Motor Drive & Control

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Digital Isolation

Digital isolation is typically used in high voltage motor drives in between the control electronics and the high voltage gate drivers to protect the controller in case of mechanical or electrical faults in the power stage. Isolation is also often used in the voltage and current sense feedback, especially when using current shunts to directly measure the phase currents.

TI offers a full line of digital isolation products based on a silicon dioxide (SiO₂) isolation barrier technology. This barrier provides galvanic isolation of up to 4000V. The digital input signal is conditioned, translated to a balanced signal, and then differentiated across the isolation barrier. Across the isolation barrier, a differential comparator receives the logic transition information and sets a flip-flop in the output circuitry appropriately. A periodic update pulse is also sent across the barrier to ensure that the proper DC level is set.

Used in conjunction with isolated power supplies, these devices prevent noise currents on a data bus or other circuits from entering the local ground, and interfering with or damaging sensitive control circuitry.

Advantages to TI's Capacitive Digital Isolation:

• Inorganic SiO₂ isolation barrier with proven stability over time, temperature and humidity
• Differential signaling across the isolation barrier offers the best noise immunity to magnetic and electrical interference
• Dual channel signaling internally with a fast AC path and secondary channel to guarantee DC stability ensures the best performance in all conditions