LPC845 Power-Down

[DirkP]

Hi All,

I'm busy on a custom made board to develop a remote control using the LPC-845.

However, I'm unable to get the system in a mode that consumes the power as stated in the device sheets.

In power down mode it will not go below 500 uA.

So I took the LPC845-BRK board to test (no peripheral devices attached and easy to measure at the JP1 jumper)

Still no luck, tried everything (see attached source code) to see if I forgot something.

Also 500 uA at power-down, 320 uA at deep power-down.

So did I forget something ?

Best regards,
Dirk.

[ZhangJennie]

Hello DirkP ,

I ever wrote article on this topic, which guides how to measure current correctly in power down mode with LPCXpresso845MAX board. 

https://community.nxp.com/t5/LPC-Microcontrollers-Knowledge/LPC-Why-My-Low-Power-Current-Is-Differen...

Hope this will help you,

Jun Zhang

[DirkP]

Hello Jun,

Thanks for your response.

I did read your article and it explains why 1.5 uA is difficult to get.

But 60 uA should easily be possible and 500 uA is a long way from it

Dirk.

[ZhangJennie]

Hi DirkP 

It seems you are using custom board.

There are two points we need to check.

1. don't connect debugger. measure the current in standalone mode

2.  set the unused GPIO as a pull-up input.

If the problem persists, measure the individual gpio. which pin has higter current?

Have a nice day

Jun Zhang

[DirkP]

Hi Jun,

I put all pins to input with pull-up (see attached source code).

Also used a wallplug socket (to USB 5Volt)  to be sure no connection was made to the programming/terminal socket.

As I expected, current dropped a bit (on account of the terminal socket) but not much:

The board itself is a regular breakout board from NXP:

As I said, I don't have connections to the GPIO pins, so how to measure ?

Best regards,

Dirk.

[ZhangJennie]

Hi DirkP ,

I don't have a bRK board to test. 

the statistics are based on the condition of Vdd=3.3 . and did you test if the result is the same for other low power mode?

Thanks,

Jun Zhang

[DirkP]

Hi Jun,

Power comes from the usb but the measurepoints are on the chip itself so that shouldn't be a problem (see attachment).

Power is:

Regular  Operation: 7.04 mA

Sleep: 2.60 mA

Deep Sleep: 0.67 mA

Power Down: 0.46 mA

Deep Power Down: 0.32 mA

I must say, it will be difficult to investigate if you don't have the hardware itself.

It's just a standard breakout board tho.

Best regards,

Dirk.

[ZhangJennie]

Hi DirkP 

I checked manual. there is one point, please check if you are aware: A narrow
PCB trace connects the two holes for JP1, so this must be cut with a knife before installing
the header in order for an ammeter to be able to measure the current.

Have a nice day,

Jun Zhang

[DirkP]

Hello Jun,

Of course I cut this trace, otherwise I would measure no current at all

Best regards,

Dirk.

[ZhangJennie · Accepted solution]

HI @DirkP  

I found a BRK board and tested it. I can reproduce the problem. The current comsuption is on PIO0_07 pin and Vdda to Vssa through RV1. This additional comsuption could be at least 0.3mA.  To verify it, removing RV1 on this pin can reduce the current from 0.36mA to 42.5 uA on my side

Hope this will help you.

Jun Zhang

[DirkP]

Hi Jun,

You're quite right, somehow I overlooked this voltage divider.

Thanks for the help.

Best regards,

Dirk.