MLX16305 DataSheet old 282 DownloadLink 4831

MLX16305
Interlock switch sensor interface IC
Features and Benefits
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6 sense Channels
Current limited supply regulator
Current and Voltage measurement mode
High measurement accuracy: 5%
Large supply current range for contact cleaning: [0; 40]mA
Large Output switch supply voltage range for hall effect switches: [3; 7]V
Automotive qualified (40V Load Dump)
Operating Supply voltage: [8; 25]V
Diagnoses open wires, shorts to Supplies and shorts between wires
Over-temperature detection
Small Package: narrow body (150mils) SO16, RoHS compliant
Applications
•
Fail safe read out of multiple safety interlock switches
o Automotive: Seat occupancy, Seat belt buckle, Air bag presence detection
o Industrial Security doors and machine guarding
General interlock switch read out
o Automotive: Door lock position, Hood and Trunk latched detection
General 2 wire analog sensors
o Industrial pressure, strain gauge, … sensors (ref. MLX90308, MLX90314)
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Ordering Information
Part No.
MLX16305
Temperature Suffix
E (-40°C to 85°C)
Package Code
DC (SOIC16 150mil)
1. Functional Diagram
2. Description
VSUP
Internal
Voltage
Regulator
Sense1
Sense2
Sense3
Sense4
Sense5
Sense6
MLX16305
MEASOUT
ADC
Resistive Switch
Rser
VREF
Simple Switch
Rpar
KL15 / IGN
V/I conversion
Hall Effect Switch
DIG
5
Control
Microctrl
Rref
3901016305
Rev. 002
Page 1 of 23
The MLX16305 simplifies monitoring of
current modulated signals in general, and
offers complete diagnostics of remote
interlock switches in particular.
An integrated and current limited supply
regulator applies a supply voltage to one
channel (switch) at a time. The supplied
current and the resulting supply voltage are
measured and presented as an analog
voltage
to
the
microcontroller
for
interpretation.
Each MLX16305 allows scanning up to 6
channels one by one for changes in switch
state or for any type of short circuit failure
mode. With its scanning approach the
power consumption of the switches is
minimized.
The high current range allows contact
cleaning for resistive switches, and the high
accuracy allows monitoring of contact aging
and early failures detection.
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
TABLE OF CONTENTS
FEATURES AND BENEFITS ....................................................................................................................... 1
APPLICATIONS............................................................................................................................................ 1
ORDERING INFORMATION......................................................................................................................... 1
1.
FUNCTIONAL DIAGRAM................................................................................................................... 1-1
2.
DESCRIPTION.................................................................................................................................... 2-1
3.
ABSOLUTE MAXIMUM RATINGS ....................................................................................................... 3
4.
MLX16305 ELECTRICAL SPECIFICATIONS ...................................................................................... 3
5.
PIN ASSIGNMENT ................................................................................................................................ 4
6.
BLOCK DIAGRAM ................................................................................................................................ 5
7.
GENERAL DESCRIPTION .................................................................................................................... 6
8.
PIN DESCRIPTION................................................................................................................................ 6
8.1.
SUPPLY RANGE (VSUP).................................................................................................................................6
8.2.
INPUT VOLTAGE REFERENCE (VREF)............................................................................................................6
8.3.
VOLTAGE REGULATION (SENSE)..................................................................................................................7
8.4.
OUTPUT VOLTAGE TO THE MICROCONTROLLER ADC (MEAS_OUT)............................................................7
8.5.
DIGITAL INPUTS .............................................................................................................................................8
8.6.
ENCODER: INTERNAL DIGITAL SIGNALS .....................................................................................................9
9.
CURRENT MODE (CM)....................................................................................................................... 12
9.1.
CURRENT MODE OFFSET..............................................................................................................................12
9.2.
CURRENT TO VOLTAGE CONVERSION ...........................................................................................................12
10. VOLTAGE MODE (VM) ....................................................................................................................... 13
11. OVERCURRENT LIMITATION............................................................................................................ 14
11.1. SHORTS ........................................................................................................................................................14
11.2. DESIGN CONSIDERATION FOR RREF AND VREF.........................................................................................14
12. DIAGNOSTICS .................................................................................................................................... 15
12.1. SHORTS ........................................................................................................................................................15
12.2. OPEN WIRE ..................................................................................................................................................15
12.3. DIAGNOSTICS FLOW .....................................................................................................................................15
12.4. OVERTEMPERATURE DETECTION .................................................................................................................16
13. MULTIPLEXING THE ADC INPUT BY SETTING MEAS_OUT HIGH IMPEDANT............................ 17
14. APPLICATION NOTES ....................................................................................................................... 18
14.1. CURRENT MODULATED HALL SWITCHES .....................................................................................................18
14.2. RESISTIVE SWITCHES ...................................................................................................................................20
14.3. 2-WIRE ANALOG SENSORS ............................................................................................................................20
15. STANDARD INFORMATION REGARDING MANUFACTURABILITY OF MELEXIS PRODUCTS
WITH DIFFERENT SOLDERING PROCESSES ........................................................................................ 21
16. ESD PRECAUTIONS........................................................................................................................... 21
17. PACKAGE INFORMATION................................................................................................................. 22
18. DISCLAIMER ....................................................................................................................................... 23
3901016305
Rev. 002
Page 2 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
3. Absolute Maximum Ratings
Supply Voltage, VSUP (overvoltage)
40V
Supply Voltage, VSUP (operating)
25V
Supply Current, IDD
6 mA
Output Current, SENSE
90 mA
Operating Temperature Range, TA
-40°C .. +85°C
Storage Temperature Range, TS
-40°C .. +150°C
ESD Sensitivity (AEC Q100 002)
1.5 kV
Exceeding the absolute maximum ratings may cause permanent damage. Exposure to absolutemaximum-rated conditions for extended periods may affect device reliability.
