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MSP430FG479: About power consumption of charge pump(LDC_A) at low power mode

Part Number: MSP430FG479

Hello,

 

Regarding to charge pump(LDC_A) on MSP430FG479, my customer is asking some question.

They are using MSP430FG479 for battery application and use LCD_A controller with charge pump..

They configure LCD_A module and charge pump as following at low power mode(LPM3).

(Low power mode :LPM3)

LCD_A module off:(LCDO=0)

Charge pump disable(LCDCPEN=0)

Charge pump voltage select(VLCDx) = 2.96V

 

In above case, when MSP430 is set to low power mode, power consumption of some MSP430 is became to high.

A ratio of high current consumption against total device(100set) is 10 (set) /100(set). (one MSP430 using/set)

・Normal power consumption(Vcc:3.3V) at LPM3: less than 1uA

・High power consumption(Vcc:3.3V) at LPM3: more than 10uA (40-50uA average)

 


 

They found out to cause high power consumption by power voltage(Vcc).

And they confirmed threshold range of power supply(Vcc) with high current consumption MSP430.

Please refer below table.

 

 

 

(Note)

・NG-min[V]:minimum voltage of increase current consumption

・NG-max[V]:maximum voltage of increase current consumption

・NG-range[mV]:voltage range of increase current consumption

・Above behavior is happened only in above supply voltage range on high power consumption MSP430.

(It isn’t happened except to above supply voltage range.)

・Regardless of supply voltage, above behavior isn’t happened on normal power consumption MSP430.

 

(Question)

(1) Is there any possible that this behavior will be caused on regulated charge pump/contrast control in MSP430?

If so, is there any possible cause?

(2) When power supply voltage(Vcc) closes to charge pump set voltage, how behavior does MSP430 become?

(3) Is there any possible that this behavior will be caused by individual specificity of device?.

 

Regards,

Tao 2199

  • Hi Tao,

    I will assign our team member to check your problem and reply you later.
  • Hello Tao,

    Please assist me in telling more about the system:

    What I understand so far - is this correct?

    -They are using LPM3
    - You are receiving higher-than average current draw from the MSP430

    Questions:

    - Do you have an LCD attached? If so, please view this similar thread
    -  Did you attach a 4.7uF (or larger) capacitor between LCDCAP and ground? See section 26.2.3, LCD Voltage Selection, page 26-5 of the MSP430x4xx Family User's Guide for more information. 

    Thanks,

    -Chris

  • Hello Chris,

    Thank you for reply.

     

    First, I have mistaken configuration at LPM3.

    At LPM3, they are using charge pump and all LCD segments are off

    Could you please correct to following configuration?

     

    (Low power mode :LPM3)

    LCD_A module off: (LCDON=0)

    All LCD segments off: (LCDSON = 0)

    Charge pump enable: (LCDCPEN=1)

    Charge pump voltage select(VLCDx) =0111( 2.96V)

     

    Next I answered to questions as following. Please see red texts.

     

    What I understand so far - is this correct?

    -They are using LPM3

    ー>Yes. It's correct.

    - You are receiving higher-than average current draw from the MSP430

    ー>Yes. Normal average current is about 1~3uA at LPM3.

    (They judge to OK with less than 5uA.)

     

    Questions:

    - Do you have an LCD attached? If so, please view this similar thread

    ー>Yes. They confirmed current with LCD attached.

    Also, in case of LCD unattached, the current decreased only by 1~2 μA.

    - Did you attach a 4.7uF (or larger) capacitor between LCDCAP and ground? See section 26.2.3, LCD Voltage Selection, page 26-5 of the MSP430x4xx Family User's Guide for more information.

    ー>Yes. They attach a 4.7uF capacitor. Also they tried a 10uF capacitor but current didn’t decreased.

     

    Regards,

    Tao 2199

  • Hi Chris.
    This is an additional information:

    They found some over-current boards in the inspection process of mass-production line. 
    Almost equipments are okay( < 5uA).

    The inspection method is as follows:
    1. Power On.
    2. Wait 4 seconds.  The equipment becomes into LPM3 less than 2 seconds.
    3. Measure the current from power supply.
    4. If current consumption is less than 5uA, this one is okay.

    Best regards,
    Massa

  • Hi Massa,

    Thanks for the information. Please make sure you are not using  a shared LCD pin as a fast toggling output as noted in the Errata (LCDA7).

    What type of LCD is the code configured for? 

    -Chris

  • Hello Chris,

    The answer questions from you are following.

    - Please make sure you are not using a shared LCD pin as a fast toggling output as noted in the Errata (LCDA7).
    (Ans.)
    -> They don’t use a shared LCD pin as a fast toggling output and already have confirmed on Errata (LCDA7).

    - What type of LCD is the code configured for?
    (Ans.)
    -> They use a 1/3 Bias type LCD. (Mux mode is 3 Mux.)

    Regards,
    Tao 2199
  • As additional information.

     

    Today, I have gotten a schematic(attached file) from my customer.

    I have sent to your MSP430 members(Brian -san and Jace -san) directly ,because of internal information.

    Could you please confirm it to your MSP430 members?

     

    Regards,

    Tao 2199

  • I have a couple of questions/suggestions for your issue:

     

    • Check to see Unused pins and unused I/O are configured correctly (section 2.5 of the MSP430x4xx Family User's Guide). Are your unused pins Px.0 to Px.7 switched to port function, output direction via software?

    • Have you tried disabling the charge pump? What is the result?

    Thanks,

    -Chris

  • Hello Chris,

     

    The answer questions from you are following.

     

    1)Check to see Unused pins and unused I/O are configured correctly

    (section 2.5 of the MSP430x4xx Family User's Guide).

    Are your unused pins Px.0 to Px.7 switched to port function, output direction via software?

    (Ans.)

    ・P3.2 -> Port and output setting.

    ・Other unused port (P3.5 to 3.7) isn't set to I/O port /output because S28(P3.4) is used for LCD segment.

    They think that this issue doesn't cause by unused port setting because when charge pump is disabled, the issue isn't happened.

    2)Have you tried disabling the charge pump? What is the result?

    (Ans.)

    They have confirmed that when charge pump was disabled, this issue wasn't happened.

    I'm asking to them about more detail information (register setting).

     

    Regards,

    Tao 2199

  • Closing this thread as it is being handled via direct communication.

    -Chris