TPS65185: How to properly set up a new power up sequence and activate it

Martin Fasani

Part Number: TPS65185

Tool/software:

Hello TI engineers and people on board this awesome knowledge forum!

I'm Martin a hardware developer from Spain that helps in https://github.com/vroland/epdiy-hardware epdiy project that is an open source parallel Eink controller (Using Espressif S3 MCU as core driver)

Recently some users have tried Eink Carta 1300 displays that seem to have a different power-up sequence that the TPS65185 standard:

ED103MC1 is the display I'm testing with. (With older display non Carta 1300 everything works. )
Power Rails must be sequenced in the following order

VSS → VDD → VNEG → VPOS (Source driver) → VCOM
VSS → VDD → VGL → VGH (Gate driver)

In order to achieve that I've read the relevant part in the datasheet and also asked the articial inteligence that was not intelligent enough to give a proper answer.

PSEUDO CODE Tested:

void tps_set_power_seq(i2c_port_t i2c_num, uint8_t seq) {

 tps_write_register(i2c_num, TPS_REG_UPSEQ0, 0x9c); // NOT CHANGE 0x9C

 tps_write_register(i2c_num, TPS_REG_ENABLE, 0x00); // Standby

 vTaskDelay(pdMS_TO_TICKS(10));

 tps_write_register(i2c_num, TPS_REG_ENABLE, 0x01); // Active

}

My question is:
After changing the UPSEQ 0x09 register is there any other step to do to "activate" this new power sequence?

Running that code trying to make a different power sequence I get in the logs:

INT1 (0x07): 0x00
INT2 (0x08): 0x02
VNEG_UV: VNEG undervoltage
VADJ (0x02): 0x03
VPOS/VNEG: ±15.000V
VCOM1 (0x03): 0xA0
VCOM2 (0x04): 0x00
VCOM voltage: -1.60V
ACQ bit: CLEAR
PROG bit: CLEAR
HiZ bit: CLEAR
AVG: 1x measurements
TMST_VALUE (0x00): 0x00
Temperature: 0°C
TMST1 (0x0D): 0x20
READ_THERM: IDLE
CONV_END: DONE
DT threshold: 2°C
TMST2 (0x0E): 0x78
COLD threshold: 0°C
HOT threshold: 50°C
UPSEQ0 (0x09): 0xE4
VDDH_UP: STROBE4
VPOS_UP: STROBE3
VEE_UP: STROBE2
VNEG_UP: STROBE1

So I'm actually not changing any STROBE order that is the default that works with most Eink displays.

Can you please tell me if I'm forgetting to do something obvious?
Many thanks in advance

5 days ago

0 Sarah Lao 4 days ago

TI__Genius 9117 points

Hi Martin,

Thanks for reaching out on E2E!

For UPSEQ0 to be written properly, the device should be in Standby mode before the write.
(Wakeup pin HIGH, while PWRUP pin is low)

And to set the device into active mode, specifically bit 7 of the ENABLE register needs to be set to '1', i.e. a value of 0x80 (1000 0000) should be written to TPS_REG_ENABLE

To debug, could you try:

Setting the device in standby mode by setting WAKEUP pin HIGH ,and keeping PWRUP pin LOW
Write 0x9C to UPSEQ0
Do an immediate readback/log of UPSEQ0 to check if 0x9C was written properly
Set device to Active mode by either writing 0x80 to ENABLE register, or pulling PWRUP pin HIGH
Check UPSEQ0 and strobe sequence.

Let me know if you have any trouble with the above steps.

Best Regards,
Sarah

0 Martin Fasani 4 days ago in reply to Sarah Lao

Prodigy 10 points

Hello Sarah,

many thanks for your answer. I was getting the wrong I2C commands that's my bad. I tried what you recommend in my code:

void tps_set_power_seq(i2c_port_t i2c_num, uint8_t seq) {
    tps_write_register(i2c_num, TPS_REG_ENABLE, 0x40); // Standby mode
    // WAKE UP mode for PMIC
    ESP_ERROR_CHECK(pca9555_set_value(I2C_NUM_0, (PCA_PIN_PC15 >> 8), 1)); // WAKE up
    ESP_ERROR_CHECK(pca9555_set_value(I2C_NUM_0, (PCA_PIN_PC13 >> 8), 0)); // PWR down
    vTaskDelay(1);
    
    // power up order
    tps_write_register(i2c_num, TPS_REG_UPSEQ1, 0x56);
    tps_write_register(i2c_num, TPS_REG_UPSEQ0, seq);  // does NOT CHANGE to 0x9C
    printf("Setting TPS_REG_UPSEQ0 to %x\n",seq);
    
    tps_write_register(i2c_num, TPS_REG_VADJ, 0x04);   // CHANGES!
    //tps_write_register(i2c_num, TPS_REG_ENABLE, 0x40); // Standby mode
    tps_write_register(i2c_num, TPS_REG_ENABLE, 0x80); // Active
}

But sadly I still cannot make it work.
In my PCB the WAKEUP and PWRUP signals are connected via an IO expander that is why it looks that way. I can change successfully other config paramenters like:

TPS_REG_VADJ to 0x04. And it does change correctly. But the UPSEQ0 and 1 still resist. No matter what I do they seem to have the same value. Tomorrow will try again. Many thanks for your help!

+1 Sarah Lao 3 days ago in reply to Martin Fasani

TI__Genius 9117 points

Hi Martin,

Thanks for the update! Do you have any other updates on how this is working now?

It is strange that you are able to write to other registers like VADJ, but not the UPSEQ registers...
Out of curiosity, are the DOWNSEQ registers able to be written to?

I will say, I think the
PWRUP should be low before WAKEUP is pulled high,
and then Standby bit (0x40 to ENABLE) would only need to be set if the device is already in ACTIVE mode prior to your code snippet.

Best Regards,
Sarah

0 Martin Fasani 2 days ago in reply to Sarah Lao

Prodigy 10 points

Thanks Sarah!

> I think the PWRUP should be low before WAKEUP is pulled high,

This is actually the key solution. And I also cleanup from any other initiallization any power off / power on that touches TPS PMIC leaving as first command the update function.
Sadly even if I can control power up sequence now this Carta 1300 display still doesn't work, is the first that does not work, if you check https://github.com/vroland/epdiy there is a list of over 20 display panels (Different resolution and bit-widths) and all work perfectly fine with TPS65185.

What recommendations would you give to start looking into, when TPS65185 reports VNEG undervoltage ?
Since in other same size displays works perfectly, what would be different in this particular Carta 1300, that it cannot stabilize the line ?
FACT is: Waveshare has a 10.3 ITE8951 controller that also uses same PMIC, a friend tried it with that upon my request, and seems to work correctly. Can it be that there is an error in our design for this specific panel?

In this schematic you can see how is the latest implementation of TI PMIC:

https://vroland.github.io/epdiy-hardware/build/boards/epdiy-v7_schematic.pdf

Thanks a lot for your great feedback. Now I fully understand how this works!

0 Ishtiaque Panhwar 1 day ago in reply to Martin Fasani

TI__Genius 16260 points

Hi Martin,

Due to national holiday in US, most of the experts are out of office today. Please expect delay in response. Thanks for your patience!

Regards,

Ishtiaque

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TPS65185: How to properly set up a new power up sequence and activate it