Repeater system, CORE

A control and readout (CORE) system [21] is required to provide the following functions:

• Analog control of the VA1 front-end chips:
  The CORE system provides bias voltages and currents. The ability to adjust the bias parameters remotely is particularly important in view of the possibility that the optimal values may change with time as the chips are irradiated.
  
• Digital control of the VA1 front-end chips:
  Various pulses and digital levels are used to control the data-acquisition sequence of the VA1 chips. The CORE serves to condition, buffer, and distribute these signals to VA1s.
  
• Analog buffering and amplification:
  Since the cable length between the detector and the electronics hut is about 30 m, CORE incorporates differential gain/buffer stages to provide immunity to electromagnetic interference. To meet the readout speed requirements of Belle DAQ, CORE is capable of supporting MUX scan rates up to 5 MHz. This allows a single FADC channel to scan all channels of a 640-channel hybrid in 128 $\mu$s.
  
• Monitoring of analog levels:
  CORE monitors a large number ( $68\times4\times8$) of analog levels to verify the bias parameters of VA1 and buffers, and the hybrid temperatures.

As shown in Fig. , each CORE system module consists of a backplane motherboard (MAMBO), four boards for readout signal buffering and front-end control (REBOs), a board for monitoring (RAMBO), and eight interface cards (ABCs). There are a total of eight cooled aluminum and copper housings (DOCKs) which hold the CORE system boards; four each in the forward and backward regions of the detector. The temperature at the surface of DOCK is maintained at $\sim$23 $^\circ$C. ABCs, which are physically situated about 20 cm from the front-end hybrids, provide a passive electrical interface between the repeater system and the hybrids. In addition, they serve as passive one-to-two fanouts for the digital control signals running from the repeater to the hybrids, thereby reducing the number of cables required. ABCs also facilitate ready disconnection for maintenance. MAMBO is an interface board for ABC, REBO, RAMBO and cables to the Belle electronics hut. MAMBO transmits digital signals to and from TTMs using the low-voltage differential signaling (LVDS) standard. LVDS reduces EMI to the analog part of CORE as well as to other parts of the detector. Mounted on MAMBO are ADCs to monitor temperature, the bias currents and voltages, the amplitude of a calibration test pulse, and the logic levels for the digital signals. REBO consists of an analog block and a digital block. The analog block comprises digital-to-analog converters (DACs), voltage-to-current converters, current-to-voltage converters and amplifiers. The digital block controls DACs in the analog block, and buffers the digital signals to the front-end electronics.