MAS6512 - Micro Analog Systems Oy

DA6512.001
7 November, 2013
MAS6512
Capacitive Sensor Signal Interface IC
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•
•
•
•
Single or Dual Capacitance Sensors
Very Low Power Consumption
1.8V Operation
On Chip Temperature Sensor
VDD Level Monitoring
16-Bit Ratiometric ∆Σ CDC
EEPROM Calibration Memory
SPI or I2C Bus with programmable
I2C device address
DESCRIPTION
MAS6512 capacitive sensor signal Interface IC can
interface both single and dual capacitance sensors.
capacitance difference (CS-CR) or to capacitance
ratio (CS-CR)/CS.
It uses a 16-bit Capacitance-to-Digital Converter
(CDC), which employs a delta-sigma (∆Σ)
conversion technique. The output data from the ∆Σmodulator 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 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 24.1 µA
with high resolution or 3.3 µA with low resolution, at
a conversion rate of one conversion per second,
can be achieved.
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.
In addition to measuring capacitance the device has
an internal temperature sensor for temperature
measurement and temperature compensation
purposes. The VDD level monitoring feature is
useful especially in battery operated systems. The
256-bit EEPROM memory stores trimming and
calibration coefficients on chip.
The measurement resolution depends on the
programmed capacitance range and over sampling
ratio (OSR) selections.
A serial interface, compatible with a bi-directional 2wire I2C bus and 4-wire SPI bus, is used for
conversion setup, starting a conversion and reading
the conversion result.
MAS6512 supports two capacitance measurement
modes. The output can be proportional either to
FEATURES
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•
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•
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•
.
Sensor Offset and Gain Adjustment
• Changing Capacitance Range ∆C 2pF…30pF
• Internal Offset Capacitance Matrix 0pF…22pF
• External Capacitance up to 40pF (or higher
using external clock)
Resolution 16.6 bit
Internal Clock Oscillator
On Chip Temperature Sensor -40°C...+85°C
VDD Level Monitoring
Low Voltage Operation 1.8 V…3.6 V
Low Supply Current: 3.3 µA...24.1 µA
Conversion Time 5.8ms...41.6ms (24Hz...173Hz)
Internal 256-bit EEPROM Calibration Memory
Internal Clock Oscillator
I2C and SPI Compatible Serial Interface
QFN-16 Package
APPLICATIONS
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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
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DA6512.001
7 November, 2013
BLOCK DIAGRAM
VDD
OSC
VDD
MISO
MUX
CS
CLK
OSC
I2C /
SDA/MOSI
SCL/SCLK
SPI
CC
CONTROL
XCS
XSPI
CR
EOC
∆Σ
XCLR
VREG
TEMP
EEPROM
VREG
TEST1
TEST
TEST2
GND
GND
Figure 1. MAS6512 block diagram
FUNCTIONAL DESCRIPTION
MAS6512 can interface both single and dual
capacitance sensors. Single capacitance sensors
should be connected between the CS and the CC
inputs. The second capacitor of a dual capacitance
sensor should be connected between the CR and
the CC inputs.
A Capacitance-to-Digital Converter (CDC) converts
the input capacitances into a 16-bit output word
(code). The converter front-end can be configured
either for capacitance difference (CS-CR) or
capacitance ratio (CS-CR)/CS measurement mode.
The ratio mode offers pre-linearization for sensor
signals CS(x) being proportional to ~1/x such as
pressure sensor signals (x=pressure).
Converter resolution is selected by the over
sampling ratio (OSR) setting. Higher OSR
corresponds to higher resolution but also longer
conversion time.
There are two internal 22pF capacitance matrices
connected to the CS and the CR inputs. These
matrices are used for sensor offset calibration and
are programmable in 8-bit steps (86fF/step).
The gain is programmable with 8-bits resolution and
sets the input range for sensor changing
capacitance ∆C=CS MAX-CS_MIN.
MAS6512 includes an internal temperature sensor
for temperature compensation purposes. A
multiplexer in the front-end is used to select the
external capacitive sensor, the internal temperature
sensor or an internal band gap reference voltage in
the VDD level monitoring mode.
.
Trim and calibration coefficients can be stored in
the 256-bit EEPROM memory. In normal mode the
stored trim values for the oscillator frequency, offset
capacitance and gain are automatically read from
the EEPROM memory in the beginning of each
conversion. However by using Trimming control
Register it is also possible to choose taking
trimming values from the trimming registers instead
of EEPROM.
To avoid modification of the EEPROM by mistake
there is an EEPROM write enable bit in the
EEPROM Control Register which needs to be set
high (1) before any changes can be done to the
EEPROM.
MAS6512 has an internal clock oscillator making an
external clock unnecessary. To save power it’s
turned on only when a conversion is running. The
frequency is factory trimmed to 200 kHz using a 6bit register. An external clock, connected to the
OSC pin, can however be used when a specific test
mode is chosen. This may be necessary when
measuring larger capacitances which require a
slower clock frequency.
In temperature measurement mode it is necessary
to always use a regulated supply voltage. This is
achieved by enabling an internal 1.8V voltage
regulator. When enabled the internal regulator is
automatically turned on during conversion and off
when conversion has been finished. Note that the
internal regulator should be enabled only in the
temperature measurement mode but kept disabled
during capacitance and VDD monitoring modes.
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FUNCTIONAL DESCRIPTION
In battery operated applications the VDD of the
MAS6512 can vary along with battery capacity. In
such case the VDD level monitoring feature can be
useful to indicate battery level, help choosing
between different power modes in the system or
even using measured VDD level for compensating
VDD dependencies. In the VDD level monitoring
mode the on-chip regulator has to be disabled.
Communication with MAS6512 is handled by the
serial interface compatible with either a bidirectional 2-wire I2C bus or a 4-wire SPI bus. The
XSPI pin is for selecting which bus type is used.
Note: The 2-wire I2C bus of MAS6512 supports only
basic I2C bus communication protocol but not for
example 10-bit addressing, arbitration and clock
stretching features of the I2C bus specification.
The XCLR pin can be used to hard reset the device
including the serial communication. However device
reset is possible also via serial bus using the reset
register. Despite of on chip power on reset (POR)
circuit it is recommended to reset the device
manually after every power up to guarantee proper
register settings after any VDD rise conditions.
The EOC pin indicates if a conversion has finished
and the result is ready to be read from the memory
via the serial interface. Using the EOC signal is not
necessary since it is alternatively possible to wait at
least maximum conversion time period before
reading out the result.
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ABSOLUTE MAXIMUM RATINGS
All Voltages with Respect to Ground
Parameter
Symbol
Supply Voltage
Voltage Range for All Pins
Latchup Current Limit
VDD
Junction Temperature
Storage Temperature
TJmax
TS
ILUT
Conditions
For all pins, test according to
JESD78A.
Note 1
Min
Max
Unit
-0.3
-0.3
-100
5.0
VDD + 0.3
+100
V
V
mA
- 55
+ 150
+125
°C
°C
Note 1: See EEPROM memory data retention at hot temperature. Storage or bake at hot temperatures will reduce the wafer level trimming
and calibration data retention time.
Note: The absolute maximum rating values are stress ratings only. Functional operation of the device at conditions between maximum
operating conditions and absolute maximum ratings is not implied and EEPROM contents may be corrupted. Exposure to these conditions
for extended periods may affect device reliability (e.g. hot carrier degradation, oxide breakdown). Applying conditions above absolute
maximum ratings may be destructive to the devices.
Note: This is a CMOS device and therefore it should be handled carefully to avoid any damage by static voltages (ESD).
RECOMMENDED OPERATION CONDITIONS
Parameter
Symbol
Supply Voltage
Operating Temperature
Conditions
VDD
TA
Min
Typ
Max
Unit
1.8
-40
2.7
+25
3.6
+85
V
°C
ELECTRICAL CHARACTERISTICS
Operating Conditions: VDD = 2.7 V, TA = -40°C to +85°C, typical values at TA = +27°C, unless otherwise specified.
Parameter
Internal regulator voltage
Standby current
Symbol
Conditions
Min
Typ
Max
Unit
VREG
Temp mode regulator enabled
Note 1.
All inputs at VDD, no load.
Note 2.
During conversion
Cap. Dif. Reg OFF
Cap. Ratio Reg OFF
Temp Reg ON
VDD Mon. Reg OFF
1 conversion/s
Cap. Dif. Reg OFF
OSR=2048
OSR=1024
OSR=512
OSR=256
Note 3.
Note 4.
