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MLX90308CAB
Programmable Sensor Interface
Features and Benefits
Microprocessor-controlled signal conditioning for bridge-type sensors Suited for low-cost sensors: reduction of non-linearity by programmable coefficients External or internal temperature sensor for compensating temperature errors Versatile output signal ranges: 4, 5, 10, or 11VDC; 4 to 20 mA loop Mass calibration easy with 2400 or 9600 baud UART Power supply from 6 to 35VDC
Applications
Pressure transducers Accelerometers Temperature sensor assemblies Linear position sensors
Ordering Information
art No. MLX90308CAB MLX90308CAB Temperature Suffix L L Package LW UD* Option Temperature Range -40C to 140C Automotive -40C to 140C Automotive
*UD denotes unpackaged die
Description
The MLX90308CAB is a dedicated microcontroller which performs signal conditioning for sensors wired in bridge or differential configurations. Sensors that can be used include thermistors, strain gauges, load cells, pressure sensors, accelerometers, etc. The signal conditioning includes gain adjustment, offset control, high order temperature and linearity compensation. Compensation values are stored in EEPROM and are reprogrammable. Programming is accomplished by using a PC, with an interface circuit (level shifting and glue logic), and provided software. The application circuits can provide an output of an absolute voltage, relative voltage, or current. The output can be range limited with defined outputs when the signal is beyond the programmed limits. Other features include alarm outputs and level steering. The robust electrical design allows the MLX90308CAB to be used where most signal conditioning and sensor interface circuits cannot be used. Voltage regulation control is provided for absolute voltage and current modes (external FET required). The standard package is a plastic SO16W. The device is static-sensitive and requires ESD precautions.
Figure 1. Pinning
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface Rev Y.X 1 Page 22/Aug/98 3.0 21/May/01 1 Page Rev
FET
VDD1
OFC
FLT
VDD
Supply Regulator
3.5V
DAC_Offset
OPA
Current Mode
GAIN
CMO CMN
0V
VBP
x 10
GAIN
2-bit CSGN
x2 1.24kOhm
MLX90308CAB Programmable Sensor Interface
0.97V/V 1-bit CSGN Hardware Gain = 20 0.48V/V Coarse Offset
VBN
INV
Analog
GAIN
Page 2
Fine Gain DAC
3.5V External Temp Sensor
ADC
VMO
TMP
Digital
ADC DAC
Voltage Mode
Microprocessor
IO1 IO2 COMS
Programmable Sensor Interface
MLX90308CAB
Rev 3.0 21/May/01
Internal Temp Sensor
GND
Temp Amp Gain GNTP [1:0]
0V
Temperature signal. Used by microproscessor to perform temperature linearity corrections.
TSTB
Figure 1. Functional Block Diagram
MLX90308CAB
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications
DC operating parameters: TA = -40 to 140oC, VDD1 = 6 to 35VDC (unless otherwise specified).
Parameter Regulator & Consumption Input voltage range Supply current Supply current Regulated supply voltage Regulated voltage temperature coefficient Supply rejection ratio
Symbol VIN IDD IDD VREG
Test Conditions VDD1 (Regulator connected) @ TA = 100C Current Mode @ TA = 100C Voltage Mode
Min 6
Typ
Max 35
Units V mA
2.1 5.0 4.5 4.75 -600 5.2
mA V uV / C dB
PSRR
VDD1 > 6V
90
Instrumentation Amplifier Differential input range Differential input range Common mode input range Pin leakage current VBP-VBN VBP-VBN IINV = 0 IINV = 1 -11.0 -32.0 38.0 32.0 11.0 65.0 8.0 78 18 CSOF[1:0] = 00 CSOF[1:0] = 01 CSOF[1:0] = 10 CSOF[1:0] = 11 Fixed offset control range High Low IA chopper frequency Gain Stage Course gain (Fixed Gain = 1023) CSGN = 000 CSGN = 001 CSGN = 010 * CSGN = 100 to 111 for voltage mode only, not applicable to current mode CSGN = 011 CSGN = 100* CSGN = 101*
Rev Y.X 3 Page
mV/V(Vdd) mV/V(Vdd) %VDD nA dB
1/2 1/2(VBP+VBN) (VBP+VBN Pins VBP & VBN to GND, VDD =
Common mode rejection Ratio CMRR Hardware gain Coarse offset control Range
22 -13.9 -3.8 5.1 15.3 8.0 -4.5 300
V/V mV/V mV/V mV/V mV/V mV/V mV/V kHz
-15.3 -5.1 3.8 13.9 6.0 -5.5
3.0 4.9 7.9 12.8 7.8 12.7
3.3 5.4 8.2 14.1 8.6 14.0
V/V V/V V/V V/V V/V V/V
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MLX90308CAB
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
Parameter Coarse gain Test Conditions CSGN = 110* CSGN = 111* Fixed gain control range
DC operating parameters: TA = -40 to 140oC, VDD1 = 6 to 35VDC (unless otherwise specified).
Min 20.4 33.1 0.480
Typ
Max 22.5 36.6 0.970
Units V/V V/V V/V
Voltage Mode Output Stage ( See Voltage Mode)
Output voltage span CSGN[2:2] = 0 CSGN[2:2] = 1 Minimum output voltage Output source current Output sink current Output resistance Digital mode output span @ 0V output voltage Over complete output range CSGN[2:2] = 0 CSGN[2:2] = 1 Digital mode step size VDD = 5V, CSGN[2:2]=0 VDD = 5V, CSGN[2:2]=1 Capacitive load VMO pin Current Mode Output Stage Fixed gain Output current CMO pin Current sense resistor Digital mode current output span Digital mode current step Size Signal Path ( General) Overall gain Voltage mode Current mode = 24 Overall non-linearity Bandwidth (-3dB) 39 nF connected from FLT to GND 25 78 -0.1 2.8 3.5 5.0 600 903 0.1 4.2 V/V mA/V % KHz mV VDD = 5V VDD = 5V,RSENSE=24 23 30 RSENSE = 24 ohm Current mode 8.4 50 24 9.3 mA/V mA mA mA 6.0 11.0 6.0 11.0 10 2.0 20 25 5.0 10.0 7.5 10.0 -0.2 V V V mA mA V V mV mV nF
Noise, VDD = 5V, CFLT=39nF, CL=5nF, Analog Mode Temperature Sensor & - Amplifier Temperature sensor sensitivity Temperature sensor output voltage
MLX90308CAB Programmable Sensor Interface Page 4
390 70 380
uV/C mV
Rev 3.0 21/May/01
MLX90308CAB
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
Parameter Input voltage range TMP pin @ VDD = 5.0V Test Conditions GNTP[1,0] = 00 GNTP[1,0] = 01 GNTP[1,0] = 10 GNTP[1,0] = 11 DAC Resolution Monotonicity Ratiometric output range (DAC output) Offset Error Differential non-linearly Integral non-linearity Storage capacitors Settling time ADC Resolution Monotonicity Ratiometric input range Offset error Differential non-linearly Integral non-linearity Conversion time TURBO = 0 TURBO=1 On-Chip RC Oscillator and Clock Untrimmed RC oscillator frequency Trimmed RC oscillator frequency (Measured at TMP pin with TSTB pin pulled low after power up) Frequency temperature coefficiency Clock Stability with temperature compensation over full temperature range Ratio of f (microcontroller main clock and (RC oscillator) TURBO = 0 TURBO = 1
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface Rev Y.X 5 Page
DC operating parameters: TA = -40 to 140oC, VDD1 = 6 to 35VDC (unless otherwise specified).