4. MLX16305 Electrical Specifications
DC Operating Parameters TA = -40oC to 85oC, VSUP = 8V to 25V (unless otherwise specified)
Symbol
Parameter
Vsup
Supply
Isense
Sense output current
Conditions
Min
Nom
Max
Unit
25
V
Vsup-Vref ≥ 2.5V
30
mA
Vsup-Vref ≥ 3.5V
40
mA
7
V
8
Vref
Analog input
3
5
IDD
Current consumption
VCC=25V,
no channel selected
6
mA
IVref
Current consumption on Vref
Vref = 5V
0.5
mA
No current limitation condition
Digital inputs
VIL
Input low voltage
-0.3
0.75
V
VIH
Input high voltage
1.9
5
V
Input pull-down
30
220
kΩ
VMEAS
Output voltage range
0
IMEAS
Current capability
300
VMEAS_DIS
Output voltage in VM with voltage
regulator disabled
ENABLE = 0, VI_CTRL=0
(VM)
Meas_Verr1
Error in Voltage Mode
3V< Vsense <7V
5%
Meas_Verr2
Error in Voltage Mode
1V< Vsense <3V
20%
Vmeas_Voffset
Offset error in Voltage Mode
1V< Vsense <7V
25
Meas_Ierr1
Error in Current Mode
5mA< Isense <40mA
5%
Meas_Ierr2
Error in Current Mode
0mA< Isense <5mA
22.5
uA
Ioffset
Forced Offset current
ENABLE = 0, VI_CTRL=1
(CM)
1
mA
100
MEASOUT output
3901016305
Rev. 002
Page 3 of 23
Vref+0.5
uA
0.05
0
V
0.2
V
mV
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
Symbol
Parameter
Conditions
Min
Nom
Max
Unit
Voltage regulation on SENSE pins
Vsense_err1
VSENSE – VREF
3V ≤ Vref ≤5V
-100
100
mV
Vsense_err2
VSENSE – VREF
5V ≤ Vref ≤7V
-150
150
mV
CSENSE
Maximum capacitive load on
SENSE pins
150
nF
250
us
Miscellaneous
Trise
SENSE rising time
Vref=5V
0
150
150
from ENABLE=1 to
V(SENSE) = [4.9, 5.1]V
Tshutdown
Thermal Shutdown (junction)
120
VMEAS_OTH
MEASOUT Voltage for
Overtemperature condition
1.9
VMEAS_OTL
MEASOUT Voltage without
Overtemperature condition
IsenseLIM
Current limitation level on SENSE
pins.
RREF=1kOhm, VREF=5V
°C
V
40
0.9
V
90
mA
5. Pin assignment
PIN No.
SHORT NAME
DESCRIPTION
FUNCTION
1
SENSE3
5V / 40mA
Driver Output
2
SENSE2
5V / 40mA
Driver Output
3
SENSE1
5V / 40mA
Driver Output
4
VSUP
Range: 8V .. 25V
Supply
5
ENABLE
TTL Levels
Digital Input
6
MUX_SENSE0
TTL Levels
Digital Input
7
MUX_SENSE1
TTL Levels
Digital Input
8
MUX_SENSE2
TTL Levels
Digital Input
9
VREF
External Voltage Reference
Analog Input
10
VI_CTRL
TTL Levels
Digital Input
11
MEAS_OUT
Analog Output
12
RREF
Analog Output
13
VSS
Ground (analog + digital)
Ground
14
SENSE6
5V / 40mA
Driver Output
15
SENSE5
5V / 40mA
Driver Output
16
SENSE4
5V / 40mA
Driver Output
3901016305
Rev. 002
Page 4 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
6. Block Diagram
VSUP
Voltage
Regulator
VDD
MUX_SUP[0:2]
VSENSE(ISENSE)
VREF
SENSE1
MUX_SUP[0:2]
MUX_SENSE[0:2]
VI_CTRL
VMEAS(VM)
VMEAS(CM)
SENSE2
SENSE3
SENSE4
SENSE5
SENSE6
*0.5
MEAS_OUT
ISENSE/10
Z
IOFFSET
OVERTEMP
MUX_SENSE[0:2]
ENABLE
Encoder
MUX_SUP[0:2]
*0.9
MUX_SUP[0:2]
GND
3901016305
Rev. 002
Page 5 of 23
RREF
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
7. General Description
The MLX16305 simplifies the monitoring and diagnostics of up to 6 mechanical switches through voltage
and current sensing. The 6 SENSE inputs are multiplexed onto a single output pin (MEAS_OUT). The
SENSE pins can be supplied by a Voltage source that forces the Vref voltage with a current limit
(IsenseLIM).
The MLX16305 is controlled by the microcontroller through a 5 wire digital interface. This allows the
microcontroller to either apply a voltage to maximum 1 SENSE pin, or leave them high impedant. At the
same time the microcontroller can evaluate the current drawn or the voltage measured on either that
same pin or any other SENSE pin. This way the state of a mechanical switch can be read or the switches
can be diagnosed to detect open wires, shorts between SENSE pins, to Ground or to Supply.
With the VI_CTRL input the MLX16305 can be set in either Current Mode (CM) or in Voltage mode (VM)
• In current measurement mode (CM), the current drawn by the selected SENSE pin
(Isense) from the voltage source is copied onto an external resistor Rref to convert it to a
proportional voltage presented on the MEAS_OUT pin.
• In voltage measurement mode (VM) the voltage on the selected SENSE pin is copied
directly onto the MEAS_OUT pin divided by two, such as to come within the voltage rail set
by Vref.
The combination of voltage and current measurements allow diagnosing multi-level currents to detect the
state of the switch, whilst allowing to check shorts to GND and to Supply failure modes.