1.75
1.8
1.85
V
0.01
0.1
µA
ISTBY
Conversion current
consumption
IDD_CONV
Average current
consumption
IDD_AVG
VDD rise time for proper
power on reset (POR)
tVDD_RISE
580
510
455
455
µA
24.1
12.2
6.3
3.3
µA
1
ms
Note 1. Internal regulator need to be enabled only in temperature mode and should be disabled in capacitance and VDD monitoring modes.
Note 2. Leakage current may increase if digital input voltages are not close to VDD (logic level high) or GND (logic level low). Also setting
XCS low activates the EEPROM memory regardless of the XSPI setting and the device consumes 20µA …30µA current. To minimize
current consumption XCS should be set low only during time periods when the device is used during SPI communication.
Note 3. Average current consumption in other measurement modes can be calculated by scaling these current consumption values with
corresponding conversion current ratios. Example: IDD_AVG(Temp Reg ON, OSR=256)=3.3µA*(455µA /580µA)=2.6µA.
Note 4. Resetting the device using the XCLR pin or reset register is necessary in case the VDD rise time is longer than specified here.
However it is recommended to reset the device manually either by XCLR pin or using reset register after every power up (VDD rise).
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ELECTRICAL CHARACTERISTICS
Operating Conditions: VDD = 2.7 V, TA = -40°C to +85°C, typical values at TA = +27°C, unless otherwise specified.
Parameter
Conversion time
Symbol
Conditions
tCONV
Normal clock (SOSC=00)
OSR=2048
OSR=1024
OSR=512
OSR=256
Normal clock (SOSC=00)
Division by 2 (SOSC=01)
Division by 4 (SOSC=10)
Division by 8 (SOSC=11)
Note 1.
Normal clock (SOSC=00)
Division by 2 (SOSC=01)
Division by 4 (SOSC=10)
Division by 8 (SOSC=11)
Internal system clock
oscillator frequency
fSYS_CLK
Sensor excitation
frequency
MCLK
Min
Typ
Max
41.6
21.1
10.9
5.8
200
100
50
25
ms
kHz
50
25
12.5
6.25
kHz
Internal offset capacitor
matrix selection
Changing capacitance
range in capacitance
difference mode
CR_OS, CS_OS
COS_STEP
∆CDIFF
Maximum allowed
sensor capacitance in
capacitance difference
mode
CS_MAX
Changing capacitance
range in capacitance
ratio mode
Maximum allowed
sensor capacitance in
capacitance ratio mode
Internal temperature
sensor
∆CRATIO
Normal clock (SOSC=00)
Division by 2 (SOSC=01)
Division by 4 (SOSC=10)
Division by 8 (SOSC=11)
Normal clock (SOSC=00)
Division by 2 (SOSC=01)
Division by 4 (SOSC=10)
Division by 8 (SOSC=11)
Note 2.
Note 3.
CS_MAX
Note 3.
Linearity
Note 4.
±0.4
°C
Gain
OSR=2048
OSR=1024
OSR=512
OSR=256
Non-calibrated, note 4.
65038
65002
8116
1012
LSB/
°C
-4.5
+3.5
%
Non-calibrated, note 4.
-12
+17
°C
Offset
RMS temperature
resolution
0
Unit
22
pF
20
30
TBD
TBD
20
40
80
160
pF
0.086
Temp mode,
TEMPREGEN=1,
OSR=512
OSR=256
2
2
2
2
2
pF
20
pF
20
>20
pF
°C
0.03
0.08
TBD = To Be Defined
Note 1. The clock oscillator is factory calibrated. Calibration stored in the Oscillator frequency trim data EEPROM address (C6/46HEX).
Note 2. In capacitance difference mode the maximum allowed sensor and reference capacitor values can be extended using lower external
oscillator frequency than which is available by SOSC division options; CS_MAX=20pF*200kHz/f OSC_EXT.
Note 3. In capacitance ratio mode also larger capacitances are possible depending on sensor characteristics. Please contact Micro Analog
Systems to check sensor suitability.
Note 4. Guaranteed by design. By first order calibration of offset and gain errors an overall temperature accuracy close to the linearity
accuracy can be achieved. Further accuracy can be achieved by second order calibration to reduce non-linearity errors. Minimum and
maximum values of temperature sensor gain and offset are guaranteed by design.
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ELECTRICAL CHARACTERISTICS
Operating Conditions: VDD = 2.7 V, TA = -40°C to +85°C, typical values at TA = +27°C, unless otherwise specified.
Parameter
RMS voltage
resolution
RMS capacitance
resolution @
∆CLIN=1.8pF
RMS capacitance
resolution @
∆CLIN=4pF
RMS capacitance
resolution @
∆CLIN=20pF
RMS capacitance
resolution @
∆CLIN=1.8pF
RMS capacitance
resolution@
∆CLIN=4pF
RMS capacitance
resolution @
∆CLIN=20pF
Symbol
Conditions
Min
VDD level monitoring
TEMPREGEN=0. Note 1.
OSR=2048
OSR=1024
OSR=512
OSR=256
Difference mode. Note 2.
TEMPREGEN=0, ∆CLIN=1.8pF
OSR=2048
OSR=1024
OSR=512
OSR=256
Difference mode. Note 2.
TEMPREGEN=0, ∆CLIN=4pF
OSR=2048
OSR=1024
OSR=512
OSR=256
Difference mode. Note 2.
TEMPREGEN=0, ∆CLIN=20pF
OSR=2048
OSR=1024
OSR=512
OSR=256
Ratio mode. Note 2.
TEMPREGEN=0, ∆CLIN=1.8pF
OSR=2048
OSR=1024
OSR=512
OSR=256
Ratio mode. Note 2.
TEMPREGEN=0, ∆CLIN=4pF
OSR=2048
OSR=1024
OSR=512
OSR=256
Ratio mode. Note 2.
TEMPREGEN=0, ∆CLIN=20pF
OSR=2048
OSR=1024
OSR=512
OSR=256
EEPROM size
EEPROM data
retention
TA = +85 °C
TA = +125 °C
10
Typ
Max
Unit
72
77
82
99
µVRMS
16.6 (22)
16.3 (27)
14.5 (99)
11.6 (733)
bit (aF)
16.6 (49)
16.1 (73)
14.5 (222)
11.6 (1631)
bit (aF)
16.1 (360)
15.8 (436)
14.4 (1149)
11.6 (8190)
bit (aF)
14.0 (133)
13.5 (196)
12.9 (291)
11.4 (817)
bit (aF)
14.7 (195)
14.4 (228)
13.8 (359)
11.5 (1699)
bit (aF)
15.7 (485)
15.5 (528)
14.3 (1215)
11.6 (8189)
256
bit (aF)
24
1
years
bit
Note 1. In case of noisy power supply the VDD level monitoring resolution can be further limited by supply noise.
Note 2. Resolution in bits is calculated as follows: CN_BIT=log(∆CFS/CN)/log(2)= log(CODEFS/CODEN)/log(2) where ∆CFS and CODEFS are
full scale changing capacitance (∆CFS=∆CLIN /0.8) and code range respectively, CN and CODEN are RMS noise in capacitance and code
respectively. Note also that when calculating resolution in bits by ratio of full scale signal range and RMS noise the result can exceed the
number of bits in the ADC. In contrast when using peak to peak signal range and noise values for bit resolution calculation the maximum
possible value is the same as number of bits in the ADC.
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ELECTRICAL CHARACTERISTICS
Operating Conditions: VDD = 2.7 V, TA = -40°C to +85°C, typical values at TA = +27°C, unless otherwise specified.
Parameter
Symbol
Conditions
Min
Typ
Max
Linear output
code range
values
(10%...90% of
full scale output
code range)
Full scale output
code range
values
CODELIN
OSR=2048
OSR=1024
OSR=512
OSR=256
5728
5722
714
89
51552
51494
6422
799
CODEFS
0
0
0
0
57280
57216
7136
888
VDD sensitivity
of capacitance
measurement
VDDSENSCAP
VDD sensitivity
of temperature
measurement
VDDSENSTEMP
OSR=2048
OSR=1024
OSR=512
OSR=256
Difference mode, ∆CLIN=4pF,
TEMPREGEN=0,
VDD=1.8V ⇒ 3.6V
Note 1.
TEMPREGEN=1,
VDD=1.9V ⇒ 3.6V
Note 1.
