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TIDA-010239: Ask about "Pilot Wire" and "Plug Lock Drive" circuit design guide

Jeff Yun
Expert 4115 points
Part Number: TIDA-010239
Other Parts Discussed in Thread: TLV1811-Q1, TMUX6219-Q1, DRV8220

Tool/software:

Hi, Team

Hope you are doing well!

My customer is bidding a small ZCU project and there is only a charging plug detection function on the board but no charging function.

Customer knows very little about this function, so after learning this reference design, customer hopes that you could help provide more information about the "Pilot Wire" and "Plug Lock Drive" part function for their reference:

  • Schematic design using automotive grade device
  • Key points for designing schematic and PCB layout

Best Regards

Jeff

  • 0
    TI__Expert 4115 points

    Hi, Team

    Kindly remind here, could you please help share some comments about this support need?

    Best Regards

    Jeff

  • +1
    TI__Prodigy 120 points

    Hello Jeff,

    The pilot wire is used for the basic communication between the EV and the EVSE. It consists of three connections, the control pilot (CP), proximity pin (PP) and the protective earth (PE).

    The control pilot is used to communicate the limit of current the EVSE is capable of supplying to the vehicle, or that further digital communication is needed for DC charging. According to the IEC 61851-1 standard the control pilot signal should have following parameters:

    1KHz PWM (980 Hz ... 1020 Hz)

    +12V (11.4 V ... 12.6V), -12V (-12,6V ... -11.4V)

    Rise/fall time: max 2us (90% ... 10%)

    Source resistance: 1kOhm (970Ohm ... 1030 Ohm)

    EVSE Capacitance: 300 ... 1600 pF + 1500pF cable

    Inductance: < 1mH

    This can be archived by using a comparator like shown in the TIDA-010239 reference design. An appropriate automotive rated part would be the TLV1811-Q1. This device has no build-in hysteresis, which should be added to prevent unwanted rapid switching at the threshold voltage. (https://www.ti.com/lit/ug/tidu020a/tidu020a.pdf)

    A second method to drive the control pilot would be a MUX switch. The TMUX6219-Q1 can be used to switch between + and -12V. You can find a design example in the TMUX6219-Q1 datasheet (https://www.ti.com/lit/ds/symlink/tmux6219-q1.pdf)  under chapter 8.2.

    According to the IEC 62196 standard the proximity pin is used to indicate the cable capacity. Therefore, a resistor is placed between the PP and PE, within the detachable cable assembly. A simple voltage divider can be created with the resistor inside the cable, to determine the resistance value. When the charging cable is fixed to the EVSE the PP is only connected on the EV side as the current capability of the cable is known by the EVSE.

    The pluck lock is needed if a detachable cable assembly is used. The actuator is located in the inlet and typically controlled by 12V or 24V with currents up to 1.5A. Therefore, a motor driver the DRV8220 is used in the reference design. The output current and power dissipation capabilities of the driver depends heavily on the PCB design and external system conditions. The thermal pad of the driver should be attached to the PCB top layer ground plane and internal ground plane (when available) through thermal vias to maximize the PCB heat sinking. Having appropriate local bulk capacitance is also an important factor in motor drive system design. The power supply bulk capacitor can be of ceramic or electrolytic type, but should also be placed as close as possible to the device to minimize the loop inductance. An additional low ESR ceramic capacitors should be placed directly to the input pin of the motor driver. X5R and X7R types are recommended. More information about the Board Layout of Motor Drivers can be found here: https://www.ti.com/lit/an/slva959b/slva959b.pdf

    To monitor the status of the lock mechanism, inlets often provide a feedback connection. This can ether be a simple switch which closes if the pluck is locked, or a resistor network which shows different states like unlocked, fault (partly locked) or locked. Depending on the resistor value of the feedback path the actual condition can then be monitored.

    Best Regards,

    Simon