ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Features
Benefits
• Digital compensation of sensor offset, sensitivity,
temperature drift and non-linearity
• Accommodates differential sensor signal spans from
1.2mV/V to 60mV/V
• ZACwireTM one-wire interface.
• Internal temperature compensation and detection
via bandgap PTAT*
• Optional sequential output of both temperature and
bridge readings on ZACwireTM digital output
• Output options: rail-to-rail analog output voltage,
absolute analog voltage, digital one-wire-interface
• Supply voltage 2.7 to 5.5V, with external JFET 5.5V
to 30V
• Current consumption, depending on adjusted
sample rate: 0.25mA to 1mA
• Wide operational temperature: –50 to +150°C
• Fast response time 1ms(typical)
• High voltage protection up to 30V with external JFET
• Chopper-stabilized true differential ADC
• Buffered and chopper-stabilized output DAC
* Proportional to absolute temperature
• No external trimming components required
• PC-controlled configuration and calibration via onewire interface – simple, low cost
• High accuracy (±0.1% FSO @ -25 to 85°C; ±0.25%
FSO @ -40 to 125°C)
• Single pass calibration – quick and precise
• Suitable for battery-powered applications
• Small SOP8 package
Application Circuit
Typical RBic Lite
TM
Brief Description
The RBicLite™ is a CMOS integrated circuit, which
enables easy and precise calibration of resistive
bridge sensors via EEPROM. When mated to a
resistive bridge sensor, it will digitally correct offset
and gain with the option to correct offset and gain
coefficients and linearity over temperature. A second
order compensation can be enabled for temperature
coefficients of gain and offset or bridge linearity.
RBicLite™ communicates via ZMD’s ZACwireTM serial
interface to the host computer and is easily mass
calibrated in a Windows® environment. Once calibrated, the output SIG™ pin can provide selectable 0
to 1V, rail-to-rail ratiometric analog output, or digital
serial output of bridge data with optional temperature
data.
•
Development Kit available
•
Multi-Unit Calibrator Kit available
•
Support for industrial mass calibration available
•
Quick circuit customization possible for large
production volumes
Application Circuit
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 1 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
CONTENTS
1
CIRCUIT DESCRIPTION ............................................................................................................................ 4
1.1
SIGNAL FLOW AND BLOCK DIAGRAM ..........................................................................................................................4
1.2
ANALOG FRONT END ................................................................................................................................................5
1.2.1
Bandgap/PTAT and PTAT Amplifier..............................................................................................................5
1.2.2
Bridge Supply ................................................................................................................................................5
1.2.3
Pre-Amp Block ..............................................................................................................................................5
1.2.4
Analog-to-Digital Converter (ADC) ................................................................................................................5
1.3
DIGITAL SIGNAL PROCESSOR ....................................................................................................................................6
1.3.1
EEPROM.......................................................................................................................................................7
1.3.2
One-Wire Interface - ZACwireTM ....................................................................................................................7
1.4
OUTPUT STAGE .......................................................................................................................................................7
1.4.1
Digital to Analog Converter (Output DAC).....................................................................................................7
1.4.2
Output Buffer .................................................................................................................................................8
1.4.3
Voltage Reference Block...............................................................................................................................8
1.5
CLOCK GENERATOR / POWER ON RESET (CLKPOR) .................................................................................................8
1.5.1
Trimming the Oscillator .................................................................................................................................9
2
FUNCTIONAL DESCRIPTION.................................................................................................................... 9
2.1
GENERAL WORKING MODE .......................................................................................................................................9
2.2
ZACWIRETM COMMUNICATION INTERFACE ................................................................................................................10
2.2.1
Properties and Parameters .........................................................................................................................10
2.2.2
Bit Encoding ................................................................................................................................................11
2.2.3
Write Operation from Master to RBicLiteTM ...................................................................................................11
2.2.4
RBICLiteTM READ Operations .......................................................................................................................11
2.2.5
High Level Protocol .....................................................................................................................................14
2.3
COMMAND/DATA PAIR ENCODING ............................................................................................................................14
2.4
CALIBRATION SEQUENCE: .......................................................................................................................................17
2.5
EEPROM BITS .....................................................................................................................................................19
2.6
CALIBRATION MATH ................................................................................................................................................22
2.6.1
Correction Coefficients ................................................................................................................................22
2.6.2
Interpretation of Binary Numbers for Correction Coefficients: .....................................................................22
2.7
READING EEPROM CONTENTS ..............................................................................................................................26
3
APPLICATION CIRCUIT EXAMPLES ...................................................................................................... 27
3.1
3.2
3.3
3.4
THREE-WIRE RAIL-TO-RAIL RATIOMETRIC OUTPUT ...................................................................................................27
ANALOG VOLTAGE OUTPUT .....................................................................................................................................28
THREE-WIRE RATIOMETRIC OUTPUT WITH OVER-VOLTAGE PROTECTION ....................................................................29
DIGITAL OUTPUT ....................................................................................................................................................29
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 2 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
4
ESD/LATCH-UP-PROTECTION ............................................................................................................... 29
5
PIN CONFIGURATION AND PACKAGE .................................................................................................. 30
6
IC CHARACTERISTICS............................................................................................................................ 31
6.1
6.2
6.3
6.4
6.5
6.6
7
ABSOLUTE MAXIMUM RATINGS ................................................................................................................................31
RECOMMENDED OPERATING CONDITIONS.................................................................................................................31
ELECTRICAL PARAMETERS ......................................................................................................................................32
ANALOG INPUTS .....................................................................................................................................................33
TEMPERATURE COMPENSATION AND TEMPERATURE OUTPUT .....................................................................................34
HIGH VOLTAGE OPERATION ....................................................................................................................................35
DIE DIMENSIONS AND PAD COORDINATES ........................................................................................ 36
7.1
7.2
DIE DIMENSIONS ....................................................................................................................................................36
PAD COORDINATES ................................................................................................................................................37
8
TEST ......................................................................................................................................................... 37
9
RELIABILITY ............................................................................................................................................. 37
10
CUSTOMIZATION..................................................................................................................................... 37
11
RELATED DOCUMENTS.......................................................................................................................... 38
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 3 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
1
Circuit Description
1.1 Signal Flow and Block Diagram
The RBicLiteTM series of resistive bridge sensor interface ICs were specifically designed as a cost-effective
solution for sensing in building automation, industrial, office automation and white goods applications.
The RBicLiteTM employs ZMD’s high precision bandgap with proportional-to-absolute-temperature (PTAT)
output; low-power 14-bit analog-to-digital converter (ADC, A2D, A-to-D); and on-chip DSP core with EEPROM
to precisely calibrate the bridge output signal.
Three selectable outputs, two analog and one digital, offer the ultimate in versatility across many applications.
The RBicLite™ rail-to-rail ratiometric analog output Vout signal (0 to 5V Vout @ VDD=5V) suits most building
automation and automotive requirements.
Typical office automation and white goods applications require the 0~1Vout signal, which in the RBicLite™ is
referenced to the internal bandgap.
Direct interfacing to μP controllers is facilitated via ZMD’s single-wire serial ZACwireTM digital interface.
RBicLite™ is capable of running in high-voltage (5.5-30V) systems when combined with an external JFET.
Figure 1.1 – RBicLite
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
TM
Page 4 of 38
Block Diagram
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
1.2
Analog Front End
1.2.1 Bandgap/PTAT and PTAT Amplifier
The Bandgap/PTAT provides the PTAT signal to the ADC, which allows accurate temperature conversion. In
addition, the ultra-low ppm Bandgap provides a stable voltage reference over temperature for the operation of
the rest of the IC.
