AD7156 Analog Devices, AD7156 Datasheet - Page 21

• Manufacturer Part Number: AD7156
• Manufacturer: Analog Devices

Specifications of AD7156

• Resolution (bits): 12bit
• # Chan: 2
• Sample Rate: 100SPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: Capacitive
• Ain Range: 0.5 pF,1 pF,2 pF,4 pF
• Pkg Type: CSP

POWER-DOWN TIMER REGISTER
Address Pointer 0x10
8 Bits, Read/Write, Factory Preset 0x40
Table 14. Power-Down Timer Register Bit Map
1
Table 15.Power-Down Timer Register Bit Descriptions
Bit
7
6
[5:0]
CAPDAC REGISTERS
Ch 1 Address Pointer 0x11
Ch 2 Address Pointer 0x12
8 Bits, Read/Write, Factory Preset 0xC0
Table 16. CAPDAC Registers Bit Map
1
Table 17. CAPDAC Registers Bit Descriptions
Bit
7
6
[5:0]
SERIAL NUMBER REGISTER
Address Pointer 0x13, Address Pointer 0x14, Address
Pointer 0x15, Address Pointer 0x16
32 Bits, Read Only, Factory Preset 0xXXXX
This register holds a serial number, unique for each individual part.
The default values are given in parentheses.
The default values are given in parentheses.
Bit 7
DacEn
Bit 7
(0)
(1)
Mnemonic
Power-down
timeout
Mnemonic
DacEn
DacAuto
DacValue
Bit 6
(1)
DacAuto
Description
This bit must be 0 for proper operation.
This bit must be 1 for proper operation.
This bit defines the period duration of the power-down timeout.
If the comparator outputs have not been activated during the programmed period, the part enters power-down
mode automatically. The part can be then returned to a normal operational mode either via the serial interface
or by the power supply off/on sequence.
The period is programmable in steps of 4 hours. For example, setting the value to 0x06 sets the duration to 24
hours. The maximum value of 0x3F corresponds to approximately 10.5 days.
The value of 0x00 disables the power-down timeout, and the part does not enter power-down mode automatically.
Description
DacEn = 1 enables capacitive the DAC.
DacAuto = 1 enables the auto-DAC function in the adaptive threshold mode.
When the auto-DAC function is enabled, the part dynamically adjusts the CAPDAC to keep the CDC in an
optimal operating capacitive range. The CAPDAC value is automatically incremented when the data average
exceeds ¾ of the CDC full range, and the CAPDAC value is decremented when the data average goes below ¼
of the CDC full range. The auto-DAC increment or decrement step depends on the selected CDC capacitive
input range.
This bit has no effect in fixed threshold mode; the auto-DAC function is always disabled in the fixed threshold mode.
CAPDAC value, Code 0x00 ≈ 0 pF, Code 0x3F ≈ CAPDAC full range.
Bit 6
(1)
1
Bit 5
Bit 5
1
Bit 4
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Bit 4
Power-down timeout (6-bit value)
CHIP ID REGISTER
Address Pointer 0x17
8 Bits, Read Only, Factory Preset 0xXX
This register holds the chip identification code, used in factory
manufacturing and testing.
Bit 3
DacValue (6-bit value)
Bit 3
(0x00)
(0x00)
Bit 2
Bit 2
Bit 1
Bit 1
AD7156
Bit 0
Bit 0