MLX16305 Datasheet, PDF (7/29 Pages) Melexis Microelectronic Systems – Interlock switch sensor interface IC

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
(Isense_LIM).
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:
• V_SUPmin =
V_REF + 2.5V
V_REF + 3.5V
V_REF + 8V
for Isense ≤ 30mA
for Isense ≤ 40mA
for Isense ≤ 45mA
• V_SUPmax = 25V
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 (I_SENSE) from the voltage regulator
• the 10:1 mirror current of I_SENSE 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. 005
Page 7 of 29
Data Sheet
Oct/06