AD7156 Analog Devices, AD7156 Datasheet
AD7156
Specifications of AD7156
Available stocks
Related parts for AD7156
AD7156 Summary of contents
Page 1
... The AD7156 operates with a 1 3.6 V power supply specified over the temperature range of −40°C to +85°C. FUNCTIONAL BLOCK DIAGRAM ...
Page 2
... Configuration Register .............................................................. 20 Power-Down Timer Register .................................................... 21 CAPDAC Registers .................................................................... 21 Serial Number Register .............................................................. 21 Chip ID Register ......................................................................... 21 Serial Interface ................................................................................ 22 Read Operation........................................................................... 22 Write Operation.......................................................................... 22 AD7156 Reset ............................................................................. 23 General Call ................................................................................ 23 Hardware Design Considerations ................................................ 24 Overview ..................................................................................... 24 Parasitic Capacitance to Ground .............................................. 24 Parasitic Resistance to Ground ................................................. 24 Parasitic Parallel Resistance ...................................................... 24 Parasitic Serial Resistance ......................................................... 25 Input Overvoltage Protection ................................................... 25 Input EMC Protection ...
Page 3
... 1000 0.4 V – 0 ±0.1 ±5 6 0.4 0.1 5 Rev Page AD7156 1 Unit Test Conditions/Comments input range input range input range pF 0.5 pF input range input range input range input range fF 0.5 pF input range ...
Page 4
... AD7156 Parameter POWER REQUIREMENTS V -to-GND Voltage Current DD I Current Power-Down Mode −12 −15 Capacitance units × The CAPDAC can be used to shift (offset) the input range. The total capacitance of the sensor can therefore the sum of the CAPDAC value and the conversion input range ...
Page 5
... Rev Page Unit Test Conditions/Comments ms Both channels per channel See Figure 2. kHz μs μs μs μs μs After this period, the first clock is generated. μs Relevant for repeated start condition. μs μs ns μs t HD;STA t t SU;STA SU;STO P AD7156 ...
Page 6
... AD7156 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter Positive Supply Voltage V to GND DD Voltage on Any Input or Output to GND ESD Rating ESD Association Human Body Model, S5.1 Field-Inducted Charged Device Model Operating Temperature Range Storage Temperature Range Maximum Junction Temperature LFCSP Package θ ...
Page 7
... OUT1 4 7 EXC2 EXC1 5 6 NOTES 1. THE EXPOSED PAD MUST BE CONNECTED TO GND OR IT MUST BE ISOLATED (FLOATING). Figure 3. Pin Configuration down mode, the EXC2 pin is internally connected down mode, the EXC1 pin is internally connected Rev Page AD7156 or power-down mode, or power-down mode, ...
Page 8
... AD7156 TYPICAL PERFORMANCE CHARACTERISTICS 2.0 1.8 1.6 1.4 1.2 1.8V 1.0 0.8 0.6 0.4 0 100 150 CAPACITANCE CIN TO GROUND (pF) Figure 4. Capacitance Input Offset Error vs. Capacitance CIN to GND 1.8 V and 3.3 V, EXC Pin Open Circuit –5 –10 1.8V –15 –20 – 100 150 CAPACITANCE CIN TO GROUND (pF) Figure 5. Capacitance Input Gain Error vs. Capacitance CIN to GND ...
Page 9
... Figure 15. Capacitance Input Gain Error vs. Parallel Resistance, Rev Page 3.3V 1. 100 RESISTANCE EXC TO GROUND (MΩ 1.8 V and 3.3 V, CIN to EXC = 3.3V 1. SERIAL RESISTANCE (kΩ 1.8 V and 3.3 V, CIN to EXC = 1.8V 3.3V 10 100 PARELLEL RESISTANCE (MΩ 1.8 V and 3.3 V, CIN to EXC = AD7156 1k 100 1k ...
Page 10
... AD7156 –1 –2 –3 –4 –5 –50 – TEMPERATURE (°C) Figure 16. Capacitance Input Offset Error vs. Temperature 1.8 V and 3.3 V, CIN and EXC Pins Open Circuit DD 0.35 0.25 0.15 0.05 –0.05 –0.15 –0.25 –0.35 –50 0 TEMPERATURE (°C) Figure 17. Capacitance Input Gain Error vs. Temperature ...
Page 11
... X 0pF TO 4pF EXC CAPDAC The AD7156 CDC core maximum full-scale input range pF. However, the part can accept a higher input capacitance, caused, for example nonchanging offset capacitance pF. This offset capacitance can be compensated for by using the programmable on-chip CAPDAC. ...
Page 12
... The AD7156 logic output (active high) indicates either a positive or a negative change in the input capacitance, in both adaptive and fixed threshold modes (see Figure 25 and Figure 26). ...
Page 13
... Figure 33. Threshold Timeout After a Large Change in CDC Data TIMEOUT APPROACHING INPUT Figure 34. Approaching Timeout in Negative Threshold Mode Shortens False Output Trigger TIMEOUT RECEDING INPUT OUTPUT ACTIVE Figure 35. Positive Timeout in Negative Threshold Mode Shortens Period of Missing Output Trigger AD7156 TIME TIME TIME ...
