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MLX90308CCC
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. Temperature Suffix Package Option Temperature Range
MLX90308CCC L LW -40C to 140C
MLX90308CCC L UD* -40C to 140C
*UD denotes unpackaged die
Description
The MLX90308CCC 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
MLX90308CCC 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
MLX90308CCC Programmable Sensor Interface Page 1 Rev 2.2 23/Oct/01
MLX90308CCC
Temp Sensor
Temp Amp Gain
GNTP [1:0]
Temperature signal. Used by
microproscessor to perform
temperature linearity corrections.
TSTB
Functional Block Diagram
Programmable Sensor Interface
CMO
GAIN
Current Mode
2-bit
CMN
CSGN
GAIN
1-bit
CSGN
0.97V/V
VMO
GAIN
Analog
0.48V/V
Voltage Mode
Digital
ADC DAC
IO1
IO2
COMS
Micro-
processor
Fine Gain DAC
3.5V
ADC
0V
FLTOFC
VDD1FET
DAC_Offset
3.5V
Supply Regulator
VDD
OPA
0V
VBP
x2
x 10
1.24kOhm
Hardware Gain = 20
INV
VBN
Coarse Offset
TMP
External
Temp Sensor
Figure 1.
Internal
GND
MLX90308CCC Programmable Sensor Interface Page 2 Rev 2.2 23/Oct/01
MLX90308CCC
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 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 = 001 4.9 5.4 V/V
CSGN = 010 8.0 8.8 V/V
* CSGN = 100 to 111: voltage mode
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
MLX90308CCC Programmable Sensor Interface Page 3 Rev 2.2 23/Oct/01
CSGN = 011 12.8 14.1 V/V
CSGN = 100*
7.9 8.7
V/V
CSGN = 101* 12.7 14.0 V/V
Programmable Sensor Interface
Table 1. MLX90308 Electrical Specifications (continued)
DC operating parameters: TA = -40 to 140oC, V
= 6 to 35VDC (unless otherwise specified).
DD1
MLX90308CCC
Parameter Test Conditions Min Typ Max Units
Coarse gain CSGN = 110* 20.4 23.0 V/V
CSGN = 111* 33.1 36.6 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 = 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
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
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
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 %
MLX90308CCC Programmable Sensor Interface Page 4 Rev 2.2 23/Oct/01
= 24 ohm 8.4 9.3 mA/V
SENSE
=24Ù 30 uA
SENSE
Current mode = 24Ù 81 750 mA/V
Overall Gain > 250V/V
-1.3
+1.3
%
MLX90308CCC
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 70 380 mV
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
Resolution 10 Bit
=39nF, CL=10nF, RL =5KÙ, Analog Mode
FLT
GNTP[1,0] = 01 145 367 mV
GNTP[1,0] = 10 101 263 mV
GNTP[1,0] = 11 71 186 mV
5.0
mVRMS
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
MLX90308CCC Programmable Sensor Interface Page 5 Rev 2.2 23/Oct/01
TURBO = 0 7
TURBO = 1 28
Guaranteed by design
40 250 kHz
86.9 87.8 88.7 kHz
MLX90308CCC
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)
Digital input levels
Output Levels @ output current = 5mA low VDD-0.4 0.4 V
TSTB Pin
Input levels Low 0.5 V
High VDD-0.5
Pull-up Resistor 66 kOhms
FLT Pin
Output resistance 1.24 kOhms
Low
High VDD-0.5
@ Output current = 5mA high VDD
= 6 to 35VDC (unless otherwise specified).
DD1
0.5
V
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
COMS pin input levels Low 0.3*VDD V
COMS Pin Output Resistance Low 100 Ohms
TURBO = 1 9600 baud
High 0.7*VDD V
High 100 kOhms
MLX90308CCC Programmable Sensor Interface Page 6 Rev 2.2 23/Oct/01
Unique Features
MLX90308CCC
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.
Table 2. Absolute Maximum Ratings
Supply voltage (ratiometric) V
Supply voltage (ratiometric) VDD Min
Supply voltage (operating), V
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
Max
DD
Max 35V
DD1
SCVMO
SCVMO
A
6V
4.5V
100mA
8mA
-40 to +140°
-55 to +150°C
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
90308CCC can replace.
ESD Precautions
Observe standard ESD control procedures for
CMOS semiconductors.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 7
MLX90308CCC Programmable Sensor Interface Page 7 Rev 2.2 23/Oct/01
MLX90308CCC
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
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.
accurate 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)
MLX90308CCC Programmable Sensor Interface Page 8 Rev 2.2 23/Oct/01
MLX90308CCC
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 MCUclock 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.
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.
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.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 9
MLX90308CCC Programmable Sensor Interface Page 9 Rev 2.2 23/Oct/01
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 STARTbit value. The RX Interrupt is set when the stop bit is
latched in the UART.
MLX90308CCC
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
].
].
MLX90308CCC Programmable Sensor Interface Page 10 Rev 2.2 23/Oct/01
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 ↓
*)48.097.0( =+−
]0:9[
1023
[V/V]
GAINDACGN_48.0
MLX90308CCC
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[
1023
OFFSETDACOF_6
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.
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.
