PN7462AU -Hard Power Down Mode

[sanath_rai]

Hello ,

I have been  working on PN7462 NFC controller.i am building my application on Door access code.

we have designed our own custom board and we are at a stage we are looking at power consumption part and 

I have gone through the hardware user document  (UM10858) and the software user manual(UM10913) .we feel that hard power down mode is the best mode for the lowest power consumption.but i have a doubt here.we found its by using the RST_N pin.Any example will be helpful .

How can we put the on PN7462 into hard power mode  using the software or just by making the RST_N pin low by giving it to some GPIO?

In document UM10858 section 8.3.5 it's given as below

8.3.5 Hard Power Down Mode
This is the lowest power mode allowing for the highest reduction of the power
consumption. All clocks are turned off, all LDOs are turned off, except the MLDO which is
set to the low power mode
The PN7462 family enters the Hard Power Down mode when RST_N is set to zero or the
VBUS voltage is going below 2.3 V.
The PN7462 family exits the Hard Power Down mode, when RST_N pin is set to high
level and VBUS voltage goes above 2.3 V

But in section 3.3.1.4 in UM10913 (software user manual) it is given as below

RST_N pin behavior
The SecRow contains the bits that control the behavior of HW related to the RST_N pin when pad voltage is not available. Two parameters define the RST_N pin behavior, 

RST_N pull-down and RST_N value.
The phhalSysSer_OTP_SecrowConfig() is used to control the RST_N pin behavior.

Table 6. RST_N pin parameters
RST_N pull down RST_N value HW operation
0 X[1] pad voltage availability is always assumed in this system;
IC checks the status of RST_N pin at POR and enters
either HPD or starts ROM booting
1 1 pad voltage availability is not assumed in this system; IC
does not check the status of RST_N Signal and starts
ROM boot normally upon POR

Regards

Sanath 

[IvanRuiz]

Hello,

As mentioned in UM10913, chapter 3.3.1.4, HPD can be achieved by the setting of RST_N pull-down value to 0 and the status of RST_N pin. You may achieve it by using the  phhalSysSer_OTP_SecrowConfig() API available in the NFC Reader Library.

Have a nice day.

BR,

Ivan.

[sanath_rai]

Hi Ivan,

Thank you for the information.

I have set  RST_N pull-down value to 0 using the  phhalSysSer_OTP_SecrowConfig() as below

SecRow.bRSTN_PullDown[0]=0;

phhalSysSer_OTP_SecrowConfig (PH_SYSRV_SET_DATA, &SecRow);

And for the RST_N pin value I was thinking to use a GPIO from our external Host to be given to the RST_N pin value so that when we make it  LOW it will go to HPD mode and when we make it high it will come out of HPD.

It can be done right?

Regards

Sanath

[IvanRuiz]

Hello,

As long as the timing is respected, I do not see any problem. Please refer to table 77 of the datasheet for this information: https://www.nxp.com/docs/en/data-sheet/PN7462.pdf 

Hope it helps.

BR,

Ivan.

[sanath_rai]

Hello Ivan,

Thank you for the reply.

Its given that RST_N Low pulse width time should be minimum 10 micro seconds. that means i need to make it low for a minimum of 10 micro seconds for it to go to the HPD mode right?

Regards,

Sanath

[IvanRuiz · Accepted solution]

Hello,

Correct!

BR,

Ivan.

[sanath_rai]

Hi Ivan,

In our custom PN7462 board,

Normal active mode its taking around 32mA and when we make RST_N pin value low its taking still 14mA which says that its not going to HPD mode where it should take around 12uA as per datasheet.

Regards

Sanath

[IvanRuiz]

Hello,

Could you please confirm it in the evaluation board to discard the variables of the custom board. Please share your results.

Thank you,

Ivan.

[sanath_rai]

Hi Ivan,

I will check it in evaluation board.

Before that a quick question

Earlier i had tried putting my application in standby mode there it had gone to stand by mode and current consumption was very low as expected but the issue i faced there was my High speed UART peripheral stopped working .

i will explain my application briefly

I have developed my application on Door access application where  we tap the NFC tag it throws out UID via SPIM.

Originally the Door access code is designed where the UID and data is been thrown out via HSU(High speed UART)

but i have changed it to SPIM interface.

And the HSU i am using to interface with another device in our application. Everything is working fine in normal mode,

but when i tried putting the code in Standby mode by enabling the PHFL_ENABLE_STANDBY macro.

The HSU is not responding .only the NFC tag part when i tap is working.

how to enable the HSU in stanby mode?

Is there any way to wake it up? or what might be the issue?

Also 

when i tried putting my application in stand by mode by using PHFL_ENABLE_STANDBY and i flashed the code.

 once i flash the code i am unable to flash the code once again using the my LPCLink-2 programmer.

what is the issue there? once we put the code in standby mode does it permanently disable the programming interface?

Regards

Sanath

[IvanRuiz]

Hello,

According to the documentation, only some modules are working to maintain the operation of the Power Control Unit, a set of registers and LFO (which operates in the KHz range). Nevertheless, it can be woken up by a corresponding source, such as a host interface (HSUART, SPI, I²C). 

It would be helpful to please refer to chapter: 8.15.5.2 Standby mode of datasheet and 8.3.2.1 Entering Standby Mode of UM10858.

BR,

Ivan.

[sanath_rai]

Hi Ivan,

I will have a detailed look at the information given by you.

and find out if any thing needs to be done particularly?

Do we need to change anything in EEPROM settings?

Anything needed to be changed in user_ee.xml which will generate user_ee.bin file to be dumped?

In my application i am using HSUART which is configured at 921600 to interface with one of my device,which should wake it up ,but the HSUART is not working.

After we put the device in standby mode we are not able to flash the code again via LPCLInk programmer,what might the issue here?

once we put the code in standby mode does it permanently disable the programming interface?

Regards,

Sanath Rai

[IvanRuiz]

Hello,

Additionally, please check the following community threads:

1. Pn7462 Door Access with Stand By 

2. https://community.nxp.com/message/912784 

BR,

Ivan.