Unit
+0.03
%FS/V
-0.04
%FS/V
Note 1. VDD sensitivity in %FS/V calculated as follows: VDDSENS =100%*(CODE(VDD=3.6V) –CODE(VDD=1.9V))/CODEFS/(3.6V-1.9V)
Digital inputs
TA = -40oC to +85oC, VDD = 1.8V to 3.6V, Typ TA = 27oC, Typ VDD = 2.7 V, RP = 4.7kΩ (I2C bus pull up) unless otherwise noted
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Input High Voltage
VIH
80% VDD
100% VDD
V
Input Low Voltage
VIL
0% VDD
20% VDD
V
Serial Bus Clock
Frequency
XCLR Reset Pulse
Length
Wait time after reset
fSCL
400
2
XCLR Pin Pull Up
Current
tXCLR
I2C bus
SPI bus
XCLR low pulse
200
kHz
MHz
ns
tRESET_WAIT
Note 1.
20
µs
IPULL_UP
XCLR=0V
-8
µA
Note 1. This is the necessary wait time after reset to allow MAS6512 reading the programmable I2C device address from the EEPROM
Digital outputs
TA = -40oC to +85oC, VDD = 1.8V to 3.6V, Typ TA = 27oC, Typ VDD = 2.7 V, RP = 4.7kΩ (I2C bus pull up) unless otherwise noted
PARAMETER
SYMBOL
CONDITIONS
Output high voltage
Output low voltage
VOH
VOL
ISource=0.6mA
ISink=0.6mA
Signal rise time
(from 10% to 90%)
Signal fall time
(from 90% to 10%)
tr
EOC pin, CL=50pF
SDA pin, CB=50pF
EOC pin, CL=50pF
SDA pin, CB=50pF
tf
MIN
TYP
80% VDD
0% VDD
14
550
11
11
MAX
UNIT
100% VDD
20% VDD
V
V
ns
ns
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OPERATING MODES
MAS6512 has two capacitance measurement
modes, a temperature measurement mode and a
VDD level monitoring mode. In capacitance
measurement mode the output is proportional to
either capacitance difference (CS-CR) or to
capacitance ratio (CS-CR)/CS. In temperature
measurement mode the output is proportional to the
absolute temperature. The VDD level monitoring
mode allows measuring supply voltage which can
be useful especially in battery operated systems.
Measurement mode configuration and start of
conversion is done by writing 8-bit configuration
data to the Measurement control register (address
E2HEX). See further details in the Measurement
control register chapter.
MAS6512 includes a 256-bit EEPROM memory for
storing trim and calibration data on chip. Five bytes
(40 bits) of EEPROM are reserved for trim values
and programmable I2C device address but the
remaining 27 bytes (216 bits) are free for storing
sensor calibration and other data.
The stored trim data consists of capacitive front-end
offset and gain setting data that are automatically
read from EEPROM memory in the beginning of
each conversion (in normal operating mode). The
programmable I2C device address is read from
EEPROM memory only during power on reset or by
manual reset using XCLR or the reset register.
The stored calibration data should comprise of
calibration
and
temperature
compensation
coefficients that can be used to calculate accurate
sensor and temperature measurement results from
the non-calibrated measurement readings. All
calculations need to be done in an external micro
controller unit (MCU) which controls the MAS6512.
A calibrated MAS6512 sensor system should be
operated as illustrated in figure 2. Connecting VDD
triggers power-on-reset (POR) but to make sure the
device is reset an additional reset should be given
using the XCLR pin or writing any data on the reset
register E0/60HEX via the serial bus.
The calibration and compensation coefficients are
necessary to be read to the MCU memory only
once. From each pair of sensor and temperature
measurement readings and using the calibration
coefficients the accurate sensor and temperature
values can then be calculated in the external MCU.
All communication with MAS6512 is done using
either the I2C bus or the SPI bus. Starting an A/D
conversion, reading the conversion result and
reading and writing data from and to the EEPROM
memory are all accomplished via serial bus
communication.
In addition to the serial buses the digital interface
includes also end-of-conversion (EOC) and master
reset (XCLR) pins. See A/D Conversion in the Serial
Data Interface (I2C Bus) Control chapter.
POWER UP / RESET
Reset device by XCLR or
by writing any data to the reset register E0/60HEX
READ EEPROM
CALIBRATION DATA
MEASURE SENSOR
MEASURE TEMPERATURE
CALCULATE CALIBRATED
TEMPERATURE
CALCULATE TEMPERATURE
COMPENSATED SENSOR VALUE
Figure 2. Flow chart for a calibrated MAS6512 sensor system
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REGISTER AND EEPROM DATA ADDRESSES
Table 1. Register and EEPROM data addresses
A7
A6
A5
A4
A3
A2
A1
A0
I2C
BUS
HEX
SPI BUS
HEX
W=write
R=read
W: 40…41
R: C0…C1
W: 42
R: C2
W: 43
R: C3
W: 44
R: C4
W: 45
R: C5
W: 46
R: C6
W: 47
R: C7
W: 48…4F
R: C8…CF
W: 50…5F
R: D0…DF
W: 60
R: E0
W: 61
R: E1
W: 62
R: E2
W: 63
R: E3
W: 64
R: E4
W: 65
R: E5
W: 66
R: E6
W: 68
R: E8
W: 69
R: E9
W: 6A
R: EA
W: 6B
R: EB
W: 6C
R: EC
W: 6D
R: ED
A7
1
0
0
0
0
0
X
C0…C1
A7
1
0
0
0
0
1
0
C2
A7
1
0
0
0
0
1
1
C3
A7
1
0
0
0
1
0
0
C4
A7
1
0
0
0
1
0
1
C5
A7
1
0
0
0
1
1
0
C6
A7
1
0
0
0
1
1
1
C7
A7
1
0
0
1
X
X
X
C8…CF
A7
1
0
1
X
X
X
X
D0…DF
A7
1
1
0
0
0
0
0
E0
A7
1
1
0
0
0
0
1
E1
A7
1
1
0
0
0
1
0
E2
A7
1
1
0
0
0
1
1
E3
A7
1
1
0
0
1
0
0
E4
A7
1
1
0
0
1
0
1
E5
A7
1
1
0
0
1
1
0
E6
A7
1
1
0
1
0
0
0
E8
A7
1
1
0
1
0
0
1
E9
A7
1
1
0
1
0
1
0
EA
A7
1
1
0
1
0
1
1
EB
A7
1
1
0
1
1
0
0
EC
A7
1
1
0
1
1
0
1
ED
Description
EEPROM; free for any
data
Programmable I2C
Device Address
EEPROM; CS capacitor
matrix trim data
EEPROM; CR capacitor
matrix trim data
EEPROM; Gain trim
data
EEPROM; Oscillator
frequency trim data
EEPROM; free for any
data
EEPROM; free for any
data
EEPROM; free for any
data
Reset register; no data,
only addressed for reset
Test register
Measurement control
register
CS capacitor matrix
register
CR capacitor matrix
register
Gain register
Oscillator frequency
control register
EEPROM data input
register
EEPROM write enable
register
1st (MSB) byte of the
conversion result
2nd (LSB) byte of the
conversion result
Status register for
EEPROM
Trimming control
register
Note
E
E
E+T
E+T
E+T
E+T
E
E
E
R
R
R
R+T
R+T
R+T
R+T
R
R
R
R
R
R
X = Don’t care, E = EEPROM, R= Register, T = Trim data
Note: When using the SPI serial interface the register address bit A7 is also used for selecting write (A7= 0) or read (A7=1) operation. For
the I2C interface address bit A7 = 1.
Note: The programmable I2C device address register C2HEX has been factory programmed to value EC HEX (%11101100) which is the
same as the hard wired device address of MAS6512. When unique device address is needed it can be programmed to this register.
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REGISTER AND EEPROM DATA ADDRESSES
MAS6512 includes a 32 bytes (256 bits) EEPROM
data memory and thirteen registers. Five bytes (40
bits) of EEPROM are reserved for trim values and
programmable I2C device address but the
remaining 27 bytes (216 bits) are free for storing
sensor calibration and other data. See table 1 on
the previous page for register and EEPROM data
addresses.
The Measurement control register (E2/62HEX) is
used for configuring and starting an A/D conversion.
In the SPI serial bus the address bit A7 selects
between write (A7=0) and read (A7=1) operation. In
the I2C serial bus A7 is always high (A7=1) and
selection between write and read operation is done
with the LSB bit of the I2C device address. See
table 11 in chapter SERIAL DATA INTERFACE
CONTROL. The MAS6512 has both hard wired and
programmable I2C device addresses. The
programmable
device
address
is
factory
programmed to value EC HEX (%11101100) which is
the same as the hard wired device address of
MAS6512. When unique device address is needed
it can be programmed to the Programmable I2C
Device Address register (C2HEX). The MAS6512 will
respond to both hard wired and programmed I2C
device addresses.