8. PIN description
8.1. Supply Range (VSUP)
For correct operation of the Voltage source, a minimum voltage drop is required between the supply
(VSUP) and the reference voltage (Vref). Therefore the main supply VSUP of the IC device is specified
as:
VREF + 2.5V for Isense ≤ 30mA
• VSUPmin =
VREF + 3.5V for Isense ≤ 40mA
25V
• VSUPmax =
The supply current IDD is specified for disabled SENSE pins (MUX_SENSE=000b: the voltage regulator
is disabled), and represents the current drawn from VSUP.
In case a SENSE pin is pulling current, the total current consumption is the addition of:
• the internal current through the device (same as IDD)
• the current drawn by the SENSE pin (ISENSE) from the voltage regulator
• the 10:1 mirror current of ISENSE on the RREF pin
8.2. Input Voltage Reference (VREF)
The VREF pin is used as an external reference for voltage regulation on the SENSE pins. Vref also
defines the clamping level of the MEAS_OUT pin. This reference voltage is generated externally and can
vary independent of VSUP and digital input levels. In a typical example with 5V microcontrollers and 5V
Hall switches Vref is directly taken from the external 5V regulator.
Remark that even though the Hall switches are supplied at VREF, the load on VREF is limited to IVref.
The regulator that supplies the Halls is drawing its current from VSUP.
3901016305
Rev. 002
Page 6 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
8.3. Voltage Regulation (SENSE)
The voltage on the SENSE pins is forced to the Vref level.
Depending on the applied Vref, the maximum deviation is specified as:
Vsense = Vref +/- Vsense_errx (see electrical specification)
•
•
•
The Voltage regulation specification is only valid for Isense and Csense values within
specification.
Maximum total capacitor load includes the wiring parasitic capacitance and Hall Switch supply
capacitor if applicable.
The Output Settling time on pins SENSE1 … SENSE6 for the selected channel is Trise after
ENABLE pin is set high.
Vref
Trise
Supply voltage
of the selected
SENSE channel
0V
ENABLE
8.4. Output voltage to the microcontroller ADC (MEAS_OUT)
The microcontroller can evaluate/diagnose the state of the interlock switch based on the voltage that its
ADC will measure on the MEAS_OUT pin.
•
•
•
The VMEASOUT output voltage is not higher than Vref + 0.5V to avoid damaging of the
microcontroller ADC input.
The MEASOUT pin is able to deliver minimum IMEAS.
MEAS_OUT can be made high impedant to allow multiplexing of 2 or more MLX16305 devices in
parallel when more than 6 channels are required.
3901016305
Rev. 002
Page 7 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
8.5. Digital Inputs
DEFINITIONS:
• Digital input pins ENABLE, VI_CTRL and MUX_SENSE[0:2] have TTL characteristic.
Additionally these pins have internal pull downs for a defined reset behavior of the complete
system.
• Logic levels : LOW : V ≤ VIL and HIGH : V ≥ VIH
•
Bit representation.
To select SENSE channel 1, set
• MUX_SENSE0: 0
• MUX_SENSE1: 0
• MUX_SENSE2: 1
In his document this is represented as MUX_SENSE[0:2]=001b
FUNCTIONALITY:
• MUX_SENSE[0:2] has a double function
o It controls the multiplexer that selects the channel that is to be sensed/measured
o And these inputs are latched into MuxSenseLatched [0:2] when ENABLE goes high.
• ENABLE has a double function
o When Enable =0 the MuxSenseLatched [0:2] signals are identical to the MUX_SENSE
inputs. When Enable=1, the MUX_SENSE signals are latched into MuxSenseLatched
[0:2]. This way a different channel can be sensed, from the one supplied (MUX_SENSE
≠ MuxSenseLatched).
o Enable resets MUX_SUP to 000b when ENABLE is logic low. This disconnects all
channels from the voltage regulator (Isense=0mA) and activates a weak pull down on all
pins.
• VI_CTRL selects Current Mode or Voltage Mode (see below)
3901016305
Rev. 002
Page 8 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
8.6. ENCODER: Internal Digital Signals
•
MuxSenseLatched[0:2] signals are defined by the MUX_SENSE and ENABLE inputs. It is used
for 3 purposes:
o to go to OVERTEMP measurement mode
o to set MEAS_OUT high impedant
o to select the channel that is to be supplied with Vref.
MuxSenseLatched = MUX_SUP if ENABLE = 1
The standard relation between MUX_SENSE, ENABLE and MuxSenseLatched can be viewed as
a latch that is controlled by ENABLE:
o ENABLE = 0
Ö then the latch is transparent: MuxSenseLatched == MUX_SENSE
o ENABLE = 1
Ö then the latch is closed: MUX_SENSE can be changed without influencing
MuxSenseLatched.
OVERTEMP
Z
MUX_SENSE[0:2]
MuxSenseLatched[0:2]
ENABLE
MUX_SUP[0:2]
MUX_SUP[0:2]
MUX_SUP == MuxSenseLatched AND ENABLE
The MUX_SUP[0:2] signals control the multiplexer that selects the channel on which the voltage
regulator will force Vref.
1. Apply on MUX_SENSE the value of the channel that should be supplied while ENABLE is
low.
2. Then switch ENABLE high to latch this state into MuxSenseLatched.
3. As long as ENABLE stays high the selected SENSE pin will be supplied with the VREF
voltage.
4. In the mean time MUX_SENSE may change. This allows diagnostics for shorts between
SENSE pins. One channel can be supplied with Vref and another can be sensed.
(MUX_SUP ≠ MUX_SENSE)
5. As soon as ENABLE goes low again, MUX_SUP is reset to 000b, hence disabling every
channel. The weak pull down on every SENSE pin will then pull VSENSE down.