Min 207 145 101 71
Typ
Max 517 367 263 186
Units mV mV mV mV
Temperature Sensor & Amplifier (continued).
10 Guaranteed By Design 1 10 1 2 OFC buffer, digital mode buffer MODSEL[1:0] = 1X 7 2 13 8 71
Bit
% VDD LSB LSB LSB pF ms
10 Guaranteed by design 1 DARDIS = 1 10 1 2 110 75 71
Bit
% VDD LSB LSB LSB s s
40 86.9 87.8 26 -3 7 28
250 88.7
kHz kHz Hz/C
+3
%
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MLX90308CAB
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
Parameter Input & Output Pins (I01 & I02) Analog input ranges Digital input levels Output Levels TSTB Pin Input levels Pull-up Resistor FLT Pin Output resistance Output voltage range OFC Pin Output voltage range Load capacitor UART & COMS Pin UART baud rate COMS pin input levels COMS Pin Output Resistance TURBO = 0 TURBO = 1 Low High Low High 100 100 0.3*VDD 2400 9600 baud baud V 0.7*VDD V k VDD = 5V 0.05 3.6 20 V pf VDD = 5V 0.05 1.24 3.6 k V Low High 66 0.5 VDD-0.5 k V Low High @ output current = 5mA low @ Output current = 5mA high Test Conditions
DC operating parameters: TA = -40 to 140oC, VDD1 = 6 to 35VDC (unless otherwise specified).
Min 0.05 0.5
Typ
Max
Units V V
VDD-0.5 VDD-0.4 VDD 0.4 V
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MLX90308CAB
Programmable Sensor Interface
Unique Features
Customization
Melexis can customize the MLX90308 in both hardware and firmware for unique requirements. Melexis can also provide all necessary development tools for the development of special firmware to customize the MLX90308. The hardware design provides 64 bytes of RAM, 3 kbytes of ROM, and 48 bytes of EEPROM for use by the firmware.
Table 2. Absolute Maximum Ratings
Supply voltage (ratiometric) VDD Max Supply voltage (ratiometric) VDD Min
6V 4.5V 35V -0.7V 3.5mA 4.5mA 8mA 100mA 8mA +11V 71mW
-40 to +140 -55 to +150
Supply voltage (operating), VDD1 Reverse voltage protection Supply current, Current Mode, IDD Supply current, Voltage Mode, IDD Output current, IOUT Output current (short to VDD), ISC Output current (short to VSS), ISC Output voltage, VOUT Power dissipation, PD Operating temperature range, TA Storage temperature range, TS Maximum junction temperature, TJ ESD sensitivity (Ratiometric Config)
Special Information
The output of the sensor bridge is amplified via offset and gain amplifiers and then converted to the correct output signal form in one of the output stages. The sensitivity and offset of the analog signal chain are defined by numbers passed to the DAC interfaces from the microcontroller core (GN[9:0] and OF[9:0]). The wide range of bridge offset and gain is accommodated by means of a 2-bit coarse adjustment DAC in the offset adjustment (CSOF [1:0]), and a similar one in the gain adjustment (CSGN[2:0]). The signal path can be directed through the processor for digital processing. Two I/O pins are available for analog inputs or digital outputs. These pins can be used for alarms on various points on the analog signal path and built-in or external temperature values.
150C 2kV
Programming and Setup
The MLX90308 needs to have the compensation coefficients programmed for a particular bridge sensor to create the sensor system. Programming the EEPROM involves some minimal communications interface circuitry, Melexis' setup software, and a PC. The communications interface circuitry is available in a development board. This circuitry communicates with the PC via a standard RS232 serial communications port.
Cross Reference
There are no known devices which the MLX 90308CAB can replace.
ESD Precautions
Observe standard ESD control procedures for CMOS semiconductors.
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Table 3. Pin Description
Pin 1,2 Signal Name I/O1, 2 Description Bi-directional I/O. Can also be used as input to A/D converter. I/O can be controlled by serial communications or by firmware as alarm inputs or level out. (unconnected when not used) Test pin for Melexis production testing. (in normal application connected to VDD) Filter pin; allows for connection of a capacitor to the internal analog path. Offset control output. Provides access to the internal programmed offset control voltage for use with external circuitry. (unconnected when not used) Bridge inputs, negative and positive. Temperature sensor input. An external temperature sensor can be used in conjunction with the internal one. The external sensor can provide a temperature reading at the location of the bridge sensor. Regulated supply voltage. Used for internal analog circuitry to ensure accurate and stable signal manipulation. Regulator FET gate control. For generating a stable supply for the bridge sensor and internal analog circuitry (generates regulated voltage for VDD). Unregulated supply voltage. Used for digital circuitry and to generate FET output. Voltage mode output. Compensated sensor output voltage. Current mode output. Compensated sensor output for current mode operation. Current mode negative rail. Current mode return path. Power supply return. Serial communications pin. Bi-directional serial communication signal for reading and writing to the EEPROM.
3 4 5 6,7 8
TSTB FLT OFC VBN,VBP TMP
9 10 11 12 13 14 15 16
VDD FET VDD1 VMO CMO CMN GND COMS
1
IO1 IO2
COMS
16
2
GND
15
3
TSTB
CMN
14
4
FLT
CMO
13
5
OFC
VMO
12
6
VBN
VDD1
11
7
VBP
FET
10
8
TMP
VDD
9
Figure 2. Pinout (SO16W (LW) Package)
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MLX90308CAB
Programmable Sensor Interface
Analog Features
Supply Regulator
A bandgap-stabilized supply-regulator is on-chip while the pass-transistor is external. The bridge-type sensor is typically powered by the regulated supply (typically 4.75V). For ratiometric operation, the supply-regulator can be disabled by connecting together the unregulated and regulated supply pins.