The Gain register (E5/65HEX) controls the gain of the
CDC front-end. Together with the CS and CR
values the gain determines the input capacitance
conversion range.
MAS6512 has four trim registers: CS capacitor
matrix register (E3/63HEX), CR capacitor matrix
register (E4/64HEX), Gain register (E5/65HEX) and
Oscillator frequency register (E6/66HEX). These are
marked with “R+T” in table 1. Each of these
registers has a corresponding EEPROM byte where
trim values can be permanently stored. These are
marked with “E+T” in table 1. Trim values are
automatically read from EEPROM in the beginning
of each conversion when this feature is enabled in
the trimming control register (ED/6DHEX). When
disabled it is possible to test different trim data in
the trim registers before final trimming values are
found and stored in the EEPROM.
Reset register (E0/60HEX) does not contain any data.
Any dummy data written to this register forces a
reset. A reset initializes all control registers
(addresses E1HEX…EEHEX) to a zero value.
Test register (E1/61HEX) is mainly used for testing
and trimming purposes. See table 2 in chapter
TEST REGISTER. If an external clock signal is
used the test register is needed for selecting the
external clock signal.
The CS (E3/63HEX) and the CR (E4/64HEX) capacitor
matrix registers select internal capacitors which are
connected from the CS and the CR pins
respectively to the CC pin. Both capacitor values
can be chosen independently between 0pF and
22pF in 86fF steps.
The Oscillator frequency control register (E6/66HEX)
is used only during internal clock oscillator trimming.
During trimming there is searched register value
which gives closest to the nominal 200 kHz
oscillator frequency. However the internal clock
oscillator frequency is trimmed by MAS during wafer
level testing and the trimming value is stored into
the Oscillator frequency trim data EEPROM
address (C6/46HEX). Thus there is no need to adjust
the factory stored clock oscillator trimming value. In
normal operation the trim value is automatically
read from the EEPROM memory in the beginning of
each conversion.
EEPROM write enable register (E9/69HEX) is used
for enabling EEPROM write since by default the
EEPROM is write protected.
The 16-bit A/D conversion result (capacitance,
temperature or monitored supply voltage) is stored
into two registers EAHEX (MSB, most significant
byte) and EBHEX (LSB, least significant byte).
The EEPROM status register (EC/6CHEX) reflects
the EEPROM error correction status. This register
can be used to verify that the EEPROM operation
has finished without errors.
The Trimming control register (ED/6DHEX) defines
whether the trim data in the EEPROM or in the
registers are used during operation. The default
setting is that all trim data is automatically read from
the EEPROM memory in the beginning of each
conversion. See the Trimming control register
description for details.
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RESET REGISTER (E0/60HEX)
This register is used to reset all control registers
(addresses E1H…EEH) to a zero value. There are
no data bits in this register. However it is necessary
to write dummy data to this register to make a reset.
The reset will take place immediately after any data
has been written to the address E0/60HEX via the
I2C or SPI interface.
TEST REGISTER (E1/61HEX)
In normal operation the Test register value is 00HEX
and the internal clock oscillator frequency 200 kHz
is used for all the measurements.
FOSC can be used to force the internal oscillator to
be on all the time. This is for internal oscillator
trimming purpose only. Normally (FOSC=0) the
internal oscillator is turned on only during the
measurements to save power and the OSC pin
output is at logic low. To get the internal 200 kHz
clock signal out from OSC pin it is necessary to set
FOSC=1.
The SEL_EXTCLK bit selects between internal
clock oscillator (OSC pin as digital output) and
external clock signal (OSC pin as digital input).
External clock selection may come necessary if the
sensor capacitance is too high to be used with the
internal 200 kHz or divided clock frequency options
(see SOSC bits in table 2). The maximum external
clock frequency depends on maximum sensor
capacitance; fEXT=200kHz*20pF/CS_MAX. Note that if
SEL_EXTCLK=1 is selected the internal oscillator is
disabled and OSC pin acts as digital input despite of
FOSC selection.
Table 2. MAS6512 test register (E1/61HEX) description
Bit
Bit Name
Description
Number
7
6
FOSC
5
SEL_EXTCLK
4-2
STEST
1-0
SOSC
The STEST bits are used for connecting different
internal signals to the TEST1 and TEST2 pins. In
STEST=101 test setup TEST1 and TEST2 operate
as positive and negative voltage inputs respectively
which are connected to the differential input of the
∆Σ-ADC.
By setting the SOSC bit it is possible to optionally
divide the internal system clock frequency by 2, 4 or
8. The undivided 200 kHz system clock frequency
allows measuring capacitances up to around 20pF
but with the maximum division option 8
capacitances up to 160pF. However note that only
sensor base capacitance scales up this much by
clock frequency but the maximum changing
capacitance range is smaller (see ELECTRICAL
CHARACTERISTICS tables).
Note that the frequency division selection SOSC
does not apply to OSC pin clock signals. The
internal 200 kHz clock signal from OSC pin and the
external clock signal applied to OSC pin are not
affected by the SOSC divider options.
Value
Function
Not used
Forces the oscillator on
without conversion
Selects external clock
X
0
1
0
1
TEST1 and TEST2
signal selection
000…100
OSC is on only during conversion
OSC is forced on
Internal clock, OSC output (default)
An external clock (OSC input)
can be connected to OSC and the
internal oscillator is disabled
Reserved for internal testing purpose
(TEST1 and TEST2 are outputs)
Select system clock
frequency
101
TEST1 and TEST2 as inputs
110…111
00
01
10
11
No function
f SYS_CLK = 200 kHz
f SYS_CLK = 100 kHz (div by 2)
f SYS_CLK = 50 kHz (div by 4)
f SYS_CLK = 25 kHz (div by 8)
X = Don’t care
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MEASUREMENT CONTROL REGISTER (E2/62HEX)
This register is used to configure and initiate a
measurement. See table 3 below. A new conversion
is started simply by writing 8-bit configuration data
having SCO=1 to the measurement control register
(E2/62HEX).
Table 3. Measurement control register (E2/62HEX) description
Bit Number
Bit Name
Description
Value
7-5
OSRS
Over Sampling Ratio
(OSR) Selection
4
TEMPREGEN
3
SCO
Temperature Mode
Regulator Enable
Start Conversion
2-1
SEL
Capacitive/ VDD
Monitoring /
Temperature Selection
0
XRC
Front end function
selector
The OSRS over sampling ratio selection bits
choose between four different OSR values. High
OSR value corresponds to high resolution but also
longer
conversion
time.
See
Electrical
characteristics for further details.
The TEMPREGEN bit enables/disables the internal
temperature mode voltage regulator. The regulator
need to be enabled (TEMPREGEN=1) only in
temperature mode and it should be disabled
(TEMPREGEN=0) in capacitance and VDD
monitoring modes. When enabled the regulator is
turned on during conversions and automatically
turned off after each conversion to save power.
Note also that if in Test register FOSC=1 and if
TEMPREGEN=1 the regulator is forced on all the
time even when measurement is not running.
000
001
010
011
0
1
0
1
00
01
10
11
0
1
Function
OSR = 256
OSR = 512
OSR = 1024
OSR = 2048
Voltage regulator disabled
Voltage regulator enabled
No conversion
Start conversion
External capacitive sensor
VDD level monitoring
Internal temperature sensor
Ratio converter
Difference converter
The SCO Start conversion bit needs to be set 1 for
every new measurement. It is automatically reset to
0 after each measurement.
The SEL sensor selection bits control the front-end
multiplexer. It connects either the external
capacitive sensor (SEL=00), VDD level monitoring
voltage (SEL=01) or the internal temperature sensor
(SEL=10) to the ∆Σ-converter.
The XRC bit selects between two external
capacitive sensor measurement modes. The XRC
bit selection does not have any effect on
temperature
or
VDD
level
monitoring
measurements. In Ratio converter mode the output
will be proportional to capacitance ratio (CS-CR)/CS.
In Difference converter mode the output will be
proportional to capacitance difference (CS-CR).
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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
corresponding non-volatile EEPROM addresses.
