High-speed, dual-channel RS-232 link in a single chip
News Release from:
27 September 2012
The traditional way of implementing a fully isolated 2-channel RS-232 interface is to use optocouplers to provide data isolation of the RS-232 link. One optocoupler is needed for each data line (TIN1, TIN2, ROUT1, ROUT2), along with an external buffer for each one.
The isolated power supply uses a transformer driver IC to drive a discrete transformer, along with a simple rectification circuit and an LDO (low-dropout regulator) to clean up the isolated 5V or 3.3V ISO VCC rail. For implementation, this design requires eight ICs and a number of passive components — plus significant board space.
In a single-chip solution, a fully isolated (2.5kV) two-channel RS-232 interface for all four signals can be implemented with just one IC (ADM3252E), plus two decoupling capacitors and four charge-pump capacitors.
The ADM3252E combines a standard RS-232 transceiver with a 4-channel iCoupler, providing signal isolation of the RS-232 data signals. It also integrates isoPower technology to provide on-chip power isolation. Integrating the RS-232 transceiver by combining iCoupler and isoPower isolation technologies enables the ADM3252E to provide a fully isolated RS-232 interface with 2.5kV RMS isolation in a single package (12 mm × 12 mm), requiring only six external capacitors.
This single-chip solution significantly reduces the design time and board space required for an isolated RS-232 interface. Reliability is enhanced and cost is reduced because of the significantly smaller number of components to be placed on the PCB, which reduces manufacturing costs and improves reliability. Furthermore, the ADM3252E can be used in 5V or 3.3V applications without any modification, avoiding the design changes that would be necessary with a discrete design.
The isoPower technology provides 2.5kV power isolation directly on chip within the 44-BGA package, eliminating the need for the expensive discrete transformer used in the traditional solution. In addition, iCoupler technology provides the signal (data) isolation, eliminating the need for the four discrete optocoupler channels.
You can read the rest of this article in the September issue of Electronic Specifier Design by clicking here.