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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
Part No. Temperature Suffix Package code
MLX90308 L (-40C to +150C) DF (SOIC16w)
MLX90308 L (-40C to +150C)
MLX90308
Programmable Sensor Interface
UF (die on foil)
Description
The MLX90308 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 MLX90308 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.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 1
3901090308 Page 1 Apr/04
Rev 006
MLX90308
Programmable Sensor Interface
Figure 1. Functional Block Diagram
3901090308 Page 2 Apr/04
Rev 006
MLX90308
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications
DC operating parameters: TA = -40 to 140oC, V
Parameter Symbol Test Conditions Min Typ Max Units
Regulator & Consumption
= 6 to 35VDC (unless otherwise specified).
DD1
Input voltage range VIN V
(Regulator connected) 6 35 V
DD1
Supply current IDD @ TA = 100ºC Current Mode 2.1 mA
Supply current IDD @ TA = 100ºC Voltage Mode 5.0 mA
Regulated supply voltage V
Regulated voltage
4.5 4.75 5.2 V
REG
-600 uV / ºC
temperature coefficient
Supply rejection ratio PSRR V
> 6V 90 dB
DD1
Instrumentation Amplifier
Differential input range VBP-VBN IINV = 0 -11.0 32.0 mV/V
Differential input range VBP-VBN IINV = 1 -32.0 11.0 mV/V
Common mode input range 1/2(VBP+VBN) 38.0 65.0 %VDD
Pin leakage current Pins VBP & VBN to GND, VDD = 8.0 nA
Common mode rejection Ratio CMRR 60 dB
Hardware gain 18 22 V/V
Coarse offset control Range CSOF[1:0] = 00 -15.3 -13.9
CSOF[1:0] = 01 -5.1 -3.8
CSOF[1:0] = 10 3.8 5.1
CSOF[1:0] = 11 13.9 15.3
Fixed offset control range High 6.0 8.0
Low -7.0 -5.0
mV/V
mV/V
mV/V
mV/V
mV/V
mV/V
IA chopper frequency 300 kHz
(Vdd)
(Vdd)
Gain Stage
Course gain CSGN = 000 3.0 3.3 V/V
(Fixed Gain = 1023)
* CSGN = 100 to 111: voltage mode
CSGN = 001 4.9 5.4 V/V
CSGN = 010 8.0 8.8 V/V
CSGN = 011 12.8 14.1 V/V
only, not applicable to current mode.
Output > 6.5V; MSB = 1
Output < 6.5V; MSB = 0
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 3
3901090308 Page 3 Apr/04
Rev 006
CSGN = 100*
CSGN = 101* 12.7 14.0 V/V
7.9 8.7
V/V
MLX90308
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
DC operating parameters: TA = -40 to 140oC, V
Parameter Test Conditions Min Typ Max Units
Coarse gain CSGN = 110* 20.4 23.0 V/V
Fixed gain control range 0.480 0.970 V/V
Digital Mode & Current Mode Coarse Gain Stage
Course Gain CSGN = 00 1.05 1.17 V/V
CSGN = 111* 33.1 36.6 V/V
CSGN = 01 1.71 1.89 V/V
CSGN = 10 2.77 3.06 V/V
CSGN = 11 4.48 4.95 V/V
Voltage Mode Output Stage ( See Voltage Mode)
Output voltage span CSGN[2:2] = 0 4.5 6.5 V
Gain 2.74 3.04 V/V
Minimum output voltage -0.2 V
Output source current 2.0 mA
Output sink current @ 0V output voltage 20 uA
Output resistance Over complete output range 25 Ohms
Digital mode output span CSGN[2:2] = 0 6.5 V
Digital mode step size VDD = 5V, CSGN[2:2]=0 6.5 mV
Capacitive load VMO pin 10 nF
Current Mode Output Stage
Fixed gain R
Output current CMO pin Current mode 27 mA
Current sense resistor 24 Ohms
Digital mode current output span VDD = 5V 23 mA
CSGN[2:2] = 1 6.5 11 V
Gain 7.24 7.86 V/V
CSGN[2:2] = 1 11.0 V
VDD = 5V, CSGN[2:2]=1 11.0 mV
SENSE
= 6 to 35VDC (unless otherwise specified).
