LPC845: can't go below 25µA in power down mode

[v_canoz]

Hello,

I'm trying to reach the current stated in the datasheet of the LPC845 in power down mode.

I'm working at Tamb = 25°C, Vdd = 3.3V, QFN33 package.

This is the code I run :

#include "fsl_debug_console.h"
#include "board.h"
#include "fsl_common.h"
#include "fsl_power.h"
#include "fsl_usart.h"
#include "fsl_syscon.h"
#include "fsl_wkt.h"
#include "fsl_iocon.h"
#include "pin_mux.h"
#include <stdbool.h>
#include "fsl_pint.h"
#include "fsl_swm.h"

/*
* Setup a GPIO input pin as wakeup source.
*/

void DEMO_PreEnterLowPower(void)
{
/* switch main clock source to FRO18M */
POWER_DisablePD(kPDRUNCFG_PD_FRO_OUT);
POWER_DisablePD(kPDRUNCFG_PD_FRO);
CLOCK_SetMainClkSrc(kCLOCK_MainClkSrcFro);
CLOCK_SetFroOscFreq(kCLOCK_FroOscOut18M);
CLOCK_SetFroOutClkSrc(kCLOCK_FroSrcFroOsc);

/* system osc power down
* application should decide if more part need to power down to achieve better power consumption
* */
POWER_EnablePD(kPDRUNCFG_PD_SYSOSC);
CLOCK_DisableClock(kCLOCK_Iocon);
CLOCK_DisableClock(kCLOCK_Uart0);
}

/*!
* @brief Main function
*/
int main(void)
{
BOARD_BootClockPll24M();

GPIO_PortInit(GPIO, 0);
CLOCK_EnableClock(kCLOCK_Iocon);

/* disable all pull ups */
for (int i =0; i< 52; i++)
{
if (i == 12) continue; //reserved
if (i == 19) continue; //reserved
if (i > 30 && i <35) continue; //reserved
if (i > 35 && i <50) continue; //reserved
IOCON->PIO[i] &= ~(IOCON_PIO_MODE_MASK);
IOCON->PIO[i] &= ~(IOCON_PIO_HYS_MASK);
}

CLOCK_DisableClock(kCLOCK_Iocon);

for (int i =0; i< 28; i++)
{
if (i == 24)// || i == 6)
{
//UART RX pin set to input
GPIO_PinInit(GPIO, 0, i, &(gpio_pin_config_t){kGPIO_DigitalInput, 0});
continue;
}
if (i == 6)
{
//S2LP shutdown must be set
GPIO_PinInit(GPIO, 0, i, &(gpio_pin_config_t){kGPIO_DigitalOutput, 1});
continue;
}
GPIO_PinInit(GPIO, 0, i, &(gpio_pin_config_t){kGPIO_DigitalOutput, 0});
}

DEMO_PreEnterLowPower();

/* disable SWD */
CLOCK_EnableClock(kCLOCK_Swm);
SWM0->PINENABLE0 = 0xFFFFFDFF; //demap everything except reset
SWM0->PINENABLE1 = 0x7F;
CLOCK_DisableClock(kCLOCK_Swm);
CLOCK_DisableClock(kCLOCK_Gpio0);

POWER_EnterPowerDown(0);

return 1;
}

1. I've disabled all the pull ups.
2. All the pins are set to output at low level, except 1 gpio as input (level is maintained high by an external device which current does not contribute to my measurement)  and 1 gpio as output to 1 (load current < 50nA). I suppose this high level could add a few µA, but currently the power consumption is way too high : about 25µA after detaching the debugger.
3. BOD and WDT are disabled
4. I need only a wake up on reset pin (by the way, does the reset wake-up the chip, or does it simply reset it as usual?)

What am I missing?

[phatpaul]

FYI for the community:

We spent a lot of time trying to achieve the 1.5uA consumption in Power-Down mode on LPC845M301JHI33, but we couldn't get it lower than ~6uA.  We finally got confirmation from NXP that the LPC845 in 33-pin package draws more current than the higher-pin-count parts. 

NXP's response was:

33pin package power down mode typical power consumption is higher than 48pin, which is normal but currently they don't have data in DS

The suggestion from application team is " using the 48pin package to replace the 33pin package".

Hope this note saves some headache and wasted time for someone else...

[phidiawang]

• I have solved this problem, please see the attachment

• 
• 
• 
• 

[ZhangJennie]

Hi wang qifei

I got time to test your power_mode_switch_lpc.c today -- replace the same file with it under SDK2.8  power_mode_switch_lpc demo . but the result is not as yours, Could you please upload your project here?

Thanks

Jun Zhang

[phidiawang]

I tested  it again(LPCXpresso845MAX),it's 1.17uA.

I disconnected the SJ6,and concatenated the multimeter between 2 pins of  JP2.

[ZhangJennie]

I tested it again. 

I think the key issue of getting 43.6uA in power down mode is that IDE is interactive with LPC845 via SWD background, LPC845 debug module was not fully power down. I just tested below code on demo code (very simple):

after downloading code, disconnected power supply, then powered on board again. the current went down to 1.5uA:

Jun Zhang

[ZhangJennie]

Good to know.

Thanks for the sharing,

Jun Zhang

[v_canoz]

Hello Jun,

The code above is extracted from the example you've mentioned. Actually the power consumption is about the same with the example.

By the way, the mode 4 (deep power down) does not work on my side, current does not go below 2mA in this mode (but this is not the problem here)

In the code I posted above, is there something missing, did I forget to disable something ?

Thanks,

[ZhangJennie]

 I checked sample code power down mode, temperature is around 26C. it's 43.6 uA. It's normal. please check the same.

[v_canoz]

Hello,

Ok, but what modifications do I have to do in the code, in order to be able to reach the current stated in page 48 of the datasheet ?

Power-down mode states 1.5µA typ current at 25°C...

Thank you,

Victor

[ZhangJennie]

Victor,

in order to get the datasheet value, you need 

- IDD measurements were performed with ALL pins configured as GPIO outputs driven LOW and pull-up resistors disabled.

- ALL oscillators and analog blocks turned off.

the SDK demo should not do all above initialization. 

BTW, I test deep power down mode with SDK demo. the Id is 1.4uA

Have a great day,
Jun Zhang

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[v_canoz]

Hello Jun,

Can you provide the project used for reaching this current ?

I honestly don't know what I forget to disable...

Thanks !

[ZhangJennie]

Sorry, I don't have the testing project for datasheet data.

User needs to follow this to implement by self.

Thanks,

Jun Zhang

[ZhangJennie]

Hi

I suggest test your board with MCUXpresso SDK demo

SDK_LPCXpresso845MAX\boards\lpcxpresso845max\demo_apps\power_mode_switch_lpc\

This demo has 4 options:
1. Sleep mode

2. Deep Sleep mode

3. Power Down mode

4. Deep power down mode

select power download mode, test if the current is as your expected.

Have a nice day,

Jun Zhang