In normal operating mode these trim values are
automatically read from the EEPROM during each
conversion start. See also table 10 Trimming control
Register (ED/6DHEX) 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
Table 5. CR capacitor matrix register (E4/64HEX), EEPROM (C4/44HEX)
Bit Number
Bit Name
Description
Value
7-0
OCDACR
CDAC control bits
0HEX…FFHEX
Function
CS offset trimming
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
relationship to the ∆Σ-modulator output:
following
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;
 C  V
QAVE = 1 − R  ∗ R
 CS  VS
In this mode the gain register value GRDAC sets
the VS level.
CODE = QAVE ⋅ CODEFS
QAVE is the average measurement result (from the
over sampling) of the ∆Σ-modulator and varies from
0 to 1. The CODEFS is the maximum output code
which depends on OSR. 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 =
In this mode the gain register value GRDAC sets
the VS level.
1 CS − C R
V
+
∗ S
2
CREF
2 ∗ VR
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
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OSCILLATOR FREQUENCY CONTROL REGISTER (E6/66HEX)
Note that the internal clock oscillator frequency has
been factory trimmed and the trim value has been
stored in the EEPROM (C6/46HEX). It is
recommended not to change the factory
programmed value!
The oscillator frequency control register (E6/66HEX)
is for trimming the internal clock oscillator to 200
kHz frequency. This 200 kHz can be measured at
the OSC pin. The six LSB bits adjust the oscillator
period in 104ns steps. The period increases when
the trim value increases. Typically a register value
of 28HEX corresponds to the nominal 200 kHz clock
oscillator frequency. After finding a suitable trim
value it can be stored to the EEPROM (C6/46HEX).
Table 7. Oscillator frequency control register (E6/66HEX)
Bit Number
Bit Name
Description
5-0
OSCF
Oscillator frequency
control bits
Value
Function
0HEX…3FHEX
Oscillator frequency control
EEPROM DATA INPUT REGISTER (E8/68HEX)
This register can be ignored by user. It is related to
internal EEPROM operations and updated
automatically during every EEPROM write
operation.
EEPROM WRITE ENABLE REGISTER (E9/69HEX)
The EEPROM is normally write protected. To
enable write the EEPROM write enable register
should be set to %00000100 (04HEX). To disable
write the register should be set to %00000000
(00HEX) which is the register default value after
power-on-rest or manual reset by XCLR or reset
register. Note: don’t use any other EEPROM write
enable register values than these two since other
register bits are reserved for internal testing
purpose only.
Table 8. EEPROM write enable register (E9/69HEX)
Bit Number
Bit Name
Description
7-3
2
EWE
EEPROM write enable
1-0
Value
Function
00000
Reserved. Keep these bits
always 0.
EEPROM write disabled
EEPROM write enabled
Reserved. Keep these bits
always 0.
0
1
00
After a power-on-reset and in normal operation the
EEPROM write enable register has the default value
00HEX.
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CONVERSION RESULT REGISTERS (EA…EBHEX)
After measuring capacitance, temperature or supply
voltage the 16-bit conversion result is stored into
two register addresses EAHEX and EBHEX. The MSB
(most significant byte) is at EAHEX and LSB (least
significant byte) at EBHEX.
EEPROM STATUS REGISTER (EC/6CHEX)
The EEPROM status register (EC/6CHEX) indicates
if the stored EEPROM byte is corrupted. The
register is updated after each EEPROM data byte
read command. See table 9 below. The ERROR bit
tells whether a data error has been detected or not.
The DED bit tells whether two or more bit errors
have been detected. The EEPROM can correct
internally only single bit errors i.e. when ERROR=1
and DED=0. The read EEPROM data byte is
corrupted if ERROR=DED=1.
Table 9. MAS6512 EEPROM status register (EC/6CHEX). Only bits (7:6) are used.
Bit Number
Bit Name
Description
Value
7
ERROR
6
DED
EEPROM error
detection
EEPROM double
error detection
0
1
0
1
000000
5-0
Function
No errors
Error detected
No errors
2 (or more) data errors
-
TRIMMING CONTROL REGISTER (ED/6DHEX)
The Trimming control register (ED/6DHEX) is used to
select between different trimming operating modes.
See table 10 showing the functions of the Trimming
control register.
After a power-up reset, master reset via XCLR or a
software reset via serial bus the Trimming control
register (ED/6DHEX) gets the value %00000000
(00HEX). This is the normal operating mode for a
trimmed MAS6512 device. In this mode the
capacitive front-end trim values to use (CS, CR and
Gain) are automatically read from the EEPROM
memory in the beginning of each conversion start.
When calibrating a sensor there is an operating
mode in which only the factory calibrated internal
Table 10. Trimming control Register (ED/6DHEX)
Bit
Bit Name
Description
Number
7-0
REGEE<7:0>
EEPROM control bits
oscillator (OSC) clock trim data is read from the
EEPROM memory. This mode is selected by writing
%10101010 (AAHEX) to the Trimming control
register. In this mode it is possible to run conversion
tests for different front-end trim register values
before suitable values are found and programmed
to the EEPROM.
There is also a trimming mode in which all trim data
including the internal oscillator trim data is taken
from the trim registers rather than from the
EEPROM. This mode is selected by writing
%11111111 (FFHEX) to the Trimming control
register.
Value
Function
00000000
All trim data from EEPROM
(normal operating mode)
Only OSC from EEPROM
All trim data from registers
All trim data from EEPROM
10101010
11111111
OTHER
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EEPROM WRITE PROCEDURE
START
POWER UP DEVICE
Connect supply voltage VDD
INITIAL CONDITIONS
Reset device by XCLR or
by writing any data to the reset register E0/60HEX
ENABLE EEPROM WRITE
Write 04HEX to the EEPROM write enable register E9/69HEX
WRITE DATA TO EEPROM
Write data byte (8-bit) to selected EEPROM memory address
WAIT
Wait minimum 16ms after writing byte (8-bit) to EEPROM
VERIFY WRITTEN DATA
Read the written data byte (8-bit) from the EEPROM memory address
yes
Write more data?
no
DISABLE EEPROM WRITE
Write 00HEX to the EEPROM write enable register E9/69HEX
STOP
Figure 3. Flow chart for MAS6512 EEPROM write
Important note: Before EEPROM programming make sure that in the Test register (E1/61HEX) the SOSC=00 is
selected. That selects 200 kHz system clock frequency which is required for the proper EEPROM programming
pulses. This condition is guaranteed by making device reset either using the reset register (E0/60HEX) or the
XCLR pin.
Note: In the “VERIFY WRITTEN DATA” step it could be also additionally checked that the EEPROM status
register (EC/6CHEX) does not indicate read errors.
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EEPROM WRITE PROCEDURE
This chapter gives instructions for writing data to the
EEPROM memory.
This selects 200 kHz clock which is required in the
EEPROM programming.
The MAS6512 16 bit Capacitance-to-Digital
Converter (CDC) has a 256 bit (32 bytes) EEPROM
memory. 8 bits (1 byte) has been reserved for
storing internal clock oscillator trimming data and
other 8 bits (1 byte) for the programmable I2C
device address. There are also 24 bits (3 bytes) for
trimming the capacitive sensor front-end. The
remaining 216 bits (27 bytes) are free for storing
sensor calibration data and other use.
EEPROM write is enabled by writing value 04HEX to
the EEPROM write enable register (E9/69HEX). The
default register value after power on is 00HEX.
See figure 3 on previous page showing the
EEPROM write procedure.
Make sure in the beginning of the EEPROM write
procedure that the MAS6512 initial conditions are
met. Connecting VDD triggers power-on-reset
(POR) but to make sure the device is reset an
additional reset should be given using the XCLR pin
or writing any data on the reset register E0/60HEX via
the serial bus. The device reset will guarantee that
SOSC=0 is selected in the test register (E1/61HEX).
Next the data can be written to the EEPROM
memory one byte (8-bit) at a time. It is necessary to
have a delay of minimum 16ms after programming
each byte (8-bit). The success of each write can be
verified by reading back the data (8-bit) and
comparing it to the original byte (8-bit). Additionally
it is also possible to check the EEPROM status
register (EC/6CHEX) value after each read back. The
EEPROM status register value should be 00HEX
when the read EEPROM data byte is free of errors.
After all data bytes are written the EEPROM
memory can be protected from write by writing
00HEX to the EEPROM write enable register
(E9/69HEX).
See table 1 showing the MAS6512 register and
EEPROM data addresses.
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SERIAL DATA INTERFACE CONTROL
Serial Interface
MAS6512 can be operated either via 2-wire serial
I2C bus or via 4-wire serial SPI bus. Selection
between I2C and SPI communication is done by
XSPI pin. XSPI=high selects I2C and XSPI=low
selects SPI communication.