DD1
= 24 ohm 8.4 9.3 mA/V
Digital mode current step Size VDD = 5V,R
Signal Path ( General)
Overall gain Voltage mode 28 600 V/V
Overall non-linearity -0.25 0.25 %
Ratiometry Error (4.75V – 5.25V) Overall Gain < 250V/V -0.5 0.5 %
3901090308 Page 4 Apr/04
Rev 006
Current mode = 24Ω 81 750 mA/V
Overall Gain > 250V/V
=24Ω 30 uA
SENSE
-1.3
+1.3
%
MLX90308
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
DC operating parameters: TA = -40 to 140oC, V
Parameter Test Conditions Min Typ Max Units
Bandwidth (-3dB) 39 nF connected from FLT to GND 2.8 3.5 4.2 KHz
= 6 to 35VDC (unless otherwise specified).
DD1
Noise, VDD = 5V, C
Temperature Sensor & - Amplifier
Temperature sensor sensitivity 390 uV/ºC
Temperature sensor output voltage
Temperature Sensor & Amplifier (continued).
Input voltage range TMP pin GNTP[1,0] = 00 207 517 mV
@ VDD = 5.0V
DAC
Resolution 10 Bit
Monotonicity Guaranteed By Design
Ratiometric output range (DAC output) 1 75 % VDD
Offset Error 10 LSB
Differential non-linearly 1 LSB
Integral non-linearity 2 LSB
ADC
=39nF, CL=10nF, RL =5KΩ, Analog Mode
FLT
70 380 mV
GNTP[1,0] = 01 145 367 mV
GNTP[1,0] = 10 101 263 mV
GNTP[1,0] = 11 71 186 mV
7.1
mVRMS
Resolution 10 Bit
Monotonicity
Ratiometric input range 1 75 % VDD
Offset error 10 LSB
Differential non-linearly 1 LSB
Integral non-linearity 2 LSB
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 26 Hz/ºC
Clock Stability with temperature compensation over full temperature range -3 +3 %
Ratio of f (microcontroller main clock
and (RC oscillator)
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 5
3901090308 Page 5 Apr/04
Rev 006
TURBO = 0 7
TURBO = 1 28
Guaranteed by design
40 250 kHz
86.9 87.8 88.7 kHz
MLX90308
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
DC operating parameters: TA = -40 to 140oC, V
Parameter Test Conditions Min Typ Max Units
Input & Output Pins (I01 & I02)
= 6 to 35VDC (unless otherwise specified).
DD1
Digital input levels
Output Levels @ output current = 5mA low VDD-0.4 0.4 V
TSTB Pin
Input levels Low 0.5 V
Pull-up Resistor 66 kOhms
FLT Pin
Output resistance 1.24 kOhms
Output voltage range VDD = 5V 0.05 3.6 V
OFC Pin
Output voltage range VDD = 5V 0.05 3.75 V
Load capacitor 20 pf
UART & COMS Pin
UART baud rate TURBO = 0 2400 baud
Low
High VDD-0.5
@ Output current = 5mA high VDD
High VDD-0.5
TURBO = 1 9600 baud
0.5
V
COMS pin input levels Low 0.3*VDD V
COMS Pin Output Resistance Low 100 Ohms
3901090308 Page 6 Apr/04
Rev 006
High 0.7*VDD V
High 100 kOhms
Unique Features
MLX90308
Programmable Sensor Interface
Customization
Melexis can customize the MLX90308 in both
hardware and firmware for unique requirements. The
hardware design provides 64 bytes of RAM, 3 kbytes
of ROM, and 48 bytes of EEPROM for use by the
firmware.
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.
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.
Table 2. Absolute Maximum Ratings
Supply voltage (ratiometric) V
Supply voltage (ratiometric) VDD Min
Supply voltage (operating),
Reverse voltage protection -0.7V
Supply current, Current Mode, IDD 3.5mA
Supply current, Voltage Mode, IDD 4.5mA
Output current, I
8mA
VMO
Output current (short to VDD), I
Output current (short to VSS), I
Output voltage, V
+11V
VMO
Power dissipation, PD 71mW
Operating temperature range, T
Storage temperature range, TS
Maximum junction temperature, TJ 150°C
DD
V
Max
DD1
SCVMO
SCVMO
Max
A
6V
4.5V
35V
100mA
8mA
-40 to +140°
-55 to +150°
Cross Reference
There are no known devices which the MLX 90308
can replace.
