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PDF MAS6512 Data sheet ( Hoja de datos )
| Número de pieza | MAS6512 | |
| Descripción | Capacitive Sensor Signal Interface IC | |
| Fabricantes | Micro Analog systems | |
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This is preliminary information on a new
product under development. Micro Analog
Systems Oy reserves the right to make any
changes without notice.
DA6512.000
11 July, 2012
MAS6512
Capacitive Sensor Signal Interface IC
• Single or Dual Capacitance Sensors
• Low Voltage Operation
• Low Power Consumption
• On Chip Temperature Sensor
• Internal Clock Oscillator
• 16-Bit Ratiometric ∆Σ CDC
• EEPROM Calibration Memory
• Serial Interface
DESCRIPTION
MAS6512 capacitive sensor signal Interface IC can
interface both single and dual capacitance sensors.
It uses a 16-bit Capacitance-to-Digital
Converter (CDC), which employs a delta-sigma
(∆Σ) conversion technique. The output data from
the ∆Σ-modulator is processed by an on-chip
decimator filter, producing a high resolution
conversion result. The converter is run by an
internal clock oscillator making an external
converter clock unnecessary.
The converter input range is programmable
to meet various sensor offset and changing
capacitance values. Maximum sensor capacitance
is 40pF but higher maximum value can be reached
by using slower conversion speed or scaling the
signal by using an external series capacitor.
The measurement resolution depends on
the programmed capacitance range and over
sampling ratio (OSR) selections.
MAS6512 supports two capacitance
measurement modes. The output can be
proportional either to capacitance difference (CS-CR)
or to capacitance ratio (CS-CR)/CS.
The IC is designed especially to meet the
requirement for low power consumption, thus
making it an ideal choice for battery powered
systems. Current consumption values of 28 µA with
high resolution or 1.9 µA with low resolution, at a
conversion rate of one conversion per second, can
be achieved.
In addition to measuring capacitance the
device has an internal temperature sensor for
temperature measurement and temperature
compensation purposes. The 256-bit EEPROM
memory stores trimming and calibration coefficients
on chip.
A serial interface, compatible with a bi-
directional 2-wire I2C bus and 4-wire SPI bus, is
used for conversion setup, starting a conversion
and reading the conversion result.
FEATURES
APPLICATIONS
• Single and Differential Capacitive Sensors
• Sensor Offset and Gain Adjustment
• Changing Capacitance Range 2pF…30pF
• Internal Offset Capacitance Matrix 0pF…22pF
• External Capacitance up to 40pF (or higher
using external clock)
• Resolution 14 bit (OSR=4096, ∆C=20pF)
• Internal Clock Oscillator
• On Chip Temperature Sensor -40°C...+85°C
• Low Voltage Operation 1.8 V…3.6 V
• Low Supply Current: 1.9 µA...28 µA
• Conversion Time 5.8ms...82.6ms (12Hz...173Hz)
• 16-bit Ratiometric ∆Σ CDC
• Internal 256-bit EEPROM Calibration Memory
• I2C and SPI Compatible Serial Interface
• QFN-16 Package
• Capacitive Pressure Sensors
• Humidity Sensors
• Medical Devices
• Flow Meters
• Sport Watches
• Altimeter and Barometer Systems
• Mobile and Battery Powered Systems
• Low Frequency Measurement applications
• Current/Power Consumption Critical Systems
• Industrial and Process Control applications in
noisy environments
I2C is a registered trademark of NXP.
1 (26)
1 page  
DA6512.000
11 July, 2012
ELECTRICAL CHARACTERISTICS
Parameter
Operating Conditions: VDD = 2.7 V, TA = -40°C to +85°C, typical values at TA = +27°C, unless otherwise specified.
