AD7147A Analog Devices, AD7147A Datasheet - Page 35

• Manufacturer Part Number: AD7147A
• Manufacturer: Analog Devices

Specifications of AD7147A

• Resolution (bits): 16bit
• # Chan: 13
• Sample Rate: 111SPS
• Interface: I²C/Ser 2-Wire,Ser,SPI
• Analog Input Type: Capacitive
• Ain Range: ± 8 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: CSP

Writing Data over the I
The process for writing to the AD7147A-1 over the I
shown in Figure 52 and Figure 54. The device address is sent
over the bus, followed by the R/ W bit being set to 0 and then
two bytes of data that contain the 10-bit address of the internal
data register to be written. The following bit map shows the
upper register address bytes. Note that Bit 7 to Bit 2 in the upper
address byte are don’t care bits. The address is contained in the
10 LSBs of the register address bytes.
MSB
7
X
The following bit map shows the lower register address bytes:
MSB
7
Reg
Add
Bit 7
The third data byte contains the eight MSBs of the data to be
written to the internal register. The fourth data byte contains
the eight LSBs of data to be written to the internal register.
The AD7147A-1 address pointer register automatically incre-
ments after each write. This allows the master to sequentially
write to all registers on the AD7147A-1 in the same write
transaction. However, the address pointer register does not
SCLK
SDA
START
NOTES
1. A START CONDITION AT THE BEGINNING IS DEFINED AS A HIGH-TO-LOW TRANSITION ON SDA WHILE SCLK REMAINS HIGH.
2. A STOP CONDITION AT THE END IS DEFINED AS A LOW-TO-HIGH TRANSITION ON SDA WHILE SCLK REMAINS HIGH.
3. 7-BIT DEVICE ADDRESS [DEV A6:DEV A0] = [0 1 0 1 1 X X], WHERE X IS A DON’T CARE BIT.
4. 16-BIT REGISTER ADDRESS [A15:A0] = [X, X, X, X, X, X, A9, A8, A7, A6, A5, A4, A3, A2, A1, A0], WHERE X IS A DON’T CARE BIT.
5. REGISTER ADDRESS [A15:A8] AND REGISTER ADDRESS [A7:A0] ARE ALWAYS SEPARATED BY A LOW ACK BIT.
6. REGISTER DATA [D15:D8] AND REGISTER DATA [D7:D0] ARE ALWAYS SEPARATED BY A LOW ACK BIT.
6
X
ACK
6
Reg
Add
Bit 6
27
D15
t
1
28
5
X
5
Reg
Add
Bit 5
DEV
A6
REGISTER DATA [D15:D8]
D14
1
29
AD7147A-1 DEVICE ADDRESS
DEV
4
X
A5
2
4
Reg
Add
Bit 4
2
C Bus
DEV
A4
3
3
X
DEV
A3
t
3
Reg
Add
Bit 3
2
D9
4
34
DEV
2
X
A2
D8
t
5
4
Figure 52. Example of I
35
2
Reg
Add
Bit 2
DEV
A1
ACK
6
1
Register
Address
Bit 9
t
36
3
DEV
A0
D7
7
1
Reg
Add
Bit 1
37
R/W
2
REGISTER DATA [D7:D0]
C bus is
D6
8
38
t
0
Register
Address
Bit 8
5
ACK
0
Reg
Add
Bit 0
9
2
LSB
LSB
C Timing for Single Register Write Operation
Rev. B | Page 35 of 68
A15
10
REGISTER ADDRESS [A15:A8]
A14
D1
11
43
wrap around after the last address. Therefore, any data written
to the AD7147A-1 after the address pointer has reached its
maximum value is discarded.
All registers on the AD7147A-1 are 16 bits. Two consecutive
8-bit data bytes are combined and written to the 16-bit registers.
To avoid errors, all writes to the device must contain an even
number of data bytes.
To finish the transaction, the master generates a stop condition
on SDO, or generates a repeat start condition if the master is to
maintain control of the bus.
Reading Data over the I
To read from the AD7147A-1, the address pointer register must
first be set to the address of the required internal register. The
master performs a write transaction and then writes to the
AD7147A-1 to set the address pointer. Next, the master outputs
a repeat start condition to keep control of the bus, or if this is
not possible, ends the write transaction with a stop condition.
A read transaction is initiated, with the R/ W bit set to 1.
The AD7147A-1 supplies the upper eight bits of data from the
addressed register in the first readback byte, followed by the
lower eight bits in the next byte. This is shown in Figure 53 and
Figure 54.
Because the address pointer automatically increments after each
read, the AD7147A-1 continues to output readback data until
the master sends a no acknowledge and stop condition to the
bus. If the address pointer reaches its maximum value and the
master continues to read from the part, the AD7147A-1 repeatedly
sends data from the last register that was addressed.
D0
44
ACK
45
A9
16
46
STOP
t
6
A8
17
ACK
t
18
8
A7
START
19
t
REGISTER ADDRESS [A7:A0]
7
2
C Bus
A6
20
DEV
AD7147A-1 DEVICE ADDRESS
A6
1
DEV
A5
A1
2
25
DEV
A4
A0
AD7147A
3
26