7])
2
CH0- (+)
CH1+ (-)
CH1- (+)
CH0+ (-)
.
CH1+
CH2+
CH3+
CH4+
CH5+
CH0+
CH6+
CH7+
COM-
COM-
2
CH2+
CH3+
CH4+
CH5+
.
{
{
COMMON REFERNCE
D - COMBINATION
B - 8 CHANNELS,
2
.
COM
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
COM
GND
GND
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
AD7689