ESD Precautions
Observe standard ESD control procedures for CMOS
semiconductors.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 7
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Rev 006
MLX90308
Programmable Sensor Interface
Table 3. Pin Description
Signal
Pin
Name
1,2 I/O1, 2 Bi-directional I/O. Can also be used as input to A/D converter. I/O can be
3 TSTB Test pin for Melexis production testing. (in normal application connected to
4 FLT Filter pin; allows for connection of a capacitor to the internal analog path.
5 OFC Offset control output. Provides access to the internal programmed offset
6,7 VBN,VBP Bridge inputs, negative and positive.
8 TMP Temperature sensor input. An external temperature sensor can be used in
9 VDD Regulated supply voltage. Used for internal analog circuitry to ensure accurate
10 FET Regulator FET gate control. For generating a stable supply for the bridge
11 V
Unregulated supply voltage. Used for digital circuitry and to generate FET
DD1
12 VMO Voltage mode output. Compensated sensor output voltage.
Description
controlled by serial communications or by firmware as alarm inputs or level
out. (unconnected when not used)
VDD)
control voltage for use with external circuitry. (unconnected when not used)
conjunction with the internal one. The external sensor can provide a
temperature reading at the location of the bridge sensor.
and stable signal manipulation.
sensor and internal analog circuitry (generates regulated voltage for VDD).
output.
13 CMO Current mode output. Compensated sensor output for current mode operation.
14 CMN Current mode negative rail. Current mode return path.
15 GND Power supply return.
16 COMS Serial communications pin. Bi-directional serial communication signal for
reading and writing to the EEPROM.
1
2
3
4
5
6
7
8 9
IO1
IO2
TSTB
FLT
OFC
VBN
VBP
TMP
COMS
GND
CMN
CMO
VMO
VDD1
FET
VDD
16
15
14
13
12
11
10
Figure 2. Pinout (SO16W (LW) Package)
3901090308 Page 8 Apr/04
Rev 006
MLX90308
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.
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.
A/D and D/A
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).
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.
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 socalled "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.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 9
3901090308 Page 9 Apr/04
Rev 006
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.
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.
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.
MLX90308
Programmable Sensor Interface
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. .
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
If measured_temp < Temp_f(n), then
Temp_f(n+1) = Temp_f(n) - [measured_temp Temp_f(n)] [2
Temp_f(n+1) = new filtered temperature value.
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 0-6.
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.
n_factor
n_factor
].
].
3901090308 Page 10 Apr/04
Rev 006
1023
1023
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
FG = Hardware Gain (~20V/V). Part of the hardware
design, and not changeable.
CSGN = Course Gain, part of byte 2 in EEPROM.
CSOF = Coarse Offset, part of byte 2 in
EEPROM.
GAIN
DAC_GAIN (new value) ~ GN[9:0] + [GNTCi * dT]
GN[9:0] = Fixed Gain, bytes 3 and 17 in EEPROM.
GNTCi = Gain TC for a given temperature
segment I. GNTCiL and GNTCiH in
EEPROM table.
dT = Temp. change within the appropriate gap.
How to calculate gain in the first temp. gap?:
DAC_GAIN = GN[9:0] - GNTC1 * (T1 – Temp_f1)
How to calculate gain in the other temp. gaps?:
2nd gap: DAC_GAIN = GN[9:0] + GNTC2 *
(Temp_f2 – T1)
3th gap: DAC_GAIN = DAC_GAIN2 + GNTC3 *
(Temp_f3 – T2)
4th gap: DAC_GAIN = DAC_GAIN3 + GNTC4 *
(Temp_f4 – T3)
Where:
Temp_f = Filtered temp. (previously described).
If GNTC1 > 2047 => DAC_GAIN ↑
If GNTC2,3,4 > 2047 => DAC_GAIN ↓
[V/V]
MLX90308
Programmable Sensor Interface
OFFSET
DAC_OFFSET (new value) ~ OF[9:0]+[OFTCi* dT]
OF[9:0] = Fixed Gain, bytes 4 and 17 in EEPROM.
OFTCi = Offset for a given temperature
segment I. OFTCiL and OFTCiH in
EEPROM table.
dT = Temp. change within the appropriate gap.
Calculation of the offset for a given temperature segment is performed the same way as for the gain.