OVERTEMP (Dominant setting):
In order to set OVERTEMP = 1 MuxSenseLatch[0:2] has to be set to 111b.
o When ENABLE = 0, the Overtemp condition can be read out on the MEAS_OUT pin by
setting MUX_SENSE = 111b.
o When ENABLE turns = 1 MuxSenseLatched remains = 111b. Changes on
MUX_SENSE[0:2] are neglected (= don’t care).
3901016305
Rev. 002
Page 9 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
Z or HIGH IMPEDANT (Dominant setting):
In order to set Z = 1 MuxSenseLatch [0:2] has to be set to 000b.
o When ENABLE = 0, MUX_SENSE has to be set to 000b.
o When ENABLE turns = 1 MuxSenseLatched remains = 000b. Changes on
MUX_SENSE[0:2] are neglected (= don’t care).
Mind that both OVERTEMP=1 or Z=1, are dominant settings on MEAS_OUT. This implies that
any changes on VI_CTRL and MUX_SENSE[0:2] are not visible.
MIND.
Do not confuse the latch with a flip-flop which is only sensitive during rising edge of the Enable. The latch
is transparent for input changes whilst ENABLE is low, not only during the rising edge.
Timing diagram
1
MUXSENSE[0:2]
000
2
3 4
100
000
5
6
7
001
8
9
10
010
111
ENABLE
MuxSenseLatched[0:2]
000
MUX_SUP[0:2]
000
001
000
001
010
000
010
111
000
111
OVERTEMP
Z
The above timing diagram shows how the inputs are converted internally:
n In case of multiplexing 2 or more devices, the system should start up with MUXSENSE[0:2] and
ENABLE = 0 for all devices in order to avoid conflicts on the MEASOUT output.
o Changes on MUXSENSE are not seen by the device as long as ENABLE is kept high.
p In order to switch from one device to another device all MUXSENSE inputs are reset to 000b.
q In order to start switch MUXSENSE at r, all other devices should have set ENABLE high.
r
a. In Current Mode Channel 0 is selected, VMEASOUT = VMEAS(offset)as long as
ENABLE is low.
b. In Voltage mode, no channel is selected, so VMEAS remains 0V.
s
a. In CM the voltage regulator supplies current to channel 0 (Isense0). Isense0 is copied
onto RREF, and can be calculated from VMEASOUT.
b. In VM the voltage regulator supplies Vref to channel 0 (Vsense0). Vsense0 is copied on
VMEASOUT.
t ENABLE remains high
a. In CM changes on MUXSENSE are neglected (don’t care)
b. In VM, the voltage is measured on channel 1, which has its weak pull down active. If
Vsense1 > 0V then a short to Channel 1 is found.
u ENABLE goes low, disabling all channels while channel 1 is selected. See r
v ENABLE goes high and low again while MUXSENSE remains unchanged.
a. In CM Isense1 can be measured while ENABLE is high.
b. In VM channel 1 is supplied with Vref and the resulting Vsense1 is copied to VMEASOUT
w MUXSENSE=111b displays the OVERTEMP condition on the MEASOUT pin.
3901016305
Rev. 002
Page 10 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
MUX_Sense
ENABLE
MuxSenseLatched
MUX_Sup
Z/Overtemp
VI_CTRL
MEAS_OUT
001
010
011
100
101
110
001
010
011
100
101
110
XXX
000
XXX
111
000
111
001
010
011
100
101
110
001
010
011
100
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
1
1
1
1
1
1
1
1
1
1
1
1
001
010
011
100
101
110
001
010
011
100
101
110
000
000
000
000
000
000
000
000
000
000
000
000
111
111
other than 000/111
other than 000/111
001
010
011
100
101
110
other than 001/000/111
other than 010/000/111
other than 011/000/111
other than 100/000/111
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
1/0
1/0
0/1
0/1
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0
0
0
0
0
0
1
1
1
1
1
1
X
X
X
X
0
0
0
0
0
0
0
0
0
0
0
0
V(SENSE1)/2
V(SENSE2)/2
V(SENSE3)/2
V(SENSE4)/2
V(SENSE5)/2
V(SENSE6)/2
0V
0V
0V
0V
0V
0V
Z
Z
OVTEMP
OVTEMP
floating node
floating node
V(SENSE1)/2
V(SENSE2)/2
V(SENSE3)/2
V(SENSE4)/2
V(SENSE5)/2
V(SENSE6)/2
V(SENSEx)/2
V(SENSEx)/2
V(SENSEx)/2
V(SENSEx)/2
101
1
other than 101/000/111
0/0
0
V(SENSEx)/2
110
XXX
XXX
XXX
XXX
XXX
XXX
1
1
1
1
1
1
1
other than 110/000/111
001
010
011
100
101
110
0/0
0/0
0/0
0/0
0/0
0/0
0/0
3901016305
Rev. 002
000
000
000
DESCRIPTION
FAULT DETECTED on MEAS_OUT
MUX_Sup=000: SENSE pins are not supplied, and
the weak pull down is active.
MUX_Sense selects the SENSE pins to be
monitored in voltage mode VMEAS_OUT =
Vsense/2.
Normal <VMEAS_DIS;
Else VMEAS>VMEAS_DIS, then the weak pull
down is overruled. A short to Vbat or to another
High Voltage node is detected.
MUX_Sup=000: SENSE pins are not supplied, and
the weak pull down is active.
MUX_Sense selects the SENSE pins to be
monitored in current mode: Since there is no current
supplied, no current can be copied on RREF.
State used in application for offset measurement
VMEAS_OUT(offset) = 0.9*Ioffset*Rref
MUX_Sense=000 is latched to set Z=1
MEAS_OUT is high impedant.
MUX_Sense=111 has been latched to set
Overtemp=1
OVERTEMP => VMEASOUT>VMEASOUT_OTH;
else: VMEASOUT<VMEASOUT_OTL;
The output shows the state of an internal floating node.