Symbol
Conditions
Min Typ Max Unit
EEPROM size
256 bit
EEPROM data retention
Output data word length
TA = +85 °C
TA = +125 °C
10 24
1
16
years
bit
Linear output code
range
(10%...90% of full
output code range)
Full output code range
CODEDIFF
CODERATIO
CODEDIFF
CODERATIO
Difference mode
Cs_min=8pF,
Cs_max=12pF, Cr=10pF,
gain setting 6Dhex
OSR=256
OSR=512
OSR=1024
OSR=2048
OSR=4096
Ratio mode
Cs_min=8pF,
Cs_max=12pF,
Cr=7.68pF,
gain setting 4Dhex
OSR=256
OSR=512
OSR=1024
OSR=2048
OSR=4096
OSR=256
OSR=512
OSR=1024
OSR=2048
OSR=4096
OSR=256
OSR=512
OSR=1024
OSR=2048
OSR=4096
89
71
5721
5727
5731
102
769
5944
5839
5786
0
0
0
0
0
0
0
0
0
0
799
6422
51494
51552
51580
790
6389
51362
51486
51547
892
7152
57280
57312
57328
888
7136
57216
57280
57312
Digital inputs
Parameter
Input High Voltage
Input Low Voltage
Serial Bus Clock
Frequency
Digital outputs
PARAMETER
Output high voltage
Output low voltage
Signal rise time
Signal fall time
Symbol
VIH
VIL
fSCL_SCLK
Conditions
VDD = 1.8…3.6V
VDD = 1.8…3.6V
Min
80%
VDD
0%
VDD
Typ Max
100%
VDD
20%
VDD
400
Unit
V
V
kHz
SYMBOL
VOH
VOL
tr
tf
CONDITIONS
ISource=0.6mA
ISink=0.6mA
MIN
80%
VDD
0%
VDD
TYP
200
200
MAX
100%
VDD
20%
VDD
UNIT
V
V
ns
ns
5 (26)
5 Page 
DA6512.000
11 July, 2012
CS AND CR CAPACITOR MATRIX REGISTERS (E3/63HEX AND E4/64HEX)
There are two internal capacitor matrices that add
capacitance in parallel to the sensor capacitor (CS)
and the reference capacitor (CR). These offset
capacitances are used to adjust the sensor signal to
an optimal range. Each capacitor matrix has a
selectable capacitance from 0pF up to 22pF in
typical 86fF steps. The three sigma process
variation of the capacitor matrix capacitance is
±10%.The CS capacitor matrix register (E3/63HEX)
has a corresponding EEPROM byte (C3/43HEX) for
storing the trim value. Also the CR capacitor matrix
register (E4/64HEX) has corresponding EEPROM
byte (C4/44HEX) for storing the trim value. After
finding suitable CS and CR capacitor matrix register
values the trim values can be stored in the non-
volatile EEPROM.
In normal operating mode these trim values are
automatically read from the EEPROM during each
conversion start. See also table 9 Trimming control
Register (EE/6EHEX) for other operating modes.
Table 4. CS capacitor matrix register (E3/63HEX), EEPROM (C3/43HEX)
Bit Number
Bit Name
Description
Value
7-0
OCDACS
CDAC control bits
0HEX…FFHEX
Function
CS offset trimming
Table5. CR capacitor matrix register (E4/64HEX), EEPROM (C4/44HEX)
Bit Number
Bit Name
Description
Value
7-0
OCDACR
CDAC control bits
0HEX…FFHEX
Function
CR offset trimming
GAIN REGISTER (E5/65HEX)
The gain register sets the excitation signal level for
the capacitive sensor. The eight bits (GRDAC) can
be programmed to values between 0 and 255.
Together with the CS and the CR capacitor matrix
trim parameters it’s used to adjust the sensor signal
to an optimal range. The goal is to get a maximum
dynamic range and keep the signal within linear
input range of the ∆Σ-modulator. This condition is
met when the signal minimum and maximum
covers the whole linear input range.
The output of MAS6512 has the following
relationship to the ∆Σ-modulator output:
CODEOUT = QAVE ⋅ CODERANGE
QAVE is the average measurement result (from the
over sampling) of the ∆Σ-modulator and varies from
0 to 1. The CODERANGE is the maximum output code
which depends on OSR and measurement mode
selections. See page 5 Full output code range
specification in the Electrical characteristics table.
The linear signal range of the modulator is from
QAVE=10% to QAVE =90%.
In case of capacitance difference measurement
mode;
QAVE
=
1
2
+
CS − CR
CREF
∗
VS
2 ∗VR
In this mode the gain register value GRDAC sets
the VS level.
VS= (VDD/1.8V)*(33mV+GRDAC*2.88mV)
VR = (VDD/1.8V)*144mV
CS = External sensor + CS matrix capacitance
CR = External reference + CR capacitance
CREF = 6pF, three sigma variation ±10%
In case of capacitance ratio measurement mode;
QAVE
=
1 −
CR
CS
∗
VR
VS
In this mode the gain register value GRDAC sets
the VS level.
VS = (VDD/1.8V)*GRDAC*0.52mV
VR= (VDD/1.8V)*100.8mV
CS = External sensor + CS matrix capacitance
CR = External reference + CR capacitance
The gain register (E5/65HEX) has a corresponding
EEPROM byte (C5/45HEX). After finding a suitable
gain register value it can be stored in the EEPROM
memory. In normal operating mode the gain trim
value is read automatically from the EEPROM
during each conversion start.
Table 6. Gain register (E5/65HEX), EEPROM (C5/45HEX)
Bit Number Bit Name
Description
Value
7-0 GRDAC RDAC control bits 0HEX…FFHEX
Function
Gain control by sensor excitation signal
level control
11 (26)
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet MAS6512.PDF ] | |
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