Power-On Reset
The Power-On Reset (POR) initializes the state of the digital part after power up. The reset circuitry is completely internal. The chip is completely reset and fully operational 3.5 ms from the time the supply crosses 3.5 volts. The POR circuitry will issue another POR if the supply voltage goes below this threshold for 1.0 us.
Test Mode
For 100% testability, a "TEST" pin is provided. If the pin is pulled low, then the monitor program is entered and the chip changes its functionality. In all other applications, this pin should be pulled high or left floating (internal pull-up).
Oscillator
The MLX90308 contains a programmable on-chip RC oscillator. No external components are needed to set the frequency (87.8 kHz +/-1%). The MCU-clock is generated by a PLL (phase locked loop tuned for 614 kHz or 2.46 Mhz) which locks on the basic oscillator. The frequency of the internal clock is stabilized over the full temperature range, which is divided into three regions, each region having a separate digital clock setting. All of the clock frequency programming is done by Melexis during final test of the component. The device uses the internal temperature sensor to determine which temperature range setting to use.
Temperature Sense
The temperature measurement, TPO, is generated from the external or internal temperature sensor. This is converted to a 10-bit number for use in calculating the signal compensation factors. A 2-bit coarse adjustment GNTP[1:0] is used for the temperature signal gain & offset adjustment.
A/D and D/A Conversions using only one DAC
For saving chip area, the "Offset DAC" is multiplexed in various ways. Both "fine offset" and "digital mode" signals are stored on a capacitor. An ADC-loop is available by using a comparator and SAR.
D/A
Before changing to another capacitor, the DAC output should be settled to the new value. For example, MODSEL moves the analog multiplexer to the so-called "open state 0." At the same time, the 10 bit mux selects OF[9:0] for the offset-DAC. After the DAC settling time, the analog multiplexer is moved to its final state and the DAC-output is stored on a capacitor.
A/D
The S/W-Signal MODSEL connects the SAR-output to the DAC and the DAC-output to the comparator. The SARegister is initialized by a rising edge of STC (S/W signal). At the end of the A/D conversion, the EOC flag is set to 1 and the controller can read the ADC values.
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Programmable Sensor Interface
Digital Features
Microprocessor, LX11 Core, Interrupt Controller, Memories
The LX11 microcontroller core is described in its own datasheet. As an overview, this implementation of the LX11 RISC core has following resources: Two accumulators, one index and two interrupt accumulators. 15 - 8 bit I/O ports to internal resources. 64 byte RAM. 4 kbytes ROM : 3 kbytes is available for the customer's application firmware. 1k is reserved for test. 48 x 8 bit EEPROM. Four interrupt sources, two UART interrupts and two timers.
Timer
The clock of the timers TMI and TPI is taken directly from the main oscillator. The timers are never reloaded, so the next interrupt will take place 2x oscillator pulses after the first interrupt.
Watch Dog
An internal watch dog will reset the whole circuit in case of a software crash. If the watch dog counter is not reset at least once every 26 milliseconds (@ 2.46 MHz main clock), the microcontroller and all the peripherals will be reset.
Firmware
The MLX90308 firmware performs the signal conditioning by either of two means: analog or digital. The analog signal conditioning allows separate offset and gain temperature coefficients for up to four temperature ranges. Digital mode allows for all of the analog capabilities plus up to five different gain values based on the input signal level. Also available in both modes is the capability of range limiting and level steering.
UART
The serial link is a potentially full-duplex UART. It is receive-buffered, in that it can receive a second byte before a previously received byte has been read from the receiving register. However, if the first byte is not read by the time the reception of the second byte is completed, the first byte will be lost. The UART's baud rate depends on the RC-oscillator's frequency and the "TURBO"-bit (see output port). Transmitted and received data has the following structure: start bit = 0, 8 bits of data, stop bit = 1.
Temperature Processing
In both analog and digital modes, the temperature reading controls the temperature compensation. This temperature reading is filtered as designated by the user. The filter adjusts the temperature reading by factoring in a portion of the previous value. This helps to minimize the effect of noise when using an external temperature sensor. The filter equation is: If measured_temp > Temp_f(n) then Temp_f(n+1) = Temp_f(n) + [measured_temp Temp_f(n)] / [2 n_factor]. If measured_temp < Temp_f(n), then Temp_f(n+1) = Temp_f(n) - [measured_temp Temp_f(n)] [2 n_factor]. Temp_f(n+1) = new filtered temperature value.
Sending Data
Writing a byte to port 1 automatically starts a transmission sequence. The TX Interrupt is set when the STOP-bit of the byte is latched on the serial line.
Receiving Data
Reception is initialized by a 1 to 0 transition on the serial line (i.e., a START-bit). The baud rate period (i. e., the duration of one bit) is divided into 16 phases. The first six and last seven phases of a bit are not used. The decision on the bit-value is then the result of a majority vote of phase 7, 8 and 9 (i.e., the center of the bit). Spike synchronization is avoided by de-bouncing on the incoming data and a verification of the START-bit value. The RX Interrupt is set when the stop bit is latched in the UART.
Temp_f(n) = previous filtered temperature value. Measured_temp = Value from temperature A to D. N_factor = Filter value set by the user (four LSB's of byte 25 of EEPROM), range 0-15. The filtered temperature value, Temp_f, is stored in RAM bytes 58 and 59. The data is a 10 bit value, left justified in a 16 bit field.
MLX90308CAB Programmable Sensor Interface
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Programmable Sensor Interface
Different Modes
Analog Mode
The parameters OF and GN represent, respectively, offset correction and span control, while OFTCi and GNTCi represent their temperature coefficients (thermal zero shift and thermal span shift). After reset, the firmware continuously calculates the offset and gain DAC settings as follows: The EEPROM holds parameters GN, OF, OFTCi and GNTCi, where "i" is the gap number and can be 1 < i < 4. The transfer function is described below. Vout = FG * DAC_GAIN * CSGN[2:0] * {Vin+DAC_OFFSET+CSOF} Iout = FG * DAC_GAIN * CSGN[1:0] * {Vin+DAC_OFFSET+CSOF} * 8.85mA/V
For the third temperature gap: OF = OF[9:0] + [OFTC2 * (T2-T1)] For the fourth temperature gap: OF = OF[9:0] + [OFTC2 * (T2-T1)] + [OFTC3 * (T3 - T2)] CSOF = Coarse Offset, part of byte 2 in EEPROM. OF[9:0] = Fixed offset Bytes 4 and 17 in EEPROM
Digital Mode
The MLX90308 firmware provides the capability of digitally processing the sensor signal in addition to the analog processing. This capability allows for signal correction.
