What is the use of PDR ON ?

[maor]

Posted on June 28, 2018 at 22:53

hello .

1.We have  done a Stm32F429 board , and we can set PDR ON to GND OR VCC (we set to gnd)

how ever in the  STM32 PDF : AN4488 Application note  STM32F4xxxx MCU hardware

it says in  IN    ....3.2.1 PDR_ON

PDR_ON = 0 is mostly intended for VDD supply between 1.7 V and 1.9V (i.e. 1.8V +/- 5% supply). Supply ranges which never go below 1.8V minimum should be better managed with internal circuitry (no additional component thanks to fully embedded reset controller). • To ensure safe power down, the external voltage supervisor (or equivalent) is required to drive PDR_ON=1 during power off sequence

1.1 we done PDR ON CONNECT to GND we use 3.3V -3.0 V to the mcu did we set pdr_on  correct ?

when should i use pdr_on to vcc and when to gnd please explain in more practical example .

thanks

yaniv

[Tilen MAJERLE]

Posted on June 29, 2018 at 00:03

Hello,

as explained in application note you are referring to, in case you need any of features below, PDR_ON must be tied to VCC:

When the internal reset is OFF, the following integrated features are no longer supported:

• The integrated power-on reset (POR) / power-down reset (PDR) circuitry is disabled.

• The brownout reset (BOR) circuitry must be disabled.

• The embedded programmable voltage detector (PVD) is disabled.

• VBAT functionality is no more available and VBAT pin should be connected to VDD.

[maor]

Posted on June 29, 2018 at 07:29

thanks for your answare ,

1. still not 100% cear '

in case you need any of features below' do you mean below 1.8V meaning power source is 1.7V ?

2,we use use vdd as 3.3V so PDR_ON should be tied to vss (gnd) 

thanks

yaniv

[STOne-32]

Posted on June 29, 2018 at 23:42

Dear Gentleman,

if your VDD is 3.3V PDR_ON pin MUST be connected to VDD.  It is dangerous to connect to GND , in case of voltage drop ; the MCU can not work properly after next power up. There is a special sequence to be followed at startup as explained in AN4488.

in your case of

mailto:VDD@3.3V

 you must connect to VDD.

Cheers,

STOne-32 .