TAS2505EVM: Issue with TAS2505EVM I²S Signals When Using External Master

Part Number: TAS2505EVM
Other Parts Discussed in Thread: TAS2505

Setup Detail

We are using the TAS2505EVM for our proof-of-concept.
When the EVM runs in standalone mode, everything works correctly.

However, when we connect an external I²S master to drive the TAS2505, the signals at the TAS2505 side do not appear correct.

Hardware Setup

• IOVDD = 3.3 V

• To isolate onboard signals:

  • W8 and W9 jumpers removed to isolate BCLK and DIN

  • BCLK and DIN connected via pin-2 of W8 and W9 to Extrenal Master.

• There is no isolation jumper for WCLK, so the external WCLK is wired directly from the WCLK test point to External master.

• I²C is connected from W2 and W3 to external master.

• External master configures the TAS2505 over I²C
  -- Verify Page 0 Registers --
  PG0[0x04] = 0x0A
  PG0[0x0B] = 0x81
  PG0[0x0C] = 0x81
  PG0[0x0D] = 0x00
  PG0[0x0E] = 0x40
  PG0[0x1B] = 0x00
  PG0[0x3F] = 0x90
  PG0[0x40] = 0x04
  PG0[0x41] = 0x00
  
  -- Verify Page 1 Registers --
  PG1[0x02] = 0x04
  PG1[0x0C] = 0x08
  PG1[0x09] = 0x20
  PG1[0x16] = 0x00
  === TAS2505 HP Ready === 
  
  

  Query

  After completing configuration and applying external I²S signals:

  Observed at TAS2505 Pins

  • BCLK

    • Correct 3.3 V logic level

  • WCLK

    • Logic level drops to ~600 mV instead of 3.3 V

  • DIN

    • No valid data

    • Only noise of 1-10 mV during data transmission

  Question

  What could be causing:

  1. The reduced WCLK logic level (600 mV instead of 3.3 V)?

  2. The absence of valid DIN signal at the TAS2505 input?