The PTAT signal is amplified through a path in the pre-amp and fed to the ADC for conversion. The most
significant 12-bits of this converted result are used for temperature measurement and temperature correction
of bridge readings. When temperature is output in digital mode only the most significant 8-bits are given.
1.2.2 Bridge Supply
The voltage driven bridge is usually connected to VDD and ground. As a power savings feature, the RBicLite™
also includes a switched transistor to interrupt the bridge current via pin 1 (Bsink). The transistor switching is
synchronized to the A-to-D conversion and released after finishing the conversion. To utilize this feature, the
low supply of the bridge should be connected to Bsink instead of ground.
Depending on the programmable update rate, the average current consumption (including bridge current) can
be reduced to approximately 20%, 5% or 1%.
1.2.3 Pre-Amp Block
The differential signal from the bridge is amplified through a chopper-stabilized instrumentation amplifier with
very high input impedance designed for low noise and low drift. This pre-amp provides gain for the differential
signal and re-centers its DC to VDD/2. The output of the Pre-Amp block is fed into the A-to-D converter. The
calibration sequence performed by the digital core includes an auto zero sequence to null any drift in the
Pre-Amp state over temperature.
The Pre-Amp is nominally set to a gain of 24. Other possible gain settings are 6, 12, and 48.
The inputs to the Pre-Amp from (VBN/VBP pins) can be reversed via an EEPROM configuration bit.
1.2.4 Analog-to-Digital Converter (ADC)
A 14-bit/1ms 2nd order charge-balancing ADC is used to convert signals coming from the pre-amplifier. The
converter, designed in full differential switched capacitor technique, is used for converting the various signals
in the digital domain. This principle offers the following advantages:
•
High noise immunity because of the differential signal path and integrating behavior
•
Independent from clock frequency drift and clock jitter
•
Fast conversion time owing to second order mode
Four selectable values for the zero point of the input voltage allow conversion to adapt to the sensor’s offset
parameter. Together with the reverse input polarity mode, this results in four possible zero point adjustments.
The conversion rate varies with the programmed update rate. The fastest conversation rate is 1k samples/s
and the response time is then 1ms. Based on a best fit, the Integral Nonlinearity (INL) is less then 4 LSB14Bit.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 5 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
1.3 Digital Signal Processor
A digital signal processor (DSP) is used for processing the converted bridge data as well as performing
temperature correction and computing the temperature value for output on the digital channel.
The digital core reads correction coefficients from EEPROM and can correct for
1. Bridge Offset
2. Bridge Gain
3. Variation of Bridge Offset over Temperature (Tco)
4. Variation of Bridge Gain over Temperature (Tcg)
5. A Single Second Order Effect (SOT) (Second Order Term)
The EEPROM contains a single SOT that can be applied to correct one and only one of the following:
•
2nd Order behavior of bridge measurement
•
2nd Order behavior of Tco
• 2nd Order behavior of Tcg
(For more details, see section 2.5.1.)
If the SOT applies to correcting the bridge reading then the correction formula for the bridge reading is
represented as a two step process as follows:
ZB
BR
= GainB[1 + ΔT*Tcg]*[BR_Raw + OffsetB + ΔT*Tco]
= ZB*(1.25+SOT*ZB)
Where: BR
ZB
BR_Raw
T_Raw
Gain_B
Offset_B
Tcg
Tco
ΔT
T_Raw
TSETL
SOT
=
=
=
=
=
=
=
=
Corrected Bridge reading that is output as digital or analog on SIGTM pin
Intermediate result in the calculations
Raw Bridge reading from ADC
Raw Temp reading converted from PTAT signal
Bridge gain term
Bridge offset term
Temperature coefficient gain
Temperature coefficient offset
=
=
=
=
(T_Raw - TSETL)
Raw Temp reading converted from PTAT signal
T_Raw reading at which low calibration was performed (typically 25C)
Second Order Term
Note: See section 2.5.2.7 for limitations.
If the SOT applies to correcting 2nd Order behavior of Tco then the formula for bridge correction is as follows:
BR
= Gain_B[1 + ΔT*Tcg]*[BR_Raw + Offset_B + ΔT(SOT*ΔT + Tco)]
Note: See section 2.5.2.7 for limitations.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 6 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
If the SOT applies to correcting 2nd Order behavior of Tcg then the formula for bridge correction is as follows:
BR
= Gain_B[1 + ΔT(SOT*ΔT + Tcg)]*[BR_Raw + Offset_B_ + ΔT*Tco)]
The bandgap reference gives a very linear PTAT signal, so temperature correction can always simply be
accomplished with a linear gain and offset term.
Corrected Temp Reading:
T
= Gain_T*[T_Raw + Offset_T]
Where
T_Raw
Offset_T
Gain_T
=
=
=
Raw Temp reading converted from PTAT signal
TempSensor offset coefficient
TempSensor gain coefficient
1.3.1 EEPROM
The EEPROM contains the calibration coefficients for gain and offset, etc., and the configuration bits, such as
output mode, update rate, etc. When programming the EEPROM, an internal charge pump voltage is used so
a high voltage supply is not needed.
The charge pump is internally regulated to 12.5 V voltage and the programming time amounts to 6ms.
1.3.2 One-Wire Interface - ZACwireTM
The IC communicates via a one-wire serial interface. There are different commands available for the
following:
1.4
•
Reading the conversion result of the ADC (Get_BR_Raw, Get_T_Raw)
•
Calibration Commands
•
Entering various test modes
o DAC test modes
o Oscillator, 1V, and Pre-Amp
o EEPROM test modes
o Oscillator override & Scan test modes
•
Reading from the EEPROM (dump of entire contents)
•
Writing to the EEPROM (trim setting, configuration, and coefficients)
Output Stage
1.4.1 Digital to Analog Converter (Output DAC)
An 11-bit DAC based on sub-ranging resistor strings is used for the digital-to-analog output conversion in the
analog ratiometric and absolute analog voltage modes. Selection during calibration configures the system to
operate in either of these modes. The design allows for excellent testability as well as low power
consumption.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 7 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
1.4.2 Output Buffer
A rail-to-rail op amp configured as a unity gain buffer can drive resistive loads (whether pull-up or pull-down)
as low as 2.5kΩ and capacitances up to 15nF. In addition, to limit the error due to amplifier offset voltage, an
error compensation circuit is included which tracks and reduces offset voltage to < 1mV.
1.4.3 Voltage Reference Block
This block uses the absolute reference voltage provided by the bandgap to produce two regulated on-chip
voltage references. A 1V reference is used for the output DAC high reference when the part is configured in
0-1V analog output mode. For this reason, the 1V reference must be very accurate and includes trim so that
its value can be trimmed within +/- 2mV of 1.00V. The 1V reference is also used as the on-chip reference for
the JFET regulator block so the regulation set point of the JFET regulator can be fine tuned using the 1V trim.