Signal Correction
While in digital mode the firmware can perform signal correction. This is an adjustment to the output level based on the input signal level. Adjustment coefficients can be set for five different signal ranges. The output is obtained by the following formula: Output = (Signal - Pi) * Pci + Poff where Signal = input signal measurement; Poff = Pressure ordinate Pi = Pressure signal point (I = 2,3,4,5) Pci = programmed coefficient. The PCi coefficients are coded on 12 bits: one bit for the sign, one for the unity, and the rest for the decimals. The Pi are coded on 10 bits (0-3FFh) in high-low order. PNB_TNB: contains the number of signal points, coded on the four MSB's. The four LSB's are reserved for the number of temperature points. See Table 4 and Table 5.
FG = Hardware Gain (~20V/V). Part of the hardware design, and not changeable. DAC_GAIN = GN[9:0] + [GNTCi * dT] where Temp_f = Filtered temperature (previously described). Ti= Temperature segment point I = 1,2, or 3. GNTCi = Gain TC for a given temperature segment i, GNTCiL and GNTCiH in EEPROM table. dT = Temperature change within the appropriate gap. For the first gap dT = T1-Temp_f. For the remaining gaps dT = Temp_f - T(i-1), i = 2,3 or 4. CSGN = Course Gain, part of byte 2 in EEPROM. GN[9:0] = Fixed Gain, bytes 3 and 17 in EEPROM.
Compensation Trade-Offs
A compromise must be made between temperature compensation and pressure correction. The EEPROM space where the signal coefficients are stored is shared with the temperature coefficients, with the result that an EEPROM byte can be used either for a temperature coefficient or for a signal coefficient, but not both. Table 6 presents the possibilities among the maximum number of temperature gaps and the maximum number of signal gaps.
OFFSET
For the first temperature gap: DAC_OFFSET = OF[9:0] + OFTCi * (Ti - Temp_f). For the second, third, and fourth temperature gaps: DAC_OFFSET = OF + OFTCi * (Temp_f - Ti) OF = Base Offset, For the second temperature gap: OF = OF[9:0]
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Programmable Sensor Interface
Table 4. PNB_TNB Bit Definition; Pressure Gaps
# of Pressure Gaps Fixed 1 2 3 4 5 4MSB of PNB_TNB Value 15 (F hex) 14 (E hex) 12 (C hex) 10 (A hex) 8 6
Table 6. Temperature & Signal Limitations
Maximum number of temperature gaps Fixed Gain and fixed Offset 2 Gaps 3 Gaps 4 Gaps Maximum number of signal gaps 5 Gaps 3 Gaps 2 Gaps Fixed signal
Table 5. PNB_TNB Bit Definition; Temperature Gaps
# of Temperature Gaps Fixed (1) 2 Gaps 3 Gaps 4 Gaps 4 LSB of PNB_TNB 0 5 8 11 (B hex)
Figure 3. Temperature Linearity Correction
OF & GN
OFTC3
Figure 4. Signal Linearity Correction
Output
PC4
MLX90308
OFTC4
MLX90308
PC5
OFTC2 GNTC4 GNTC3 OFTC1 PC3
Output (units)
Parameter
PC2
OF0
GNTC2 i4 i3 i2 i1 1 Gap 0 T1 T2 T3 3FFh
PC1
GN0
GNTC1
0
P2
P3
P4
P5
Baseline Calibration
MLX90308CAB Programmable Sensor Interface
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Programmable Sensor Interface
Alarm Option
This option allows controlling the low and high limits of the output (See Figure 5.). The output level is set when the output tries to exceed the programmed limits. Five bytes are reserved for this option. The first byte is the low trigger limit and the second the low output. The third and fourth bytes are used for the high limit and the output. The fifth byte is the alarm control, used to select the alarm input. The different levels are programmed as eight bit numbers. These correspond to the 8 upper bits of the 10 bit signal measurement. When the alarm mode is not used, all of the data is 0. The control code is coded as shown in Table 7. The six possible signals are listed below and are encoded on the 4 MSB's of byte 31 of the EEPROM.
IO1 & IO2
IO1 and IO2 are used in the alarm and level steering modes. For custom firmware, they can be used for a digital input, an analog input, or a digital output.
Figure 6. Alarm & Steering Source Points
OFC FLT VDD1 FET VDD GND Power Supply Regulation VBP
IAO
Offset Gain
GNO
VM
Table 7. Alarm Source Bit Definition
Selected input TPO IAO GNO VMO IO1 IO2 MUX Value 0010 0110 0000 0011 0100 0101
VMO
VBN
TPO
CM
CMO
CMN
TMP
Temp Sense & Amp ADC & DAC Microcontroller Core, Memory, EEPROM Reset,Test,& Oscillator
IO1 IO2
TSTB
Bidirectional I/O
UART COMS
Figure 5. Alarm Function OUTPUT
MLX90308
Figure 7. Level Steering Function IO1, IO2
MLX90308
High Output
Output
1 -1
Parameter
1-0
Low Output
0-1
Low Trigger
High Trigger
0-0 (I02,I01)
Input Signal
Level 1
Level 2
Level 3
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Level Steering
The level steering option allows configuration of the IO pins as outputs to indicate the relative level of a selected signal. See Figure 7. The levels at which the two outputs change state are programmed by the user. The programmed levels are set as eight bit numbers and compared to the upper eight bits of the digitized signal. This function utilizes the same resources as the alarm function. The two functions (level steering and alarm) can not be used simultaneously. Four bytes in the EEPROM command this option. The first byte is used to select the input, while the last three comprise the transition levels. The control byte for the level steering is the same as for the alarm. The four MSB's hold the code for the selected input. The control byte has several possibilities as designated by the MUX settings (See Table 8)
Communications
The MLX90308 firmware transfers a complete byte of data into and from the memory based on a simple command structure. The commands allow data to be read and written to and from the EEPROM and read from the RAM. RAM data that can be read includes the current digitized temperature and digitized GNO. The commands are described below. Melexis provides setup software for programming the MLX90308.
