We are using TMS320C6746 DSP in multiple products.
We are getting issues in some boards with DSP running at 456MHz with core voltage 1.3V. Issue is related to, power-up and crystal/oscillator.
On working board, DSP (TMS320C6746EZWT3) is running at 300MHz with core voltage 1.2V
Clock source is like this.
We never had any problem with this board.
Now, on a new board, DSP (TMS320C6746EZWT4) is expected to run at 456MHz with core voltage 1.3V
It doesn’t boot with every power on. It is random. Sometimes boots up, sometimes doesn’t.
Some boards never boot.
When it doesn’t boot, pressing reset button to processor makes the DSP boot and run.
Same board works fine when we parallel two 18pF caps on each leg. That means 36pF on each leg. Each power On, it boots fine.
We tried,
- single 36pF on each leg – doesn’t work
- single 33pf on each leg – doesn’t work
- 47pf on each leg – doesn’t work
- single 18pF on each leg – doesn’t work
- two 18pF on each leg - works fine
Placing a probe on one leg makes it boot fine.
If core voltage reduced to 1.2V, the board works fine at 456MHz also. But TI recommended core voltage is 1.3V for 456MHz for the part TMS320C6746EZWT4
It looks like core voltage is causing this issue.
TI recommends to use external Osc, as done in c6748 reference design.
Any suggestions.
