ZMD ZMD31050 Datasheet
(4 to 20) mA configuration [(7 to 40) V],
Refer also chapter
2
for additional application circuits and details.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Datasheet
Features
• Digital compensation of sensor offset, sensitivity,
temperature drift and non-linearity
• Accommodates nearly all bridge sensor types
(signal spans from 1 up to 275mV/V processable)
• Digital one-shot calibration: quick and precise
• Selectable compensation temperature T1 source:
bridge, thermistor, internal diode or external diode
• Output options: voltage (0V to 5V),
current (4mA to 20mA), PWM, I2C, SPI,
ZACwire
TM
(one-wire-interface), alarm
• Adjustable output resolution (up to 15 bits) versus
sampling rate (up to 3.9kHz)
• Selectable bridge excitation: ratiometric voltage,
constant voltage or constant current
• Input channel for separate temperature sensor
• Sensor connection and common mode check
(Sensor aging detection)
• Operation temperature -40 to +125°C (-40 to
+150°C derated, depending on product version)
• Supply voltage +2.7V to +5.5V
• Available in SSOP16 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°C to 85°C;
±0.25% FSO @ -40°C to 125°C)
Application Circuit (Examples)
Brief Description
ZMD31050 is a CMOS integrated circuit for highlyaccurate 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 with
correction coefficients stored in non-volatile
EEPROM.
The ZMD31050 accommodates virtually any bridge
sensor (e.g. piezo-resistive, ceramic-thick film or steel
membrane based). In addition, the IC can interface a
separate temperature sensor.
The bi-directional digital interfaces (I2C, SPI,
ZACwireTM) 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 ZMD31050
are mated digitally: fast, precise and without the cost
overhead associated with laser trimming, or
mechanical potentiometer methods.
Application kit available (SSOP16 samples,
calibration PCB, calibration software, technical
documentation)
Support for industrial mass calibration
available
Quick circuit customization possible for large
production volumes
Fig.1: Ratiometric measurement with voltage output,
temperature compensation via external diode
Datasheet, Rev. 1.0, April 11, 2006 Page 1 of 19 © ZMD AG, 2006
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.
Fig.2: Two-wire-
temperature compensation via internal diode
ZMD31050
Advanced Differential Sensor Signal Conditioner
Datasheet
Contents
1.
CIRCUIT DESCRIPTION ..............................................................................................................3
1.1 S
1.2 A
1.3 A
1.4 S
1.5 O
1.6 V
1.7 W
IGNAL FLOW
PPLICATION MODES
NALOG FRONT END
1.3.1. Programmable Gain Amplifier ............................................................................................. 5
1.3.2. Extended Zero Point Compensation (XZC).........................................................................5
1.3.3. Measurement Cycle realized by Multiplexer........................................................................6
1.3.4. Analog-to-Digital Converter ................................................................................................. 7
YSTEM CONTROL
UTPUT STAGE
1.5.1. Analog Output ...................................................................................................................10
1.5.2. Comparator Module (ALARM Output) ............................................................................... 10
1.5.3. Serial Digital Interface ....................................................................................................... 10
OLTAGE REGULATOR
ATCHDOG AND ERROR DETECTION
.............................................................................................................................. 3
...................................................................................................................4
(AFE) .........................................................................................................5
....................................................................................................................... 8
........................................................................................................................... 9
...............................................................................................................11
..........................................................................................11
2.
3.
4.
5.
5.1 A
5.2 O
5.3 B
5.4 E
5.5 I
6.
7.
8.
