DLPC3470: DLPC3470 Crystal Oscillator not running

Scott Grodevant

Part Number: DLPC3470
Other Parts Discussed in Thread: DLPA2005

Hi All,

I am debugging a projector board that employs the DLPC3470 and DLPA2005. I am at the point of setting the projector on signal to enable the system, but there is no activity on the 3470's SPI bus that is connected to a Flash ROM that contains its firmware (programmed ahead of mounting). The 2005 is producing its non-switches voltages and the RESETZ signal correctly (low when proj_on is low) and goes high after proj_on switches high.

I am using the data sheet's recommended crystal circuit: 10pF load caps, 100 ohm series resistance and a 953K shunt resistance. The crystal is a TXC 24 MHz fundamental with 10 pF recommended loading capacitors. I have attached the PCB layout.

The 1.1, 1.8, 2.5 and 3.3V supplies are OK. The +10 supply sits at 2.6, and 6V supply is at ground and the -14V supply is about ground jumps to about a volt when the projector on signal changes.

I assume the crystal should be running when power is on the 3470, that it's not enabled with projector on or any other signal other than the logic supply voltage.

Any thoughts are must appreciated.

over 6 years ago

0 Kyle Rakos over 6 years ago

TI__Mastermind 20045 points

Hello Scott,

Could you please confirm which signals you are referring to when you mean +10V, 6V, and -14V? Do you also have waveforms of the crystal input? Also please confirm what firmware you loaded on the flash.

Thanks,
Kyle

0 Scott Grodevant over 6 years ago in reply to Kyle Rakos

Intellectual 925 points

Hi Kyle,

These are the supplies generated by the DLPA2005: VCORE (1.1), VSPI (1.8), V2V5 (2.5), VRST(-14 *), VOFS(+10 *), V6V(6V *), VBIAS(+15 *). Those I've marked with * are not working properly. I assume that's because the 2005 hasn't been commanded by the 3470 to enable them (e.g. isn't in active mode).

The crystal isn't oscillating. The input side (PLLREFIN H1) sits at about 1V DC, the output side (PLLREFOUT J1) sits at ground. I'll be verifying that J1 isn't shorted to ground, since I'd expect it to be at some positive voltage (output of a logic inverter). I tried yesterday removing the loading cap from the J1 side, which of course didn't make any difference.

Not that it matters at this point, but the firmware in the Flash rom is the code you sent me a few weeks back (ASIC routing option 4). But since none of the SPI signals run, I can't imagine it matters what's in Flash at this point.

Thanks,
Scott

0 Kyle Rakos over 6 years ago in reply to Scott Grodevant

TI__Mastermind 20045 points

Hello Scott,

Thank you for confirming. I would expect the supplies you mentioned to not be initialized until the controller boots up (as you also suspected).

Are you also able to share your schematic. Specifically I'd like to take a look at the crystal. If VCORE, VSPI, and V2V5 are operating correctly (along with your 1.8V input to the controller) I would expect the oscillator to be active.

Thanks,
Kyle

0 Scott Grodevant over 6 years ago in reply to Kyle Rakos

Intellectual 925 points

Hi Kyle,

I've attached the schematic.

Scott

0 Kyle Rakos over 6 years ago in reply to Scott Grodevant

TI__Mastermind 20045 points

Hello Scott,

Are you able to upload a PDF? The image that got uploaded is too low of a resolution. If you also have a version with the pins labeled on the DLPC3470 that would help.

Thanks,
Kyle

0 Scott Grodevant over 6 years ago in reply to Kyle Rakos

Intellectual 925 points

AK-05-00277_A Interoral Projector board schematic.pdf

Hi Kyle,

Can't tell if this worked, but it should have.

Scott

0 Scott Grodevant over 6 years ago in reply to Scott Grodevant

Intellectual 925 points

Hi Kyle,

Apparently I have a bad board. I brought up a second board whose oscillator is running.

Thanks for your help,

Scott

DLP®︎ products

DLP products forum

DLPC3470: DLPC3470 Crystal Oscillator not running