query regarding the change in value of the Vcap in STM8S microcontroller

[piyushpandey]

I am using the STM8S103F2P6 microcontroller of the ST microelectronics and when I was studying the power supply section of the microcontroller there it is specified to connect an external capacitor with the value ranging in between the 470 to 3300 nf . the specifications for the external VCAP capacitor are as follows:

Value = 470 to 3300 nf

ESL = 15 nH max.

ESR = .3 ohm at 1 MHz.

But I have connected the 1 uF value capacitor to the Vcap pin of the microcontroller , because I was not getting the microcontroller of that range .


So I want to know that is it ok , or it is going to effect my microcontroller in any way. I mean what will be the effect and how it will effect my whole circuit and the microcontroller.

Please describe me in detail.

Thank you

 

[milind.a.kulkarni]

V cap are generally the coupling capacitors and the values that you mention if those are near to pin then i thin it is better to put one small capacitor like 100 nf in parallel to it ....How ever at least with the best of my knowledge V cap will not affect your micro-controller.... In case if there is a power sequence description in the datasheet please read it carefully....That will give you a clue...In my the chip that you are using the Vcap is one 1.8 v regulator pine I think that is core voltage so make sure that you follow the guide lines mentioned in the datasheet....

Good Luck

 

[piyushpandey]

V cap are generally the coupling capacitors and the values that you mention if those are near to pin then i thin it is better to put one small capacitor like 100 nf in parallel to it ....How ever at least with the best of my knowledge V cap will not affect your micro-controller.... In case if there is a power sequence description in the datasheet please read it carefully....That will give you a clue...In my the chip that you are using the Vcap is one 1.8 v regulator pine I think that is core voltage so make sure that you follow the guide lines mentioned in the datasheet....

Good Luck

hi milind

actually I didn't get the point regarding the power sequence description , can you please tell me some thing in detail about it.

Thanks

 

[milind.a.kulkarni]

ok ....In the case of micro-controller ( especially high end ) Have various interfaces like their peripheral voltage is say 3.3 v they have core working at 1.2 v and it can be connected to DDR2 ram which works on 1.8 v ....so while powering -up such a micro-controller ..... There exits a sequence from which you need to give the power to IC..... Like 1.2 v Core voltage first then after 100 usec you need to give 1.8v and after 250 us you need to give peripheral voltage..... this is generally specified by the manufacture of the IC......and they generally explain this in the term of waveform.... One need to study this before choosing the right component and power section design for Micro-controller....In the IC that you are using I think don't have power sequence....I searched it in the datasheet....

 

[piyushpandey]

ok ....In the case of micro-controller ( especially high end ) Have various interfaces like their peripheral voltage is say 3.3 v they have core working at 1.2 v and it can be connected to DDR2 ram which works on 1.8 v ....so while powering -up such a micro-controller ..... There exits a sequence from which you need to give the power to IC..... Like 1.2 v Core voltage first then after 100 usec you need to give 1.8v and after 250 us you need to give peripheral voltage..... this is generally specified by the manufacture of the IC......and they generally explain this in the term of waveform.... One need to study this before choosing the right component and power section design for Micro-controller....In the IC that you are using I think don't have power sequence....I searched it in the datasheet....

I think milind you are talking about the Power on reset POR term if I am getting you right, I think in your terms you are defining the POR as power sequencing.

am I right.

also yes there no description about the power sequencing in the datasheet of the microcontroller whcih you are talking and it's a simple 8 bit ST microcontroller.

 

[milind.a.kulkarni]

Hi Piyush,

POR or POR timer bits are required to stabilized the clock ( I mean Crystal frequency ) .....That is some thing different....

There is also a way for powering-up the chip.....this is what I was talking about.....Generally in case of micro-controllers as I said in previous post have different Power section like core or processing power, Peripheral or I/O driving power , Different memory technology works on different power rating like SD RAM 3.3 V ( generally ) DDR-I ( 2.5 Volts ) DDR-II(1.8V) etc......So the chip need to be powered in the such a way that the the optimum utilization of time and power for boot will be taken care...some times there are also dependency for loading the internal component of micro-controller .....This is called a power sequence of chip..... This is specified by the chip vendor in their datasheet....

Refer the links -
http://www.t-es-t.hu/download/microchip/an522e.pdf
**broken link removed**

Hope you are able to understand what I mean to say now
Good Luck

---------- Post added at 11:13 ---------- Previous post was at 11:12 ----------

Hi Piyush,

POR or POR timer bits are required to stabilized the clock ( I mean Crystal frequency ) .....That is some thing different....

There is also a way for powering-up the chip.....this is what I was talking about.....Generally in case of micro-controllers as I said in previous post have different Power section like core or processing power, Peripheral or I/O driving power , Different memory technology works on different power rating like SD RAM 3.3 V ( generally ) DDR-I ( 2.5 Volts ) DDR-II(1.8V) etc......So the chip need to be powered in the such a way that the the optimum utilization of time and power for boot will be taken care...some times there are also dependency for loading the internal component of micro-controller .....This is called a power sequence of chip..... This is specified by the chip vendor in their datasheet....

Refer the links -
http://www.t-es-t.hu/download/microchip/an522e.pdf
**broken link removed**

Hope you are able to understand what I mean to say now
Good Luck

 

[saochandan]

check out page no 19 for reference design

https://www.st.com/internet/com/TEC...AL_LITERATURE/APPLICATION_NOTE/CD00194637.pdf