APPLICATION CIRCUIT EXAMPLES........................................................................................12
ESD/LATCH-UP-PROTECTION.................................................................................................13
PIN CONFIGURATION AND PACKAGE ...................................................................................13
IC CHARACTERISTICS ............................................................................................................. 14
BSOLUTE MAXIMUM RATINGS
PERATING CONDITIONS (VOLTAGES RELATED TO
UILD IN CHARACTERISTICS
LECTRICAL PARAMETERS (VOLTAGES RELATED TO
NTERFACE CHARACTERISTICS
RELIABILITY .............................................................................................................................. 19
CUSTOMIZATION ...................................................................................................................... 19
RELATED DOCUMENTS ...........................................................................................................19
...................................................................................................14
VSS) .......................................................14
.......................................................................................................15
VSS)...................................................... 17
...................................................................................................18
Datasheet, Rev. 1.0, April 11, 2006 Page 2 of 19 © ZMD AG, 2006
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.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Datasheet
1. Circuit Description
1.1 Signal Flow
Fig.3: ZMD31050 Block Diagram
PGA Programmable gain amplifier
MUX Multiplexer
ADC Analog-to-digital converter
CMC Calibration microcontroller
DAC Digital-to-analog converter
FIO1 Flexible I/O 1: analog out (voltage/current), PWM2,
ZACwire
FIO2 Flexible I/O 2: PWM1, SPI data out, SPI slave select, Alarm1, Alarm2
SIF Serial interface: I2C data I/O, SPI data in, clock
PCOMP Programmable comparator
EEPROM Non volatile memory for calibration parameters and configuration
TS On-chip temperature sensor (pn-junction)
ROM Memory for correction formula and –algorithm
PWM PWM module
TM
(one-wire-interface)
The ZMD31050’s signal path is partly analog (blue) and partly digital (red). The analog part is realized
differential – this means internal is the differential bridge sensor signal also handled via two signal
lines, which are rejected symmetrically around a common mode potential (analog ground = VDDA/2).
Consequently it is possible to amplify positive and negative input signals, which are located in the
common mode range of the signal input.
The differential signal from the bridge sensor is pre-amplified by the programmable gain amplifier
(PGA). The Multiplexer (MUX) transmits the signals from bridge sensor, external diode or separate
Datasheet, Rev. 1.0, April 11, 2006 Page 3 of 19 © ZMD AG, 2006
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.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Datasheet
temperature sensor to the ADC in a certain sequence (instead of the temperature diode the internal pnjunction (TS) can be used optionally). Afterwards the ADC converts these signals into digital values.
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 sensor-specific coefficients (stored into the
EEPROM during calibration). Dependent on the programmed output configuration the corrected sensor
signal is output as analog value, as PWM signal or in digital format (SPI, I2C,
ZACwire
signal is provided at 2 flexible I/O modules (FIO) and at the serial interface (SIF). The configuration
data and the correction parameters can be programmed into the EEPROM via the digital interfaces.
The modular circuit concept enables fast custom designs varying these blocks and, as a result,
functionality and die size.
1.2 Application Modes
For each application a configuration set has to be established (generally prior to calibration) by
programming the on-chip EEPROM regarding to the following modes:
Sensor channel
− Sensor mode: ratiometric voltage or current supply mode.
− Input range: The gain of the analog front end has to be chosen with respect to the maximum
sensor signal span and to this has also adjusted the zero point of the ADC
− Additional offset compensation: The extended analog offset compensation has to be enabled if
required, e.g. if the sensor offset voltage is near to or larger than the sensor span.
− Resolution/response time: The A/D converter has to be configured for resolution and converting
scheme (first or second order). These settings influence the sampling rate, signal integration time
and this way the noise immunity. The Sample Order influences the response time too.
− Ability to invert the sensor bridge inputs
Analog output
− Choice of output method (voltage value, current loop, PWM) for output register 1.
− Optional choice of additional output register 2: PWM via IO1 or alarm out module via IO1/2.
Digital communication: The preferred protocol and its parameter have to be set.
Temperature
−
The temperature measure source for the temperature correction has to be chosen.
−
The temperature measure source T1 sensor type
(only T1 is usable
for correction!!!)
for the temperature correction has to be chosen
− Optional: the temperature measure channel as the second output has to be chosen.
Supply voltage : For non-ratiometric output the voltage regulation has to be configured.
Note: Not all possible combinations of settings are allowed (see section 1.5).
The calibration procedure must include
− Set of coefficients of calibration calculation
and, depending on configuration,
− Adjustment of the extended offset compensation,
− Zero compensation of temperature measurement,
− Adjustment of the bridge current
and, if necessary,
− Set of thresholds and delays for the alarms and the reference voltage.
TM
). The output
Datasheet, Rev. 1.0, April 11, 2006 Page 4 of 19 © ZMD AG, 2006
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.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Datasheet
1.3 Analog Front End (AFE)
The analog front end consists of the programmable gain amplifier (PGA), the multiplexer (MUX) and the
analog-to-digital converter (ADC).
1.3.1. Programmable Gain Amplifier
The following tables show the adjustable gains, the processable sensor signal spans and the allowed
common mode range.