*)67( =−−−
]0:9[
OFFSETDACOF_6
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:
1st gap: Output = (Signal ) * PC1 + Poff
Where:
Signal = input signal measurement;
Poff = Pressure ordinate = P1
PC1 = programmed coefficient first gap.
Following gaps:
Gap i: Output = (Signal – Pi) * PCi + Poff_i
Where
Signal = input signal measurement;
Poff_i = Pressure ordinate (i = 2,3,4,5)
Pi = Pressure signal point (i = 2,3,4,5)
PCi = programmed coefficient first gap (i = 2,3,4,5).
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.
[mV/V]
Digital
*)48.097.0( =+−
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 11
3901090308 Page 11 Apr/04
Rev 006
]0:9[
GAINDACGN_48.0
MLX90308
Programmable Sensor Interface
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.
Table 4. PNB_TNB Bit Definition;
Pressure Gaps
# of Pressure Gaps 4MSB of PNB_TNB Value
Fixed 15 (F hex)
1 14 (E hex)
2 12 (C hex)
3 10 (A hex)
4 8
5 6
Table 5. PNB_TNB Bit Definition;
Temperature Gaps
# of Temperature Gaps 4 LSB of PNB_TNB
Fixed (1) 0
2 Gaps 5
3 Gaps 8
4 Gaps 11 (B hex)
Table 6. Temperature
& Signal Limitations
Maximum number of
temperature gaps
Fixed Gain and
fixed Offset
2 Gaps 3 Gaps
3 Gaps 2 Gaps
4 Gaps Fixed signal
Maximum number of
signal gaps
5 Gaps
Figure 4. Signal
Linearity Correction
Output
PC3
PC2
Output (units)
PC1
P4P3P20 P5
3901090308 Page 12 Apr/04
Rev 006
MLX90308
PC5
PC4
MLX90308
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.
Table 7. Alarm Source Bit Definition
Selected input
TPO 0010
IAO 0110
GNO 0000
VMO 0011
IO1 0100
IO2 0101
MUX Value
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
VBP
VBN
TMP
IO1
IO2
OFC FLT VDD1 FET VDD GND
IAO
Offset
TPO
Temp
Sense
& Amp
ADC
&
DAC
Bidirectional
I/O
UART
Gain
Power Supply
GNO
Regulation
VM
CM
Microcontroller
Core, Memory,
EEPROM
Reset,Test,&
Oscillator
VMO
CMO
CMN
TSTB
Figure 5.
COMS
Alarm Function
OUTPUT
MLX90308
Figure 7. Level Steering
Function
High
Output
Output
Low
Output
Low
Trigger
Input Signal
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 13
3901090308 Page 13 Apr/04
High
Trigger
Parameter
IO1, IO2
0 - 0
(I02,I01)
Level 1
0 - 1
Level 2 Level 3
Rev 006
MLX90308
1 -1
1 - 0
MLX90308
Programmable Sensor Interface
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)
Table 9. Mode Byte Bit Definition
Function Remarks
Bit
7 1= EEPROM Checksum test active
0= EEPROM Checksum test inactive
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).
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 0010
IAO 0110
GNO 0000
VMO 0011
MUX Value
6 0 = Analog Mode
1 = Digital Mode
5 0 = Alarm function inactive
1 = Alarm function active
4 0 = IO1/IO2 are not active outputs
1 = level steering: IO1/IO2 are active
outputs
3 0 = Turbo inactive
1 = Turbo active
2 0 = VMO inactive
1 = VMO active
1 0 = Internal temperature sensor active
1 = External temperature sensor
active
0 0 = CMO inactive
1 = CMO active
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.
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.
3901090308 Page 14 Apr/04
Rev 006
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).
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.
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.
EEPROM Data
All user-settable variables are stored in the EEPROM
within the MLX90308. The EEPROM is always reprogrammable. 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 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.
MLX90308
Programmable Sensor Interface
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.
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 doesn’t 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.
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.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 15
3901090308 Page 15 Apr/04
Rev 006
MLX90308
Programmable Sensor Interface
Table 10. Examples of Fixed Point
Signed Numbers
Decimal
Value
0 0000h +0.00
1023 3FFh +0.9990234
1024 400h +1.000
2047 7FFh +1.9990234
2048 800h -0.000
3071 0BFFh -0.9990234
3072 0C00h -1.000
4095 0FFFh -1.9990234
Hexadecimal
Equivalent
Fixed Point Signed
Number Equivalent
Table 11. EEPROM Byte Definitions
Data Range
Various data are arranged as follows:
Temperature points: 10 bits, 0-03FF in high-
low 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.)