Digital interface includes also end of conversion
(EOC) and master reset (XCLR) pins. Rising edge
in the EOC pin indicates that the conversion is
ready and the result can be read out through serial
interface.
2-wire serial I2C bus type interface comprises of
serial clock input (SCL) and bi-directional serial data
(SDA) input/output. I2C bus is used to write
configuration data to sensor interface IC and read
the measurement result when A/D conversion has
been finished. The interface is also used for reading
the calibration EEPROM memory.
XCLR is used to reset the MAS6512. A reset
initializes registers (set to value 00HEX), counters
and the serial communication bus. Alternatively
device can be reset via serial bus by writing any
data to Reset register (address E0/60HEX). The
Reset register bits don’t have any function. Reading
from the reset register is not possible.
Note: The 2-wire I2C bus of MAS6512 supports only
basic I2C bus communication protocol but not for
example 10-bit addressing, arbitration and clock
stretching features of the I2C bus specification.
After connecting the supply voltage to MAS6512,
and before starting operating the device via the
serial bus, it is required to reset the device if the
supply voltage rise time has been longer than 1ms.
However it is recommended to reset the device
manually after every power up to guarantee proper
register settings after any VDD rise conditions
The alternative 4-wire serial SPI bus type interface
comprises of serial clock input (SCLK), serial data
input (MOSI), serial data output (MISO) and chip
select input (XCS).
I2C Bus Communication
In MAS6512 the I2C bus communication is selected
by setting XSPI pin high.
The I2C bus standard makes it possible to connect
several devices on same bus. The devices are
distinguished from each other by unique device
addresses. In MAS6512 there is both a hard wired
and programmable device address. Both hard wired
and programmable addresses can be used to
address MAS6512. The MAS6512 hard wired
device address is shown in the following table. The
LSB bit of the device address defines whether the
bus is configured to Read (1) or Write (0) operation.
The programmable device address is located in the
EEPROM register C2HEX which has been factory
programmed to value ECHEX (%11101100) which is
the same as the fixed device address of MAS6512.
When unique device address is needed it can be
programmed to this register. The programmable
I2C device address is read from EEPROM memory
only during power on reset or manual reset
situations. To guarantee that the programmable
address is read from EEPROM the device can be
reset manually by using XCLR pin or Reset register
(E0/60HEX).
Table 11. MAS6512 hard wired I2C bus device address (EC/EDHEX)
A7
A6
A5
A4
A3
A2
A1
W/R
1
1
1
0
1
1
0
0/1
I2C Bus Protocol Definitions
Data transfer is initiated with a Start bit (S) when
SDA is pulled low while SCL stays high. Then, SDA
sets the transferred bit while SCL is low and the
data is sampled (received) when SCL rises. When
the transfer is complete, a Stop bit (P) is sent by
releasing the data line to allow it to be pulled up
while SCL is constantly high.
when SCL is high. Data at the SDA pin can change
value only when SCL is low.
Each SDA line byte transfer must contain 8-bits
where the most significant bit (MSB) always comes
first. Each byte has to be followed by an
acknowledge bit (see further below). The number of
bytes transmitted per transfer is unrestricted.
Figure 4 shows the start (S) and stop (P) bits and a
data bit. Data must be held stable at the SDA pin
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2-WIRE SERIAL DATA INTERFACE (I2C BUS)
S
SDA
SCL
1
0
P
Figure 4. I2C bus protocol definitions
Bus communication includes Acknowledge (A) and
not Acknowledge (N) messages. To send an
acknowledge the receiver device pulls the SDA low
for one SCL clock cycle. For not acknowledge (N)
Abbreviations:
A= Acknowledge by Receiver
N = Not Acknowledge by Receiver
S = Start
Sr = Repeated Start
the receiver device leaves the SDA high for one
SCL clock cycle in which case the master can then
generate either a Stop (P) bit to abort the transfer,
or a repeated Start (Sr) bit to start a new transfer.
P = Stop
= from Master (MCU) to Slave (MAS6512)
= from Slave (MAS6512) to Master (MCU)
Conversion Starting – Write Sequence
Conversion is started by writing configuration bits
into the Measurement control register (address
E2HEX). The write sequence is illustrated in Table
12.
Table 12. MAS6512 I2C bus write sequence of Measurement control register
S
AW
A MC A DC A
P
Abbreviations:
AW = Device Write Address ECHEX (%1110 1100)
AR = Device Read Address EDHEX (%1110 1101)
MC = Meas. control register 62HEX (%0110 0010)
Ax = Conversion Result Registers’ Addresses; MSB
(x=M, 6AHEX %0110 1010), LSB (x=L, 6BHEX %0110
1011)
Each serial bus operation, like write, starts with the
start (S) bit (see figure 4). After start (S) the
MAS6512 device address with write bit (AW, see
table 11) is sent followed by an Acknowledge (A).
After this the Measurement control register address
(see table 1) is sent and followed by an
Acknowledge (A). Next the Measurement control
DC = Measurement Control Register Data
Dx = Conversion Result Register Data; MSB (x=M),
LSB (x=L)
register data (DC, see table 3) is written and
followed by an Acknowledge (A). Finally the serial
bus operation is ended with stop (P) command (see
figure 4). A new A/D conversion starts right after
Measurement control register bits containing
SCO=1 are received.
A/D Conversion
After power on reset or external reset (XCLR) the
EOC output is high. After an A/D conversion is
started the EOC output is set low until the
conversion is finished and the EOC goes back high,
indicating that the conversion is done and data is
ready for reading. The EOC is set low only by
starting a new conversion. To save power the
internal oscillator runs only during conversion.
During an A/D conversion the input signal is
sampled continuously leading to an output
conversion result that is a weighted average of the
samples taken.
19 (31)
DA6512.001
7 November, 2013
2-WIRE SERIAL DATA INTERFACE (I2C BUS)
Conversion Result – Read Sequence
Table 13 presents a general control sequence for a
single register data read.
Table 13. MAS6512 I2C bus single register (address Ax) read sequence bits
S
AW
A
Ax
A
Sr AR
A
Dx
N
P
Table 14 shows the control sequence for reading
the 16-bit A/D conversion result from the
Conversion result registers. The LSB (DL) register
data read can follow right after the MSB register
data (DM) read since if the read sequence is
continued (not ended by a Stop bit P) the register
address is automatically incremented to point to the
next register.
Table 14. MAS6512 I2C bus MSB (first byte) and LSB (second byte) A/D conversion result read sequence
S AW
A AM A Sr
AR A DM A DL
N
P
4-WIRE SERIAL DATA INTERFACE (SPI BUS)
SPI bus communication is selected by setting XSPI
pin low.
“Register and EEPROM data addresses”). In write
access bit A7 cleared (0) and in read access it is set
(1).
SPI communication differs from I2C bus in the
following way. It requires four wires for bi-directional
communication since each line operates in one
direction only. Device selection is done by using
separate chip select XCS control lines instead of
using device address. Each SPI bus device has its
own XCS control line and a device is selected by
pulling its XCS line low (see figure 5 below). The
fourth wire in the SPI bus is the serial clock line,
SCLK. Data is transferred at rising edges of the
serial clock during which the data line should be
stable.
Figure 5 illustrates write access communication.
MAS6512 has an auto increment function which
means that if there are more than one data byte
transferred the additional data bytes are delivered to
following
register
addresses.
In
write
communication the MISO line is high impedance.
In SPI bus communication it is good to note that
setting XCS low activates the EEPROM memory
regardless of the XSPI setting and the device
consumes 20µA …30µA current. To minimize
current consumption XCS should be set low only
during time periods when the device is used during
SPI communication.
The selection between write or read access is done
by register address MSB bit A7 (see table 1
XCS
SCLK
SCK
MOSI
SDA
MISO
MSB Register Address Byte
LSB
MSB
Data Byte
LSB
High Z
Figure 5. SPI Protocol – Write Access (register address MSB bit A7=0)
20 (31)
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7 November, 2013
4-WIRE SERIAL DATA INTERFACE (SPI BUS)
Figure 6 illustrates read access communication.
The auto increment function can be utilized also in
read access and if there are more than one data
XCS
byte read the additional data bytes are delivered
from following register addresses.