This value is undefined because the IC tries to measure voltage on a non-existing channel
MEAS_OUT = Voltage on SENSE1 Pin divided by 2
MEAS_OUT = Voltage on SENSE2 Pin divided by 2
MEAS_OUT = Voltage on SENSE3 Pin divided by 2
MEAS_OUT = Voltage on SENSE4 Pin divided by 2
MEAS_OUT = Voltage on SENSE5 Pin divided by 2
MEAS_OUT = Voltage on SENSE6 Pin divided by 2
MEAS_OUT = Voltage on SENSE1 Pin divided by 2
MEAS_OUT = Voltage on SENSE2 Pin divided by 2
MEAS_OUT = Voltage on SENSE3 Pin divided by 2
MEAS_OUT = Voltage on SENSE4 Pin divided by 2
Normal = VREF/2 ;
Else VMEASOUT> Normal: Short to Vbat
Else VMEASOUT< Normal: Short to GND
on the sensed channel
Normal <VMEAS_DIS;
Else VMEASOUT =VREF/2 reflecting a short
between sensed channel and supplied channel
MEAS_OUT = Voltage on SENSE5 Pin divided by 2
0
V(SENSEx)/2
MEAS_OUT = Voltage on SENSE6 Pin divided by 2
1
ISENSE1*Rref/10
MEAS_OUT = Current on SENSE1 Pin
1
ISENSE2*Rref/10
MEAS_OUT = Current on SENSE2 Pin
Switch state: current levels OPEN/CLOSE
1
ISENSE3*Rref/10
MEAS_OUT = Current on SENSE3 Pin
DIAGNOSTICS:
VMEASOUT = 0
=> Open wire
1
ISENSE4*Rref/10
MEAS_OUT = Current on SENSE4 Pin
VMEASOUT > VREF*0.9: => Short to GND
1
ISENSE5*Rref/10
MEAS_OUT = Current on SENSE5 Pin
1
ISENSE6*Rref/10
MEAS_OUT = Current on SENSE6 Pin
(*)in CM VMEASOUT in the above table is the calculated value after subtracting the contribution of the offset = VMEASOUT - VMEASOUT (offset)
Page 11 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
9. Current mode (CM)
9.1. Current Mode Offset
For current measurements, a significant offset current (Ioffset) is forced by design in order to prevent any
low current information to be clamped due to negative process offsets. Therefore a current measurement
is done in 3 steps:
1. Do the offset measurement on MEAS_OUT:
Vmeasout0 = 0.9*Ioffset*Rref
2. Do the actual measurement on MEAS_OUT:
Vmeasout1 = 0.9*(Ioffset+Isense/10)*Rref
3. The Microcontroller calculates Current (Isense) information by software:
Isense = (Vmeasout1 – Vmeasout0) * 10/ Rref / 0.9
The offset is measured on MEAS_OUT in Current Mode (CM) while Isense = 0:
• VI_CTRL = HIGH (CM)
• ENABLE = LOW => MUX_SUP[0:2] = 000: Voltage regulator is disable, therefore no Isense
current is mirrored into RREF. Shorts on the SENSE channels have no influence on the offset
measurement.
• Since ENABLE is low, the latch is transparent. Therefore make sure MUX_SENSE ≠ 000b or
111b in order to avoid the Z or the Overtemp condition (MuxSenseLatched ≠ 000b or 111b)
Remarks:
• Mind that offset can only be measured as a voltage over RREF. Therefore any change to Rref
implies a new offset measurement.
• Offset may drift over longer periods of time and important temperature variations. Before every
measurement sequence the Offset measurement should be repeated.
• In case multiple MLX16305 devices are used in parallel, the offset should be measured and
stored for every device.
• Between 2 subsequent offset measurements the error is less than +/-Meas_Ierr2. This is
important for the OPEN WIRE condition which is very similar to an offset measurement:
An OPEN WIRE condition has Isense = 0mA. Therefore the output voltage VMEASOUT will be
within +/-0.9*Rref*Meas_Ierr2.
9.2. Current to Voltage conversion
The current ISENSE, supplied by the voltage regulator, is copied (mirrored) on the RREF pin with a 10:1
ratio. This current is converted into voltage information via the external RREF resistor. This VRref is then
copied on the MEASOUT pin with a factor of 0.9, i.e.: V(MEASOUT) = VRref * 0.9
• V(MEASOUT) = Voffset + [(ISENSE / 10) * RREF *0.9] ± Meas_Ierr1
• V(MEASOUT) = Voffset + [(ISENSE / 10 ± Meas_Ierr2) * RREF *0.9]
for 5mA < ISENSE ≤ 40mA
for ISENSE ≤ 5mA
The error over the total chain in CM (Meas_Ierrx) does not include error due to the external RREF
resistor.
Remarks:
• No specific channel has to be selected for current measurement, as the current is mirrored from
the voltage regulator. Therefore in CM mode MUX_SENSE is don’t care! As soon as ENABLE
has gone high to fix MUX_SUP.
3901016305
Rev. 002
Page 12 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
10. Voltage Mode (VM)
To go into Voltage Mode (VM) VI_CTRL is set low. In this mode the voltage on the SENSE pin (VSENSE) is
copied onto the MEAS_OUT pin. It can be calculated back as:
VMEASOUT = VSENSE / 2 ± (Vmeas_Verr1 + Vmeas_Voffset ) for 3V < VSENSE < 7V
•
•
For VSENSE higher than 7V, a short to supply is assumed. This can be diagnosed with the SENSE
pin in high impedant state.
In Voltage Mode the maximum output voltage is Vref + 0.5V. This occurs for VSENSE > 10V, for
instance in case of a short to VBAT.
For VSENSE lower than 3V, either a short to GND is assumed, or a voltage is applied on a high impedant
SENSE pin (not selected by MUX_SUP, only by MUX_SENSE). A slightly reduced spec is applicable for
this range:
VMEASOUT = VSENSE / 2 ± (Vmeas_Verr2 + Vmeas_Voffset) for 1V < VSENSE < 3V
When in VM VMEASOUT < VMEAS_DIS, a channel is selected with an active pull down, without short to
the supplied channel or to Vbat.
