100 MHz SPI isolators enable faster data conversion

November 22, 2016 // By Graham Prophet
LTM2893 and LTM2895 are recently-announced SPI (serial peripheral interface) µModule (“micromodule”) isolators, that Linear Technology has configured for use with its high performance data converters.

The isolators support SPI clock speeds up to 100 MHz, more than doubling the effective 40 MHz limit of existing digital isolators and enabling the use of higher resolution and higher speed data converters while maintaining zero latency operation. With a fast SPI interface, 6 kVRMS of galvanic isolation, and additional high speed control signals, the ICs require no external components and provide a simple µModule solution for isolated data converter communications.

 

The LTM2893 (read only) and LTM2893-1 (read/write) are designed to isolate Linear Technology’s general purpose successive approximation register (SAR) analog-to-digital converters (ADCs), including the LTC2378 family of 20-, 18- and 16-bit 1Msps SAR ADCs or the LTC2348 family of octal, 18- and 16-bit 200ksps/channel simultaneous sampling SAR ADCs. Additional high speed control signals provide support for parallel or chain-connected configurations, as well as analog multiplexers or programmable gain amplifiers. Configurable word length allows SPI access to be tailored to a specific ADC to maximize throughput. With only 30psRMS of additive jitter from input to output, the LTM2893 and LTM2893-1 minimize signal-to-noise ratio (SNR) degradation in ADCs due to jitter.

 

The LTM2895 is designed to isolate Linear Technology’s general purpose digital-to-analogue converters (DACs), including the unipolar LTC2641 family or bipolar LTC2642 family of 16-/14-/12-bit unbuffered voltage output DACs. Additional high speed control signals provide support for dual channel, dual DAC, or host-to-host (i.e., FPGA to isolated FPGA with page mode data transfer) configurations, while a configurable word length allows SPI access to be tailored to a specific DAC to maximize throughput. A low 30 psRMS jitter /LOAD signal path is also available for DACs with an asynchronous LOAD input.

 

The LTM2893, LTC2893-1 and LTM2895 are housed in a low profile 15 x 6.25 x 2.06 mm surface mount BGA package; all integrated circuits and passive components are housed in this RoHS-compliant μModule package. All devices are available in commercial, industrial and automotive versions, supporting operating temperature ranges from 0°C to 70°C, –40°C to 85°C and –40°C to 125°C, respectively. The LTM2893 and LTM2893-1 are available now in production quantities, and the LTM2895 will be available later in 2016. Pricing starts at $8.95 (1000).

 

Linear Technology; www.linear.com/isolator

 

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