AD7156

Rev. 0 | Page 21 of 28

POWER-DOWN TIMER REGISTER

Address Pointer 0x10

8 Bits, Read/Write, Factory Preset 0x40

Table 14. Power-Down Timer Register Bit Map1

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Power-down timeout (6-bit value)

(0)

(1)

(0x00)

Table 15.Power-Down Timer Register Bit Descriptions

Bit

Mnemonic

Description

7

This bit must be 0 for proper operation.

6

This bit must be 1 for proper operation.

[5:0]

Power-down

timeout

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.

CAPDAC REGISTERS

Ch 1 Address Pointer 0x11

Ch 2 Address Pointer 0x12

8 Bits, Read/Write, Factory Preset 0xC0

Table 16. CAPDAC Registers Bit Map1

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

DacEn

DacAuto

DacValue (6-bit value)

(1)

(1)

(0x00)

Table 17. CAPDAC Registers Bit Descriptions

Bit

Mnemonic

Description

7

DacEn

DacEn = 1 enables capacitive the DAC.

6

DacAuto

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.

[5:0]

DacValue

CAPDAC value, Code 0x00 ≈ 0 pF, Code 0x3F ≈ CAPDAC full range.

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.

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.