3901016305
Rev. 002
Page 13 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
11. Overcurrent Limitation
11.1. Shorts
The MLX16305 has a built-in overcurrent limitation as protection against destruction and overheating, and
as means for detecting short circuits to Ground on any of the SENSE channels.
[mA]
50
The current limiting of the voltage regulator is
activated as soon as the voltage over the
external Rref resistance (VRREF) reaches
VREF.
In this case the forced output voltage on the
SENSE pin (VSENSE) drops until the
voltage VRREF = VREF.
[V]
6
5
40
Isense
Vsense
30
The graph shows the trends of Isense
(~VRREF) and Vsense for Vref=5V and
Rref=1kΩ. As Rsense drops from normal
operating values a short circuit condition
Isense is theoretically clamped between 40
and 50mA, depending on Ioffset. In practice
see the IsenseLIM specification for actual
design limits.
4
3
20
2
10
0
1
Current
limiting
Rsense
Operating range
0
Current limitation can be monitored via the voltage on MEAS_OUT:
• In Current Mode:
VMEASOUT = 0.9* VREF
• In Voltage Mode:
VMEASOUT = VSENSE / 2 < VREF / 2
11.2. Design consideration for RREF and VREF
Overcurrent limit in combination with the operating temperature range and the maximum operating battery
voltage (see Overtemperature detection) is an important system design parameter to define the values of
VREF and RREF.
1. For instance assuming:
• Worst case Ioffsetmax = 1mA
• VREF = 5V
• VSUP >8.5V, such that ISENSEMAX = 40mA
Then the maximum RREF to have full ISENSE range can be calculated as:
VRREF (=5V) = RREF * [Ioffset(=1mA) + ISENSEMAX (=40mA)/10]
=>
Rref = 1kOhm
2. In applications which use low currents, it can be of interest to select a higher value of RREF to
amplify the useful signal. Mind that the offset gets amplified as well, and therefore the effective
range of ISENSE is quickly reduced.
For instance, if RREF = 2.2kOhm, then current limitation can be activated above ISENSE = 12.7mA
3. For applications which may benefit a Lower Value of RREF, it should be taken into account that
the accuracy specifications in Current Mode are only applicable up 40mA
3901016305
Rev. 002
Page 14 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
12. DIAGNOSTICS
12.1. Shorts
Long wires to the remote switches are prone to shorts to Ground, to supply or between the wires. The
MLX16305 allows continuous failure mode diagnostics on each SENSE pin individually. The circuit works
also if one of the SENSE pins is shorted to GND or Vbat (up to +25V); this means that such a short does
not influence the measurement on other SENSE pins.
A. Shorts to GND
A short between a SENSE pin and GND can be diagnosed either in Current Mode (CM) or in Voltage
mode. The short will cause the voltage source to go in current limitation. As described in the ‘Overcurrent
limitation’ paragraph above, the voltage over Rref (VRREF) will rise to VREF.
• In Current Mode (CM) over current is detected as VMEASOUT = 0.9* VREF
• In Voltage Mode over-current is detected as VMEASOUT < VREF/2 . This value may however
also indicate an open or closed switch. Therefore it is recommended to diagnose Shorts to GND
in CM.
B. Shorts to Supply
A short between a SENSE pin and a high voltage level, like VIGN or even directly to the battery supply
VBAT, can be diagnosed as follows
• Set all SENSE pins high impedant (MUX_SUP[0:2]=000b),
• Then select the respective SENSE pins one by one in Voltage Mode (VM).
The weak pull down on each SENSE pin should yield VMEAS < VMEAS_NSC. Any higher value
indicates a short to a Supply voltage.
C. Shorts Between wires
A short between a SENSE pins, or between the wires connecting the sense pins to the switches can be
diagnosed in a similar way as shorts to supply:
• Select a SENSE pin. This channel will be supplied with VREF, and act as the supply in the ‘Short
to Supply’ case.
• Then select the other SENSE pins one by one in Voltage Mode (VM).
The weak pull down on the other SENSE pin should yield VMEAS < VMEAS_DIS. Any higher value
indicates a short to the selected SENSE pin. To have an unambiguous diagnostics first check ‘Shorts to
Supply’ before checking ‘Shorts between Wires’.
12.2. Open Wire
In an Open Wire condition, the regulator can not supply any current (Isense= 0mA). Therefore only Ioffset
generates a signal on RREF. For the analog measurement chain, an open wire conditions is identical to
an offset measurement. The maximum error between 2 subsequent offset measurements is ±Meas_Ierr2.
12.3. Diagnostics flow
To have unambiguous diagnostics it is recommended to start in Voltage mode, and first check Shorts to
Supply, followed by shorts between wires. If no failures are diagnosed then switch to Current Mode for
binning the 4 other cases: Short to GND, Open Wire and Switch OPEN or CLOSED.
3901016305
Rev. 002
Page 15 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
12.4. Overtemperature Detection
The MLX16305 has an internal overtemperature detection to protect against destruction and overheating.
By applying the correct sequence on the digital input pins the OVERTEMP state is readable via the
MEAS_OUT pin coded as:
•
•
VMEAS ≤ VMEAS_OTL = normal operation
VMEAS ≥ VMEAS_OTH = Overtemperature condition detected.
When an overtemperature condition is detected all channels should remain disabled until the overtemp
condition is removed. Then diagnostics should show the root cause of the overtemperature condition.
Depending on the layout of the PCB, the thermal resistance of a narrow body SO16 package can be as
low as 82oC/W (ideal reference value for a 4 layer pcb).
