How much current ''LCD step-up converter'' of STM32L053 consumes?

[ygkim550]

Posted on December 17, 2015 at 08:45

Hello..

  I have a question that How much current  ''LCD step-up converter'' of STM32L053 consumes.  I tested two cases that VLCD power is supplied from internal or external VLCD power.  In Our H/W board, the internal power source for LCD consumed more 10 uA than the external LCD power source.  I know that  if VLCD is supplied from internal source,  the internal step-up converter is used.  And then I wondered that How much current  ''LCD step-up converter'' of STM32L053 consumes.  Searching the data sheet, reference manual, googling.... but I have not found it.Our product have longer sleep time(in STOP mode) than working time,  and during sleep time, our product have to display LCD. So, it is important that I can reduce 10 uA in our product.Could you kelp me know the following- 10 uA is the current of ''LCD step-up converter''?- The internal power source of LCD uses the current more than the external power source.- What is the method that I can reduce the current consumption of the internal power source of LCD?Best Regards Young, Kim

[AvaTar]

Posted on December 17, 2015 at 11:35

Perhaps your converter is inherently less optimal, or is not in the optimal range.

The design of those switched-power-supply converters is a science itself. Losses in the switch (MOSFET), coil, C's and diodes play a significant role, giving each design a rather small range of optimal efficiency. Better ask you hardware designer, and post your question to hardware design fora, too. In my experience most software guys are not so deep into this.

[waclawek.jan]

Posted on December 17, 2015 at 21:23

Something is wrong - according to the datasheet, the LCD module (without LCD itself) should consume slightly above 3uA including the internal step-up converter.

How is your VLCD pin connected? Show us relevant portion of your schematics. JW

[ygkim550]

Posted on March 04, 2016 at 11:49

I want to share my experience.

Could you kelp me know the following

- 10 uA is the current of ''LCD step-up converter''? - The internal power source of LCD uses the current more than the external power source. - What is the method that I can reduce the current consumption of the internal power source of LCD?

  - 10 uA is the current of ''LCD step-up converter''?

    LCD with step-up converter not use 10 uA     reference : data sheet STM32L053C8(September 2015, DocID025844 Rev 5),      p110 ~ 111 6.3.21 LCD controller   ILCD : about 3 uA - typical   1. LCD enabled with 3 V internal step-up active, 1/8 duty, 1/4 bias, division ratio= 64,     all pixels active, no LCD connected.     - The internal power source of LCD uses the current more than the external power source.    I used ULP bit (ultra-low-power) in the PWR_CR register to reduce the current consumption in STOP mode.     reference : 6.2.4 Internal voltage reference (VREFINT) ( RM0367, DocID025274 Rev 3, 04-May-2015)    ''The functions managed through the internal voltage reference (VREFINT) are BOR, PVD, ADC,      HSI48, LCD and comparators. The internal voltage reference (VREFINT) is always enabled      when one of these features is used.      The internal voltage reference consumption is not negligible, in particular in Stop and  Standby mode. To reduce power consumption, the ULP bit (ultra-low-power) in the PWR_CR register  can be set to disable the internal voltage reference.''    There is not a notice whether the ULP bit is available to be off to reduce in STOP with LCD.  and then I use ULP bit with external LCD power.    Today, I check the current consumption after changing ULP function into NOT using with LCD, external VLCD mode.  beecause the recommend the changed RM0367(DocID025274 Rev 4, 19-Feb-2016).    reference : p151 6.2.4 Internal voltage reference (VREFINT) RM0367(DocID025274 Rev 4, 19-Feb-2016).   ''Note: When the LCD is active (LCDEN bit of LCD_CR set), VREFINT is required. ULP bit must       consequently be reset.''     The result of the current comsomption including  LCD controller is simimilar between  internal LCD power(step-up) and external LCD power(VLCD).