MLX16305 Interlock switch sensor interface IC Features and Benefits • • • • • • • • • • • 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) • • 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