Page 14
... In power sensitive applications, the AD7156 can be set to automatically enter power-down mode after a programmed period of time in which the outputs have not been activated. The AD7156 can then be returned to a normal operational mode either via the serial interface or by the power supply off/on sequence. ...
Page 15
... Hyst1 ThrSettling1 (4-bit value) (0) (0) (0x0B) 0x08 0x86 ThrSettling2 (4-bit value) Hyst2 (0) (0) (0x0B) EnCh1 EnCh2 MD2 (0) (1) (1) (0) Power-down timeout (6-bit value) (0x00) DacValue1 (6-bit value) (0x00) DacValue2 (6-bit value) (0x00) AD7156 Bit 1 Bit 0 RDY2 RDY1 (1) (1) MD1 MD0 (0) (1) ...
Page 16
... AD7156 STATUS REGISTER Address Pointer 0x00 8 Bits, Read Only Default Value 0x53 Before Conversion, 0x54 After Conversion The status register indicates the status of the part. The register can be read via the 2-wire serial interface to query the status of the outputs, check the CDC finished conversion, and check whether the CAPDAC has been changed by the auto-DAC function. ...
Page 17
... The nominal AD7156 CDC transfer function (an ideal transfer function excluding offset and/or gain error) maps the input capacitance between zero scale and full scale to output data codes between 0x3000 and 0xD000 only (see Table 8) ...
Page 18
... AD7156 AVERAGE REGISTERS Ch 1 Address Pointer 0x05, Address Pointer 0x06 Ch 2 Address Pointer 0x07, Address Pointer 0x08 16 Bits, Read Only Default Value 0x0000 These registers show the average calculated from the previous CDC data. The 12-bit CDC result corresponds to the 12 MSBs of the average register ...
Page 19
... ThrSettlin − TimeConst ) Average ( ) 0 Change (CDC DATA) CHANGE DATA AVERAGE RESPONSE Figure 39. Data Average Response to Data Step Change Rev Page Bit 2 Bit 1 ThrSettling (4-Bit Value) (0x0B) Auto-DAC Step (CAPDAC LSB − (ThrSettling + 1) TIME AD7156 Bit 0 ...
Page 20
... AD7156 CONFIGURATION REGISTER Address Pointer 0x0F 8 Bits, Read/Write, Factory Preset 0x19 Table 12. Configuration Register Bit Map Bit 7 Bit 6 ThrFixed ThrMD1 (0) (0) 1 The default values are given in parentheses. Table 13.Configuration Register Bit Descriptions Bit Mnemonic Description 7 ThrFixed ThrFixed = 1 sets the fixed threshold mode; the outputs reflect the comparison of data and a fixed (constant) value of the threshold registers. ThrFixed = 0 sets the adaptive threshold mode ...
Page 21
... Bit 5 Bit 4 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. Rev Page Bit 2 Bit 1 (0x00) Bit 3 Bit 2 Bit 1 DacValue (6-bit value) (0x00) AD7156 Bit 0 Bit 0 ...
Page 22
... In this case, the AD7156 becomes a slave transmitter. In all instances, the AD7156 acts as a standard slave device on the serial bus. The start byte address for the AD7156 is 0x90 for a write and 0x91 for a read. READ OPERATION When a read is selected in the start byte, the register that is currently addressed by the address pointer is transmitted to the SDA line by the AD7156 ...
Page 23
... The AD7156 acknowledges this address and reads in the following data byte. If the second byte is 0x06, the AD7156 is reset, completely uploading all default values. The AD7156 does not respond to the serial bus commands (do not acknowledge) during the default values upload for approximately 2 ms ...
Page 24
... On the input side, Sensor C can be connected directly between X the AD7156 EXC and CIN pins. The way it is connected and the electrical parameters of the sensor connection, such as parasitic resistance or capacitance, can affect the system performance. Therefore, any circuit with additional components in the capacitive ...
Page 25
... PARASITIC SERIAL RESISTANCE R S1 CIN EXC Figure 45. Parasitic Serial Resistance The AD7156 CDC result is affected by a resistance in series with the measured capacitance. The total serial resistance ( Figure 45) should the order of hundreds of Ω (see Figure 14). INPUT OVERVOLTAGE PROTECTION R ...
Page 26
... EXC2 LED1 GND Figure 49. AD7156 Standalone Operation Application Diagram 0.1µF 1kΩ VDD AD7156 CIN1 SDA SCL CIN2 OUT1 OUT2 GND Figure 50. AD7156 Interfaced to a Host Microcontroller 1kΩ 0.1µF 10µF VDD CIN1 1kΩ 1kΩ AD7156 SDA EXC1 SCL OUT1 CIN2 OUT2 EXC2 GND Figure 51 ...
Page 27
... Figure 52. 10-Lead Lead Frame Chip Scale Package [LFCSP_WD × Body, Very Thin, Dual Lead (CP-10-9) Dimensions shown in millimeters Package Description 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] Evaluation Board Rev Page 0.50 BSC 10 1.74 PAD 1.64 1.49 1 2.48 2.38 2.23 Package Option CP-10-9 CP-10-9 AD7156 Branding C6L C6L ...
Page 28
... AD7156 NOTES Purchase of licensed components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I 2 Rights to use these components system, provided that the system conforms to the I ©2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners ...