AD7148 Analog Devices, AD7148 Datasheet - Page 2

• Manufacturer Part Number: AD7148
• Manufacturer: Analog Devices

Specifications of AD7148

• Resolution (bits): 16bit
• # Chan: 8
• Sample Rate: 250kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: ± 8 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: CSP

AD7148
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Absolute Maximum Ratings ............................................................ 6
Pin Configuration and Function Descriptions ............................. 7
Typical Performance Characteristics ............................................. 8
Theory of Operation ...................................................................... 10
Capacitance-to-Digital Converter ................................................ 13
Capacitance Sensor Input Configuration .................................... 16
Noncontact Proximity Detection ................................................. 17
REVISION HISTORY
1/10—Rev. 0 to Rev. A
Changes to Figure 4 and Table 6 ..................................................... 7
Changes to BIAS Pin Section ........................................................ 11
Changes to Table 15 ........................................................................ 28
Changes to Figure 45 ...................................................................... 33
Added Exposed Pad Notation to Outline Dimensions ............. 56
12/07—Revision 0: Initial Version
Typical Average Current in Low Power Mode ......................... 4
Maximum Average Current in Low Power Mode .................... 4
I
ESD Caution .................................................................................. 6
Capacitance Sensing Theory ..................................................... 10
BIAS Pin ....................................................................................... 11
Operating Modes ........................................................................ 11
Oversampling the CDC Output ............................................... 13
Capacitance Sensor Offset Control .......................................... 13
Conversion Sequencer ............................................................... 13
CDC Conversion Sequence Time ............................................ 14
CDC Conversion Results ........................................................... 15
CINx Input Multiplexer Setup .................................................. 16
Single-Ended Connections to the CDC .................................. 16
Recalibration ............................................................................... 18
2
C Timing Specifications (AD7148-1) ..................................... 5
Rev. A | Page 2 of 56
Environmental Calibration ........................................................... 22
Adaptive Threshold and Sensitivity ............................................. 24
Interrupt Output ............................................................................. 26
AC
I
PCB Design Guidelines ................................................................. 31
Power-Up Sequence ....................................................................... 32
Typical Application Circuit ........................................................... 33
Register Map ................................................................................... 34
Detailed Register Descriptions ..................................................... 35
Outline Dimensions ....................................................................... 56
2
C-Compatible Serial Interface ................................................... 28
Proximity Sensitivity .................................................................. 20
FF_SKIP_CNT ............................................................................ 20
Capacitance Sensor Behavior Without Calibration ............... 22
Capacitance Sensor Behavior with Calibration ...................... 22
SLOW FIFO ................................................................................ 23
SLOW_FILTER_UPDATE_LVL .............................................. 23
CDC Conversion-Complete Interrupt .................................... 26
Sensor Touch Interrupt.............................................................. 26
V
Capacitive Sensor Board Mechanical Specifications ............. 31
Chip Scale Packages ................................................................... 31
Bank 1 Registers ......................................................................... 35
Bank 2 Registers ......................................................................... 43
Bank 3 Registers ......................................................................... 48
Ordering Guide .......................................................................... 56
SHIELD
DRIVE
Output .............................................................................. 27
Input ................................................................................. 30