Byte
0
Designation Note
MODE byte Contents described in Table 9.
1 Cadj Controls system clock during boot.
2 Coarse Control Contents described in Table 12.
3 GN1L The eight LSB's of the Fixed Gain, GN[7:0].
4 OF1L The eight LSB's of Fixed Offset OF[7:0].
5 GNTC1L The eight LSB's of the first gain TC GNTC1[7:0].
6 OFTC1L The eight LSB's of the first offset TC OFTC1[7:0].
7 TR1L
PC5L
8 GNTC2L
P5L
9 OFTC2L
PC4L
10 TR2L
P4L
11 GNTC3L
PC3L
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].
3901090308 Page 16 Apr/04
Rev 006
Programmable Sensor Interface
Table 11. EEPROM Byte Definitions (continued)
MLX90308
Byte
12
13
14
15
16
17
18
Designation Note
OFTC3L or
P3L
TR3L or
PC2L
GNTC4L or
P2L
OFTC4L or
PC1L
PoffL
Upper Lower
Four Four
Bits Bits
GN1[9:8] OF1[9:8]
GNTC1[11:8] OFTC1[11:8]
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
Two MSB's of fixed gain Two MSB's of fixed offset
GN[9:8]. OF[9:8]
Four MSB's of first gain TC Four MSB's of the first offset
GNTC1[11:8]. TC OFTC1[11:8].
19
20
21
22
23
TR1[9:8] GNTC2[11:8]
PC5[11:8] P5[9:8]
OFTC2[11:8] TR2[9:8]
PC4[11:8] P4[9:8]
GNTC3[11:8] OFTC3[11:8]
PC3[11:8] P3[9:8]
TR3[9:8] GNTC4[11:8]
PC2[9:8] P2[9:8]
OFTC4[11:8] Poff[9:8]
PC1[11:8]
Two MSB's, first temperature Four MSB's, second gain
point T1[9:8] or TC GNTC2[11:8] or
Four MSB's, Pressure TC GNTC2[11:8] or
Coefficient 5 PC5[11:8]. Two MSB's Pressure Point 5
P5[9:8].
Four MSB's second offset Two MSB's second
TC OFTC2[11:8] or temperature point T2[9:8] or
Four MSB's Pressure Two MSB's Pressure Point 4
Coefficient 4 PC4[11:8]. P4[9:8].
Four MSB's third gain TC Four MSB's third offset
GNTC3[11:8] or TC OFTC3[11:8] or
Four MSB's Pressure Two MSB's Pressure Point 3
Coefficient 3 PC3[11:8]). P3[9:8].
Two MSB's third Four MSB's fourth gain TC
temperature point t3[9:8] or GNTC4[11:8] or
Four MSB's Pressure Two MSB's Pressure
Coefficient 2 PC2[11:8]. Point 2 P2[9:8].
Four MSB's fourth offset TC Two MSB's Pressure
ordinate
OFTC4[11:8] or Poff[9:8].
Four MSB's Pressure
Coefficient 1 PC1[11:8].
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 17
3901090308 Page 17 Apr/04
Rev 006
Programmable Sensor Interface
Table 11. EEPROM Byte Definitions (continued)
MLX90308
Byte
24
25 n_factor Temperature filter coefficient, four LSB's. Four MSB's must
26 Not used This byte is not used.
27 ALARM low trigger
28 ALARM low output
29 ALARM high trigger
30 ALARM high out level Value of DIGMO during “ALARM high” condition. See
31 ALARM control byte
Designation Note
PNB_TNB Number of temperature and pressure gaps. See Tables 4, 5,
and 6, and Figures 3 and 4.
all be zero.
Value below which ALARM will go on.
Level1 IO2/IO1
Level2 IO2/IO1
Level3 IO2/IO1
IO1/IO2 control byte
Four LSB's are unused
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.
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.
32 ClkTC1 Value of Cadj at low temperature (Don’t change; factory set).
33 ClkTC2 Value of Cadj at mid temperature (Don’t change; factory set).
34 ClkTC3 Value of Cadj at high temperature Don’t change; factory set).
35 Ctemp1 First Cadj temperature point, eight MSB’s of the 10 bit
internal temperature value (set at factory; do not change).
