The Sidecar Asic

Most contemporary astronomy SCA designs, including visible CCDs and infrared SCAs, are analog devices that require external electronics for operating the SCA. Support electronics tend to be bulky and power hungry, with a complex interface to the SCA. To dramatically improve SCA integration by reducing size, weight, and power, and to greatly improve overall system performance, RSC has developed an Application Specific Integrated Circuit (ASIC) called SIDECAR (System for Image Digitization, Enhancement, Control And Retrieval) [4]. SIDECAR is a SCA interface chip that provides clocks and biases to the SCA, and performs amplification and analog-to-digital conversion of the SCA analog outputs. SIDECAR has 36 analog input channels, and digitization can be done with 12 or 16 bit resolution. SIDECAR presents an all-digital interface to the external world, providing the following advantages to system design:

• Simplifies the overall system architecture and reduces the number of wires within the system

• Eliminates the risks and problems of transmitting low-noise analog signals over long distances

• Reduces the risk of integrating one or more SCAs into mosaics

• Offers high flexibility and redundancy due to broad programmability

• Digitizes 16-bit data at 500 kHz (per port) or 12-bit data at up to 10 MHz (per port) for a maximum total 12-bit pixel rate of 160 MHz

Figure 5 shows a schematic diagram of the SIDECAR ASIC and interfaces with SCA (multiplexer) and the host (external) electronics. For more detail, see the paper by Loose, et al. in these proceedings [4].

Inside the dewar at cryogenic temperatures

Inside the dewar at cryogenic temperatures

Figure 5. Schematic diagram of a system using the SIDECAR ASIC

Testing of the 2nd version of the ASIC is completed and all major functional blocks have been demonstrated. When configured for low power astronomy applications, the total power consumption is 8.4 mW for a 2Kx2K H2RG SCA and SIDECAR (four 16 bit ports at 100 kHz).

The Analog-to-Digital Converters (ADCs) have demonstrated excellent performance. The 12 bit ADCs have excellent linearity (DNL < ± 0.3 LSB, INL < ± 0.8 LSB) and noise is less than 0.3 LSB. The 16 bit ADCs also have excellent characteristics: DNL < ± 0.3 LSB, INL < ± 0.7 LSB. When the SIDECAR is used in conjunction with a HAWAII-2RG SCA, the total noise in a 1000 sec exposure has been measured to be less than 6 electrons (after averaging multiple reads). The first shipments of SIDECAR ASICs to astronomers will be in the fourth quarter of 2005.

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