[mV/V]
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MLX90308CCC Programmable Sensor Interface Page 11 Rev 2.2 23/Oct/01
MLX90308CCC
Programmable Sensor Interface
Table 4. PNB_TNB Bit Definition;
# 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
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 3. Temperature
Linearity Correction
OF & GN
OFTC3
OFTC2
OFTC1
OF0
Parameter
GN0
GNTC1
Baseline Calibration
GNTC2
i1
GNTC3
i3
i2
1 Gap
T2T10 3FFh
MLX90308
OFTC4
GNTC4
i4
T3
Figure 4. Signal
Linearity Correction
Output
PC3
PC2
Output (units)
PC1
MLX90308
PC5
PC4
P4P3P20 P5
MLX90308CCC Programmable Sensor Interface Page 12 Rev 2.2 23/Oct/01
MLX90308CCC
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 MUX Value
TPO 0010
IAO 0110
GNO 0000
VMO 0011
IO1 0100
IO2 0101
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
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
MLX90308CCC Programmable Sensor Interface Page 13 Rev 2.2 23/Oct/01
High
Trigger
IO1, IO2
Parameter
(I02,I01)
0 - 0
Level 1
0 - 1
Level 2 Level 3
MLX90308
1 -1
1 - 0
MLX90308CCC
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)
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
Table 9. Mode Byte Bit Definition
Bit Function Remarks
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).
Selected input MUX Value
TPO 0010
IAO 0110
GNO 0000
VMO 0011
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.
MLX90308CCC Programmable Sensor Interface Page 14 Rev 2.2 23/Oct/01
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 MLX90308CCC. 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 1.5 bytes. The 4 MSB’s are stored in a
MLX90308CCC
Programmable Sensor Interface
separate byte and shared with the four MSB’s of
another 12-bit variable.
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
MLX90308CCC Programmable Sensor Interface Page 15 Rev 2.2 23/Oct/01
MLX90308CCC
Programmable Sensor Interface
Table 10. Examples of Fixed Point
Signed Numbers
Decimal Hexadecimal
Equivalent
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
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
Byte Designation Note
0
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].
MLX90308CCC Programmable Sensor Interface Page 16 Rev 2.2 23/Oct/01
Programmable Sensor Interface
Table 11. EEPROM Byte Definitions (continued)
Byte Designation Note
MLX90308CCC
12
13
14
15
16
17
18
19
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]
TR1[9:8] GNTC2[11:8]
PC5[11:8] P5[9:8]
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].
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].
20
21
22
23
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 17
MLX90308CCC Programmable Sensor Interface Page 17 Rev 2.2 23/Oct/01
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]
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].
Programmable Sensor Interface
Table 11. EEPROM Byte Definitions (continued)
Byte Designation Note
MLX90308CCC
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
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.
MLX90308CCC Programmable Sensor Interface Page 18 Rev 2.2 23/Oct/01
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.
MLX90308CCC
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
MLX90308CCC Programmable Sensor Interface Page 19 Rev 2.2 23/Oct/01
Table 13. RAM Byte Definitions (continued)
Byte Functions Remarks
MLX90308CCC
Programmable Sensor Interface
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.
MLX90308CCC Programmable Sensor Interface Page 20 Rev 2.2 23/Oct/01
Table 13. RAM Byte Definitions (continued)
Byte Functions Remarks
MLX90308CCC
Programmable Sensor Interface
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 justi-
fied 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
MLX90308CCC Programmable Sensor Interface Page 21 Rev 2.2 23/Oct/01
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.
MLX90308CCC
Programmable Sensor Interface
Figure 8. MLX90308 Evaluation Kit with MLX Software
MLX90308CCC Programmable Sensor Interface Page 22 Rev 2.2 23/Oct/01
Programmable Sensor Interface
Typical 90308 Applications
Figure 9a. Absolute Voltage Mode
MLX90308CCC
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
MLX90308CCC Programmable Sensor Interface Page 23 Rev 2.2 23/Oct/01
VBP
VBN
TMP
GND
CMO
FLT
CMN
75 Ohms
39 nF
24 Ohms
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.
MLX90308CCC
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
Communication
GND
Signal Out
V
+
s
Pressure
Sensor
1
2
3
4
5
6
7
8
IO1
IO2
TSTB
FLT
OFC
VBN
VBP
TMP
COMS
GND
CMN
CMO
VMO
VDD1
MLX90308CCC
FET
VDD
16
15
14
13
12
11
10
9
External FET
for Regulation
D
G
S
Oil
Pressure
(psi)
MLX90308CCC Programmable Sensor Interface Page 24 Rev 2.2 23/Oct/01
MLX90308CCC
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
Voltage (in mV)
25oC
-40oC
0
0% 100%
Pressure
Figure 11b. Conditioned Sensor
Output
4
)
DC
Voltage (V
1
140oC
25oC
-40oC
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
-12
farads
MLX902xx Name of Sensor Rev Y.X 22/Aug/98 Page 25
MLX90308CCC Programmable Sensor Interface Page 25 Rev 2.2 23/Oct/01
MLX90308CCC
Programmable Sensor Interface
Figure 12. MLX90308CCC Physical Characteristics, LW Package
7.60
0.51
0.33
10.50
10.10
1.27
7.40
Notes:
1. All dimensions in millimeters.
2. Body dimensions do not include mold flash or
protrusion, which are not to exceed 0.15mm.
10.65
10.00
0o to
8
o
0.32
0.23
1.27
0.40
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: All other locations:
Phone: +32 13 61 16 31 Phone: +1 603 223 2362
E-mail: sales_europe@melexis.com E-mail: sales_usa@melexis.com
QS9000, VDA6.1 and ISO14001 Certified
MLX90308CCC Programmable Sensor Interface Page 26 Rev 2.2 23/Oct/01
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