1V Reference Trim (1V vs. Trim for Nominal Process Run):
1Vref_trim3
1Vref_trim2
1Vreft_trim1
1Vref_trim0
1Vref deltaV
5Vref deltaV
1
1
1
1
-0.0184
-0.0920
1
1
1
0
-0.0161
-0.0805
1
1
0
1
-0.0138
-0.0690
1
1
0
0
-0.0115
-0.0575
1
0
1
1
-0.0092
-0.0460
1
0
1
0
-0.0069
-0.0345
1
0
0
-0.0046
-0.0230
1
0
0
1
0
-0.0023
-0.0115
0
1
1
1
Nominal
Nominal
0
1
1
0
+0.0023
+0.0115
0
1
0
1
+0.0046
+0.0230
0
1
0
0
+0.0069
+0.0345
0
0
1
1
+0.0092
+0.0460
0
0
1
0
+0.0115
+0.0575
0
0
0
+0.0138
+0.0690
0
0
0
1
0
+0.0161
+0.0805
Sample: Programming “0000” → the trimmed voltage = nominal value + 0.0161V
1.5 Clock Generator / Power On Reset (CLKPOR)
If the power supply exceeds 2.5V (maximum), the reset signal de-asserts and the clock generator starts
working at a frequency of approximately 512kHz (±20%). The exact value only influences the conversion
cycle time and communication to the outside world but not the accuracy of signal processing. In addition, to
minimize the oscillator error as the VDD voltage changes, an on-chip regulator is used to supply the oscillator
block.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 8 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
1.5.1 Trimming the Oscillator
Trimming is performed at wafer level, and it is strongly recommended that this not be changed during
calibration because ZACwireTM communication is no longer guaranteed at different oscillator frequencies.
Trimming Bits
Delta Frequency (KHz)
100
+385
101
+235
110
+140
111
000
001
010
011
+65
Nominal
-40
-76
-110
Sample: Programming “011” → the trimmed frequency = nominal value – 110KHz
2
Functional Description
2.1 General Working Mode
The command/data transfer takes place via the one-wire Sig™ pin using the ZACwireTM serial communication
protocol.
After Power ON the IC waits for 6ms(=Command window) for the Start_CM command.
Without this command, the Normal Operation Mode (NOM) starts. In this mode, raw bridge values are
converted, and the corrected values are presented on the output in analog or digital format (depending on the
configuration stored in EEPROM).
Command Mode (CM) can only be entered during the 6ms command window after Power ON. If the IC
receives the Start_CM command during the command window, it remains in the Command Mode. The CM
allows changing to one of the other modes via command. After command Start_RW, the IC is in the Raw
Mode. Without correction, the raw values are transmitted to the digital output in a predefined order. The RM
can only be stopped by Power OFF. Raw Mode is used by the calibration software for collection of raw bridge
and temperature data so the correction coefficients can be calculated.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 9 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Power
ON
Command
Window (6ms)
Send Start CM
Start_CM
No Command
Normal Operation Mode
Start_NOM
No commands possible
Measurement cycle
Conditioning calculation
(Corrected bridge and
temperature values)
Depending on the conTM
figuration, the Sig pin is
•
0V-1V
•
Rail-to-rail ratiometric
•
Digital output
Diagnostics functions
Command Mode
Start_RM
Measurement cycle
stopped
Full command set
Command routine will be
processed after each
command
Raw Mode
Measurement cycle
TM
Sig pin provides raw
bridge and temperature
values in the format
st
Bridge_high (1 Byte)
nd
Bridge_low
(2 Byte)
rd
Temp
(3 Byte)
Power OFF
Figure 2.1 – General Working Mode
ZACwireTM Communication Interface
2.2
2.2.1
Properties and Parameters
Parameter
Symbol
Min Typ Max
Unit
Comments
30
kΩ
On-chip pull-up resistor switched on
during Digital Output Mode and
during CM Mode (first 6ms power up)
1
Pull-up resistor
(on-chip)
RZAC,pu
2
ZACwireTM rise time
TZAC,rise
5
μs
Any user RC network included in
SigTM path must meet this rise time
3
ZACwire™ line resistance
RZAC,line
3.92
kΩ
Also see section 6.3
4
ZACwireTM load capacitance
CZAC,load
1
15
nF
Also see section 6.3
5
Voltage level - low
VZAC,low
0
0.2
VDD
Rail-to-rail CMOS driver
6
Voltage level - high
VZAC,high
VDD
Rail-to-rail CMOS driver
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
0
0.8
1
Page 10 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
2.2.2
Bit Encoding
Bit window
Start bit
=> 50% duty cycle used to set up strobe time
Logic 1
=> 75% duty cycle
Logic 0
=> 25% duty cycle
Start Bit
Logic 1
Logic 0
Figure 2.2 – Duty Cycle Manchester
2.2.3 Write Operation from Master to RBicLiteTM
The calibration master sends a 19-bit packet frame to the IC.
S
Start Bit
P
Parity Bit Command Byte
or Parity Bit Data Byte
2
Command Bit (Example: Bit 2)
2
Data Bit (Example: Bit 2)
19-Bit Frame (WRITE)
S 7 6 5 4 3 2 1 0 P 7 6 5 4 3 2 1 0 P
Command Byte
Data Byte
Figure 2.3 – 19-Bit Write Frame
The incoming serial signal will be sampled at a 512kHz clock rate. This protocol is very tolerant to clock skew
and can easily tolerate baud rates in the 6kHz to 48kHz range.
2.2.4
RBICLiteTM READ Operations
The incoming frame will be checked for proper parity on both command and data bytes, as well as for any
edge timeouts prior to a full frame being received.
Once a command/data pair is received, the RBicLiteTM will perform that command. Once the command has
been successfully executed by the IC, it will acknowledge success by a transmission of an A5H byte back to
the master. If the master does not receive an A5H transmission within 130msec of issuing the command, it
must assume the command was either improperly received or could not be executed.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 11 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
1 DATA Byte Packet
S
Start Bit
P
Parity Bit Data Byte
0
Data Bit (Low)
1
Data Bit (High)
10-Bit Byte A5H
S 1 0 1 0 0 1 0 1 P
Data Byte
Figure 2.4 – Read Acknowledge
RBicLiteTM
The
transmits 10-bit bytes (1 start bit, 8 data, 1 parity). During calibration and configuration,
transmissions are normally either A5H or data. A5H indicates successful completion of a command. There are
two different digital output modes configurable (digital output with temperature and digital output with only
bridge data). During Normal Operation Mode, if the part is configured for digital output of the bridge reading, it
first transmits the high byte of bridge data followed by the low byte. The bridge data is 14-bits in resolution, so
the upper two bits of the high byte are always zero padded. There is a half stop bit time between bytes in a
packet. That means for the time of a half a bit width, the signal level is high.
2 DATA Byte Packet
S
Start Bit
P
Parity Bit Data Byte
2
Data Bit (Example: Bit 2)
Digital Bridge Output
S 0 0 5 4 3 2 1 0 P
½ S 77 6 5 4 3 2 1 0 P
Stop
Data Byte Bridge High
Data Byte Bridge Low
½
Stop
½ Stop Bit
Figure 2.5 – Digital Output (NOM) Bridge Readings
The second different digital output mode is digital output bridge reading with temperature. It will be transmitted
as 3 data packets. The temperature byte represents an 8-bit temperature quantity spanning from –50°C to
150°C.
3 DATA Byte Packet
Digital Bridge Output with Temperature
S 0 0 5 4 3 2 1 0 P
½ S 77 6 5 4 3 2 1 0 P ½ S 77 6 5 4 3 2 1 0 P
Stop
Stop
Data Byte Bridge High
Data Byte Bridge Low
Data Byte Temperature
Figure 2.6 – Digital Output (NOM) Bridge Readings with Temperature
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 12 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
The EEPROM transmission occurs in a packet with 14 data bytes as shown in Figure 2.7.
Figure 2.7 – Read EEPROM Contents
There is a variable idle time between packets. This idle time varies with the update rate setting in EEPROM.
Packet Transmission
(This example shows 2 data packets.)
