Cremat's two evaluation boards CR-150-R6 and CR-160-R9 can be powered using one of two methods. The first is to apply both positive and negative 12V to the board using your power supply. The second method is to use the CR-24V wall-mounted power supply to provide this power.
Using the CR-24V wall mounted power supply, rail-splitter circuitry on the evaluation boards transform the 24V power into + and - 12V. Here is a simplified description:
- The negative side of the 24V power becomes -12V on the evaluation board.
- The positive side of the 24V power becomes +12 on the evaluation board.
- A divider circuit finds the midpoint between these voltages and creates a virtual ground at this voltage. This virtual ground becomes the evaluation board's ground.
The two Cremat evaluation boards use an IC from Texas Instruments (TLE2426) to create this virtual ground.
More information on the creation of virtual grounds can be found here.
Another method creating both positive and negative DC voltages from a single DC supply is a buck/boost circuit (switching supply). Switching power supplies are difficult to use with sensitive preamplifier electronics because the switching frequencies are similar to the signal frequencies. The noise generated by the switching cannot be easily filtered out. The rail-splitter is much quieter for this reason.
Important!:
The rail-splitter circuit demands that the incoming power supply be floating with respect to the electronics being powered. If you were to try to power Cremat's evaluation boards using a bench-top power supply set to 24V with the negative side of the bench-top supply grounded you will overload the rail-splitter circuit on the evaluation board burning out the TLE2426 chip. The CR-24V wall mounted power supply is the safest way to power Cremat's evaluation boards.
Using a common power supply for multiple boards:
You may also be tempted to use a single floating +24V power supply to power more than one evaluation board. If you have several channels of preamplifiers and shaping amplifiers, the number of wall mounted power supplies can be cumbersome. Do not do this! The virtual grounds of the multiple evaluation boards will not exactly match each other and the various TLE2426 chips will struggle against each other to set the common ground.
The CR-150-R6 and CR-160-R9 both have provisions for using +/- DC power (in the range of +/-8V to +/-13V). If you want to use a single common power supply to power multiple evaluation boards then use this option. The concerns with using a floating power supply to power each individual board can this way be avoided.