Table 8. Level Steering Bit Definitions
Selected input TPO IAO GNO VMO Remarks MUX Value 0010 0110 0000 0011
Table 9. Mode Byte Bit Definition
Bit 7 Function 1= EEPROM Checksum test active 0= EEPROM Checksum test inactive 0 = Analog Mode 1 = Digital Mode 0 = Alarm function inactive 1 = Alarm function active
EEPROM Checksum test. Checksum test failure will force the output to the value programmed in bytes 40 and 41 of the EEPROM (See Table 10). Digital mode must be activated when VMO and CMO both active. Alarm functions are like "limiting functions": If defined ADC INPUT is below low alarm trigger, then DIGMOD becomes active with alarm low output). If defined ADC INPUT is above high alarm trigger, then DIGMOD becomes active with alarm high output. Note: Deactivated if the level steering mode is active Depending on the sampled input, IO1/IO2 will be a two bit digital output. If IO1/IO2 are not active outputs, then they will be analog inputs.
6 5
4
0 = IO1/IO2 are not active outputs 1 = level steering: IO1/IO2 are active outputs 0 = Turbo inactive 1 = Turbo active 0 = VMO inactive 1 = VMO active 0 = Internal temperature sensor active 1 = External temperature sensor active 0 = CMO inactive 1 = CMO active
3 2 1
0
CMO has fixed digital value (EEPROM byte - see below) if both VMO and CMO are active. To activate this value, the digital mode must be activated.
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MLX90308CAB
Programmable Sensor Interface
1.5 bytes. The 4 MSB's are stored in a separate byte and shared with the four MSB's of another 12-bit variable.
UART Commands
The commands can be divided into three parts: (1) downloading of data from the ASIC, (2) uploading of data to the ASIC and (3) the reset command. All the commands have the same identification bits. The two MSB's of the sent byte indicate the command while the last six MSB's designate the desired address. The commands are coded as followed: 11 to read a RAM byte. 10 to read an EEPROM byte. 01 to write in the EEPROM. 00 to write in the RAM. The addresses can include 0-63 for the RAM, 0-47 for the EEPROM, and 63 for the EEPROM, RESET Command (read).
Clock Temperature Stabilization
To provide a stable clock frequency from the internal clock over the entire operating temperature range, three separate clock adjust values are used. Shifts in operating frequency over temperature do not effect the performance but do, however, cause the communications baud rate to change. The firmware monitors the internal temperature sensor to determine which of three temperature ranges the device currently is in. Each temperature range has a factory set clock adjust value, ClkTC1, ClkTC2, and ClkTC3. The temperature ranges are also factory set. The Ctemp1 and Ctemp2 values differentiate the three ranges. In order for the temperature A to D value to be scaled consistently with what was used during factory programming, the CLKgntp (temperature amplifier gain) valued is stored. The Cadj value stored in byte 1 of the EEPROM is used to control the internal clock frequency while the chip boots.
Downloading Command
With one byte, data can be downloaded from the ASIC. The ASIC will automatically send the value of the desired byte.
Uploading Command
Writing to the RAM or EEPROM involves a simple handshaking protocol in which each byte transmitted is acknowledged by the firmware. The first byte transmitted to the firmware includes both command and address. The firmware acknowledges receipt of the command and address byte by echoing the same information back to the transmitter. This "echo" also indicates that the firmware is ready to receive the byte of data to be stored in RAM or EEPROM. Next, the byte of value to be stored is transmitted and, if successfully received and stored by the firmware, is acknowledged by a "data received signal," which is two bytes of value BCh. If the "data received signal" is not observed, it may be assumed that no value has been stored in RAM or EEPROM.
Unused Bytes
There are eight unused bytes in the EEPROM address map. These bytes can be used by the user to store information such as a serial number, assembly date code, production line, etc. Melexis makes no guarantee that these bytes will be available to the user in future revisions of the firmware.
EEPROM Checksum
A checksum test is used to ensure the contents of the EEPROM. The eight bit sum of all of the EEPROM addresses should have a remainder of 0FFh when the checksum test is enabled (mode byte). Byte 47 is used to make the sum remainder totals 0FFh. If the checksum test fails, the output will be driven to a user defined value, Faultval. When the checksum test is enabled, the checksum is verified at initialization of RAM after a reset.
Reset Command
Reading the address 63 of the EEPROM resets the ASIC and generates a received receipt indication. Immediately before reset, the ASIC sends a value of BCh to the UART, indicating that the reset has been received.
RAM Data
All the coefficients (pressure, temperature) are compacted in a manner similar to that used for the EEPROM. They are stored on 12 bits (instead of keeping 16 bits for each coefficient). All the measurements are stored on 16 bits. The user must have access to the RAM and the EEPROM, while interrupt reading of the serial port. Therefore, bytes must be kept available for the return address, the Aaccu and the B-accu, when an interrupt occurs. The RAM keeps the same structure in the both modes.
22/Aug/98 3.0 21/May/01 15 Page Rev
EEPROM Data
All user-settable variables are stored in the EEPROM within the MLX90308CAB. The EEPROM is always re-programmable. Changes to data in the EEPROM do not take effect until the device is reset via a soft reset or power cycle. 12 bit variables are stored on
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface
Rev Y.X 15 Page
MLX90308CAB
Programmable Sensor Interface
Table 10. Examples of Fixed Point Signed Numbers
Decimal 0 1023 1024 2047 2048 3071 3072 4095 Hexadecimal Equivalent 0000h 3FFh 400h 7FFh 800h 0BFFh 0C00h 0FFFh Fixed Point Signed Number Equivalent +0.00 +0.9990234 +1.000 +1.9990234 -0.000 -0.9990234 -1.000 -1.9990234
Data Range
Various data are arranged as follows: Temperature points: 10 bits, 0-03FF in highlow order. Pressure points: 10 bits, 0-03FF in high-low order. GN1: 10 bits, 0-03FF in high-low order. OF1: 10 bits, 0-03FF in high-low order. GNTCi: signed 12 bits (with MSB for the sign), [-1.9990234, +1.9990234]. OFTCi: signed 12 bits (with MSB for the sign), [-1.9990234, +1.9990234]. Pci: signed 12 bits (with MSB for the sign), [-1.9990234, +1.9990234] DIGMO: 10 bits, 0-03FF in high-low order (See Table 13 for examples of fixed point signed numbers.)
