(Also see EL-3161.) This board lives inside the CCD controller and its primarily function is to gather all of the signals generated within the CCD controller for a single CCD and connect them to the umbilical cable which delivers them to the CCD dewar electronics box. One nice feature of this board is that it has an external connector, P3, with each of the board’s signals available for troubleshooting the system.

Sheet 1

In the upper left-hand of the drawing is connector P7. This cable brings in the heater, temperature diode, and bias select signals and sends out the selected bias voltage via pin 12. This is also where the +5 volt and +/-16 volt supplies enter the card. Below P7 is the onboard filtering of the supply voltages. Again, notice that the +5 volt ground is kept separate from the +/-16 volt analog ground. The right side of the drawing shows the 61-pin MS-style connector that connects the CCD controller to the dewar. An attempt has been made here to pass as many ground signals as possible through the cable. What doesn’t show up here is the overall shield connection for the cable. This is done using a banana plug and jack arrangement where length of wire is soldered to the shield and is terminated into a banana plug which is then connected to a jack on the back of the chassis.

Sheet 2

This sheet shows the connectors that bring the clocks and bias voltages from the SDSU2 clock and bias boards. The connector P4 receives the bias voltages for the first CCD amplifier that is used in the chain. If a second amplifier is available on the CCD, it’s signals come into the board via P6. P2 receives the clock signals from the clock driver board. P5, if used, brings in the extra clock signals for frame transfer devices or for the transfer gate of a Lick/Orbit CCD. The rest of the sheet shows the various jumper options available on the board. These are determined by the configuration of the CCD chip used in the dewar. Also, see sheet 5 as a guide for configuring these jumpers.

Sheet 3

This sheet shows the various circuits used to read back the bias levels that are being sent to the CCD chip. The upper left hand circuit show the bias level RD(A). Due to the input range of the ADC (sheet 4), this level is divided by ten via the precision resistor network RN4. This level is then wired into the op-amp U1 voltage divider. The resistor network RN3 in the feedback loop presents the same impedance as is seen at the non-inverting input and compensates for any bias current flowing into that input. The other circuits work in the same manner. Notice however, several of the circuits do a division by two rather than ten. This is due to the normal level expected on these bias levels. Notice too that the signals that actually go out to the CCD are the levels that show up as inputs on this page. The outputs of these circuits are fed only to the analog multiplexer and then back to the CCD controller for monitoring purposes only.

Sheet 4

This sheet contains the analog multiplexer that selects the bias level to be read back into the CCD controller. Under software control, the four select lines can be set to read in any of the eight biases or four spare levels on the board. In practice, none of the spare lines have yet to be used in any of the controllers. The output of the multiplexer is wired to a voltage follower circuit that sends it’s output to pin 12 of P7 and back to the Utility board via the Utility Support board. Below the multiplexer is a set of jumpers. Each of these jumpers can be inserted to tie its signal line to ground. Again, these lines are not presently used and the jumpers are normally installed to keep the wires in the umbilical cable from floating. On the right-hand side of the page is the test connector that sticks out of the panel on which the board mounts and provides scope probe access to any of the signals on the board. This of course is meant as a troubleshooting aide and does not have a mating connector.

Sheet 5

The final sheet gives the jumper settings for the various configurations of the CCDs that the controller supports at this time. It is hoped that the controller has been made general purpose enough that future CCDs will be able to be accommodated with only jumper and cabling changes.