IDLE
½
IDLE
½
IDLE
6 5 4 3 2 1 0 P TIME S 070 5 4 3 2 1 0 P Stop S 77 6 5 4 3 2 1 0 P TIME S 07 0 5 4 3 2 1 0 P Stop S 776 5 4 3 2 1 0 P TIME S 07 0 5 4 3
Figure 2.8 – Transmission of a Number of Data Packets
The table below shows the idle time between packets versus update rate. This idle time can vary by nominal
+/-15% between parts and over a temperature range of –50°C to 150°C
Update Rate Setting:
00
01
10
11
Idle Time between Packets:
1ms
4.85ms
22.5ms
118ms
Transmissions from the IC occur at one of two speeds depending on the update rate programmed in
EEPROM. If the user chooses one of the two fastest update rates (1ms or 5ms) then the baud rate of digital
transmission will be 32kHz. If however, the user chooses one of the two slower update rates (25ms or
125ms), then the baud rate of digital transmission will be 8kHz.
One can easily program any standard μcontroller to communicate with the RBicLiteTM. ZMDA can provide
sample code for a MicroChip PIC μController.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 13 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
2.2.5 High Level Protocol
The RBicLiteTM will listen for a command/data pair to be transmitted for the 6ms after the de-assert of its
internal Power On Reset (POR). If a transmission is not received within this time frame, then it will transition
to Normal Operation Mode (NOM). In NOM, it will output bridge data in either 0-1V analog, rail-to-rail
ratiometric analog output, or digital depending on how the part is currently configured.
If the RBicLiteTM receives a Start CM command within the first 6ms after the de-assert of POR, then it will go
into Command Mode(CM). In this mode, calibration/configuration commands will be executed. The RBicLiteTM
will acknowledge successful execution of commands by transmission of an A5H. The calibrating/configuring
master will know a command was not successfully executed if no response is received after 130ms of issuing
the command. Once in command interpreting/executing mode, the RBicLiteTM will stay in this mode until power
is removed, or a Start NOM (Start Normal Operation Mode) command is received. The START CM command
is used as an interlock mechanism to prevent a spurious entry into command mode on power up. The first
command received within the 6ms window of POR must be a START CM command to enter into command
interpreting mode. Any other commands will be ignored.
2.3 Command/Data Pair Encoding
The 16-bit command/data stream sent to the RBicLiteTM can be broken into four 4-bit nibbles. The most
significant nibble encodes the command. The 2nd nibble is reserved for possible future expansion, and should
be sent as “0x0”. The last two nibbles encode the data byte.
Command nibble:
Data:
Description:
0H
0XXH
Read EEPROM Command via SIGTM pin.
2H
0YXH
Enter Test Mode (Subset of command mode for testing
purpose only): SIGTM pin will assume the value of different
internal test points, depending on most significant nibble of
data sent.
Y = 0H => Internal oscillator
Y = 1H => 2.5V reference
Y = 2H => PTAT
Y = 3H => Pre-Amp Output+
Y = 4H => Scan Mode (SDO* routed to SIG TM pin, part goes
into Clock Override Mode and Scan Mode)
Y = 5H => DAC Ramp testmode. Gain_b[13:3] contains the
starting point, and the increment is (offset_b/8). The
increment will be added every 125usec.
Y = 6-7H => Part goes into Clock Override Mode.
Y = 8-FH => Undefined.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 14 of 38
© ZMD AG, 2006
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written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Command nibble:
Data:
Description:
3H
0WDH
X => Don’t care
W =>
What
Trim/Configure: 3rd nibble determines what is
trimmed/configured. 4th nibble is data to be programmed.
3rd
4th
nibble
data nibbles
Description:
0H
XH
Trim oscillator least significant
3 bits of data used.
1H
XH
Trim 1V reference. Least
significant 4 bits of data used.
2H
XH
Offset Mode. Least significant
2 bits of data used.
3H
XH
Set output mode. Least
significant 2 bits used.
4H
XH
Set update rate. Least
significant 2 bits used.
5H
XH
Configure JFET regulation
6H
XH
Program the tc_cfg register.
Least significant 3-bits used.
Most significant bit of data
nibble should be 0.
7H
XH
Program bits [99:96] of
EEPROM.
{SOT_cfg,Pamp_Gain}
8H
XH
Clear all case: Used to clear all
bits in EEPROM to 0.
H => Hex
D =>
Data
H => Hex
9H
XH
AH
XH
BH
XH
CH
XH
7H &
C-FH
XH
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 15 of 38
0101… case: Used to set
whole EEPROM to alternating
pattern.
1010…case: Used to set
opposite alternating pattern.
Set all case: Used to set all bits
in EEPROM to 1.
EEPROM Endurance Mode.
Initial setting of Offset_B[13:3]
determines the # of cycles.
Offset_t must be programmed
to zero initially.
Reserved.
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Command nibble:
Data:
Description:
4H
000H
Start NOM => Ends Command Mode, transition to Normal
Operation Mode Mode.
4H
010H
Start Raw Mode (RM)
In this mode if Gain_B = 800H, and Gain_T = 80H then the
digital output will simply be the raw values of the A2D for the
Bridge reading, and the PTAT conversion.
5H
000H
START CM => Start the Command Mode, used to enter
command interpret mode. If data is sent with this command
then that data sets up the start data for the DAC Test Mode.
6H
0YYH
Program SOT (2nd Order Term).
7H
0YYH
Program TSETL
8H
0YYH
Program Gain_B upper 7-bits (Set MSB of YY to 0.)
9H
0YYH
Program Gain_B lower 8-bits
AH
0YYH
Program Offset_B upper 6-bits (Set two MSBs of YY to 0.)
BH
0YYH
Program Offset_B lower 8-bits
CH
0YYH
Program Gain_T
DH
0YYH
Program Offset_T
EH
0YYH
Program Tco
FH
0YYH
Program Tcg
*SDO: Scan Data Out
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 16 of 38
© ZMD AG, 2006
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written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Calibration Sequence:
Although the RBicLiteTM can function with many different types of resistive bridges, assume it is connected to a
pressure bridge for the following calibration example.
In this case, calibration essentially involves collecting raw bridge and temperature data from the RBicLiteTM for
different known pressures and temperatures. This raw data can then be processed by the calibration master
(the PC), and the calculated coefficients can then be written to the EEPROM of the RBicLiteTM.
ZMDA can provide software and hardware with samples to perform the calibration.
There are three main steps to calibration:
1. Assigning a unique identification to the IC. This identification is programmed in EEPROM and can be
used as an index into the database stored on the calibration PC. This database will contain all the raw
values of bridge readings and temp reading for that part, as well as the known pressure and
temperature the bridge was exposed to. This unique identification can be stored in a combination of
the following EEPROM registers TSETL, Tcg, Tco. These registers will be overwritten at the end of the
calibration process, so this unique identification is not a permanent serial number.
2. Data collection. Data collection involves getting raw data from the bridge at different known pressures
and temperatures. This data is then stored on the calibration PC using the unique identification of the
IC as the index to the database.
3. Coefficient calculation and write. Once enough data points have been collected to calculate all the
desired coefficients then the coefficients can be calculated by the calibrating PC and written to the IC.
Step 1 Assigning Unique Identification
Assigning a unique identification number is as simple as using the commands Program TSETL, Program Tcg,
and Program Tco. These 3 8-bit registers will allow for 16Meg unique devices. In addition Gain_B needs to be
programmed to 800H (unity) and Gain_T needs to be programmed to 80H (unity).
