How to implement galvanic isolation for power and signal lines in high-voltage systems
Ferrite cores can handle more power. When power needs are below about 100 mW, an air core can provide a lower-cost and simpler solution. Each of the three technologies supports different combinations of signal and power transmission (Figure 2). Power and signal isolation Designers that need up to 650 mW of isolated power and four isolated signal channels capable of 100 megabits per second (Mbps) transmission rates can turn to the ISOW7841FDWER from Texas Instruments. This general purpose device has an isolation rating of 5 kilovolts root mean square (kVRMS) and a ±100 kV/ µs minimum CMTI. It uses SiO2 isolation on the signal channels and thin film polymer isolation for the on-chip power transformer (Figure 3). The ISOW7841EVM eval board can help designers evaluate device performance in isolated systems and speed time to market.
Isolated automotive DC/DC Automotive systems that need 500 mW with 5 kV RMS isolation can use the AEC-Q100 qualified UCC12051QDVERQ1 from Texas Instruments. It features a minimum CMTI of 100 V/ns, a surge capability of 10 kV peak , and a working voltage internal oscillator and an optimized internal layout to minimize radiated emissions. It includes undervoltage lockout, thermal shutdown, an enable pin, a synchronization of 1.2 kV RMS . It uses spread spectrum modulation for the function, and delivers an output of 5.0 or 3.3 volts direct current (VDC). The UCC12050EVM-022 eval board enables designers to test the enable/disable function, synchronize to an external clock source, detect external clock faults, and select the output voltage. It has test points for ripple and transient response measurements. The board can simplify system integration by serving as an example of a layout that supports the rated isolation and provides good electromagnetic interference (EMI) performance (Figure 4). CAN transceivers with capacitive isolation For applications that need a Controller Area Network (CAN) transceiver with 1 Mbps signaling and a CMTI of 50 kV/μs, Texas
Figure 4: In addition to speeding evaluation of the UCC12051QDVERQ1 isolated DC/DC converter IC, the UCC12050EVM-022 eval board provides a suggested layout for system integration. (Image source: Texas Instruments)
Instruments offers the ISO1050DWR with an isolation rating of 5 kVRMS, and the ISO1050DUB rated for 2.5 kV RMS . These transceivers meet the specifications of ISO 11898-2 for high-speed CAN operation (Figure 5). They are specified for operation
from -55 to 105 degrees Celsius (°C) and include overvoltage, cross-wire, and loss of ground protection from -27 to 40 volts, overtemperature shutdown, and a -12 to +12 volt common-mode range.
Figure 2: Optocouplers (A) can only transmit signals, capacitive isolators (B) can transmit limited amounts of power and signals, and magnetic isolators (C) can handle higher power levels as well as signals. (Image source: Texas Instruments)
Figure 3: The ISOW7841FDWER uses polymer insulation in the power transformer (top) and SiO2 isolation capacitors in the signal chain (bottom). (Image source: Texas Instruments)
Figure 5: The isolated ISO1050DWR and ISO1050DUB transceivers meet ISO 11898-2 for high-speed CAN operation. (Image source: Texas Instruments)
45
we get technical
44
Powered by FlippingBook