TMS320F28377D: TMS320F28377D external crystal schematic

cyan zhou

Part Number: TMS320F28377D

Dear Sir,

Now we are using TMS320F28377D, checking external crystal schematic, then find:

In TMS320F28377D datasheet, page 39 and page 66, montioned, Vssosc pin, When using an external crystal, do not connect this pin to the board ground.

But in AUNCHXL-F28379D User's Guide (SPRUI77B), page 14, Figure 8. P07_F28379D-PWR: VSSOSC PIN connect to the GND. R66 is layout for what?

Can you help me, how can I understand it? what's the difference? Two kinds of connection are both correct, right?

wait for your reply, thanks for your great support.

over 6 years ago

0 Frank Ankapong over 6 years ago

TI__Mastermind 28275 points

Hi Cyan,

Vssosc is a kelvin ground that helps localize the crystal loop current. The launchpad schematic is correct. By default, Q1 is installed and R66 is not installed which means Vssosc(crystal) only goes to Vssosc(device). If Q1 is removed, Vssosc can be connected to ground (this is the reason for R66).

0 cyan zhou over 6 years ago in reply to Frank Ankapong

Expert 1500 points

Thanks for your quick reply.

Also have another problem, this is my schematic and layout, crystal pin2&4 have connected to Vssosc too, is there any problem? or is it necessary pin2&4 must connect to GND?

0 Frank Ankapong over 6 years ago in reply to cyan zhou

TI__Mastermind 28275 points

Cyan,

That should be fine but you should double check the crystal's datasheet to see what the manufacturer recommends for pins 2 and 4.

0 Frank Ankapong over 6 years ago in reply to cyan zhou

TI__Mastermind 28275 points

Hi Cyan,

If you don't have anymore questions on this, i'm going to go ahead and mark it as resolved. Feel free to respond if that's not the case.

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TMS320F28377D: TMS320F28377D external crystal schematic