Copyright 2004, ZMD AG, Rev. 1.6, 2005-05-19
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All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31020
Sensor Signal Conditioner
Datasheet
Features
Digital compensation of sensor offset, sensitivity,
temperature drift and non-linearity
Adjustable to nearly all piezo-resistive bridge
sensor types
Digital one-shot calibration: quick and precise
Selectable temperature compensation reference:
internal or external diode
Output options: 0...5V analog ratiometric voltage
or 12 bit digital I
2
C interface
Product traceability by user-defined EEPROM
entries
Operation temperature range, depending on
product version, up to 40...+125C
Supply voltage +4.5...+5.5V
Sampling rate 100Hz
Available in SSOP14 or as die
Benefits
No external trimming components required
PC-controlled configuration and calibration via
digital bus interface - simple, low cost
High accuracy (0.1% FSO @ -25 to 85C;
0.25% FSO @ -40 to 125C)
Brief Description
ZMD31020 is a CMOS integrated circuit for highly-
accurate amplification and sensor-specific correction
of bridge sensor signals. The device provides digital
compensation
of
sensor
offset,
sensitivity,
temperature drift and non-linearity by a 16-bit RISC
micro controller running a correction algorithm.
ZMD31020 accommodates nearly all piezo-resistive
bridge sensor types.
The bi-directional digital I
2
C interface can be used for
a
simple
PC-controlled
one-shot
calibration
procedure, in order to program a set of calibration
coefficients into an on-chip EEPROM. Thus a specific
sensor and a ZMD31020 are mated digitally: fast,
precise and without the cost overhead associated with
trimming by external devices or laser.
ZMD31020 has been designed for industrial and
consumer applications and is specifically suited for
most pressure sensors.
Demo kit available (incl. calibration PCB,
SSOP14 samples, software, technical
documentation)
Support for industrial calibration available
Quick circuit customization possible for large
production volumes
Application Circuit Example
Copyright 2004, ZMD AG, Rev. 1.6, 2005-05-19
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All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31020
Sensor Signal Conditioner
Datasheet
CONTENT
1.
PIN DESCRIPTION ......................................................................................................................................3
2.
CIRCUIT DESCRIPTION .............................................................................................................................4
2.1 Signal Flow ....................................................................................................................................................4
2.2 Configuration Word........................................................................................................................................5
2.3
Differential Sensor ....................................................................................................................................5
2.4
Temperature Sensing ...............................................................................................................................5
2.5
Analog Input Channel ...............................................................................................................................6
2.5.1
Bridge Polarity Setting .......................................................................................................................6
2.5.2
Programmable Gain Amplifier PGA...................................................................................................6
2.5.3
Analog-to-digital Converter ADC .......................................................................................................6
2.5.4
Temperature Measurement ...............................................................................................................7
2.6
Correction Microcontroller CMC................................................................................................................7
2.7
Parameter EEPROM.................................................................................................................................7
2.8
Sensor Signal Correction Method and Sequence.....................................................................................8
2.9
Digital I
2
C Interface ...................................................................................................................................8
2.9.1
Digital Corrected Sensor Signal Output and I/O for Calibration and Device Test .............................8
2.9.2
Data Communication Specifics..........................................................................................................8
2.10
The Analog Output Stage....................................................................................................................10
3.
ELECTRICAL SPECIFICATION.................................................................................................................10
3.1
Absolute maximum ratings......................................................................................................................10
3.2
Operating Conditions ..............................................................................................................................10
3.3
Electrical Parameters..............................................................................................................................11
3.3.1
Power Supply...................................................................................................................................11
3.3.2
PGA & 12-bit Input ADC ..................................................................................................................11
3.3.3
Temperature Measurement: Current Sources, on-chip Diode & 12-bit ADC
(4)
..............................11
3.3.4
12-bit ADC
(1)
...................................................................................................................................12
3.3.5
EEPROM programming ...................................................................................................................12
3.3.6
Serial I
2
C Interface...........................................................................................................................12
3.3.7
11-bit Output DAC & Output BUFFER
(2)
.........................................................................................14
3.3.8
Total System ....................................................................................................................................14
4.
PACKAGE DIMENSIONS ..........................................................................................................................15
5.
DIE DIMENSIONS AND PAD COORDINATES .........................................................................................16
5.1
Die Dimensions .......................................................................................................................................16
5.2
Pad Coordinates .....................................................................................................................................17
6.
EVALUATION KIT "ZMD31020KIT" ...........................................................................................................18
7.
ORDERING INFORMATION ......................................................................................................................19
8.