36 Ctemp2 Second Cadj temperature point, eight MSB’s of the 10 bit
internal temperature value (set at factory; do not change).
37-38 Not used These bytes are not used by the firmware and are available
to the user.
39 CLKgntp Setting for temperature amplifier for clock temperature
adjustment temperature reading (set at factory; do not
change).
40-41 Faultval Value sent to output if checksum test fails is a 10 bit value.
42-46 Not Used These bytes are not used by the firmware and are available
to the user.
47 Checksum EEPROM checksum; value needed to make all bytes add to
0FFh. Must be set by user if checksum test is active.
3901090308 Page 18 Apr/04
Rev 006
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.
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.
MLX90308
Programmable Sensor Interface
Table 12. Bit Definitions;
Coarse Control , Byte 2
Bit Symbol Function
7 IINV
6 GNTP1 Gain & offset of temperature
5 GNTP0
4 CSOF 1 Coarse offset of signal amplifier.
3 CSOF 0
2 CSGN2
1 CSGN1
0 CSGN0
Invert signal sign.
amplifier.
GNTP = 0 to 3.
CSOF = 0 to 3.
Coarse gain of signal amplifier.
CSGN = 0 to 7. If CSGN > 3,
output range = 0 to 10V. If
CSGN <= 3, output range = 0 to
5V.
Table 13. RAM Byte Definitions
Byte
Functions Remarks
0 MODE byte See Table 9.
1 GN1L Fixed gain number (8LSB).
2 OF1L Fixed offset number (8LSB).
3 GNTC1L First gain TC (8LSB).
4 OFTC1L First offset TC (8LSB).
5 TR1L
PC5L
6 GNTC2L
P5L
7 OFTC2L
PC4L
8 TR2L
P4L
9 GNTC3L
PC3L
10 OFTC3L
P3L
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).
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 19
3901090308 Page 19 Apr/04
Rev 006
Table 13. RAM Byte Definitions (continued)
MLX90308
Programmable Sensor Interface
Byte Functions Remarks
11 TR3L
PC2L
12 GNTC4L
P2L
13 OFTC4L
PC1L
14 DIGMOP1L Fixed pressure (8LSB).
15 GN1[9:8] OF1[9:8] Two MSB's of fixed gain Two MSB's of fixed offset
16 GNTC1 OFTC1
[11:8] [11:8]
17 TR1[9:8] GNTC2
[11:8]
PC5[11:8] P5[9:8]
18
19
20
21
22 PNB_TNB Same as EEPROM.
OFTC2[11:8] TR2[9:8]
PC4[11:8] P4[9:8]
GNTC3[11:8] OFTC3
[11:8]
PC3[11:8] P3[9:8]
TR3[9:8] GNTC4
[11:8]
PC2[9:8] P2[9:8]
OFTC4[11:8] P1[9:8]
PC1[11:8]
Third temperature point.
Pressure Coefficient 2 (8LSB).
Fourth gain TC.
Pressure Point 1 (8LSB).
Fourth offset TC.
Pressure Coefficient 1 (8LSB).
GN[9:8]. OF[9:8].
Four MSB's of first gain TC Four MSB's of the first
GNTC1[11:8]. offset TC OFTC1[11:8]
Two MSB's, first temperature Four MSB's, second gain
point T1[9:8] or TC GNTC2[11:8] or
Four MSB's Pressure Two MSB's, Pressure
Coefficient 5 PC5[11:8]. Point 5 P5[9:8]
Four MSB's, second offset TC Two MSB's, second temp.
OFTC2[11:8] or point T2[9:8] or
Four MSB's, Pressure Two MSB's, Pressure
Coefficient 4 PC4[11:8]. Point 4 P4[9:8].
Four MSB's, Third Gain TC Four MSB's Third Offset
GNTC3[11:8] or TC OFTC3[11:8] or
Four MSB's, Pressure Two MSB's Pressure
Coefficient 3 PC3[11:8]). Point 3 P3[9:8]
Two MSB's, third temperature Four MSB's, Fourth Gain
point t3[9:8] or TC GNTC4[11:8] or
Four MSB's, Pressure Two MSB's, Pressure
Coefficient 2 PC2[11:8]. Point 2 P2[9:8].
Four MSB's Fourth Offset TC Two MSB's Pressure
OFTC4[11:8] or Point 1 P1[9:8].