Step 2 Data Collection
The number of different unique (pressure, temperature) points that calibration needs to be performed at
depends on the customer’s needs. The minimum is a 2-point calibration, and the maximum is a 5-point
calibration. To acquire raw data from the part one has to get RBicLiteTM to enter Raw Mode. This is done by
issuing a Start CM (Start Command Mode 5000H) command to the IC followed by a Start RM (Start Raw
Mode 4010H) command with the LSB of the upper data nibble set. Now if the Gain_B term was set to unity
(800H) and the Gain_T term was also set to unity (80H) then the part will be in the Raw Mode and will be
outputting raw data on its SIGTM pin instead of corrected bridge and temperature. The calibration system
should now grab several of these data points (16 each of bridge and temperature is recommended) and
average them. These raw bridge and temperature setting should be stored in the database along with the
known pressure and temperature. The ouput format during Raw Mode is Bridge_High, Bridge_Low, Temp.
Each of these being 8-bit quantities. The upper 2-bits of Bridge_High are zero filled. The Temp data (8-bits
only) would not really be enough info for accurate temperature calibration. Therefore the upper three bits of
temp information are not given, but rather assumed known. Therefore effectively 11-bits of temperature
information is provided in this mode.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 17 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Step 3 Coefficient Calculations
The math to perform the coefficient calculation is very complicated and will not be discussed in detail. There is
a rough overview in the “Calibration Math” section. Rather ZMDA will provide software to perform the
coefficient calculation. ZMDA can also provide source code of the algorithms in a C code format. Once the
coefficients are calculated the final step is to write them to the EEPROM of the RBicLiteTM.
The number of calibration points required can be as few as two or as many as five. This depends on the
precision desired, and the behavior of the resistive bridge in use.
1. 2-point calibration would be used if one simply wanted a gain and offset term for a bridge with no
temperature compensation for either term.
2. 3-point calibration would be used if one wanted to have 1st order compensation for the Tco.
3. 3-point calibration could also be used if one wanted 2nd order correction for the bridge, but no
temperature compensation of the bridge output.
4. 4-point calibration would be used if one wanted 1st order compensation for both Tco and Tcg.
5. 4-point calibration could also be used if one wanted 1st order compensation for the Tco and 2nd order
correction for the bridge measurement.
6. 5-point calibration would be used if one wanted both 1st order Tco correction and 1st order Tcg
correction, plus a 2nd order correction that could be applied to one and only one of the following: 2nd
order Tco, 2nd order Tcg, or 2nd order bridge.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 18 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
2.4 EEPROM Bits
Programmed through the serial interface:
EEPROM
Range
Description
Note
2:0
Osc_Trim
See the table in the “Trimming the Oscillator”
section for complete data
100 => Fastest
101 => 3 clicks faster than nominal
.
111 => 1 click faster than nominal
000 => Nominal
001 => 1 click slower than nominal
.
010 => 2 clicks slower than nominal
011 => Slowest
6:3
1V_Trim/JFET_Trim
See table in the “Voltage Reference Block”
section.
8:7
A2D_Offset
Offset selection:
11 => [-1/2,1/2] mode bridge inputs
10 => [-1/4,3/4] mode bridge inputs
01 => [-1/8,7/8] mode bridge inputs
00 => [-1/16,15/16] mode bridge inputs
To change the bridge signal polarity set
Tc_cfg[3](=Bit 87)
10:9
Output_Select
00 => Digital (3-bytes with parity)
Bridge High {00,[5:0]}
Bridge Low [7:0]
Temp [7:0]
01 => 0-1V Analog
10 => Rail-to-rail ratiometric analog output
11 => Digital (2-bytes with parity) (No Temp)
Bridge High {00,[5:0]}
Bridge Low [7:0]
12:11
Update_Rate
00 => 1 msec (1kHz)
01 => 5 msec (200Hz)
10 => 25 msec (40Hz)
11 => 125 msec (8 Hz)
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 19 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
EEPROM
Range
Description
Note
14:13
JFET_Cfg
00 => No JFET regulation (lower power)
01 => No JFET regulation (lower power)
10 => JFET regulation centered around 5.0V
11 => JFET regulation centered around 5.5V
(i.e. over-voltage protection).
29:15
Gain_B
Bridge Gain:
Gain_B[14] => mult x 8
Gain_B[13:0] => 14-bit unsigned number
representing a number in the range [0,8).
43:30
Offset_B
Signed 14-bit offset for bridge correction
51:44
Gain_T
Temperature gain coefficient used to correct
PTAT reading.
59:52
Offset_T
Temperature offset coefficient used to correct
PTAT reading.
67:60
TSETL
Stores Raw PTAT reading at temperature in
which low calibration points were taken
75:68
Tcg
Coefficient for temperature correction of bridge
gain term.
Tcg = 8-bit magnitude of Tcg term. Sign is
determined by tc_cfg (bits 87:84)
83:76
Tco
Coefficient for temperature correction of bridge
offset term.
Tco = 8-bit magnitude of Tco term. Sign and
scaling are determined by tc_cfg (bits 87:84)
87:84
Tc_cfg
This 4-bit term determines options for
Temperature compensation of the bridge.
Tc_cfg[3] => If set, Bridge Signal Polarity flips
Tc_cfg[2] => If set Tcg is negative
Tc_cfg[1] => Scale magnitude of Tco term by 8,
and if SOT applies to Tco, scale
SOT by 8.
Tc_cfg[0] => If set Tco is negative
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 20 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
EEPROM
Range
Description
Note
95:88
SOT
2nd Order Term. This term is a 7-bit magnitude
with sign.
SOT[7] = 1 Î negative
SOT[7] = 0 Î positive
SOT[6:0] = magnitude [0-127]
This term can apply to a 2nd order Tcg, Tco or
bridge correction. (See Tc_cfg above)
99:96
{SOT_cfg,
Pamp_Gain}
Bits [99:98] = SOT_cfg
00 = SOT applies to Bridge
01 = SOT applies to Tcg
10 = SOT applies to Tco
11 = Prohibited
Note: For more details, see section 2.5.1.
Bits [97:96] = Pre-Amp Gain
00 => 6
01 => 24 (default setting)
10 => 12
11 => 48
(Only the default gain setting (24) is tested at
the factory, all other gain settings are not
guaranteed)
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 21 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
2.5
Calibration Math
2.5.1 Correction Coefficients
(All terms calculated external to the DUT and then programmed to EEPROM through serial interface)
Gain_B =
Gain term used to compensate span of Bridge reading.
Offset_B=
Offset term used to compensate offset of Bridge reading
Gain_T =
Gain term used to compensate span of Temp reading
Offset_T =
Offset term used to compensate offset of Temp reading
SOT =
Second Order Term. This term can be used applied as a second order correction term for:
1. The bridge measurement
2. Temperature coefficient of offset (Tco)
3. Temperature coefficient of gain (Tcg)
EEPROM bits 99:98 determine what SOT applies to.
Note: There are limitations for the SOT for the bridge measurement and for the SOT for the Tco
which are explained in section 2.5.2.7.
2.5.2
TSETL =
RAW PTAT reading at low temperature at which calibration was performed (typically at
room temp)
Tcg =
Temperature correction coefficient of bridge gain term
This term has a 8-bit magnitude and a sign bit (Tc_cfg[2]).
Tco =
Temperature correction coefficient of bridge offset term
This term has a 8-bit magnitude, a sign bit (Tc_cfg[0]) and a scaling bit (Tc_cfg[1])which
can multiply its magnitude by 8.
Interpretation of Binary Numbers for Correction Coefficients:
BR_Raw should be interpreted as an unsigned number in the set [0,16383] with resolution of 1.