RELATED DOCUMENTS...........................................................................................................................19
Copyright 2004, ZMD AG, Rev. 1.6, 2005-05-19
3/19
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31020
Sensor Signal Conditioner
Datasheet
1. PIN DESCRIPTION
PIN
Number
Name
Description
1
VOUT
analog conditioned sensor signal output
2
VDDA (*)
analog device functions positive supply
3
VDD
digital device functions positive supply
4
VSS
digital device functions negative supply
5
SCL
IC clock input, on-chip pull-up resistor
6
SDA
IC data input / output, on-chip pull-up resistor
7
VPP
positive EEPROM programming voltage
8
VBN
differential sensor signal negative input
9
VDDB2 (*) positive supply for sensor and temperature sensing diode
10
VTN
input for temperature sensing diode
11
VDDB1 (*) positive supply for sensor and temperature sensing diode
12
VBP
differential sensor signal positive input
13
VSSB (**)
sensor negative supply
14
VSSA (**)
analog device functions negative supply
(*)
VDDA, VDDB1 and VDDB2 tied to common on-chip positive supply rail
(**)
VSSA and VSSB tied to common on-chip negative supply rail
Copyright 2004, ZMD AG, Rev. 1.6, 2005-05-19
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All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31020
Sensor Signal Conditioner
Datasheet
2. CIRCUIT DESCRIPTION
Block diagram of ZMD31050
PGA
programmable gain amplifier
MUX
multiplexer
ADC
analog-to-digital converter
CMC
calibration microcontroller
DAC
digital-to-analog converter
BAMP
buffer amplifier
TS
on-chip temperature sensor (pn-junction)
EEPROM
for calibration parameters and configuration
ROM
for correction formula and algorithm
I
2
C
serial interface: I
2
C data I/O, clock
The ZMD31020's signal path is partly analog (blue) and partly digital (red). The differential signal from the
resistive bridge sensor is pre-amplified by the programmable gain amplifier (PGA). There are 3 different
adjustable gains.
The Multiplexer (MUX) transmits the differential signal or the temperature signal to the ADC in a certain
sequence. (The external temperature sensing diode or the internal temperature sensor can be used optionally.)
The ADC converts the differential signal with 12 bits resolution and the temperature signal with 10 bits resolution
into digital values.
2.1 Signal Flow
Copyright 2004, ZMD AG, Rev. 1.6, 2005-05-19
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All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31020
Sensor Signal Conditioner
Datasheet
The digital signal correction takes place in the calibration micro-controller (CMC). It is based on a special
correction formula located in the ROM and on a set of sensor-specific calibration parameters stored in the
EEPROM. The resulting corrected sensor signal is output via the I
2
C-interface (with 12 bits resolution) , or, after
conversion by the DAC, as analog voltage (with 11 bits resolution) at the buffer amplifier (BAMP). The
programming of the configuration data and of the calibration parameters into the EEPROM (during the
calibration procedure) is also realized via the I
2
C interface.
Many of the following sections, describing each block of ZMD31020 in detail, will refer to configuration bits, part
of the configuration word stored under address &H09 of the parameter EEPROM. These bits are settings for a
number of on-chip device functions and select specific functional or parametrical behaviour.
The contents of the parameter EEPROM are determined and calculated, written and stored under PC-control
during the calibration procedure. Hence the configuration bits are coded and non-volatile stored once calibration
of a ZMD31020 device / sensor pair has taken place, and will remain unchanged during regular sensing
operation, unless re-calibration is performed
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
-
CH
TS
BP
G1
G0
O1
O0
Configuration word, stored under address &H09 of the parameter EEPROM
Only 7 bits of the configuration word are relevant settings as follows:
Bit 0, Bit 1
O0, O1: select ADC's offset compensation
Bit 2, Bit 3
G0, G1: select PGA's gain
Bit 4
BP: cross-switches differential sensor inputs VBP and VBN
Bit 5
TS: selects on-chip vs. off-chip temperature sensor
Bit 6
CH: enables PGA's chopper-stabilization
The possible options of these settings are shown in table form in the following paragraphs.
ZMD31020 has been specifically designed for ratiometric differential sensors, e.g. Wheatstone bridge type
sensors. A ratiometric sensor typically generates a differential output signal proportional to the supply voltage
applied to it. The sensor is supplied from VDDB1 or VDDB2 (whichever pin/pad is more favourable layoutwise)
at the + side and tied to VSSB at the side. The sensor's differential output signal is routed to VBP and VBN.
Sensor and signal conditioner ZMD31020 have the same supply (see block schematic in section 2.1), hence the
differential input voltage seen by ZMD31020 is ratiometric to it's supply voltage.
The characteristic of a sensor element tends to change with temperature. To compensate for this, ZMD31020 is
equipped to measure temperature by an external diode or by an on-chip pn-junction. TS configuration bit 5
will select the desired sensor option as follows:
TS
Temperature sensing diode
0
off chip
1
on chip
2.2 Configuration Word
2.3 Differential Sensor
2.4 Temperature Sensing
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