F405 & F411 versions of the BluePill

What are you developing?
racemaniac
Posts: 699
Joined: Sat Nov 07, 2015 9:09 am

Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Dec 06, 2017 11:10 am

if we use a diode there, it should be big enough i assume? it should be able to handle the 0.5A we're aiming for in the supply (so it should be able to handle 0.3W power dissipation assuming it has a 0.6V voltage drop)

User avatar
Squonk42
Posts: 325
Joined: Thu Dec 29, 2016 9:25 am
Location: Bordeaux, France

Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Dec 06, 2017 2:12 pm

OK, from the linked article, the MOSFET is always on:
Because if the left is high, and the right isn't, the right will get lifted up by the body diode, then the source becomes higher than the gate, causing the FET to turn on. If the right goes high, the source goes up relative to the gate right away and again the FET turns on. Not much for diode action.
It is working in TI's AN only if you reverse the battery, and because there is only a load on the right side.

In the Arduino Due schematic, there is one that is polarized by a comparator circuit. How the MOSFET bottom circuit works is still a mystery.

Max current is 1A with the AP2114, and this may be used by external components in addition to the STM32F405 current consumption. But if we use a Schottky diode, the drop is only 0.3V, not 0.6V, so the max power dissipation is the diode is 0.6W. A 4mm x 2mm (vs. 3 mm x 2.5 mm for the MOSFET) diode such as an PMEG3010ER or MBRM130LT1G could handle that...

EDIT: well, maybe not: Taj is 220°C/W, so for 0.6W, this is a 132°C temperature rise... with a max Tj of 150°C, you blow the diode @1A above 18°C! It can only stand up to 0.5A @ 40°C.

victor_pv
Posts: 1868
Joined: Mon Apr 27, 2015 12:12 pm

Re: F405 & F411 versions of the BluePill

Post by victor_pv » Wed Dec 06, 2017 2:42 pm

Perhaps the bottom FET is just short circuit protection?
If the drain voltage was equal to the gate (so drain shorted to gate, which is ground), the FET would stay closed, and the internal diode is reversed, so there is no current flowing to the short.


Just read thru TI note, so it's for reverse current protection, not short circuit. I wonder why it needs that on the USC2 power source, is not like you can reverse a USB cable... But on the other hand, it also blocks current flowing from the load to the USB port, so that port can be used to power the board, but the board will not power something connected to that port.
Makes sense in the DUE since that's not the native port. In our case since we can use the USB port as host and connect a slave, we don't want that circuit or would prevent us from powering a slave.
Am I right?

racemaniac
Posts: 699
Joined: Sat Nov 07, 2015 9:09 am

Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Dec 06, 2017 2:46 pm

Lol, it's really nice seeing us figure things like this out as a group XD

User avatar
Squonk42
Posts: 325
Joined: Thu Dec 29, 2016 9:25 am
Location: Bordeaux, France

Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Dec 06, 2017 3:06 pm

victor_pv wrote:
Wed Dec 06, 2017 2:42 pm
Perhaps the bottom FET is just short circuit protection?
If the drain voltage was equal to the gate (so drain shorted to gate, which is ground), the FET would stay closed, and the internal diode is reversed, so there is no current flowing to the short.


Just read thru TI note, so it's for reverse current protection, not short circuit. I wonder why it needs that on the USC2 power source, is not like you can reverse a USB cable... But on the other hand, it also blocks current flowing from the load to the USB port, so that port can be used to power the board, but the board will not power something connected to that port.
Makes sense in the DUE since that's not the native port. In our case since we can use the USB port as host and connect a slave, we don't want that circuit or would prevent us from powering a slave.
Am I right?
For a MOSFET to pass/block, what matters is the Vgs compared to its threshold value (negative for a P-type).

But you are probably right for the Due. In our case, we cannot use this solution, and I cannot find a single-component solution to implement this protection, except for a Schottky diode that will heat the birds!

racemaniac
Posts: 699
Joined: Sat Nov 07, 2015 9:09 am

Re: F405 & F411 versions of the BluePill

Post by racemaniac » Wed Dec 06, 2017 3:11 pm

Squonk42 wrote:
Wed Dec 06, 2017 3:06 pm
victor_pv wrote:
Wed Dec 06, 2017 2:42 pm
Perhaps the bottom FET is just short circuit protection?
If the drain voltage was equal to the gate (so drain shorted to gate, which is ground), the FET would stay closed, and the internal diode is reversed, so there is no current flowing to the short.