T_Raw should be interpreted as an unsigned number in the set [0,16383] with resolution of 4
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 22 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
2.5.2.1 Gain_B interpretation
Gain_B should be interpreted as a number in the set [0,8). The MSB (bit 14) is a scaling bit that will multiply
the effect of the Gain_B term by 8. The remaining bits (Gain_B[13:0]) represent a number in the range of [0,8)
with Gain_B[13] having a weighting of 4, and each subsequent bit has a weighting of ½ the previous bit.
Table 2.1 – Gain_B Weightings
Bit Position:
13
12
11
.
.
.
1
0
Weighting:
4
2
1
2-10
2-11
Examples:
The binary number: 010010100110001 = 4.6489; The scaling number is 0 so there is no multiply by 8 of the
number represented by Gain_B[13:0]
The binary number: 101100010010110 = 24.586; The scaling number is 1 so there is a multiply by 8 of the
number represented by Gain_B[13:0]
Limitation: Using the 5-point calibration 5pt-Tcg&Tco&SOT_Tco (including the second order SOT_Tco), the
Gain_B is limited to a value equal or less than 8 (instead of 64).
2.5.2.2 Offset_B Interpretation
Offset_B is a 14-bit signed binary number in two’s complement form. The MSB has a weighting of –8192. The
following bits then have a weighting of: 4096, 2048, 1024, …
Table 2.2 – Offset_B Weightings
Bit Position:
13
12
11
.
.
.
1
0
Weighting:
-8192
4096
2048
21 = 2
20 = 1
Thus the binary number: 11111111111100 = -4
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 23 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
2.5.2.3 Gain_T interpretation
Gain_T should be interpreted as a number in the set [0,2). Gain_T[7] has a weighting of 1, and each
subsequent bit has a weighting of ½ the previous bit.
Table 2.3 – Gain_T Weightings
Bit Position:
7
6
5
.
.
.
1
0
Weighting:
1
0.5
0.25
2-6
2-7
2.5.2.4 Offset_T Interpretation
Offset_T is an 8-bit signed binary number in two’s complement form. The MSB has a weighting of –128. The
following bits then have a weighting of: 64, 32, 16 …
Table 2.4 – Offset_T Weightings
Bit Position:
7
6
.
.
.
1
0
Weighting:
-128
64
21 = 2
20 = 1
Thus the binary number: 00101001 = 41
2.5.2.5 Tco Interpretation
Tco is specified as an 8-bit magnitude with an additional sign bit (Tc_cfg[0]) and a scalar bit (Tc_cfg[1]). When
the scalar bit is set, the signed Tco is multiplied by 8.
Tco Resolution:
Tco Range:
0.175uV/V/oC
+/- 44.6uV/V/oC
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
(input referred)
(input referred)
Page 24 of 38
© ZMD AG, 2006
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written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
If the scaling bit is used then the above resolution and range are scaled by 8 to give
Tco Scaled Resolution:
Tco Scaled Range:
1.40uV/V/oC input referred
+/- 357uV/V/oC input referred
2.5.2.6 Tcg Interpretation
Tcg is specified as an 8-bit magnitude with an additional sign bit (Tc_cfg[2]).
The resolution of Tcg is:
The range of Tcg is:
17.0ppm/oC
+/- 4335ppm/oC
2.5.2.7 SOT Interpretation
SOT is a second order term that can apply to one and only one of the following: bridge non-linearity
correction, Tco non-linearity correction, or Tcg non-linearity correction.
As it applies to bridge non-linearity correction:
The resolution is:
0.25% @ Full Scale
The range is:
+25% @ Full Scale to -25% @ Full Scale
(Saturation in internal arithmetic will occur at greater negative non-linearities)
Limitation: Using the 5-point calibration method for which SOT_BR is applied to the bridge measurement,
there is a possibility of calibration math overflow. This only occurs if the sensor input exceeds 200% of the
calibrated full span, which means the highest applied pressure should never go higher than this value.1
As it applies to Tcg:
The resolution is:
The range is:
0.3 ppm/(oC)2
+/- 38ppm/(oC)2
As it applies to Tco:
2 settings are possible. It is possible to scale the effect of SOT by 8. If Tc_cfg[1] is set, then both Tco and
SOT’s contribution to Tco are multiplied by 8.
1
Example of the Limitation When SOT is Applied to the Bridge Reading
This example of the limitation when SOT is applied to the bridge reading uses a pressure sensor bridge that outputs
-10mv at the lowest pressure of interest. That point is calibrated to read 0%. The same sensor outputs +40mV at the
highest pressure of interest. That point is calibrated to read 100%.
This sensor has a 50mV span over the pressure range of interest. If the sensor were to experience an over-pressure
event that took the sensor output up to 90mV (200% of span), the internal calculations could overflow. The result would be
a corrected bridge reading that would not be saturated at 100% as expected but instead read a value lower than 100%.
This problem only occurs when SOT is applied to correct the bridge reading.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 25 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Resolution at unity scaling:
1.51nV/V/(oC)2
(input referred)
+/- 0.192μV/V/(oC)2
Range:
(input referred)
Resolution at 8x scaling: 12.1nV/V/(oC)2
(input referred)
+/- 1.54μV/V/(oC)2
Range:
(input referred)
Limitation: If the second order term SOT applies to Tco, the bridge gain Gain_B is limited to values equal or
less than 8 (instead of 64).
2.6 Reading EEPROM Contents
The contents of the entire EEPROM memory can be read out using the Read EEPROM Command (00H).
This command will cause the IC to output consecutive bytes on the ZACwireTM. The interpretation of these
bytes is given in the following table.
Read EEPROM (Bit order):
Bit 7
Bit 6
Bit 5
Bit 4
Byte 1:
Bit 3
Bit 2
Gain_T[1:0]
Offset_B[13:8]
Byte 3:
Offset_T[1:0]
Gain_T[7:2]
Byte 4:
TSETL[1:0]
Offset_T[7:2]
Byte 5:
Tcg[1:0]
TSETL[7:2]
Byte 6:
Tco[1:0]
Tcg[7:2]
Byte 7:
Tc_cfg[1:0]
Tco[7:2]
Byte 8:
SOT[5:0]
Osc_Trim[1:0]
Byte 10: Output_Select[0]
Byte 11:
Tc_cfg[3:2]
SOT_cfg[3:0]*
A2D_offset[1:0]
Gain_B[2:0]
Byte 12:
Byte 13:
Bit 0
Offset_B[7:0]
Byte 2:
Byte 9:
Bit 1
SOT[7:6]
1V_Trim[3:0]**
JFET_Cfg[1:0]
Update_Rate[1:0]
Osc_Trim[2]
Output_Select[1]
Gain_B[10:3]
Offset_B[3:0]***
Byte 14:
Gain_B[14:11]
A5H
* SOT_cfg/Pamp_Gain
** 1V_Trim/JFET_Trim
*** Duplicates first 4 bits of Byte 1
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 26 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
3
Application Circuit Examples
Typical output analog load resistor RL= 10kΩ (minimum 2.5kΩ). This optional load resistor can be configured
as a pull-up or pull-down. If it is configured as a pull-down, it cannot be part of the module to be calibrated
because this would prevent proper operation of the ZACwireTM. If a pull-down load is desired, it must be
added to system after module calibration.
There is no output load capacitance needed.
EEPROM contents: OUTPUT_select, JFET_Cfg, 1V_Trim/JFET-Trim
3.1
Three-Wire Rail-to-Rail Ratiometric Output
Figure 3.1 – Rail-to-Rail Ratiometric Voltage Output, Temperature Compensation via Internal PTAT.
The optional bridge sink allows a power savings of bridge current. The output voltage can be either
a) Rail-to-rail ratiometric analog output VDD(=Vsupply).
b) 0 to 1V analog output is also possible. The absolute voltage output reference is trimmable 1V (+/-2mV) in
the 1V output mode via a 4-bit EEPROM field. (See section 1.4.3.)