Four MSB's Pressure
Coefficient 1 PC1[11:8].
23 N_Factor Temperature filter coefficient — 4 LSB’s, 4 MSB = 0
24 Not Used
25-26 GN Offset Ordinate of the current gap.
27-28 OF Gain Ordinate of the current gap.
29 Taddress 4 bits for the max. temperature address of the current gap; 4
bits for the min. temperature address of the current gap.
3901090308 Page 20 Apr/04
Rev 006
Table 13. RAM Byte Definitions (continued)
MLX90308
Programmable Sensor Interface
Byte Functions Remarks
30 ALARM control byte
IO1/IO2 control byte
31 ALARM low trigger level
IO1/IO2 level 1
32 ALARM low output level
IO1/IO2 level 2
33 ALARM high trigger
level
IO1/IO2 level 3
34 ALARM high output
level
35-36 A_16 16 bits A Register.
37-38 B_16 16 bits B Register.
39-42 RESULT_32 32 bits result (for 16 bit multiplication).
43-44 Tempo1 Measured temperature, internal or external, and temporary
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).
Value of DIGMO during “ALARM high” condition.
variable 1.
45 Tempo2 Temporary variable 2.
46-47 Signal_In Digitized signal value, analog and digital mode
48 Coms_backup Address saved when command is send.
49 P3_copy Port 3 setting copy.
50 Adsav1 Address saved at interrupt.
51-52 Aaccsav A-Accumulators saved at interrupt.
53 Baccsav B-Accumulators saved at interrupt.
54-55 DAC_gain DAC gain (GN).
56-57 DAC_offset DAC offset (OF).
58-59 Temp_f Filtered temperature. This is a 10 bit number that is left
justified in a 16 bit field.
60-61 Signal_Out Digitized linearity corrected signal value. Digital mode only.
62-63 Adsav2 Address saved when call.
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 6.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 21
3901090308 Page 21 Apr/04
Rev 006
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.
MLX90308
Programmable Sensor Interface
Figure 8. MLX90308 Evaluation Kit with MLX Software
3901090308 Page 22 Apr/04
Rev 006
Programmable Sensor Interface
Typical 90308 Applications
Figure 9a. Absolute Voltage Mode
MLX90308
Supply
5K
VDD1VDD FET
COMS
100 nF
VBP
VBN
VMO
FLT
GND
Figure 9b. Ratiometric Voltage Mode
5K
VDD1VDD
COMS
100 nF
VBP
VBN
TMP
VMO
FLT
GND
39 nF
39 nF
Automotive
apps
100 nF 10 nF
10 nF
100 nF
Output
10K
Ground
Supply
Output
10K
Ground
Figure 9c. Current Mode
Supply
5K
VDD1VDD
FET
COMS
100 nF
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 23
3901090308 Page 23 Apr/04
VBP
VBN
TMP
GND
CMO
FLT
CMN
75 Ohms
39 nF
24 Ohms
Rev 006
100 nF 100 nF
Depends on
stability of the
current loop
Ground
Communications
Signal Out
GND
V+
Figure 10. Application Example
Figure 10a. Programmable Oil Pressure Gauge
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.
MLX90308
Programmable Sensor Interface
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
Figure 10b. Programmable Oil Pressure Gauge Electrical Connections
3901090308 Page 24 Apr/04
Rev 006
Voltage (in mV)
Voltage (V
)
MLX90308
Programmable Sensor Interface
Figure 11. Error Compensation Table 14. Glossary of Terms
A/D analog to digital conversion
Figure 11a. Raw Sensor Output
(measured between VPB and VBN)
170
140oC
25oC
-40oC
0
0% 100%
Pressure
Figure 11b. Conditioned Sensor
Output
4
DC
140oC
25oC
-40oC
1
0% 100%
Pressure
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.