Table 11. EEPROM Byte Definitions
Byte 0 1 2 3 4 5 6 7 8 9 10 11 Designation MODE byte Cadj Coarse Control GN1L OF1L GNTC1L OFTC1L TR1L PC5L GNTC2L P5L OFTC2L PC4L TR2L P4L GNTC3L PC3L Note Contents described in Table 9. Controls system clock during boot. Contents described in Table 12. The eight LSB's of the Fixed Gain, GN[7:0]. The eight LSB's of Fixed Offset OF[7:0]. The eight LSB's of the first gain TC GNTC1[7:0]. The eight LSB's of the first offset TC OFTC1[7:0]. The eight LSB's of the first temperature point, T1[7:0]. The eight LSB's of Pressure Coefficient 5 PC5[7:0]. The eight LSB's of the second gain TC GNTC2[7:0]. The eight LSB's of Pressure Point 5 P5[7:0]. The eight LSB's of the second offset TC OFTC2[7:0]. The eight LSB's of Pressure Coefficient 4 PC4[7:0]. The eight LSB's of the second temperature point T2[7:0]. The eight LSB's of Pressure Point 4 (or Signature) P4[7:0]. The eight LSB's of the third gain TC GNTC3[7:0]. The eight LSB's of Pressure Coefficient 3 (or Signature) PC3 [8:0].
Page 16 Rev 3.0 21/May/01
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MLX90308CAB
Programmable Sensor Interface
Table 11. EEPROM Byte Definitions (continued)
Byte 12 Designation OFTC3L or P3L 13 14 TR3L or PC2L GNTC4L or P2L OFTC4L or PC1L PoffL Upper Four Bits 17 GN1[9:8] GNTC1[11:8] TR1[9:8] PC5[11:8] Lower Four Bits OF1[9:8] OFTC1[11:8] GNTC2[11:8] P5[9:8] Note The eight LSB's of the third offset TC OFTC3[7:0]. The eight LSB's of Pressure Point 2 (or Signature) P2[7:0]. The eight LSB's of the third temperature point T3[7:0]. The eight LSB's of Pressure Coefficient 2 PC2[7:0]. The eight LSB's of the fourth gain TC GNTC4[7:0]. The eight LSB's of Pressure Point 2 P2[7:0]. The eight LSB's of the fourth offset TC OFTC4. The eight LSB's of Pressure Coefficient 1 PC1 The eight LSB's of Pressure (output signal) Ordinate Poff[7:0]. Upper four bits. Lower four bits
15
16
Two MSB's of fixed gain GN[9:8]. Four MSB's of first gain TC GNTC1[11:8]. Two MSB's, first temperature point T1[9:8] or Four MSB's, Pressure Coefficient 5 PC5[11:8]. Four MSB's second offset TC OFTC2[11:8] or Four MSB's Pressure Coefficient 4 PC4[11:8]. Four MSB's third gain TC GNTC3[11:8] or Four MSB's Pressure Coefficient 3 PC3[11:8]). Two MSB's third temperature point t3[9:8] or Four MSB's Pressure Coefficient 2 PC2[11:8]. Four MSB's fourth offset TC ordinate OFTC4[11:8] or Four MSB's Pressure Coefficient 1 PC1[11:8].
Rev Y.X 17 Page
Two MSB's of fixed offset OF[9:8] Four MSB's of the first offset TC OFTC1[11:8]. Four MSB's, second gain TC GNTC2[11:8] or TC GNTC2[11:8] or Two MSB's Pressure Point 5 P5[9:8]. Two MSB's second temperature point T2[9:8] or Two MSB's Pressure Point 4 P4[9:8]. Four MSB's third offset TC OFTC3[11:8] or Two MSB's Pressure Point 3 P3[9:8]. Four MSB's fourth gain TC GNTC4[11:8] or Two MSB's Pressure Point 2 P2[9:8]. Two MSB's Pressure Poff[9:8].
18
19
20
OFTC2[11:8] PC4[11:8]
TR2[9:8] P4[9:8] OFTC3[11:8] P3[9:8] GNTC4[11:8] P2[9:8] Poff[9:8]
21
GNTC3[11:8] PC3[11:8]
22
TR3[9:8] PC2[9:8]
23
OFTC4[11:8] PC1[11:8]
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Programmable Sensor Interface
Table 11. EEPROM Byte Definitions (continued)
Byte 24 25 26 27 28 Designation PNB_TNB n_factor Not used ALARM low trigger Level1 IO2/IO1 ALARM low output Level2 IO2/IO1 ALARM high trigger Level3 IO2/IO1 ALARM high out level ALARM control byte Note Number of temperature and pressure gaps. See Tables 4, 5, and 6, and Figures 3 and 4. Temperature filter coefficient, four LSB's. Four MSB's must all be zero. This byte is not used. Value below which ALARM will go on. Value of first level ([IO2, IO1]= 00-01). See Figures 5 & 7. Value of DIGMO during "ALARM low" condition. Value of second level ([IO2,IO1] = 01-10). See Figures 5 and 7 Value above which ALARM will go on. Value of third level ([IO2,IO1]=10-11). See Figures 5 and 7. Value of DIGMO during "ALARM high" condition. See Figures 5 and 7. Three bits needed for choice of input for ALARM detection (TPO, IAO, GNO, VMO, IO1 or IO2). Two bits needed for choice of input for LEVEL-steering (TPO, IAO, GNO or VMO). The above bits are multiplexed according to the mode. If both CMO and VMO are active, then alarm is not active. Value of Cadj at low temperature (Don't change; factory set). Value of Cadj at mid temperature (Don't change; factory set). Value of Cadj at high temperature Don't change; factory set). First Cadj temperature point, eight MSB's of the 10 bit internal temperature value (set at factory; do not change). Second Cadj temperature point, eight MSB's of the 10 bit internal temperature value (set at factory; do not change). These bytes are not used by the firmware and are available to the user. Setting for temperature amplifier for clock temperature adjustment temperature reading (set at factory; do not change). Value sent to output if checksum test fails is a 10 bit value. These bytes are not used by the firmware and are available to the user. EEPROM checksum; value needed to make all bytes add to 0FFh. Must be set by user if checksum test is active.
Page 18 Rev 3.0 21/May/01
29 30 31
IO1/IO2 control byte
Four LSB's are unused 32 33 34 35 36 37-38 39 ClkTC1 ClkTC2 ClkTC3 Ctemp1 Ctemp2 Not used CLKgntp
40-41 42-46 47
Faultval Not Used Checksum
MLX90308CAB Programmable Sensor Interface
MLX90308CAB
Programmable Sensor Interface
Table 12. Bit Definitions; Coarse Control , Byte 2
Bit Symbol Function 7 6 5 4 3 2 1 0 IINV Invert signal sign.
Notes For Table 11
1. Not all the temperature and pressure coefficients must be used. When a coefficient is unused, the eight LSB's and the four MSB's are replaced by 0. 2. The level steering and the alarm mode cannot be active simultaneously because the levels bytes are shared with the two modes. 3. If the alarm mode and the level steering are both active, the level steering mode is dominant. The firmware will run with the level steering mode, by default. 4. If the DIGMO mode (VMO and CMO both active) is active, the alarm will be automatically disabled by the firmware. 5. At PNB_TNB address, the four MSB's correspond to the address of the last pressure point and the four LSB's to the address of the last temperature point.