The increase in junction temperature due to energy dissipation in the linear voltage regulator can be
calculated as follows:
• Assuming worst case operating conditions VSUP=18V and Tamb = 85oC.
• And VREF=5V and RREF = 1kOhm,
Example1.
The normal operating supply current per channel is limited to 40mA. RREF will supply 40/10 +
Ioffset (<1mA), so 5mA additionally.
Ö The maximum power dissipation on the MLX16305 is 45mA*13V=0.59W.
Ö The maximum junction temperature is then 85oC+82oC/W*0.59W = 133oC.
This is above the minimum temperature for over temperature shut down of 120C, so the
MLX16305 may go in shut down at high battery voltages, at maximum ambient temperature.
Furthermore this is for an ideal 4 layer pcb. A more practical example is given below.
Example2.
For a max Sense current of 20mA with a 100C/W thermal resistance of the package:
Ö The maximum power dissipation on the MLX16305 is 23mA*13V=0.3W.
Ö The maximum junction temperature is then 85oC+100oC/W*0.59W = 115oC.
•
In practice the voltage regulator is toggled between the different SENSE outputs. The junction
temperature can also be reduced by switching the regulator off (no channel selected) with a duty
cycle.
A measurement on the sense inputs can be executed in Trise (250us). Switching the regulator on
and off with a duty cycle of for instance 50%, then assumes switching the regulator ON for
0.25ms and then OFF for 0.25ms. The time between measurements is doubled but the average
power dissipation is halved, or still the usefull current range is doubled.
3901016305
Rev. 002
Page 16 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
13. Multiplexing the ADC input by setting MEAS_OUT High Impedant
By applying the correct sequence on the digital input pins the MEAS_OUT pin can be set high impedant.
This is of interest when using 2 or more MLX16305 in parallel for applications with more than 6 switches
to be monitored. The MLX16305 devices are then multiplexed on the same ADC input channel.
The AD input from the microcontroller can be shared by multiple MLX16305 devices in parallel.
With 1 extra digital IO serving as ENABLE for a second device, 6more channels can be controlled.
Procedure:
• First while ENABLE2=0, set MUX_SENSE[0:2] = 000b
• Then latch this value by setting ENABLE2 = 1
• From now on MEASOUT2 is high impedant, and regardless the values of VI_CTRL or
MUX_SENSE[0:2], this remains.
• Switching from device one to device two is done by setting MUX_SENSE[0:2] = 000b while
ENABLE1=0. Setting ENABLE1=1 makes MEASOUT1 high impedant.
• Now ENABLE2 can be reset to 0 without possible conflict between the 2 MEASOUT outputs.
K L 1 5 / IG N
VSUP
VREF
ADC
M EAS_O UT
EN ABLE1
V I_ C T R L
M UX_SENSE0
M UX_SENSE1
M UX_SENSE2
M LX16305
S ense1
S ense2
S ense3
S ense4
S ense5
S ense6
R re f
M LX16305
M ic ro c tr l
3901016305
Rev. 002
EN ABLE2
Page 17 of 23
S ense1
S ense2
S ense3
S ense4
S ense5
S ense6
R re f
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
14. Application Notes
14.1. Current Modulated Hall Switches
Example 1.
The MLX16305 can be used with special designed Hall switches for 2 wire connections. These require
typically a minimum operating voltage of 3.5V, and have 2 current states. For instance:
• Ioff:
[5; 6.9]mA
• Ion:
[12; 17]mA
An example is elaborated for a minimum VIGN=8.5V using Vref=5V and Rref=1kOhm.
Since the output voltage in Current Mode is undefined in case of a short to supply, we start in Voltage
Mode to diagnose this fault condition first.
VI_CTRL=0
1. Short to VBAT
All SENSE channels are disabled (ENABLE=0) and scanned one by one. If any of the output values
rises above VMEAS_NSC, this means the weak pull down is overruled by a short to the supply.
2. Short between wires.
In a similar way if one channel is supplied with Vref, all other channels can be checked on a short to
this supplied channel. If any of the output values rises above VMEAS_DIS, this means the weak pull
down on the selected channel is overruled by a short to the supplied channel. In a 6 channel
application, 15 different wire-to-wire shorts can be checked and diagnosed one by one.
VI_CTRL=1
In Current Mode (CM) 4 more conditions can be diagnosed. Remark that even a 5bit ADC will do.
Before each current measurement sequence the offset should be measured. However for defining the
system design parameters the worst case extreme values for offsets should be taken into account.
In the table below the actual VMEASOUT values with the extreme offsets are calculated:
VMEASOUT (offset) = 0V
VMEASOUT (offset) = 0.9V
3. Open wire
VMEASOUT ~ VMEASOUT (offset)
VMEAS_OUT ~ VMEASOUT (offset)
4. Switch OFF
0.43V < VMEASOUT < 0.65V
1.33V < VMEASOUT < 1.55V
5. Switch ON
1.03V < VMEASOUT < 1.61V
1.93V < VMEASOUT < 2.51V
6. Short to ground
VMEASOUT > 1.61V (~4.5V)
VMEASOUT > 2.51V (~4.5V)
For instance the 5mA lower limit of the OFF state results in an effective signal at the output
=> Isense/10*Rref*0.9 = 0.45V. Since ISense > 5mA, a 5% error should be taken into account, so the
lowest possible voltage on MEASOUT in case the switch is OFF is 0.45*0.9=0.43V.
A well specified system has to make sure the maximum VMEASOUT value for the ON state remains below
the value indicating a short circuit condition (VMEASOUT =4.5V) :
=> Isense = 17mA results in a maximum signal of 1.53*1.05=1.61V, adding VMEASOUT (offset) = 0.9V,
results in 2.51V well below 4.5V.
