This board lives at the dewar inside the electronics box. It is designed to filter the DC power coming from the CCD controller chassis and to pass the heater, temperature, and analog switch signals. It consists of input and output connectors, PI filters on the 5, +16, and –16 volt power lines, and an Opto-isolator for the analog switch enable signal. Sheet 1 shows the inputs to the board on connector P1. To the right of the connectors is shown the filtering on the DC voltage lines. The filtering consists of the 820 mH inductors and the 100 m F capacitors. The 1.0 mF and 0.1 m caps provide a low impedance path to ground for any AC noise.

On the upper left-hand side of sheet 2, P2 connects the heater resistor and temperature diode signals as follows:

P1 pin D to P2 pin 1 – COM_TEMP_DIODE The temperature diode in the dewar.
P1 pin P to P2 pin 2 – COM_TEMP_DIODE_RTN
P1 pin E to P2 pin 3 – UTIL_HEATER The heater resistor in the dewar.
P1 pin R to P2 pin 4 – UTIL_HEATER

Below P2 is the circuit that isolates and buffers the analog switch signal. The ANALOG_SW_EN-IN signal comes in on pin G of P1. Also, a connection to the utility support board’s 5-volt supply comes in on pin F of P1. These two inputs connect to the 4N35 opto-isolator at U1. When the ANALOG_SW_EN-IN signal is driven low, the output of the isolator also goes low. This level is applied to the input of the 74LS240 bus driver chip and as the output is inverted, output 1 is then routed to the other drivers of the chip. The final outputs are then the same sense as the input signal. These outputs are then routed to the Analog Switch Board connectors P5, P6, P7, and P8 (shown on the right-hand side of the page.) At the bottom left-hand side of the page is a set of spare contacts for future use or customization.

The middle column of connectors are for the CCD pre-amplifiers in the dewar electronics boxes. Pin 1 connects to the output of the +16V onboard filter, pin 3 connects to the –16v filter and pins 2 and 4 provide analog grounds to the pre-amps. The right-hand side column of connectors provide connections for the Analog Switch boards. These connectors provide the following connections:

Pin 1 +5 volt logic supply
Pin 2 5 volt ground (digital ground)
Pin 3 ANALOG_SW_EN_n
Pin 4 no connection
Pin 5 +16 volt analog supply
Pin 6 +16 volt ground (analog)
Pin 7 -16 volt analog supply
Pin 8 -16 volt ground (analog)

Note: this board was designed to provide interconnections for from 1 to 4 CCD signal chains. In DEIMOS, three of these boards are used. Two of which connect four channels each and a third that connects only two channels. In ESI, there is only a single board used as there is only one CCD used.