I'm trying to learn Eagle and smd soldering and stuff so I decided to pick TFT Friend. I've already all the parts except for the zener diode which says MM5Z24V on the schematics. I have that one too already but it's way smaller than what's on the Eagle board file and looking at the TFT Friend pictures online. May I know what part should I get? Any link please? Thank you!
Can you identify the package name in Eagle: One way is click on the wrench and select "package" then click on the crosshairs on the package and the name will come up. (I think). SMA also has other names like DO-214AC.
It's a Schottky diode rather than a Zener. The names and part label are a bit funky because we didn't have a single Eagle component for the Schottky in an SOD-323 package.
adafruit_support_mike wrote:It's a Schottky diode rather than a Zener. The names and part label are a bit funky because we didn't have a single Eagle component for the Schottky in an SOD-323 package.
The MBR0540 is a Schottky diode with a forward current rating of 500mA and a reverse voltage rating of 40V, but it's currently listed as obsolete. Apparently the manufacturer updated their component lineup and changed the names or something.
Any of the Schottky diodes on the page linked above will be a suitable replacement. Their forward current and reverse voltage ratings are at least as good.
adafruit_support_mike wrote:The MBR0540 is a Schottky diode with a forward current rating of 500mA and a reverse voltage rating of 40V, but it's currently listed as obsolete. Apparently the manufacturer updated their component lineup and changed the names or something.
Any of the Schottky diodes on the page linked above will be a suitable replacement. Their forward current and reverse voltage ratings are at least as good.
I actually have the MBR0540 diodes. So i just soldered those two diodes to this circuit but it keeps getting hot. Very hot. I checked my watt meter and it consumes around 9 watts using a USB power adapter. Just can't get it to work. It keeps killing the fan5333 chip.
Last edited by tinkerBOY on Wed Jul 11, 2018 5:14 am, edited 1 time in total.
Post a photo showing your hardware and connections please.
Boost converters are touchy, and can fall into spurious modes that consume a lot more current than they should. That usually means the PWM frequency has dropped a lot lower than it should.
Do you have an oscilloscope you can use to check the signals?
The inherently high peak currents and switching frequency of
power supplies require careful PCB layout design. Therefore,
use wide traces for high current paths and place the input
capacitor, the inductor, and the output capacitor as close as
possible to the integrated circuit terminals. The FB pin connec-
tion should be routed away from the inductor proximity to pre-
vent RF coupling. A PCB with at least one ground plane
connected to pin 2 of the IC is recommended. This ground plane
acts as an electromagnetic shield to reduce EMI and parasitic
coupling between components.
I don't know if you saw that warning. Every switching regulator data sheet I have ever seen has a similar statement, and many go so far as to show an exact layout they want to see. I think you can see some of your traces are fairly skinny. That is a typical cause of trouble. You can see how Adafruit's layout is tighter in that area. Often the mfg will provide a reference design, but it does not appear that Fairchild/ON have provided anything for that part.
Also try connecting the converter's SHDN pin to GND while the board is powered, then releasing it.
I ran into that with some boost converters a while back.. having the converter active while power was applied would put the converter in a low-frequency/high-current state. Giving the power even a few milliseconds to stabilize before enabling the converter make things work without any trouble.
If that works, drop about a 1uF resistor from SHDN to GND to give you a bit of startup delay.
adafruit_support_mike wrote:Also try connecting the converter's SHDN pin to GND while the board is powered, then releasing it.
I ran into that with some boost converters a while back.. having the converter active while power was applied would put the converter in a low-frequency/high-current state. Giving the power even a few milliseconds to stabilize before enabling the converter make things work without any trouble.
If that works, drop about a 1uF resistor from SHDN to GND to give you a bit of startup delay.
The inherently high peak currents and switching frequency of
power supplies require careful PCB layout design. Therefore,
use wide traces for high current paths and place the input
capacitor, the inductor, and the output capacitor as close as
possible to the integrated circuit terminals. The FB pin connec-
tion should be routed away from the inductor proximity to pre-
vent RF coupling. A PCB with at least one ground plane
connected to pin 2 of the IC is recommended. This ground plane
acts as an electromagnetic shield to reduce EMI and parasitic
coupling between components.
I don't know if you saw that warning. Every switching regulator data sheet I have ever seen has a similar statement, and many go so far as to show an exact layout they want to see. I think you can see some of your traces are fairly skinny. That is a typical cause of trouble. You can see how Adafruit's layout is tighter in that area. Often the mfg will provide a reference design, but it does not appear that Fairchild/ON have provided anything for that part.
adafruit_support_mike wrote:Yeah, that was a typo.. 1uF capacitor below the 10k resistor.
That works! But i noticed it consumes too much power. Around 800ma when a screen is connected. Powering it on without the screen consumes twice and kills the fan5333 instantly. :(.
That might be the normal operating range, based on the amount of power your display uses.
High-gain boost converters are usually about 70% efficient, and what you gain in voltage you lose in current. Assuming 800mA @ 3.7V of input (3W), you'd lose about 30% of the power to heat in the converter, taking the output to about 2.1W. That would be 100mA @ 20V, or 210mA @ 10V.
Check the output voltage and current to see what you're getting there.