SCK
SCLK
SDA
MOSI
MISO
MSB Register Address Byte
High Z
Ignored
LSB
MSB
Data Byte
LSB
Figure 6. SPI Protocol – Read Access (register address MSB bit A7=1)
21 (31)
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TRIMMING FOR SENSOR CAPACITANCE
MAS6512
has
two
different
capacitance
measurement modes. The output can be
proportional either to capacitance difference (CS-CR)
or to capacitance ratio (CS-CR)/CS.
range minimum and maximum limits the average of
the ∆Σ-modulator output is 10% and 90%
respectively. In the following trimming equations we
denote these by
For trimming it is necessary to know the sensor
capacitance CS range CS MIN…CS MAX. For optimal
utilization of the MAS6512 input range the trimming
is based on selecting the minimum linear range
capacitance same as CS MIN and maximum linear
range capacitance same as CS MAX. At the linear
DMIN = 0.1
DMAX = 0.9
In the capacitance measurement the internal
regulator should be disabled (TEMPREGEN=0) and
the external capacitive sensor selected (SEL=00).
MAS6512 in capacitance difference mode
The reference capacitor value CR is calculated from
CR = [CS MIN*(DMAX-0.5)-CS MAX*(DMIN-0.5)] / (DMAX-DMIN)
If an external CR is used, it is connected between pins CR and CC. If an internal CR is used, the trim code for CR
is calculated from
REGE4HEX = (CR/CR MAX)*255
where CR MAX is nominally 22pF, but subject to ±10 % (±3 sigma) process variation.
The reference voltage, VS, can be calculated using the following equation:
VS = [144mV*(DMAX-DMIN)*2*CREF] / (CS MAX-CS MIN)
where CREF is nominally 6 pF, but also has ±10 % variation.
The gain register trim value is calculated from
REGE5HEX = [(VS-33 mV) / 734mV]*255
REGE4HEX and REGE5HEX are 8-bit values, so they range from 0 to 255. When their values are found, the same
values can be written to corresponding EEPROM addresses C4HEX and C5HEX. However, with SPI bus, the
address MSB in write operation is 0, so the addresses are actually 44HEX and 45HEX.
Example: Single capacitance sensor
CS MIN=8pF
CS MAX=12pF
CR = [8pF*(0.9-0.5)-12pF*(0.1-0.5)]/(0.9-0.1) = 10pF
REGE4HEX = (10pF/22pF)*255 = 115.9 ~ 116
VS = [144mV*(0.9-0.1)*2*6pF] / (12pF-8pF) = 345.6mV
REGE5HEX = [(345.6-33 mV) / 734mV]*255 = 108.6 ~109
REGE3HEX = 0 (no internal CS capacitor matrix used)
22 (31)
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TRIMMING FOR SENSOR CAPACITANCE
MAS6512 in capacitance ratio mode
The reference capacitor CR is calculated from
CR = [CS MIN*CS MAX*(DMAX-DMIN)] / (CS MAX*DMAX-CS MIN*DMIN)
If an external CR is used, it is connected between pins CR and CC. If an internal CR is used, the trim code for CR
is calculated from
REGE4HEX = (CR/CR MAX)*255
where CR MAX is nominally 22pF, but subject to ±10 % (±3 sigma) process variation.
The reference voltage, VS, can be calculated using the following equation:
VS = 100.8mV * (CS MAX-CS MIN) / (CS MAX*DMAX-CS MIN*DMIN)
The gain register trim value is calculated from
REGE5HEX = (VS / 133.3mV)*255
REGE4HEX and REGE5HEX are 8-bit values, so they range from 0 to 255. When their values are found, the same
values can be written to corresponding EEPROM addresses C4HEX and C5HEX. However, with SPI bus, the
address MSB in write operation is 0, so the addresses are actually 44HEX and 45HEX.
Example: Single capacitance sensor
CS MIN=8pF
CS MAX=12pF
CR = [8pF*12pF*(0.9-0.1)] / (12pF*0.9-8pF*0.1) = 7.68pF
REGE4HEX = (7.68pF/22pF)*255 = 89.0 ~ 89
VS = 100.8mV*)/(12pF-8pF)/(12pF*0.9-8pF*0.1)=40.32mV
REGE5HEX = (40.32mV/133.3mV)*255 = 77.1 ~ 77
REGE3HEX = 0 (no internal CS capacitor matrix used)
23 (31)
DA6512.001
7 November, 2013
TEMPERATURE MODE
The MAS6512 has an internal temperature sensor
for temperature measurement. The temperature
sensor output is proportional to absolute
temperature (PTAT). The temperature information
is needed for temperature indication and
temperature compensation.
already the smallest over sampling ratio (OSR)
selection 256 offers sufficient resolution for the
temperature measurement.
The internal temperature sensor has offset and gain
variation but small non-linearity (see Electrical
Characteristics table). Depending on temperature
measurement accuracy requirement the offset, the
gain and the non-linearity all can be compensated
by external calculations. In low precision the offset
and gain calibration is sufficient but in high precision
the second order non-linearity calibration can be
included.
The temperature measurement is started by writing
configuration data to the measurement control
register
(E2/62HEX).
In
the
temperature
measurement the internal regulator has to be
enabled (TEMPREGEN=1) and the internal
temperature sensor selected (SEL=10). The ratio
and difference converter bit (XRC) selection does
not have any influence on the result. Typically
Linear temperature sensor model
The linear temperature measurement model for output code is following.
CODE = CODEFS ⋅ (a + b ⋅ (T − TREF ))
The OSR selects full scale output code range value CODEFS. See Electrical Characteristics for CODEFSDIFF at
different OSR values. If the temperature T is presented in °C and referenced to TREF=0°C then the typical
linearized temperature sensor model parameter values a and b are as follows.
a=0.38944
b=4.4329e-3
However it should be noted that the sensor has significant offset (parameter a) variation and also the gain
(parameter b) has some variation and that the above values represent only typical values. The non-linearity
temperature error after offset and gain calibration (best fit line) is typically <±0.5°C in the temperature range 40°C…+85°C.
2nd order temperature sensor model
nd
For higher precision the 2 order temperature measurement model for output code is following
(
2
CODE = CODEFS ⋅ a + b ⋅ (T − TREF ) + c ⋅ (T − TREF )
)
nd
If the temperature T is presented in °C and referenced to TREF=0°C then the typical 2 order temperature sensor
model parameter values a, b and c are as follows.
a=0.38826
b=4.3967e-3
c=8.1098e-7
Above sensor model parameters are typical values which are subject to variations. The temperature error after
nd
offset, gain and 2 order non-linearity calibration is typically <±0.1°C in the temperature range -40°C…+85°C.
24 (31)
DA6512.001
7 November, 2013
VDD LEVEL MONITORING MODE
The MAS6512 has VDD level monitoring feature to
measure supply voltage level which is useful
especially in battery operated systems. In systems
in which VDD can vary the VDD level monitoring
could be also used to compensate VDD
dependency.
monitoring mode the regulator has to be disabled
(TEMPREGEN=0) and VDD level monitoring
selected (SEL=01). The ratio and difference
converter bit (XRC) selection does not have any
influence on the result.
Typically the smallest over sampling ratio (OSR)
selection 256 offers sufficient resolution for the VDD
level monitoring.
The VDD level monitoring measurement is started
by writing configuration data to the measurement
control register (E2/62HEX). In the VDD level
VDD level monitoring model
The VDD level monitoring model for output code is following.
b 

CODE = CODEFS ⋅  a −

VDD 

The output has inverse relationship to supply voltage VDD. The OSR selects full scale output code range value
CODEFS. See Electrical Characteristics for CODEFS at different OSR values.
The typical VDD level monitoring model parameter values a and b are as follows.
a=1.6375
b=2.6942
Note that these parameter values are subject to about two percent variations.
The supply voltage VDD can be solved from the output result as follows.
VDD =
b
CODE
a−
CODEFS
Figure 7 presents typical output code as function of supply voltage at OSR=256 (CODEFS=888).
Figure 8 present supply voltage as function of output code at OSR=256 (CODEFS=888).
800
3.6
3.4
700
3.2
600
500
VDD [V]
CODE [LSB]
3
400
2.8
2.6
2.4
300
2.2
200
2
100
1.8
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
VDD [V]
Figure 7. CODE(VDD) at VDD level monitoring
3.6
100
200
300
400
500
600
700
800
CODE [LSB]
Figure 8. VDD(CODE) at VDD level monitoring
25 (31)
DA6512.001
7 November, 2013
APPLICATION INFORMATION
VDD 100n
VDD
GND
OSC
MUX
CS
VDD
4k7
MISO
CLK
OSC
I2C /
MCU
SCL/SCLK
Cs
SPI
CC
XCS
CONTROL
VDD
XSPI
Cr
optional
4k7
SDA/MOSI
CR
∆Σ
VREG
TEMP
EEPROM
EOC
optional
XCLR
optional
VREG
TEST1
TEST
TEST2
GND
GND
GND
NOTE: It is recommended to use the XCLR reset feature to solve unexpected error state
conditions. The XCLR pin can be left unconnected if not used. It has internal pull up to VDD.