After subtracting the offset, the microcontroller software can now easily define
fixed thresholds:
3. | VMEASOUT - VMEASOUT (offset) | < 0.9*Rref* Meas_Ierr2 = 20.25mV
4. 0.43V < VMEASOUT - VMEASOUT (offset) < 0.65V
5. 1.03V < VMEASOUT - VMEASOUT (offset) < 1.61V
6. VMEASOUT - VMEASOUT (offset) > 1.61V
3901016305
Rev. 002
Page 18 of 23
the switch condition using
=> Open Wire
=> OFF
=> ON
=> Short to GND
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
Example 2.
The MLX16305 can also be applied with a general
purpose (3 wire) Hall effect switches like the Melexis
US5782 with a current biasing circuit.
Using Rb= 1.2kΩ and RL = 0.6kΩ the threshold levels are
almost the same as in example 1.
However the MLX16305 can operate also without the
biasing resistance Rb:
The US5782 has Ioff = [0.5 ; 5]mA. For
• Vref = 5V
• Rref = 2.2k Ω
• RL = 820 Ω
=> Ion = [6.6 ; 11.1]mA.
Remark that with Rref = 2.2kOhm current limitation can
switch on starting at IsenseLIM > 12.7mA !!
Yielding as Threshold levels: VMEASOUT - VMEASOUT (offset)
• [77mV ; 1.04V ]
=> OFF
• [1.24V ; 2.31V]
=> ON
Two Wire current Biasing Circuit
ISENSE
IDD
RL
IBIAS
VDD
RB
OUT
IOUT
10nF
GND
The resistors RB and RL can be used to
bias the input current Isense.
BRP = Ioff = (VDD/RB + IDD)
BOP = IoN = (Ioff + VDD/RL)
Mind that since the minimum Ioff < 5mA, the worst case
error for the 0.5mA case is now defined by MEAS_Ierr2.
3901016305
Rev. 002
Page 19 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
Example 3 using comparators in stead of an AD input.
The MLX16305 can be applied to micros without AD as well, using 3 low cost comparators that digitize the
output.
With comparators, no offset subtraction is possible; therefore RL has to generate strong signals to
overcome the worst case IOffset values including a worst case measurement error of 5%.
With RL = 220Ohm and Rref = 1kOhm this can be realized within a 5V supply range. Adding
Rb=2.2kOhm allows to increase the minimum OFF value to allow bigger margin for differentiating the
open wire condition. The final current ranges (for VREF=5V) become
• IOFF = [2.77; 7.27] mA
(Rref = 1kOhm so IsenseLIM>40mA)
• ION = [25.5; 30.0] mA.
And the VMEASOUT threshold values become:
• Minimum OFF value becomes = 227mV
• Maximum OFF value becomes = 1.59 V
• Minimum ON value becomes
= 2.18 V
• Maximum ON value becomes = 3.74 V
3 comparators allow differentiating all conditions, for example:
• Level1 = 100 mV
• Level2 = 1.9 V
• Level3 = 4 V
In Voltage Mode VMEASOUT voltages above Level 1 allow to diagnose
• shorts to VBAT
• and shorts between Wires.
In Current Mode VMEASOUT voltages below Level 1 indicate an Open Wire. VMEASOUT voltages
• between Levels 1 and 2 indicate the OFF state of the Hall switch,
• voltages between 2 and 3 indicate the ON state of the Hall switch,
• and voltages above Level3 indicate a short to Ground.
14.2. Resistive Switches
Resistive switches are essentially also acting like current modulated switches. Therefore diagnostics are
done in the same manner.
The MLX16305 can supply plenty of cleaning current to allow the use of low cost switches.
Nevertheless, aging may cause drift of the contact resistance values over life. The high accuracy of the
MLX16305 allows tracking of such a case and early triggering of eminent failures.
14.3. 2-wire analog sensors
Industrial sensors and sensor interfaces like the MLX90308 have a 4 to 20 mA current range. The
MLX16305 can be used to sequentially read them out.
The offset and any non-linearity induced by the 16305 in current mode can be calibrated together with the
sensor in production such that a VMEASOUT value is directly related to the sensor output.
3901016305
Rev. 002
Page 20 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
15. Standard information regarding manufacturability of Melexis
products with different soldering processes
Our products are classified and qualified regarding soldering technology, solderability and moisture
sensitivity level according to following test methods:
Reflow Soldering SMD’s (Surface Mount Devices)
•
•
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)
Wave Soldering SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)
•
•
EN60749-20
Resistance of plastic- encapsulated SMD’s to combined effect of moisture and soldering heat
EIA/JEDEC JESD22-B106 and EN60749-15
Resistance to soldering temperature for through-hole mounted devices
Solderability SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)
•
EIA/JEDEC JESD22-B102 and EN60749-21
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.
Melexis is contributing to global environmental conservation by promoting lead free solutions. For more
information on qualifications of RoHS compliant products (RoHS = European directive on the Restriction
Of the use of certain Hazardous Substances) please visit the quality page on our website:
http://www.melexis.com/quality.asp
16. ESD Precautions
Electronic semiconductor products are sensitive to Electro Static Discharge (ESD).
Always observe Electro Static Discharge control procedures whenever handling semiconductor products.
3901016305
Rev. 002
Page 21 of 23
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
17. Package Information
Unit : mm
Package Type
SOIC16
Narrow Body
3901016305
Rev. 002
min
D
9.80
E
3.80
H
5.80
A
1.35
A1
0.10
max
10.00
4.00
6.20
1.75
0.25
e
b
0.33
L
0.40
α
0º
0.51
1.27
8º
1.27
Page 22 of 23
Package Code
DC16
Data Sheet
Jan/06
MLX16305
Interlock switch sensor interface IC
18. 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.
© 2005 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 1367 0495
E-mail: [email protected]
Phone: +1 603 223 2362
E-mail: [email protected]
ISO/TS 16949 and ISO14001 Certified
3901016305
Rev. 002
Page 23 of 23
Data Sheet
Jan/06