The EL-1274 High Resistivity CCD controller box has been built by the UCO/Lick Observatory Electronics Lab. The controller is built around the San Diego State University (SDSU) rev. 1 board set. There are several aspects that make this controller different from any of the earlier CCD controllers. Most notably, this controller provides a different set of power supply voltages for the bias levels . While all controllers have +5V, +15V, and -15V supplies, due to the characteristics of the High Resistivity CCD (Hi-Rho), this controller has replaced the +35V supply with a +120VDC supply. Also, this controller has an additional -35V supply. This impacts the wiring and the layout of the chassis. Because the Hi-Rho system has been put together using parts from the old Lick Dewar #8 and an unused controller that was originally built for the ESI instrument in Hawaii, this system is unique and very little of it is interchangeable with other controllers.

The SDSU board set.

TIMING BOARD
The SDSU board set is made up of three different boards. First, the TIMING board, perform all of the timing, control, and communications functions. The communications and transfer of data occurs over a set of duplex fiber cables. The fibers connect the controller to a VME bases box that then talks over a private ethernet link to the data taking computer. The TIMING board is also used to setup the clock waveforms for the CCD chip. The waveforms are determined by the CCD Lab and the Lick Scientific Programming Group (SPG) and then are programmed into the TIMING board.

VIDEO BOARD
The VIDEO board performs three functions. First, it is where the actual CCD waveforms are generated. Each waveform is built up using two separate DACs. One DAC is programmed for the high level of the waveform while the other DAC is programmed for the low level of the waveform. For example, say the first DAC is programmed to output a level of +9 volts and the second one is programmed -3.5 volts. By alternately enabling the two DACs the resulting waveform would alternate between +9 and -3.5 volts with the duty cycle being determined by the timing of the TIMING board. In this way the waveforms can be generated to shift the charge both along the columns and the rows. Each VIDEO board can generate up to twelve separate clocks.
Next, the VIDEO board can generate as many as seven bias levels. As noted on drawing EL-1277, the first four outputs are geared toward specific uses such as Vdd and Vr. The last three are general purpose and can be set anywhere within the specified range. The bias levels are set and applied to the CCD as required.
The last function of the VIDEO board is to receive the video signal from the preamp and digitize it via a ADC. This digitized value is then sent to the VME Crate via the TIMING board during the readout cycle of an exposure.

UTILITY BOARD
The UTILITY board provides general I/O and miscellaneous functions. EL-1276 presents a table of the functions used specifically for the Hi-Rho controller. Among these functions are a control line for the shutter, a current source and input for reading the temperature diode mounted in the dewar, and an analog output to control the heater resistor in the dewar. Also shown are an analog output at pin A25 to control the front panel temperature meter and the input and outputs associated with the Lick Power Monitor card.

UCO/Lick Boards

The controller also houses two boards built by Lick. These are the EL-1281 CCD INTERCONNECT board and the EL-1198 POWER MONITOR board.

CCD INTERCONNECT BOARD
This board connects the SDSU VIDEO and UTILITY boards to the output connectors and the rest of the controller. Viewing both the board schematic and the EL-1280 Jumper drawings shows how the INTERCONNECT board is general purpose enough to allow for just about any configuration of a CCD controller. Each of the jumpers can be positioned to route it's associated general purpose connection to the rear connector of the board -or- to instead tie the output pin to ground. This allows us to add more grounds to the ribbon cable that leaves the board's output connector when not otherwise used for a signal. In non-standard applications, we can use wire-wrap instead of jumpers to allow signals follow any necessary path. On the jumper drawing rectangles around sets of pins represent shorting blocks while lines represent wire-wrap wires.

POWER MONITOR BOARD
The POWER MONITOR board acts as a power supervisor for the controller. (See the detailed write-up in the Boards portion of this manual.) It controls the application and removal of the +/-15 volts from the backplane, controls the High Voltage application and removal from the Dewar Electronics box, and turns the analog switches in the Dewar Electronics box on and off. The general idea is that the HV and analog switches can not turn on until the +/- 15V is on and the +/-15V can not turn off until the HV and analog switches are off. This sequence is important to keep wrong voltages off of the CCD chip. It also monitors the AC input for an under-voltage condition and the same for the +5V supply. Also, in the case of the +5V supply going too low a reset signal is sent to the processor on the SDSU Timing board. Again, these conditions will cause the removal of power to the CCD in the proper order.

Controller Wring

The front panel of the controller should look similar to both the old style Lick CCD controller and a newer SDSU boxes. On the leftmost panel, is the AC power switch and two toggle switches. The toggle switch on the left is marked 15V and provides a manual means of turning off both the +15V and the -15V supplies. The other switch provides control of the +48 volt supply. These switches are actually inputs to the EL-1183 Power Monitor board. This board contains circuitry to monitor the AC voltage, The +5V logic power supply, the +/-15V supplies, and the +48V supply. Each of these voltages are feed to voltage monitor circuits and if any one of then fall below a set point, the voltages will be removed from the backplane and dewar electronic box in a controlled fashion. The sequence is as follows: first, the +48V supply is turned off and then the +/-15V supplies are turned off. Also, as mentioned, the front panel switches are inputs to this board and can only turn on the supplies if the software inputs to the Power Monitor board are asserted. Again, the application of power is controlled such that the +/-15V supplies must be turned on before the +48V will be allowed to come on. See the description on the EL-1183 Power Monitor for a more complete details.

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