Just read thru TI note, so it's for reverse current protection, not short circuit. I wonder why it needs that on the USC2 power source, is not like you can reverse a USB cable... But on the other hand, it also blocks current flowing from the load to the USB port, so that port can be used to power the board, but the board will not power something connected to that port.
Makes sense in the DUE since that's not the native port. In our case since we can use the USB port as host and connect a slave, we don't want that circuit or would prevent us from powering a slave.
Am I right?
For a MOSFET to pass/block, what matters is the Vgs compared to its threshold value (negative for a P-type).

But you are probably right for the Due. In our case, we cannot use this solution, and I cannot find a single-component solution to implement this protection, except for a Schottky diode that will heat the birds!
Maybe a diode like this: https://www.vishay.com/docs/88746/ss12.pdf
(also easily & cheaply found on aliexpress)
or a bit bigger & certainly capable of 1A: https://www.vishay.com/docs/88712/s2a.pdf
Last edited by racemaniac on Wed Dec 06, 2017 3:13 pm, edited 1 time in total.

victor_pv
Posts: 1868
Joined: Mon Apr 27, 2015 12:12 pm

Re: F405 & F411 versions of the BluePill

Post by victor_pv » Wed Dec 06, 2017 3:12 pm

So we want something similar to the top circuit, but in single component, rather than comparator + Fet?
When Luke first posted here about the SY6280 I read thru a bunch of other USB protection ICs, but I can't remember is any allowed current to flow back in some condition.

I'm trying to understand, so correct me if I'm wrong, but we want to achieve this:
-Power the board from USB.
-Power a slave device from the board usb
-Prevent current flowing back to the USB port if the USB has some voltage, but the board +5 voltage is higher.

Something like this, but single component:
http://www.linear.com/product/LTC4160

Actually reading thru that, is achieves multiple functions. Current limiter, battery charger, and switching regulator. Perhaps is worth it since it would replace multiple components.

User avatar
Squonk42
Posts: 325
Joined: Thu Dec 29, 2016 9:25 am
Location: Bordeaux, France

Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Dec 06, 2017 3:29 pm

racemaniac wrote:
Wed Dec 06, 2017 3:11 pm
Maybe a diode like this: https://www.vishay.com/docs/88746/ss12.pdf
(also easily & cheaply found on aliexpress)
or a bit bigger & certainly capable of 1A: https://www.vishay.com/docs/88712/s2a.pdf
The first one has a Vf of 0.5V and is already 4 mm x 2.54 mm but may be acceptable with Tja of 88°C/W (44°C rise), the second has Vf of 1.15V and is even larger, so no way.

The MAX40200 ideal diode would match perfectly, but it is not cheap and cannot be found on Aliexpress:
MAX40200.png
MAX40200.png (10.37 KiB) Viewed 58 times

victor_pv
Posts: 1868
Joined: Mon Apr 27, 2015 12:12 pm

Re: F405 & F411 versions of the BluePill

Post by victor_pv » Wed Dec 06, 2017 3:40 pm

There are multiple power management IC that achieves multiple functions, but none seems to be cheap.
This is another one, a bit cheaper than the Linear one:
http://www.ti.com/lit/ds/symlink/bq24296.pdf

Can do power management + battery charging, and works with USB OTG, but cheapest cost seems around $1, and still needs a few external components.

User avatar
Squonk42
Posts: 325
Joined: Thu Dec 29, 2016 9:25 am
Location: Bordeaux, France

Re: F405 & F411 versions of the BluePill

Post by Squonk42 » Wed Dec 06, 2017 3:45 pm

victor_pv wrote:
Wed Dec 06, 2017 3:12 pm
Something like this, but single component:
http://www.linear.com/product/LTC4160

Actually reading thru that, is achieves multiple functions. Current limiter, battery charger, and switching regulator. Perhaps is worth it since it would replace multiple components.
This component is $0.30 on Taobao, plus power inductor, MOSFET and other components: probably too expensive and too large. All PMIC will have the same problems.

I am trying to understand how FET2 works in this schematic:
https://www.olimex.com/Products/Duino/A ... rev_A3.pdf

Post Reply