Burr-Brown PCM63 Datasheet: Notes on a Classic DAC Chip

The Burr-Brown PCM63 is a 20-bit multibit digital-to-analogue converter from around 1990. Burr-Brown is now part of Texas Instruments, and the chip has long been discontinued, yet it remains a reference point for listeners and designers who prefer multibit conversion to delta-sigma. These notes explain what the datasheet says and which parts of it still matter.

The chip’s defining feature is what Burr-Brown called its Colinear architecture. A conventional multibit converter has its most difficult transition at the centre of its range, around digital zero, where many bits change at once. Any error there falls exactly where quiet music lives. The PCM63 uses two converter sections per channel, arranged around the zero point, so that this major-carry error is avoided. The result is good linearity at low signal levels without external trimming.

It is a single-channel converter, so a stereo design needs at least two. It accepts serial data in two’s-complement format, normally from a separate digital filter, and runs from separate analogue and digital bipolar supplies.

The chip was sold in grades sorted by distortion performance, with the K grade the most tightly specified. The grade is marked on the package and is worth checking, because it is the main difference between otherwise identical parts.

The PCM63 provides a current output, and the designer must convert that current into a voltage. The datasheet’s reference circuit uses an op-amp for this. Many designers prefer a discrete stage, a simple resistor or a tube stage, and that choice shapes much of the final sound. It is often a bigger factor than the converter itself.

The sections that matter most in practice are the timing diagrams for data, bit clock and word clock, the recommended decoupling and grounding layout, the reference and bypass capacitor connections, and the low-level distortion figures. A board that ignores the layout guidance will rarely reach the chip’s potential, whatever the components.

Two cautions apply today. First, obtain the datasheet from Texas Instruments rather than from an unofficial copy, so that you have the definitive revision. Second, buy chips only from a source you trust: counterfeit and remarked parts of classic Burr-Brown converters circulate on the secondary market, and a lower grade re-marked as a K is not unusual.

For listeners rather than builders, the PCM63 explains a good deal about the multibit sound that many still seek: a direct, solid presentation shaped as much by its analogue stage as by its digital core.

Which Demograf Audio piece fits

• Reference Tube DAC: one chassis built in five versions, each named after its chip; the Artemis version uses the PCM63. It takes 16-bit / 44.1 kHz PCM over S/PDIF coaxial, with no upsampling and no DSD.
• Bellerophon (Class AB amplifier) and Hades (Class D amplifier) carry a built-in DAC chosen at order time; the PCM63 is one of the options.