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 27 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
3.2
Analog Voltage Output
Figure 3.2 – Absolute Voltage Output with Temperature Compensation via Internal
Temperature PTAT External JFET Regulation for all Industry Standard Applications
The output signal range is either
a) 0 to 1V analog output. The absolute voltage output reference is trimmable 1V (+/-2mV) in the 1V output
mode via a 4-bit EEPROM field. (See section 1.4.3.)
b) Rail-to-rail analog output. The on-chip reference for the JFET regulator block is trimmable 5V (+/-~10mV)
in the ratiometric output mode via a 4-bit EEPROM field. (See section 1.4.3.)
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 28 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
3.3
Three-Wire Ratiometric Output with Over-Voltage Protection
+5 ...+5.5 V
J107
Vsupply
Vishay
1 Bsink
2 VBP
VSS 8
TM
Sig
7
OUT
3 N/C
4 VBN
VDD 6
Vgate 5
Optional
0.1µF
Bsink
Ground
Figure 3.3 – Ratiometric Output, Temperature Compensation via Internal Diode
In this application, the JFET is used for voltage protection. The JFET_Cfg bits (14:13) in EEPROM are
configured to 5.5V. There is an additional maximal error of 8mV caused by non-zero rON of the limiter JFET.
3.4 Digital Output
For all three circuits the output signal can also be digital. Depending from the output select bits bridge signal
or the bridge signal and temperature signal are sent.
For the digital output no load resistor or load capacity are necessary. No pull down resistor is allowed. If a line
resistor or pull up resistor is used, the requirement for the rise time must be met (≤ 5 μs). The IC output
includes a pull up resistor of about 100kΩ. The digital output can easily be read by firmware from a
microcontroller and ZMD can provide the customer with software in developing the interface.
4
ESD/Latch-Up-Protection
All pins have an ESD Protection of >4000V and a Latch-up protection of ±100mA or of +8V/ –4V (to
VSS/VSSA). ESD Protection referred to the human body model is tested with devices in SOP-8 packages
during product qualification. The ESD test follows the human body model with 1.5kOhm/100pF based on MIL
883, Method 3015.7.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 29 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
5
Pin Configuration and Package
Figure 5.1 – RBicLiteTM Pin Out Diagram
1
8
2
7
3
6
4
5
The standard package of the RBicLiteTM is SOP-8 (3.81mm body (150mil) wide) with lead-pitch. 1.27mm
(50mil).
Pin-No.
Name
Description
1
Bsink
Optional ground connection for bridge ground.
Used for power savings
2
VBP
Positive Bridge Connection
3
N/C
No Connection
4
VBN
Negative Bridge Connection
5
Vgate
Gate control for external JFET regulation/overvoltage protection
6
VDD
Supply voltage (2.7-5.5V)
7
SigTM
ZACwireTM interface (analog out, digital out,
calibration interface)
8
VSS
Ground supply
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 30 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
6
6.1
IC Characteristics
Absolute Maximum Ratings
PARAMETER
SYMBOL MIN
TYP
MAX
UNITS
Analog Supply Voltage
VDD
-0.3
6.0
V
Voltages at Analog I/O – In Pin
VINA
-0.3
VDD+0.3
V
Voltages at Analog I/O – Out Pin
VOUTA
-0.3
VDD+0.3
V
Storage Temperature Range
TSTG
-50
150
°C
Storage Temperature Range
TSTG<10h
-50
170
°C
TYP
MAX
UNITS
6.2
Recommended Operating Conditions
PARAMETER
SYMBOL MIN
Analog Supply Voltage to Gnd
VDD
2.7
5.0
5.5
V
Analog Supply Voltage (with external JFET
Regulator)
VSUPP
5.5
7
30
V
Ambient Temperature Range 1&2
TAMB
-50
150
°C
External Capacitance between VDD and
Gnd
CVDD
100
220
470
nF
Output Load Resistance to VSS or VDD3
RL,OUT
2.5
10
4
Output Load Capacitance
CL,OUT
Bridge Resistance
RBR
Power ON Rise Time
tPON
10
0.25
kΩ
15
nF
100
kΩ
100
ms
1
Note that the maximum calibration temperature is 85°C.
2
If buying die, designers should use caution not to exceed maximum junction temperature by proper package selection.
3
When using the output for digital calibration, no pull down resistor is allowed.
4
Using the output for digital calibration, CL,OUT is limited by the maximum rise time TZAC,rise.
5
Note: Minimum bridge resistance is only a factor if using the Bsink feature. The nominal RDS(ON) of the Bsink transistor is 10Ω when
operating at VDD=5V, and 15Ω when operating at VDD=3.0V. This does give rise to a ratiometricity inaccuracy that becomes greater with
low bridge resistances.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 31 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
6.3
Electrical Parameters
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2.7
5.0
5.5
V
SUPPLY VOLTAGE / REGULATION
Supply Voltage
VDD
Supply Current (varies with
update rate and output mode)
IDD
At minimum update rate.
250
At maximum update rate.
1000
μΑ
Temperature -10°C to 120°C
35
ppm/K*
Temperature <-10°C and>120°C
100
ppm/K*
Temperature Coefficient –
Regulator (worst case)
TCREG
Power Supply Rejection Ratio
PSRR
DC < 100 Hz (JFET regulation
loop using mmbf4392 and 0.1μF
decoupling cap)
60
dB*
Power Supply Rejection Ratio
PSRR
AC < 100 kHz (JFET regulation
loop using mmbf4392 and 0.1μF
decoupling cap)
45
dB*
Power-On Reset Level
POR
1.4
2.6
V
ANALOG TO DIGITAL CONVERTER (ADC)
Resolution
rADC
Common Mode Voltage
VCM
Integral Nonlinearity (INL)
INLADC
Differential Nonlinearity (DNL)
DNLADC
Response Time
TRES,ADC
14
Based on ideal slope
Bit
1
VDDA-1.3
V
-4
+4
LSB1
-1
+1
LSB*
Varies with update rate. Value
given at fastest rate.
1
ms
ANALOG OUTPUT PARAMETERS (DAC + BUFFER)
Max. Output Current
IOUT
Max current maintaining
accuracy
Resolution
rOUT
Referenced to VDD
Absolute Error
EABS
DAC input to output
Differential Nonlinearity
DNL
Upper Output Voltage Limit
VOUT
Lower Output Voltage Limit
VOUT
2.2
mA
11
Bit
-10
+10
mV
No missing codes
-0.9
+1.5
LSB11Bit*
RL =2.5kΩ
95%
VDD
2.5
mV
RZAC,line
3.92
kΩ
CZAC,load
2
nF
™
*
ZACwire Serial Interface
ZACwire™ Line Resistance
™
ZACwire Load Capacitance
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
0
Page 32 of 38
1
15
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
PARAMETER
SYMBOL
™
ZACwire Rise Time
TZAC,rise
Voltage Level Low
VZAC,low
Voltage Level High
VZAC,low
CONDITIONS
MIN
TYP
0
0.8
MAX
UNITS
5
μs
0.2
VDD
1
VDD
TOTAL SYSTEM
Start-Up-Time
tSTA
Power-up to output
10
ms
Response Time
tRESP
Update_rate=<1ms
1
2
ms
Sampling Rate
fS
Update_rate=<1ms
1000
Hz
Supply Current
IDD
Update_rate=<1ms
1
mA
Overall Linearity Error
ELIND
Bridge input to output -- Digital
0.025
0.04
%
Overall Linearity Error
ELINA
Bridge input to output -- Analog
0.1
0.2
%
Overall Ratiometricity Error
REout
Not using Bsink feature
0.035
%
Overall Accuracy – Digital
(only IC, without sensor bridge)
ACoutD
-25°C to 85°C
±0.1%
-40°C to 125°C3
±0.25%
%FSO
%FSO
Overall Accuracy – Analog
(only IC, without sensor bridge)
ACoutA
-25°C to 85°C
±0.25%
-40°C to 125°C3
±0.35%
%FSO
%FSO
* The parameters with an * under “Units” are tested by design.
