MSP430F67471A: Question about LCD power consumption

Hi Keirs,

In addition to the current values, I suggest that you take a look at the following document: www.ti.com/lit/an/slaa654a/slaa654a.pdf

This covers many of the considerations that you should take into account when connecting the LCD to the MSP430 and choosing the correct register settings.

Regards,
Nathan

Hi Keirs,

1. The value in the datasheet (ILPM 3 LCD, CP) is the typical value. The other document is simply stating that ICC, Peak, CP is the maximum value that this current can be.
2. To determine how much the average current will decrease, you will need to use the time to charge C_LCD and the peak current, as stated in the other document. Please find these values in table 5-38 of the datasheet.
3. There should not be. As stated in the other document, when charge pump is not at its peak current, the module will be in its lower current state.

Regards,

Nathan

Hi Nathan,

the module will be in its lower current state.
->When it is "lower current state", does the current consumption be ILPM 3 LCD, CP(when charge pump is enabled)? 

When measuring the consumption current of Vcc under the following conditions, it was 17 uA. The maximum consumption current consumed by the connected LCD panel is 4 uA. I assumed supply cutrrent is :total of the ILPM 3 LCD, CP(3.2uA) + LCD panel supply current(4uA), but what other points do you think is consuming current consumption?

・All inputs are tied to 0 V or to VCC
・The currents are defined with crystal capacity of a load capacitance of 12.5 pF
・RTC is disabled
・ACLK = low frequency crystal operation (XTS = 0, XT 1 DRIVE x = 0)
・CPUOFF = 1, SCG 0 = 1, SCG 1 = 1, OSCOFF = 0 (LPM 3); fACLK = 32768 Hz, fMCLK = fSMCLK = fDCO = 0 MHz
・SVS is disabled
・LCDMx = 10, LCDREXT = 0, LCDEXTBIAS = 0 (internal biasing), VLCDREFx = 3.02 V, Flcd = 384 Hz

Regards,

Hi NathanS,

Thank you for your reply.

Yes, the lower current state is when the device is in LPM3.

Did you take the peak current into account (as discussed above)?

-> No. Is it correct by understanding as shown in the figure below? Also, could you tell me how to calculate the marked part?

　How does the ICP, Load of data sheet table 5-38 affect the following figure?

Are these measurements taken while writing to the LCD?

->Yes, writing to the LCD as follows.

LCDM1 0x77
LCDM2 0x77
LCDM3 0x77
LCDM4 0x77 
LCDM5 0x77 
LCDM6 0x77 
LCDM7 0x77
LCDM8 0x77 
LCDM9 0x07 

LCDM10～LCDM40 =0x00

LCD Blinking Memory is All 0.

Regards,

Hi Nathean,

Thank you for your reply.

I do not see the time that the charge pump is off in the datasheet or user's guide, so I will try to find that information. 

->I am waiting for new information about your investigation.

Please keep in mind that the current that you are calculating is only what is being consumed by the MSP430. The LCD itself will be drawing current as well, and you will need to find out how much current that is drawing.

->By connecting the LCD and the MSP 430, what additional current can be considered in addition to the current consumption measured by each?

Do you have any updates on my question below?

>How does the ICP, Load of data sheet table 5-38 affect the following figure?

Regards,

Hi Nathan,

Thank you for your reply.

I understand.

I'm waiting for your contact.

Connecting the LCD to the MSP430 will not necessarily draw extra current, but it is important to keep in mind that many other factors will affect your current such as the LCD glass and the number of segments that you are driving.

->If there are other possible factors, can you tell me specifically?

   What can I do to reduce power consumption when handling LCD with MSP 430?

Regards,

Hi Nathan,

Thank you so much for checking out.

I understand.

I will try to examine the current consumption based on the measurement and the advice I gave you.

Regards,