LPC54606 VBAT current consumption

[wangchunzhongwa]

Hi,

We designed a board with LPC54606J512.The VBAT pin was supplied by one rechargeable lithium battery,so when the board is powered down,the VBAT is still powered on and other power pins are powered down.The lithium battery's capacity is 5.5mAh.But we found the VBAT was powered down in 2 weeks board testing.I tested the VDD pin's voltage was about 0.9V while the VBAT was 2.8V.The VDD is designed 2.8V and the lithium battery is charged when the board is powered on.

So I want to ask what's the VBAT current consumption in my board when powered down? I found table 18 in UM10912 but I doubt my board's VBAT current consumption.

Thank you!

[wangchunzhongwa]

Hi

Thanks for your reply.

After I removed the resistor pulled the RESET pin up to VDD,the VDD was 0V and the VBAT current was less than 1uA when the board was powered down while the VBAT was 2.8V.The problem was sovled.But I found the sentence"If VBAT> VDD, the external reset pin must be floating to prevent high VBAT leakage."was added in datasheet revision v.2.4 that release date 20180524.So I wonder if my question caused the release?

[sergedemaseneer]

I don't know if it is of any value but i found this in the data sheet page 92:

[3] If VBAT> VDD, the external reset pin must be floating to prevent high VBAT leakage

So what is the state of this external reset pin when VDD is switched off?

[wangchunzhongwa]

The VBAT current  I tested when board was powered down was 19uA! Is this normal?

[jeremyzhou]

Hi,

Thanks for your reply.

I'd like to know whether the MCU enter some low power mode after the MCU is supplied by lithium battery.

If not, the above screenshot is not in accord with your implementation.

Have a great day.

TIC

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[wangchunzhongwa]

Hi

There‘s a switch in the board to shut down all the power except the VBAT.Before the switch shut down,the LPC54606 is working normally.After the switch shut down,only the VBAT is powered by the  lithium battery.

Thank you!

[jeremyzhou]

Hi wang chunzhong wang,

Thanks for your reply.

However I still having some inquiries about the implementation and need you help.

1. After the switch shut down all the power except the VBAT, does it mean the lithium battery only connect the VBAT or include other power pins simultaneously?

2. You said the the LPC54606 is working normally when all power is removed except the VBAT, does it mean the MCU still are executing coding?

Have a great day.i

TIC

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[wangchunzhongwa]

Hi

1.After the switch shut down,the lithium battery only connect the VBAT,no other power pins are powered by the lithium battery.

2.I think the MCU shouldn't execute coding because all power of MCU is shut down except the VBAT.

Thank you!

[jeremyzhou]

Hi wang chunzhong wang,

Thanks for your reply.

Before you shut down the switch, whether the MCU enter the deep-power down mode, if not, please give a try.

I think it's appropriate way of reducing the power consumption.

Hope it helps.

Have a great day.

TIC

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[jeremyzhou]

Hi,

Thank you for your interest in NXP Semiconductor products and 

the opportunity to serve you.

I was wondering if you can share the schematic of your aboard, as I'd like to know how you design the VBAT supply circuit.

Have a great day,

TIC

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[wangchunzhongwa]

The VDD33 was generated by one DC-DC power supply.The VBAT was directly connected to the VBAT pin of LPC54606.

Thank you!