1
Note this is +/- 4 LSBs to the 14-bit A-to-D conversion. This implies absolute accuracy to 12-bits on the A-to-D result. Non-linearity is
typically better at temperatures less than 125°C.
2
The rise time must be TZAC,rise = 2 RZAC,line * CZACload ≤ 5μs . If using a pull up resistor instead of a line resistor, it must meet this specification.
3
Overall accuracy specifications for –50°C to 150°C are pending.
6.4 Analog Inputs
RBic LiteTM incorporates an extended 14-bit charge-balanced ADC which allows for a single gain setting on the
Pre-Amplifier to handle bridge sensitivities from 1.2 to 36mV/V while maintaining 8 to 12 bits of output
resolution (default analog gain 24). The tables below illustrate the minimum resolution achievable for a variety
of bridge sensitivities.
Analog Gain 12
Input Span (mV/V)
Min
Typ
Max
43.3
36.1
25.3
18.0
14.5
60.0
50.0
35.0
25.0
20.0
79.3
66.1
46.3
33.0
26.45
Allowed Offset
(+/- % of Span)1
3%
17%
53%
101%
142%
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Minimum Guaranteed
Resolution (Bits)
13.0
12.7
12.2
11.7
11.4
Page 33 of 38
© ZMD AG, 2006
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written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
Analog Gain 12
Input Span (mV/V)
Min
Typ
Max
7.2
3.6
10.0
5.0
13.22
6.6
Allowed Offset
(+/- % of Span)1
351%
767%
Minimum Guaranteed
Resolution (Bits)
10.4
9.4
1
In addition to Tco,Tcg
Analog Gain 24
Input Span (mV/V)
Min
Typ
Max
16
12.8
6.4
3.2
1.6
0.8
25.0
20.0
10.0
5.0
2.5
1.2
36
28.8
14.4
7.2
3.6
1.7
Allowed Offset
(+/- % of Span)1
25%
50%
150%
400%
900%
2000%
Minimum Guaranteed
Resolution (Bits)
12.6
12
11
10
9
8
1
In addition to Tco,Tcg
Analog Gain = 48
Input Span (mV/V)
Min
Typ
Max
10.8
7.2
4.3
2.9
1.8
1.0
0.72
15.0
10.0
6.0
4.0
2.5
1.4
1.0
19.8
13.2
7.9
5.3
3.3
1.85
1.32
Allowed Offset
(+/- % of Span)1
3%
35%
100%
190%
350%
675%
975%
Minimum Guaranteed
Resolution (Bits)
13
12.4
11.7
11.1
10.4
9.6
9.1
1
In addition to Tco,Tcg
6.5 Temperature Compensation and Temperature Output
A highly-linear Bandgap/PTAT circuit is used in order to produce a signal which can be used in compensation
of the bridge over temperature. In addition, when digital mode is activated both bridge and temperature
signals (8-bit temperature quantity) can be broadcast on the ZACwireTM pin.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 34 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
6.6 High Voltage Operation
A linear regulator control circuit is included on the IC to interface with an external JFET to allow for operation
in systems where the supply voltage exceeds 5.5V. This circuit can also be used for over-voltage protection.
The regulator set point has a coarse adjust (EEPROM bit) that can adjust the set point around 5.0 or 5.5V. In
addition, the 1V trim will also act as a fine adjust for the regulation set point. Note: If using the external JFET
for over-voltage protection purposes (i.e., 5V at JFET drain and expecting 5V at JFET source), there will be a
voltage drop across the JFET, thus ratiometricity will be compromised somewhat depending on the rds(on) of
the chosen JFET. A Vishay J107 is the best choice that would produce only an 8mV drop worst case. If using
as regulation instead of over-voltage, a MMBF4392 also works well.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 35 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
7
7.1
Die Dimensions and Pad Coordinates
Die Dimensions
• Die size (including scribeline): 2230µm x 1681µm ≈ 3.75sqmm
• Core die size (without scribeline): 2080µm x 1531µm ≈ 3.19sqmm
• Die thickness: 390µm
• Scribeline (distance between two core dice on wafer): 150µm
• Pads size: 68µm x 68µm
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 36 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
7.2 Pad Coordinates
All pads coordinates are for pad centers and related to the corner.
8
Name
X Coordinate in μ
bsink
106.3
Y Coordinate in μ
85.9
por_n
1109.7
85.9
vbp
1210.0
85.9
vdd
1389.3
77.3
vbn
1568.1
85.9
vss
107.2
1444.7
vssa
198.3
1444.7
vpp
356.1
1444.7
sig_pd
1428.6
1444.7
vdd
1672.3
1435.8
vgate
1809.2
1444.7
Test
The test program is based on this datasheet. The final parameters that will be tested during series production
are listed in the tables of section 6.3.
The digital part of the IC includes a scan path, which can be activated and controlled during wafer test. It
guarantees failure coverage more than 98%. Further test support for testing of the analog parts on wafer level
is included in the DSP.
9
Reliability
A reliability investigation according to the in-house non-automotive standard will be performed.
10 Customization
For high-volume applications, which require an up- or downgraded functionality compared to the ZM31010,
ZMD can customize the circuit design by adding or removing certain functional blocks.
For it ZMD has a considerable library of sensor-dedicated circuitry blocks.
Thus ZMD can provide a custom solution quickly. Please contact ZMD for further information.
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
Page 37 of 38
© 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.
ZMD31010
RBicLiteTM Low-Cost Sensor Signal Conditioner
Datasheet
11 Related Documents
ZMD31010 RBicLiteTM Development Kit Documentation
ZMD31010 RBicLiteTM SSC Kits Feature Sheet (includes ordering codes and price information)
ZMD31010 RBicLiteTM Technical Notes – Rev_A_Production
ZMD31010 RBicLiteTM Application Notes – In-Circuit Programming Boards
ZMD31010 RBicLiteTM Die Dimensions and Pad Coordinates
ZMD31010 RBicLiteTM Mass Calibrator Kit Documentation
For the most recent revisions of this document and of the related documents, please go to www.zmd.biz
This information applies to a product under development. Its characteristics and specifications are subject to change without notice. ZMD
assumes no obligation regarding future manufacture unless otherwise agreed in writing. The information furnished hereby is believed to
be correct and accurate. However, ZMD shall not be liable to any customer, licensee or any other third party for any damages in
connection with or arising out of the furnishing, performance or use of this technical data. No obligation or liability to any customer,
licensee or any other third party shall result from ZMD’s rendering of technical or other services.
For further
information:
ZMD AG
Grenzstrasse 28
01109 Dresden, Germany
Phone +49 (0)351-8822-366
Fax +49 (0)351-8822-337
[email protected]
www.zmd.biz
RBicLite™ Datasheet, Rev. 1.2, February 28, 2006
ZMD America, Inc.
201 Old Country Road, Suite 204
Melville, NY 11747, USA
Phone +01 (631) 549-2666
Fax +01 (631) 549-2882
[email protected]
www.zmd.biz
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© 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.