No. PGA
Gain a
1 420 30 7 2 2 43 - 57
2 280 30 4,66 2 3 40 - 59
3 210 15 7 2 4 43 - 57
4 140 15 4,66 2 6 40 - 59
5 105 15 3,5 2 8 38 - 62
6 70 7,5 4,66 2 12 40 - 59
7 52,5 7,5 3,5 2 16 38 - 62
8 35 3,75 4,66 2 24 40 - 59
9 26,3 3,75 3,5 2 32 38 - 62
10 14 1 7 2 50 43 - 57
11 9,3 1 4,66 2 80 40 - 59
12 7 1 3,5 2 100 38 - 62
13 2,8 1 1,4 2 280 21 - 76
Table 1: Adjustable gains, resulting sensor signal spans and common mode ranges
IN
Gain
Amp1
Gain
Amp2
Gain
Amp3
Max. span
V
in mV/V
IN_SP
Input range
V
in % VDDA
IN_CM
∗∗∗∗
1.3.2. Extended Zero Point Compensation (XZC)
The ZMD31050 supports two methods of sensor offset cancellation (zero shift):
• Digital offset correction
• XZC – an analog cancellation for large offset values (up to approx 300% of span)
The digital sensor offset correction will be processed at the digital signal correction/conditioning by the
CMC. The analog sensor offset pre-compensation will be needed for compensation of large offset
values, which would be overdrive the analog signal path by uncompensated gaining. For analog sensor
offset pre-compensation a compensation voltage will be added in the analog pre-gaining signal path
(coarse offset removal). The analog offset compensation in the AFE can be adjusted by 6 EEPROM
bits. It allows an analog zero point shift up to 300% of the processable signal span.
The zero point shift of the temperature measurements can also be adjusted by 6 EEPROM bits
(Z
= -20…+20) and is calculated by:
XZC
V
/ VDDBR= k * Z
XZC
/ ( 20 * aIN)
XZC
∗
Bridge in voltage mode, refer “ZMD31050 Functional description” for usable input signal/common mode range at bridge in current mode
Datasheet, Rev. 1.0, April 11, 2006 Page 5 of 19 © ZMD AG, 2006
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.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Datasheet
PGA gain
aIN
420 2 3,0 15% +/- 7 330
280 3 1,833 9% +/- 6 200
210 4 3,0 15% +/- 14 330
140 6 1,833 9% +/- 12 200
105 8 1,25 6% +/- 12 140
70 12 1,833 9% +/- 24 200
52,5 16 1,25 6% +/- 22 140
35 24 1,833 9% +/-48 200
26,3 32 1,25 6% +/- 45 140
14 50 3,0 15% +/- 180 330
9,3 80 1,833 9% +/- 160 200
7 100 1,25 6% +/- 140 140
2,8 280 0,2 1% +/- 60 22
Note: Z
Max. span
V
IN_SP
in mV/V
Calculation
factor k
Offset shift per step
in % full span
Approx. maximum
offset shift in mV/V
Approx. maximum
shift in [% V
Table 2: Extended Zero Point Compensation Range
can be adjusted in range –31 to 31, parameters are guaranteed only in range –20 to 20.
XZC
IN_SP]
(@ ± 20 steps)
1.3.3. Measurement Cycle realized by Multiplexer
The Multiplexer selects, depending on EEPROM settings, the following inputs in a certain sequence.
Internal offset of the input channel measured by input short circuiting
Bridge temperature signal measured by external and internal diode (pn-junction)
Bridge temperature signal measured by bridge resistors
Separate temperature signal measured by external thermistor
Pre-amplified bridge sensor signal
The complete measurement cycle is
controlled by the CMC. The cycle diagram
at the right shows its principle structure.
The EEPROM adjustable parameters are:
Pressure measurement count,
n=<1,2,4,8,16,32,64,128>
Enable temperature measurement 2,
e2=<0,1>
After Power ON the start routine is called. It
contains the pressure and auto zero
measurement. When enabled it measures the
→
→
→
→
→
→
→
→
→
→
→
Start routine
n Pressure measurement
1 Temp 1 auto zero
n Pressure measurement
1 Temp 1 measurement
n Pressure measurement
1 Pressure auto zero
n * e2 Pressure measurement
e2 Temp 2 auto zero
n * e2
Pressure measurement
*
e2 * Temp 2 measurement
temperature and its auto zeros.
Fig. 4: Measurement cycle ZMD31050
Datasheet, Rev. 1.0, April 11, 2006 Page 6 of 19 © ZMD AG, 2006
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.
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