ELMB + LMB-DAC
This is a block schematic overview of the ELMB with the ELMB-DAC connected to it.
The ELMB is connected to the CAN bus via a CAN transceiver. This transceiver translate the differential and bi-directional CAN signals into two unidirectional TTL level signals. The transceiver is optically separated from the CAN controller and its associated micro-controllers. So the CAN-transceiver gets its own power-supply via the same cable as the CAN signals. The micro-controller has it's one power namely Digital power plus and ground. (VDG&VDP) The micro controller is connected with the outside world with a SPI or Microlink bus. On the same ELMB is also an analogue part. A 64 channel multiplexer and a 16-bit ADC are connected via opto-couplers with the SPI bus. This analogue part has its own power namely Analogue voltage plus and ground. So, if you have to make very sensitive and accurate measurements then you should use a separate analogue power-supply.
 

The ELMB DAC
The DAC (MAX525) is connected via opto-couplers with the SPI bus. It has an on board address selection that enables one to connect four DAC PCB's to one ELMB. This number has been chosen because the DAC gets its power from the ELMB and that power is limited. There are four DAC's on one PCB and each DAC has four channels so each PCB has 16 channels. Each DAC channel has an output circuit that can be supplied with the internal power-supply of the ELMB or can be externally supplied with an external power supply. In case the DAC is internally fed, the output current can be within 0 to 1 mA. In case of an external power supply, the output current can be 0 to 20 mA.

Output circuit
This is the output circuit of the LMB-DAC. An op-amp inside the MAX525 DAC is used and one op-amp from Burr brown the OPA4336. Both the MAX525 and the OPA4336 are not certified for use in a radiation area, so the have to be tested. The maximum output current is 1 mA when R1 and R7 are 2.2 Kohm. If these two resisters are lowered to 110 ohm, the maximum current increases to 20 mA. The accuracy of the output is determined by the accuracy of R1, R2 and R7. So if one uses resistors of 0.1 % the output current will be 0.1 % accurate. Through a single event upset of the DAC registry the output voltage can be changed. In case of the use of the LMB-DAC in radiation conditions, one should monitor the output voltage or current with an ADC channel of the ELMB.

 

If we make 100 LMB-DAC's, the estimated price of one channel is 17.5 Sfr This high price is caused by the high price of the semiconductors and the PCB. The price of semiconductors is based on real citations of real suppliers. The price of the PCB is based on a rough estimate.

The spec's of the ELMB-DAC