ADC analog to digital converter
ASCII American Standard Code for Information
Interchange
ASIC application specific integrated circuit
CM current mode
CMN current mode negative (supply connection)
CMO current mode output
COMS communication, serial
CR carriage return
CSGN coarse gain
CSOF coarse offset
CV current / voltage mode select bit
DAC digital to analog converter
DACFnew filtered DAC value, new
DACFold filtered DAC value, old
DARDIS DAC resistor disable
dB decibel
DOGMO digital mode
EEPROM electrically erasable programmable read only
memory
EOC end of conversion flag bit
ESD electrostatic discharge
ETMI timer interrupt enable
ETPI enable temperature interrupt
FET field effect transistor
FG fixed gain
FLT filter pin
GNO gain and offset adjusted digitized signal
GNOF gain, offset
GNTP temperature gain / offset coarse adjustment
HS hardware / software limit
I/O input / output
IFIX fixed current output value
IINV input signal invert command bit
ILIM current limit
kHz kilohertz, 1000 Hz
LSB least significant bit
mA milliamperes, 0.001 amps
MODSEL mode select
ms millisecond, 0.001 second
MSB most significant bit
MUX multiplexer
mV millivolts, 0.001 Volts
nF nanofarads, 1 X 10-9 farads
OFC offset control
PC personal computer, IBM clone
pF picofarad, 1 X 10
PLL phase locked loop
POR power on reset
RAM random access memory
RISC reduced instruction set computer
ROM read only memory
RS-232 industry std. serial communications protocol
RX receive
SAR successive approximation register
STC start A/D conversion
Tdiff temperature difference
Text temperature, external
TMI timer Interrupt
TMP temperature signal
TPI temperature interrupt
Tref temperature reference
TSTB test mode pin
TX transmit
UART universal asynchronous receiver / transmitter
VBN bridge, positive, input
VBP bridge, negative, input
VDD supply voltage
VM voltage mode
VMGN voltage mode gain
VMO voltage mode output
WCB warn / cold boot
WDC watch dog counter
-12
farads
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 25
3901090308 Page 25 Apr/04
Rev 006
Programmable Sensor Interface
Figure 12. MLX90308 Physical Characteristics, DF Package
7.60
7.40
10.65
10.00
MLX90308
0.32
0.23
0.51
0.33
10.50
10.10
1.27
0o to
o
Notes:
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.
8
1.27
0.40
3901090308 Page 26 Apr/04
Rev 006
MLX90308
Programmable Sensor Interface
Reliability Information
This Melexis device is classified and qualified regarding soldering technology, solderability and moisture sensitivity level, as defined in this specification, according to following test methods:
■
IPC/JEDEC J-STD-020
Moisture/Reflow Sensitivity Classification For Nonhermetic Solid State Surface Mount Devices
(classification reflow profiles according to table 5-2)
■
EIA/JEDEC JESD22-A113
Preconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing
(reflow profiles according to table 2)
■
CECC00802
Standard Method For The Specification of Surface Mounting Components (SMDs) of Assessed Quality
■
EIA/JEDEC JESD22-B106
Resistance to soldering temperature for through-hole mounted devices
■
EN60749-15
Resistance to soldering temperature for through-hole mounted devices
■
MIL 883 Method 2003 / EIA/JEDEC JESD22-B102
Solderability
For all soldering technologies deviating from above mentioned standard conditions (regarding peak
temperature, temperature gradient, temperature profile etc) additional classification and qualification tests
have to be agreed upon with Melexis.
The application of Wave Soldering for SMD’s is allowed only after consulting Melexis regarding
assurance of adhesive strength between device and board.
Based on Melexis commitment to environmental responsibility, European legislation (Directive on
the Restriction of the Use of Certain Hazardous substances, RoHS) and customer requests, Melexis has
installed a Roadmap to qualify their package families for lead free processes also.
Various lead free generic qualifications are running, current results on request.
For more information on manufacturability/solderability see quality page at our website:
http://www.melexis.com/html/pdf/MLXleadfree-statement.pdf
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 27
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Rev 006
MLX90308
Programmable Sensor Interface
Disclaimer
Devices sold by Melexis are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. Melexis makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices
from patent infringement. Melexis reserves the right to change specifications and prices at any
time and without notice. Therefore, prior to designing this product into a system, it is necessary to
check with Melexis for current information. This product is intended for use in normal commercial
applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by Melexis for each application.
The information furnished by Melexis is believed to be correct and accurate. However, Melexis
shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interrupt of business or indirect, special
incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any
third party shall arise or flow out of Melexis’ rendering of technical or other services.
© 2002 Melexis NV. All rights reserved.
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: All other locations:
Phone: +32 13 67 04 95 Phone: +1 603 223 2362
E-mail: sales_europe@melexis.com E-mail: sales_usa@melexis.com
ISO/TS16949 and ISO14001 Certified
3901090308 Page 28 Apr/04
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