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PDF AD7156 Data sheet ( Hoja de datos )
| Número de pieza | AD7156 | |
| Descripción | 2-Channel Capacitance Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AD7156 (archivo pdf) en la parte inferior de esta página. Total 29 Páginas | ||
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Ultralow Power, 1.8 V, 3 mm × 3 mm,
2-Channel Capacitance Converter
AD7156
FEATURES
Ultralow power
Power supply voltage: 1.8 V to 3.6 V
Operation power supply current: 70 μA typical
Power-down current: 2 μA typical
Fast response time
Conversion time: 10 ms per channel
Wake-up time from serial interface: 300 μs
Adaptive environmental compensation
2 capacitance input channels
Sensor capacitance (CSENS): 0 pF up to 13 pF
Sensitivity up to 3 fF
2 modes of operation
Standalone with fixed settings
Interfaced to a microcontroller for user-defined settings
2 detection output flags
2-wire serial interface (I2C-compatible)
Operating temperature: −40°C to +85°C
10-lead LFCSP package (3 mm × 3 mm × 0.8 mm)
APPLICATIONS
Buttons and switches
Proximity sensing
Contactless switching
Position detection
Level detection
Portable products
GENERAL DESCRIPTION
The AD7156 delivers a complete signal processing solution for
capacitive sensors, featuring an ultralow power converter with
fast response time.
The AD7156 uses an Analog Devices, Inc., capacitance-to-
digital converter (CDC) technology, which combines features
important for interfacing to real sensors, such as high input
sensitivity and high tolerance of both input parasitic ground
capacitance and leakage current.
The integrated adaptive threshold algorithm compensates for
any variations in the sensor capacitance due to environmental
factors like humidity and temperature or due to changes in the
dielectric material over time.
By default, the AD7156 operates in standalone mode using the
fixed power-up settings and indicates detection on two digital
outputs. Alternatively, the AD7156 can be interfaced to a micro-
controller via the serial interface, the internal registers can be
programmed with user-defined settings, and the data and status
can be read from the part.
The AD7156 operates with a 1.8 V to 3.6 V power supply. It is
specified over the temperature range of −40°C to +85°C.
CSENS1
CSENS2
CIN1
EXC1
CIN2
EXC2
FUNCTIONAL BLOCK DIAGRAM
VDD
Σ-Δ CDC
MUX AD7156
DIGITAL
FILTER
THRESHOLD
SERIAL
INTERFACE
EXCITATION
THRESHOLD
GND
Figure 1.
SCL
SDA
OUT1
OUT2
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2008 Analog Devices, Inc. All rights reserved.
1 page  
AD7156
Parameter
POWER REQUIREMENTS
VDD-to-GND Voltage
IDD Current4, 8
IDD Current Power-Down Mode4, 8
Min Typ Max Unit1
1.8 3.6
65 75
70 85
2 10
2 17
V
μA
μA
μA
μA
Test Conditions/Comments
VDD ≤ 2.7 V, see Figure 20
VDD = 3.6 V, see Figure 20
VDD ≤ 2.7 V, see Figure 21
VDD = 3.6 V, see Figure 21
1 Capacitance units: 1 pF = 1 × 10−12 F; 1 fF = 10−15 F.
2 The CAPDAC can be used to shift (offset) the input range. The total capacitance of the sensor can therefore be up to the sum of the CAPDAC value and the conversion
input range. With the auto-DAC feature, the CAPDAC is adjusted automatically when the CDC input value is lower than 25% or higher than 75% of the CDC nominal
input range.
3 The maximum capacitance of the sensor connected between the EXCx and CINx pins is equal to the sum of the minimum guaranteed value of the CAPDAC and the
minimum guaranteed input range.
4 The maximum specification is not production tested but is supported by characterization data at initial product release.
5 The resolution of the converter is not limited by the output data format or output data LSB (least significant bit) size, but by the converter and system noise level. The
noise-free resolution is defined as level of peak-to-peak noise coming from the converter itself, with no connection to the CIN and EXC pins.
6 These specifications are understood separately. Any combination of the capacitance to ground and serial resistance may result in additional errors, for example gain
error, gain drift, offset error, offset drift, and power supply rejection.
7 Specification is not production tested but is guaranteed by design.
8 Digital inputs equal to VDD or GND.
Rev. 0 | Page 4 of 28
5 Page 
AD7156
5
4
3
2 3.3V
1
1.8V
0
–1
–2
–3
–4
–5
–50
–25
0 25 50
TEMPERATURE (°C)
75 100
Figure 16. Capacitance Input Offset Error vs. Temperature,
VDD = 1.8 V and 3.3 V, CIN and EXC Pins Open Circuit
0.35
0.25
0.15
0.05
–0.05
–0.15
–0.25
–0.35
–50
0 50
TEMPERATURE (°C)
100
Figure 17. Capacitance Input Gain Error vs. Temperature,
VDD = 2.7 V, CIN to EXC = 4 pF
16.50
16.25
16.00
15.75
15.50
2V 2.7V
1.8V
3.6V
15.25
15.00
14.75
14.50
–50
–25
0 25 50
TEMPERATURE (°C)
75
Figure 18. EXC Frequency Error vs. Temperature,
VDD = 1.8 V, 2 V, 2.7 V, and 3.6 V
100
20
10
0
–10
–20
0
5
10 15 20 25 30
CAPDAC CODE
Figure 19. CAPDAC Differential Nonlinearity (DNL), VDD = 1.8 V
80
70
60
1.8V
50
3.6V
2.7V
2V
40
–50
–25 0 25 50
TEMPERATURE (°C)
Figure 20. Current vs. Temperature,
VDD = 1.8 V, 2 V, 2.7 V, and 3.6 V
75
4.0
3.5
3.0
2.5
2.0
1.5
3.6V
1.0
0.5
0
–50
–25
2.7V
2V
0 25 50
TEMPERATURE (°C)
1.8V
75
Figure 21. Power-Down Current vs. Temperature,
VDD = 1.8 V, 2 V, 2.7 V, and 3.6 V
Rev. 0 | Page 10 of 28
11 Page | ||
| Páginas | Total 29 Páginas | |
| PDF Descargar | [ Datasheet AD7156.PDF ] | |
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