GNTP1 Gain & offset of temperature amplifier. GNTP0 GNTP = 0 to 3. CSOF 1 Coarse offset of signal amplifier. CSOF 0 CSOF = 0 to 3. CSGN2 Coarse gain of signal amplifier. CSGN = 0 to 7. If CSGN > 3, CSGN1 output range = 0 to 10V. If CSGN0 CSGN <= 3, output range = 0 to 5V.
6. In the alarm_control variable, the selected input is stored on the three MSB's.
7. Pi and OFi are 10 bit values, right justified in 12 bits fields.
Table 13. RAM Byte Definitions
Byte 0 1 2 3 4 5 6 7 8 9 10 Functions MODE byte GN1L OF1L GNTC1L OFTC1L TR1L PC5L GNTC2L P5L OFTC2L PC4L TR2L P4L GNTC3L PC3L OFTC3L P3L Remarks See Table 9. Fixed gain number (8LSB). Fixed offset number (8LSB). First gain TC (8LSB). First offset TC (8LSB). First temperature point. Pressure Coefficient 5 (8LSB). Second gain TC. Pressure point 5 (8LSB). Second offset TC. Pressure coefficient 4 (8LSB). Second temperature point. Pressure Point 4 (or Signature) (8LSB). Third gain TC. Pressure Coefficient 3 (or Signature) (8LSB). Third offset TC. Pressure Point 2 (or Signature) (8LSB).
Rev Y.X 19 Page 22/Aug/98 3.0 21/May/01 19 Page Rev
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface
MLX90308CAB
Programmable Sensor Interface
Table 13. RAM Byte Definitions (continued)
Byte 11 Functions TR3L PC2L GNTC4L P2L 13 OFTC4L PC1L DIGMOP1L GN1[9:8] GNTC1 [11:8] TR1[9:8] OF1[9:8] OFTC1 [11:8] GNTC2 [11:8] P5[9:8] TR2[9:8] P4[9:8] OFTC3 Four MSB's, Pressure Coefficient 4 PC4[11:8]. Four MSB's, Third Gain TC GNTC3[11:8] or Four MSB's, Pressure Coefficient 3 PC3[11:8]). Two MSB's, third temperature point t3[9:8] or Four MSB's, Pressure Coefficient 2 PC2[11:8]. Four MSB's Fourth Offset TC OFTC4[11:8] or Four MSB's Pressure Coefficient 1 PC1[11:8]. Same as EEPROM. Temperature filter coefficient -- 4 LSB's, 4 MSB = 0 Two MSB's, Pressure Point 4 P4[9:8]. Four MSB's Third Offset TC OFTC3[11:8] or Two MSB's Pressure Point 3 P3[9:8] Four MSB's, Fourth Gain TC GNTC4[11:8] or Two MSB's, Pressure Point 2 P2[9:8]. Two MSB's Pressure Point 1 P1[9:8]. Remarks Third temperature point. Pressure Coefficient 2 (8LSB). Fourth gain TC. Pressure Point 1 (8LSB). Fourth offset TC. Pressure Coefficient 1 (8LSB). Fixed pressure (8LSB). Two MSB's of fixed gain GN[9:8]. Four MSB's of first gain TC GNTC1[11:8]. Two MSB's, first temperature point T1[9:8] or Four MSB's Pressure Coefficient 5 PC5[11:8]. Four MSB's, second offset TC OFTC2[11:8] or Two MSB's of fixed offset OF[9:8]. Four MSB's of the first offset TC OFTC1[11:8] Four MSB's, second gain TC GNTC2[11:8] or Two MSB's, Pressure Point 5 P5[9:8] Two MSB's, second temp. point T2[9:8] or
12
14 15 16 17
PC5[11:8] 18 OFTC2[11:8] PC4[11:8] GNTC3[11:8] [11:8] PC3[11:8] TR3[9:8] [11:8] PC2[9:8] OFTC4[11:8] PC1[11:8] 22 23 24 25-26 27-28 29 PNB_TNB N_Factor Not Used GN OF Taddress
19
20
P3[9:8] GNTC4
21
P2[9:8] P1[9:8]
Offset Ordinate of the current gap. Gain Ordinate of the current gap. 4 bits for the max. temperature address of the current gap; 4 bits for the min. temperature address of the current gap.
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Programmable Sensor Interface
Table 13. RAM Byte Definitions (continued)
Byte 30 Functions ALARM control byte IO1/IO2 control byte Remarks Three bits needed for choice of input for ALARM detection (TPO, IAO, GNO, VMO, IO1 or IO2). Two bits needed for choice of input for LEVEL-steering (TPO, IAO, GNO or VMO). These bits are multiplexed according the mode. Note: if both CMO and VMO are active, then alarm is not active. Value below which ALARM will go on. Value of first level ([IO2,IO1]=00-01). Value of DIGMO during "ALARM low" condition. Value of second level ([IO2,IO1]=01-10). Value above which ALARM will go on. Value of third level ([IO2,IO1] = 10-11). 34 35-36 37-38 39-42 43-44 45 46 47-48 49 50 51-52 53 54-55 56-57 58-59 60-61 62-63 IO1/IO2 level 3 ALARM high output level A_16 B_16 RESULT_32 Tempo1 Tempo2 Tempo3 Rx_char P3_copy Adsav1 Aaccsav Baccsav DAC_gain DAC_offset Temp_f Pressure Adsav2 Value of DIGMO during "ALARM high" condition. 16 bits A Register. 16 bits B Register. 32 bits result (for 16 bit multiplication). Measured temperature, internal or external, and temporary variable 1. Temporary variable 2. Temporary variable 3. Received character on the serial port. Port 3 setting copy. Address saved at interrupt. A-Accumulators saved at interrupt. B-Accumulators saved at interrupt. DAC gain (GN). DAC offset (OF). Filtered temperature. This is a 10 bit number that is left justified in a 16 bit field. Pressure Address saved when call.
31
ALARM low trigger level IO1/IO2 level 1 ALARM low output level IO1/IO2 level 2
32
33
ALARM high trigger level
Note: Because of space considerations, the measured temperature can't be kept in the RAM at all times. If the measured temperature is to be available, the temperature filter variable, N_Factor, must be set to 15.
