TPS65987D: external power for flash memory

Eriks Austrums

Part Number: TPS65987D

Hello,

We want to program the flash memory for TPS65987D from a connector and use external 3.3V from the connector to power it , then , when the flash is programmed , power it from LDO_3V3 as recommended.

The TPS65987D is in dead battery mode "BP_NoWait". So after we connect the USB-C cable it can read the flash and load the configs.

My question is, how to connect the external 3.3V from connector , to power the flash memory?

Should the connection be : external 3.3V to LDO_3V3 that is connected to flash memory , or external 3.3V to VIN_3V3 pin that's gonna supply the power to LDO_3V3 and connect the flash memory to LDO_3V3?

Thanks in advance,

Eriks

over 5 years ago

0 Kedar_Sirdeshpande over 5 years ago

TI__Expert 3370 points

Hi Eriks,

Can you elaborate on "We want to program the flash memory for TPS65987D from a connector and use external 3.3V from the connector to power it" ?

Did you take a look at some of our reference designs here: https://www.ti.com/product/TPS65987D ?

Regards,
Kedar

0 Eriks Austrums over 5 years ago in reply to Kedar_Sirdeshpande

Intellectual 675 points

Hi,

Yes, we looked at some of the reference designs.

But we want to write the firmware to the flash only one time without powering on the entire system.

>> Can you elaborate on "We want to program the flash memory for TPS65987D from a connector and use external 3.3V from the connector to power it" ?

We connect the SPI programmer through a connector and power the flash 3.3V from that connector without powering the rest of the system. So we can write the firmware to it and then start the whole system by using the USB-C cable so that the TPS65987D starts with configs from flash.

Regards,

Eriks

0 Kedar_Sirdeshpande over 5 years ago in reply to Eriks Austrums

TI__Expert 3370 points

Hi Eriks,

The SPI lines are used by the PD controller once during boot and not after. If it does not find a valid patch (blank/corrupted flash), it would boot into default using ADCIN settings. Once the boot is complete, you can use only the SPI lines to program the flash. A cold start will try to load the patch again. This is the way it works in the EVM.

Please take a look at the reference design where the SPI lines are brought out to a header: https://www.ti.com/lit/ug/tiduef4/tiduef4.pdf?ts=1595434563292&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS65987D

Is there a particular reason why the PD controller needs to be powered off?

Regards,
Kedar

0 Eriks Austrums over 5 years ago in reply to Kedar_Sirdeshpande

Intellectual 675 points

Hi,

It's so after the assembly It's not needed for 2 cables to program the board.

So the question still is, can we connect an external 3.3V to LDO_3V3 while the TPS65987D is not powered , or should we connect the external 3.3V to VIN_3V3 ?

Regards,

Eriks

0 Kedar_Sirdeshpande over 5 years ago in reply to Eriks Austrums

TI__Expert 3370 points

HI Eriks,

So, your arrangement would be to power up only the flash, and not the PD controller.

In the EVM's schematic EEPROM is directly powered by the LDO_3V3 pin. This means the PD controller is powered up first.

Let me check if any isolation would be required for your case.

Regards,
Kedar

0 Kedar_Sirdeshpande over 5 years ago in reply to Kedar_Sirdeshpande

TI__Expert 3370 points

Hi Eriks,

You can use a diode to block the 3V3 coming from the connector to the LDO_3V3.

This works well if your EEPROM's minimum operating voltage is slightly lower, say 2.7 Volts or so.

Regards,
Kedar

Interface

Interface forum

TPS65987D: external power for flash memory