IMPLEMENTED SO FAR

- Support for 4x20 LCD Display and large number display
- Brightness and contrast adjustment with remote
- (OPUS/Wolfson WM8741) DAC volume control: remote and rotary encoder
- (OPUS/Wolfson WM8741) DAC random filter selection 1 to 5 with remote
- (OPUS/Wolfson WM8741) DAC upsampling selection (L, M, H -this is the OSR setting)
- I2C level shifting (5V to 3.3V)
- Optimized power-up sequence

Wednesday, February 10, 2010

Buffalo II Specification and FAQ

This post is to summarize information I find elsewhere

EXTERNAL POWER SUPPLY REQUIREMENTS

POWER SUPPLY CURRENT [link]














POWER SUPPLY VOLTAGE [link]

The Buff II board has a single PS connection. Because it feeds both the on board LT1763 regulators and the AVCC dual shunt regulator, it must comply to the design of the AVCC dual shunt:
  • Vmin=5V
  • Vmax=5.5V (The AVCC shunt regulator is optimized to this voltage)
AVCC

According the the ESS Sabre DAC white paper,  AVCC is specified as follows:
  • Minimum: 1.8V
  • Nominal: 3.3V (DNR= -132db)
  • Maximum: 4.0V (DNR> -133db) - see footnote 17 of paper
INSTALLATION OF AVCC DUAL SHUNT REGULATOR [link] [link]



"Also of note, although the AVCC header has four pins, only three are used by our AVCC module.
The AVCC module does not use the DVCC pin. It is there as a convenience to any who might want to use an ESS demo board style AVCC supply (where DVCC is a VREF). Our AVCC module uses its own low noise VREF, not DVCC."

Note: Buffalo I also derived the AVCC from the DVCC. In the case you wish to replicate such AVCC implementation, you can tap into DVCC as reference and VD will be powering the buffer opamp:


Normal Operating Conditions [link]
(This is one board, there is slight variations between boards)

VD=5V. Notice that one LED is brighter than the other. According to TPA this is perfectly normal.

AVCC1=3.523V, VCC2=3.5626V


VD=5.5V. Notice that the LEDs' brightness is more uniform.

AVCC1=3.556V, AVCC2=3.554V


The shut regulator board can also be installed on the back side of the Buffalo II board (It will get on the way if you are stacking above IVY III)


ON BOARD LINEAR REGULATORS






  • There are 3 linear regulators LT 1763. Two are 3.3 V and one is variable set to 1.2V
  • Noise level: 20uVrms 10Hz to 100KHz (meaning you can't do better than this even if you feed it a cleaner supply). For more information on regulator noise see this post.
  • Regulator Vin max=20V (5.5V max is specified because the same input traces feed the the shunt AVCC regulator which is designed for 5.5V max)
  • Comments by Russ on the use of LT1763 as regulator for the Crystek clock: "The reason the LT1763 is a good fit for the clock we use is because that clock in essence has a form of local regulation and decoupling internally."
    OUTPUT IMPEDANCE BUFFALO I, II (from diyaudio)
    • 195 ohm each output
    According to the ESS Sabre DAC whitepaper page 4, each of the 8 DACs can be modeled as a voltage source having an output impedance of approx 800 ohm. Since in stereo configuration 4 such dacs are wired in parallel, the effective output impedance is thus 800/4 ~ 200 ohm.

    DUAL MONO INSTALLATION

    Latest diagram posted at diyaudio

    DIMENSIONS

    • Buffalo II board: 2" x 3.3". This is the same size as the other modules such as OPUS, COD, Buffalo I, etc.
    • IVY III: From the layout it appears it is a double size board: 4" x 3.3" 
    • Supplied Standoffs: .5" base standoffs. Inter-board standoffs (not included with the Buffalo II board are .625")

      2 comments:

      emiliano said...

      hello
      I would ask you for help, before making trouble ...
      tensions (+5.50 ve +15 v - 15v), the two power supply, the buffalo dac II and to the Ivy III, I have to adjust.... with the DAC and IVY III connected or disconnected?
      I noticed that if you adjust the voltage to +15 V and-15V without load, then when I connect the IVY III, the voltage drops to approximately +9 V .... Is this normal?

      The Lazy Engineer said...

      Hello emiliano. You adjust with the DAC and IVY disconnected. One pot adjusts for current, the other adjusts for voltage. Please refer to the manuals in the TPA website. After adjustment, and if enough current can be provided, the voltage is stable. If your voltage drops to 9V, then something is wrong.