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface Rev Y.X 21 Page 22/Aug/98 3.0 21/May/01 21 Page Rev
MLX90308CAB
Programmable Sensor Interface
Prototyping
Melexis offers an MLX90308 evaluation kit which contains an evaluation circuit board, serial interface cable, and software diskette. The circuit board provides the necessary circuitry for all three applications circuits shown on the next page. Also included in the circuit board is level shifting and glue logic necessary for RS-232 communications. The board has a socket with a single MLX90308 installed, and direct access to the pins of the IC. The user can easily attach bridge sensor to the board for in-system evaluation. The serial interface cable connects the evaluation board directly to a PC's serial port for in-system calibration. The software runs in the familiar Windows platform and allows for programming and evaluation of all compensation parameters within the EEPROM.
Figure 8. MLX90308 Evaluation Kit with MLX Software
MLX90308CAB Programmable Sensor Interface
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Programmable Sensor Interface
Typical 90308 Applications
Figure 9a. Absolute Voltage Mode
Supply
5K Automotive apps 100 nF
VDD FET VDD1 COMS
100 nF
VBP VMO VBN GND FLT
Output
39 nF 100 nF 10 nF 5K
Ground
Figure 9b. Ratiometric Voltage Mode
Supply
5K
VDD COMS
100 nF
VDD1
VBP VMO VBN FLT TMP GND
39 nF 10 nF 5K
Output
Ground
Figure 9c. Current Mode
Supply
5K
VDD COMS
FET VDD1
100 nF 100 nF
CMO
100 nF
VBP
75 Ohms
VBN FLT TMP GND CMN
39 nF 24 Ohms
Depends on stability of the current loop
Ground
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface Rev Y.X 23 Page 22/Aug/98 3.0 21/May/01 23 Page Rev
MLX90308CAB
Programmable Sensor Interface
Figure 10. Application Example
Figure 10a. Programmable Oil Pressure Gauge
Communications Signal Out GND V+
Programmable Oil Pressure Gauge
This application example illustrates a fundamental application of the MLX90308 and a bridge type pressure sensor element. In this application, the MLX90308 uses an external FET as a pass transistor to regulate the voltage to the sensor and the analog portion of the IC. This is known as Absolute Voltage Mode, where voltage to the sensor and analog circuit is regulated independent of the supply voltage. The MLX90308 can be operated in Ratiometric Voltage Mode, in which the output (VMO) is tied to an A/D converter sharing the same supply and ground reference. A third wiring option is Current Mode, which allows the user a 4 to 20 milliampere current range to use as a 2-wire analog sensor.
Figure 10b. Programmable Oil Pressure Gauge Electrical Connections
MLX90308CAB
1
IO1 IO2
COMS GND CMN CMO
16
Communication s
2
15
GND
3
TSTB FLT OFC VBN
14
4
13
Oil Pressure (psi) Signal Out
5
VMO VDD1 FET VDD
12
Pressure Sensor
6
11 D 10 G External FET for Regulation
V +
7
VBP TMP
S
8
9
MLX90308CAB Programmable Sensor Interface
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Programmable Sensor Interface
Figure 11. Error Compensation Figure 11a. Raw Sensor Output (measured between VPB and VBN)
170
Table 14. Glossary of Terms
A/D ADC ASCII ASIC CM CMN CMO COMS CR CSGN CSOF CV DAC DACFnew DACFold DARDIS dB DOGMO EEPROM EOC ESD ETMI ETPI FET FG FLT GNO GNOF GNTP HS I/O IFIX IINV ILIM kHz LSB mA MODSEL ms MSB MUX mV nF OFC PC pF PLL POR RAM RISC ROM RS-232 RX SAR STC Tdiff Text TMI TMP TPI Tref TSTB TX UART VBN VBP VDD VM VMGN VMO WCB WDC analog to digital conversion analog to digital converter American Standard Code for Information Interchange application specific integrated circuit current mode current mode negative (supply connection) current mode output communication, serial carriage return coarse gain coarse offset current / voltage mode select bit digital to analog converter filtered DAC value, new filtered DAC value, old DAC resistor disable decibel digital mode electrically erasable programmable read only memory end of conversion flag bit electrostatic discharge timer interrupt enable enable temperature interrupt field effect transistor fixed gain filter pin gain and offset adjusted digitized signal gain, offset temperature gain / offset coarse adjustment hardware / software limit input / output fixed current output value input signal invert command bit current limit kilohertz, 1000 Hz least significant bit milliamperes, 0.001 amps mode select millisecond, 0.001 second most significant bit multiplexer millivolts, 0.001 Volts nanofarads, 1 X 10-9 farads offset control personal computer, IBM clone picofarad, 1 X 10-12 farads phase locked loop power on reset random access memory reduced instruction set computer read only memory industry std. serial communications protocol receive successive approximation register start A/D conversion temperature difference temperature, external timer Interrupt temperature signal temperature interrupt temperature reference test mode pin transmit universal asynchronous receiver / transmitter bridge, positive, input bridge, negative, input supply voltage voltage mode voltage mode gain voltage mode output warn / cold boot watch dog counter
Voltage (in mV)
0 0%
140 oC 25oC -40oC
Pressure
100%
Figure 11b. Conditioned Sensor Output
4
Voltage (V DC)
1 0%
140 oC 25oC -40oC
Pressure
100%
Figures 11a and 11b above illustrate the performance of an unconditioned sensor output and a conditioned sensor output versus stimulus (pressure) and temperature. It can be seen that Figure 11a has a range of only 170 mV (maximum range with a 5V supply) and has a non-linear response over a 0-100 psi range. The sensitivity of the unconditioned output will also drift over temperature, as illustrated by the three slopes. The MLX90308 corrects these errors and amplifies the output to a more usable voltage range as shown in Figure 11b.
MLX902xx Name of Sensor MLX90308CAB Programmable Sensor Interface
Rev Y.X 25 Page
22/Aug/98 3.0 21/May/01 25 Page Rev
MLX90308CAB
Programmable Sensor Interface
Figure 12. MLX90308CAB Physical Characteristics, LW Package
0.32 0.23
10.65 10.00
7.60 7.40
1.27 0.40 0.51 0.33 1.27 0o to 8o
Notes:
10.50 10.10
1. All dimensions in millimeters. 2. Body dimensions do not include mold flash or protrusion, which are not to exceed 0.15mm.
2.65 2.35
0.010 min.
For the latest version of this document, go to our website at:
www.melexis.com
Or for additional information contact Melexis Direct:
Europe and Japan:
Phone: +32 13 61 16 31 E-mail: sales_europe@melexis.com
All other locations:
Phone: +1 603 223 2362 E-mail: sales_usa@melexis.com
QS9000, VDA6.1 and ISO14001 Certified
MLX90308CAB Programmable Sensor Interface
Page 26
Rev 3.0 21/May/01

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