Figure 9. MAS6512 configured for I2C bus communication
Note: MAS6512 has an effective ESD clamp protection structure that can be triggered if the VDD rises too fast.
For this reason it’s recommended to use a supply decoupling capacitor having a value of 100nF or higher to slow
down the VDD rise time.
Note: The voltage regulator output VREG does not require external capacitor as shown in figure 9. However if an
output capacitor is wanted to be used for extra filtering the capacitor value should not be higher than 6.8nF.
Accuracy Improvement – Averaging
An averaging technique can be used to remove
conversion errors caused by noise and thus
improve measurement accuracy. By doing several
A/D conversions and calculating the average result
it’s possible to average out noise. Theoretically the
noise is reduced by a factor N where N is the
number of averaged samples. A/D converter
nonlinearities cannot be removed by averaging.
26 (31)
DA6512.001
7 November, 2013
9 CR
10 CC
11 CS
12 GND
MAS6512 IN QFN-16 4x4x0.75 PACKAGE
TEST1 15
XCS 1
EOC 16
8 VREG
7 XCLR
6 SCL_SCLK
5 SDA_MOSI
VDD 4
TEST2 14
MISO 3
OSCOUT 13
XSPI 2
MAS6512
AA1
YYWW
XXXXX
Top Marking Information:
MAS6512 = Product Number,
AA1 = Version Number
YYWW = Year Week
XXXXX = Lot Number
QFN-16 4x4x0.75 PIN DESCRIPTION
Pin Name
Pin
Type
XCS
XSPI
1
2
DI
DI
MISO
VDD
SDA_MOSI
3
4
5
DO
P
DI/O
SCL_SLCK
XCLR
VREG
CR
CC
CS
GND
OSC
TEST2
TEST1
EOC
6
7
8
9
10
11
12
13
14
15
16
DI
DI
AO
AI
AI
AI
G
DI/DO
AI/O
DO
DO
Function
Chip Select (SPI)
SPI / I2C Bus Selection
SPI: XSPI=low
I2C: XSPI=high
Master Input Slave Output (SPI)
Power Supply Voltage
Serial Bus Data (I2C)
Master Output Slave Input (SPI)
Serial Bus Clock (I2C / SPI)
Master Reset
Voltage Regulator Output 1.8V
Reference Capacitance Pin
Common Capacitance Pin
Sensing Capacitance Pin
Power Supply Ground
Oscillator Input / Output
Test pin 2
Test pin 1
End of Conversion
Note
1
P = Power, G = Ground, DO = Digital Output, , DI = Digital Input, AO = Analog Output, AI = Analog Input
Note 1: The XCLR pin has internal pull up to VDD. If not used the XCLR pin can be left unconnected.
Note: The exposed pad of the QFN package should be connected to the GND.
27 (31)
DA6512.001
7 November, 2013
PACKAGE (QFN-16 4X4x0.75) OUTLINE
D
D/2
E/2
TOP VIEW
A3
A
PIN 1 MARK AREA
SIDE VIEW
DETAIL A
A1
SEATING
PLANE
Package Center Line X or Y
D2
b
D2/2
L
e
BOTTOM VIEW
EXPOSED PAD
DETAIL A
Symbol
Terminal Tip
e/2
E2
E2/2
SHAPE OF PIN #1
IDENTIFICATION
IS OPTIONAL
Min
Nom
Max
PACKAGE DIMENSIONS
A
0.700
0.750
0.800
A1
0.000
0.020
0.050
A3
0.203 REF
b
0.250
--0.350
D
3.950
4.000
4.050
D2 (Exposed.pad)
2.700
--2.900
E
3.950
4.000
4.050
E2 (Exposed.pad)
2.700
--2.900
e
0.650 BSC
L
0.350
--0.450
Dimensions do not include mold or interlead flash, protrusions or gate burrs.
Unit
mm
mm
mm
mm
mm
mm
mm
mm
mm
mm
28 (31)
DA6512.001
7 November, 2013
SOLDERING INFORMATION
◆ For Lead-Free / Green QFN 4mm x 4mm
Resistance to Soldering Heat
Maximum Temperature
Maximum Number of Reflow Cycles
Reflow profile
According to RSH test IEC 68-2-58/20
260°C
3
Thermal profile parameters stated in IPC/JEDEC J-STD-020
should not be exceeded. http://www.jedec.org
Solder plate 7.62 - 25.4 µm, material Matte Tin
Lead Finish
EMBOSSED TAPE SPECIFICATIONS
P2
PO
P1
D0
T
X
E
F
W
B0
R 0.25 typ
K0
X
A0
User Direction of Feed
Orientation on tape
Dimension
Ao
Bo
Do
E
F
Ko
Po
P1
P2
T
W
Min/Max
4.30 ±0.10
4.30 ±0.10
1.50 +0.1/-0.0
1.75
5.50 ±0.05
1.10 ±0.10
4.0
8.0
±0.10
2.0
±0.05
0.3
±0.05
12.00 ±0.3
All dimensions in millimeters
Unit
mm
mm
mm
mm
mm
mm
mm
mm
mm
mm
mm
29 (31)
DA6512.001
7 November, 2013
REEL SPECIFICATIONS
W2
A
D
C
Tape Slot for Tape Start
N
B
W1
Carrier Tape
Cover Tape
End
Start
Trailer
Dimension
A
B
C
D
N
W 1 (measured at hub)
W 2 (measured at hub)
Trailer
Leader
Components
Min
Leader
Max
330
1.5
12.80
20.2
100
12.4
13.50
14.4
18.4
160
390,
of which minimum 160 mm of
empty carrier tape sealed with
cover tape
Unit
mm
mm
mm
mm
mm
mm
mm
mm
mm
Reel Material: Conductive, Plastic Antistatic or Static Dissipative
Carrier Tape Material: Conductive
Cover Tape Material: Static Dissipative
30 (31)
DA6512.001
7 November, 2013
ORDERING INFORMATION
Product Code
Product
Description
MAS6512AA1WA100
Capacitive Sensor
Signal Interface IC
Capacitive Sensor
Signal Interface IC
Capacitive Sensor
Signal Interface IC
EWS-tested wafer, thickness 480 µm
MAS6512AA1WA105
MAS6512AA1Q1706
Dies on waffle pack, thickness 480 µm
QFN-16 4x4x0.75 Package, Pb-free, RoHS compliant,
Tape & Reel, 1000 / 3000 pcs components on reel
Contact Micro Analog Systems Oy for other wafer thickness options.
LOCAL DISTRIBUTOR
MICRO ANALOG SYSTEMS OY CONTACTS
Micro Analog Systems Oy
Kutomotie 16
FI-00380 Helsinki, FINLAND
Tel. +358 10 835 1100
Fax +358 10 835 1119
http://www.mas-oy.com
NOTICE
Micro Analog Systems Oy (MAS) reserves the right to make changes to the products contained in this data sheet in order to improve the
design or performance and to supply the best possible products. MAS assumes no responsibility for the use of any circuits shown in this data
sheet, conveys no license under any patent or other rights unless otherwise specified in this data sheet, and makes no claim that the circuits
are free from patent infringement. Applications for any devices shown in this data sheet are for illustration only and MAS makes no claim or
warranty that such applications will be suitable for the use specified without further testing or modification.
MAS products are not authorized for use in safety-critical applications (such as life support) where a failure of the MAS product would
reasonably be expected to cause severe personal injury or death. Buyers represent that they have all necessary expertise in the safety and
regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safetyrelated requirements concerning their products and any use of MAS products in such safety-critical applications, notwithstanding any
applications-related information or support that may be provided by MAS. Further, Buyers must fully indemnify MAS and its representatives
against any damages arising out of the use of MAS products in such safety-critical applications.
MAS products are neither designed nor intended for use in military/aerospace applications or environments. Buyers acknowledge and agree
that any such use of MAS products which MAS has not designated as military-grade is solely at the Buyer's risk, and that they are solely
responsible for compliance with all legal and regulatory requirements in connection with such use.
MAS products are neither designed nor intended for use in automotive applications or environments. Buyers acknowledge and agree that, if
they use any non-designated products in automotive applications, MAS will not be responsible for any failure to meet such requirements.
31 (31)