BASE power + utility board

External power is supplied to the power pcb from a 48 V DC power supply. On-board DC-DC converters provide ±15 volts, ±5 volts, and +30 volts DC. The outputs of the DC--DC converters are filtered with LC networks and ferrite beads to suppress the switching noise as much as possible.



In addition, the high voltage +30 volt supply is linear regulated to reduce the output noise further, as this supply powers the op-amps which provide bias voltages to the CCD. (The actual voltages are generated by a DAC with 80 nV/sqrt{Hz} noise, and a precision reference).



BASE power/utility pcb


The DC--DC converters from DATEL/Murata were chosen for their compact size. Equivalent linear power supplies would have been too large to conveniently fit in the housing.

All analog circuits operate from the ±15 volt supplies. Where necessary, linear regulators provide ±10 volts (a reduced voltage for the analog switches).  The digital circuits operate in a mixed 5V/3.3V environment. Power is provided at +5V, and is regulated to +3.3V where necessary.

A separate single output +5 volt DC-DC converter provides sufficient current (1 amp) to drive the heater resistors used to control the temperature of the ccds.  Each heater resistor is handled by a seperate power transistor, with the current to set by a programmable D/A converter output.  Feedback voltages from the temperature sensors (inside the dewar head) are read by a serial ADC.
Greg Burley (burley@obs.carnegiescience.edu)
Ian Thompson (ian@obs.carnegiescience.edu)