Hi Fabian,
TPL stands for transformer physical layer.
The MC33771/MC33772 (battery cell controller) and MC33664 (TPL transceiver) communication solution is based on a passive electrical bus (no repeater, no amplifier).
High-speed differential isolated communication is achieved through the use of transformers.
The benefits of such a solution are:
• more robust Electromagnetic Compatibility (EMC) characteristics (intrinsic transformer
common mode rejection)
• greater high-voltage isolation
• better communication speeds and synchronized measurements
• lower cost
The picture below illustrates how the MC33664 TPL transceiver exchanges data between the MCU and the MC33771.
First, you can notice that the MCU needs two SPI ports for the SPI to TPL translation; one for MOSI and one for MISO. At the top of the waveforms, the MCU is going to initiate a command to the MC33771. CS1\ being asserted by the MCU causes a start of message double positive pulse on the TPL bus. This double pulse in turn causes CS2\ to be asserted on the MC33664. This starts the process of the command message from the MCU to be echoed back to the MCU on the MISO pin. After the start of message double pulse, data is clocked out of MOSI and translated onto the TPL bus. The signal on the TPL bus is a differential sine wave. The phase of the sine wave dictates whether it is a one or a zero. After the MOSI data is completed, CS1\ is de-asserted by the MCU and this causes an end of message double negative pulse. After the MC33771 processes the command, it then initates putting it is response data on the TPL bus. The reverse process occurs where the start of message double pulse on the TPL bus is translated to by the MC33664 and it asserts the CS2\ pin on the MCU so it can now receive data on MISO.
I hope it clarifies your question. Let us know if you need any further information.
Best regards,
Tomas
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