Configurable CMOS Voltage DAC for Multichannel Detector Systems'
Oak Ridge National Laboratory, Oak Ridge, TN 37831-6006
A CMOS voltage DAC has
integration into multiple
front-end electronics ASICs
associated with the PHENIX detector located at the RHIC
accelerator of Brookhaven National Laboratory. The topology
allows wide-range output programmability by selection of an
offset voltage and on-chip resistor and transistor sizing. The
DAC is trimless and requires no external components, making
it ideal for highly integrated collider detector systems. Errors
associated with on-chip bias are minimized using a topology
that implements a ratiometric relationship which compensates
for absolute resistance value changes and is limited only by
errors in the on-chip matching of MOSFETs and resistive
Temperature-induced errors associated with the
integrated resistors are also minimized by the circuit topology
and monolithic construction.
All reference voltages and
currents are derived using a single regulated voltage supply.
This paper presents the general DAC architecture and design
method, discusses on-chip matching issues and tradeoffs
associated with device sizing and monolithic layout, and
presents measured performance of various gate length DACs
fabricated in a 1.2ym CMOS process including integral non-
linearity, differential nonlinearity, and slope and offset errors.
Highly integrated front-end electronics are commonplace
requirements for higher spatial resolution and lower energy
particle detection will only increase the need for improvement
in electronic function and implementation. In order to meet
this need, electronics will need to continue technological
growth in the following areas:
circuit area, higher level of integration (which implies
reduction or elimination of off-chip components), and low-
noise performance. Contemporary monolithic DAC designs
rely on precision elements to ensure accuracy and linearity
[2,3]. Precision passive elements are obtained by either tight
process control, resistive trimming, or the use of external
precision components. These methods typically increase the
fabrication cost or increase the circuit implementation size.
This paper presents a CMOS monolithic, compatible DAC
that is ideal for use in high density collider detector systems.
to its usefulness
small area, low-power
consumption, no need for external components or trimming,
'Research sponsored by the U.S. Department of Energy and
performed at Oak Ridge National Laboratory, managed by Lockheed
Martin Energy Research Corporation for the U.S. Department of
Energy under Contract No. DE-AC05-960R22464.