A team from IIT Bombay has developed and demonstrated an EMI-immune PAM-4 transceiver integrated circuit (IC). The PAM-4 (pulse amplitude modulation 4-level) transmitter is capable of driving an electrically long transmission line, which can act as an undesired antenna for external electromagnetic interference (EMI). This induced EMI manifests as common-mode interference on the differential transmission line.
To address this, the chip features an EMI-immune transmitter that incorporates both an input level shifter (ILS) and a modified ESD protection circuit. EMI level which trigger the ESD protection diode are considered as high level EMI, and EMI power levels below that are considered as low level EMI. For low levels of EMI power, the ILS reduces the input common-mode voltage, thereby increasing the circuit’s EMI immunity. At higher EMI power levels, the modified ESD protection circuit clamps the differential signals at the transmitter output to a predefined voltage, further enhancing immunity.
Additionally, the chip’s PAM-4 receiver is designed to tolerate a wider input common-mode range by utilizing a dual-input amplifier topology, making it more resistant to EMI.
The EMI immunity of the transceiver was experimentally verified across an EMI frequency range of 1MHz to 1.5GHz. Measurements show that the system maintained the minimum eye-opening of 110mV required for successful data transmission at a bit rate of 6.5Gbps. The bit error rate remained within acceptable limits for varying EMI power levels (0–16dBm) and EMI frequencies (1MHz–1.5GHz).
The chip was fabricated using 130nm STMicroelectronics BiCMOS technology. Funding for EDA tools was provided by MeitY, Government of India and IIT-Monash Research Academy supported funding for chip fabrication. The work receive best paper award at EMC Compo 2024 at Italy.
Image: (a) Chip micrograph containing A) EMI immune PAM-4 transmitter, B) Traditional PAM-4 transmitter, C) EMI immune PAM-4 receiver and D) traditional PAM-4 receiver. Team Members: Mohit S. Choudhary, Jean-Michel Redoute and M. Shojaei Baghini (b) Best paper award received for the work in EMC Compo 2024 at Italy.
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Authors/Contributors: Mohit S. Choudhary, Jean-Michel Redoute, M. Shojaei Baghini
Broad Field of Work: IC Design
Ph.D. scholar: Mohit Singh Choudhary
Faculty: Maryam Shojaei Baghini and Jean Michel Redoute
Funding Agencies: MeitY, DST and IIT Bombay Monash Research Academy.
Year the work was published: 2023 and 2024
Reference(s):
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- Mohit S. Choudhary, Jean-Michel Redoute and M. Shojaei Baghini, “Comprehensive Study of EMI Effects on Wireline Transceiver Systems: A review of silicon-proven techniques,” 2024 14th International Workshop on the Electromagnetic Compatibility of Integrated Circuits (EMC Compo), Torino, Italy, 2024, Best Paper Award
- Mohit S. Choudhary, Sandip Goyal, N. S. Anjan. K. Pudi, Jean-Michel Redoute and M. Shojaei Baghini, “An Electromagnetic Interference Immune PAM-4 Transceiver System,” in IEEE Transactions on Electromagnetic Compatibility, vol. 65, no. 4, pp. 1098-1107, Aug. 2023
Group Website: Maryam Shojaei Baghini, Jean Michel Redote