TPS6594-Q1: TPS6594+LP8764 can not work

wang kun

Prodigy 100 points

Part Number: TPS6594-Q1
Other Parts Discussed in Thread: DRA829, TDA4VM

Hi TI expert,

Hardware platformL TDA4+ TPS65941213RWERQ1+LP876411B4RQKRQ1, Reference PDN: DRA829_TDA4VM_Leo2.0_Hera2.0_PDN-1A_v0.16;

Question : BUCK and LDO are not output ,all BUCK and LDO have 15 pulses after power up .All The timing is normal .

Only one timing does not match the PDN:SOC_PWR_EN and EN_3V3IO_LDSW,as shown below.actual test result is 6.8ms.

SCHEMATIC

values of all registers :

please give us some debug suggestion,thanks .

over 2 years ago

0 Michael Gambrill over 2 years ago

TI__Genius 17945 points

The 6.8ms seems long. Can you share a scope capture that includes the SOC_PWR_EN, VCCA, and EN_3V3IO_LDSW signals?

Can you read the LP8764 device registers as well?

Is nINT toggling during this time?

0 wang kun over 2 years ago in reply to Michael Gambrill

Prodigy 100 points

0x4c is the address of LP8764,as below :

please ask a question ,which registers do we focus on?

SOC_PWR_EN, VCCA, and EN_3V3IO_LDSW timing.

0 wang kun over 2 years ago in reply to wang kun

Prodigy 100 points

0 Michael Gambrill over 2 years ago in reply to wang kun

TI__Genius 17945 points

Hello Wang,

For both devices, the registers of concern are 0x5A to 0x6C. These are the interrupt registers and if you compare their values against the datasheet, they are always the best place to start looking for a problem.

I've also just noticed your schematic has two VCCA lines. Are these scope shots of VCCA_TDA4_A_3V3?

Both your scope captures register read out of the LP8764 indicate the spikes on your VCCA line are causing a VCCA_OV interrupt that immediately turns off the rails.

Please try setting SOC_PWR_EN high after VCCA_TDA4_A_3V3 has turned on all the way.

Are C15004 and C15005 close to pin 18 of the LP8764? Could you increase this capacitance temporarily for debugging purposes?

Can you send a zoomed in scope shot of the voltage spikes on VCCA_TDA4_A_3V3?

0 wang kun over 2 years ago in reply to Michael Gambrill

Prodigy 100 points

Hi Michael:

I have increased the capacitance here(C15004 and C15005) to 47uf ，and then the register of LP8764 does not report the VCCA_OV error .as below .

but the register of TPS6594 report this error ,BUCK3_SC_INT.

The FB of buck3 is grounded through 0ohm,is it possible that this problem is caused??

Please try setting SOC_PWR_EN high after VCCA_TDA4_A_3V3 has turned on all the way.

-->this problem i have tested,but it still did not work.

The address of LP8764 written in EVM and PDN is inconsistent .

I'm not sure whether there is a problem with the OTP configuration.Because this LP8764 is a sample, not a mass production chip.

(the version of reference PDN is :DRA829_TDA4VM_Leo2.0_Hera2.0_PDN-1A_v0.16)

Or can I modify the value of the register and force two PMICs to output.

0 Michael Gambrill over 2 years ago in reply to wang kun

TI__Genius 17945 points

wang kun said:
The FB of buck3 is grounded through 0ohm,is it possible that this problem is caused??

Yes, this is the cause of the problem. For this PDN, TPS65941213's FB3 pin is expecting 3.3V. Please see Note 9a in the PDN reference document.