BQ78350-R1: IC doesn't sleep when LCD is active

Hi,

In Section 8.3 of the BQ78350-R1A Technical Reference Manual , it describes the conditions that may prevent the device from entering sleep mode. Check that the Sleep Current setting is correct for your system with the LCD enabled. 

Best regards,

Matt

I have checked the current was 0.

Everything has been met with the sleep conditions except Lcd.

When I disable the lcd feature, devide can get into sleep mode. There is no current difference on sense resistor between Lcd is disable or enable.

I have to fix this problem.

My battery should get into sleep mode also shows  segments on Lcd.

What is the LDS_SLEEP_DIS bit set to? Can you send your data flash settings (.gg file can be exported from Data Memory screen of BQStudio)?

Thanks,

Matt

Hi Matt,

LCD_SLEEP_DIS bit was reset at the beginning.

I set that bit high. Then battery get into sleep mode. But LCD didnt show anything. 

I need to figure out LCD activation in sleep mode. Is it possible or not with TI BQ78350-R1?

It should be possible. Can you send me your data flash settings? 

All data flash settings are default. 

I set only LCDEN and LCD_SLEEP_DIS bits. 

I can see the bars on LCD when device is awake. After 5 seconds, device goes into sleep mode but bars disappears too. 

Could you help me to find a way to stay LCD visible when IC in sleep mode?

The LCD_SLEEP_DIS bit should be set to zero. This should leave the display on in SLEEP mode.

Can you let me know if that works?

When LCD_SLEEP_DIS is reset, Ic doesn't get into sleep mode.

There are 3 different results.

1)LCDEN bit is reset. LCD_SLEEP_DIS is reset. All requirements for sleep mode are met. Ic get into sleep mode but Lcd doesn't show the bars. This situation is not suitable for my project.

2)LCDEN bit is set. LCD_SLEEP_DIS is reset. All requirements for sleep mode are met. Ic doesn't get into sleep mode. Lcd shows bars. This situation is not suitable for me.

3)LCDEN bit is set, LCD_SLEEP_DIS is set. All requirements for sleep mode are met. Ic get into sleep mode but LCD bars are not visible in sleep mode. This situation is not suitable for me.

Matt, you said that Ic should get into sleep mode and lcd should be visible when LCDEN is set, LCD_SLEEP_DIS is reset. But it doesn't happen. Is there anything else effect this situation?

What is the status of your PRES pin? Is it tied to GND (unused)? if so, you also need to program the [IN_SYSTEM_SLEEP] bit in the DA Configuration register.

Matt

Hello again,

I had run some current consumption tests. Then I understand that IC get into sleep mode also shows segments on LCD. But the current was higher than I expected.

LCD effects current consumption too much.

When I disable LCD, my card spends 0.1mA in sleep mode, 0.6mA in operation mode.

But when I enable LCD, my card spends 0.6mA in sleep mode, 1mA in operation mode.

So it means I misjudge about sleep mode. IC shows segments in sleep mode. My LCD spends current.

But I need to learn why my lcd spends too much? I use same LCD with BQ20z655-R1. Bq20z655-r1 spends less current using LCD.

Hi,

Unfortunately the LCD on the BQ78350 is known for increasing the current consumption considerably. Reducing the refresh rate or using the LCD in 4-bar mode may both help to reduce the current. I do not know why this specific device uses much higher current, but suspect it may be an efficiency issue with the firmware.

Another thread related to this issue:

https://e2e.ti.com/support/power-management/f/196/t/907032?BQ78350-R1-High-Current-Consumption-LCD-Blinking-Issue

Best regards,

Matt

I will not be suprised if TI says IC spend less current when I disconnect cells :)

Thank you Matt. You always spend your time for my problems. 

If LCD cause higher current consumption with BQ78350, it means BQ78350 is not able to drive LCD. Its not usefull if it drains the battery :)