hybridfree/eevblog-posts huggingface dataset:
MCP1652 strange behaviour  - Page 1
Forum section: electronics / projects

author: MarkoAnte
author_rank: Regular Contributor
timestamp: February 17, 2016, 05:29:00 pm
content: Hi,I have made a boost converter for my LCD led back light. I have followed the Graphics display truly 7" schematic for the display back light. The pcb is made to the attached schematic.This produced 6V output. So I replaced R604 with 10K and added 68.6K from FB to LED+. I also cut the LED- and connected the -LED form the display directly to gnd. If the display is not plug in I now get 9.7 V as I want. When I connect the display the voltage drops to 7.7 and it looks stable. The voltage on FB is 1.07-1.1 V and looks stable. I tried different inductor values I had 18 uH then I tried 2 two 18 uH in parallel and I have also tried one that I think is 2-3 uH. Same results.Then I probed the SW node and replaced the display with a switch and ~60R resistor. (LCD LED = 0.16A @ 9.4V) When I pressed the button the SW node goes to 3.3V. The PWM is still there @80% duty and @742 KHz.I have tried 2 different mosfets and no change. I have replaced the switch with a potentiometer (the resistor is still there). As I turn the 10K 10 turn pot to 0R the wave form decreases in amplitude and at the last turn or so stops and collapse to 3.3V. Almost like the transistor stops turning on. The feed back node also drops with the output voltage but the pwm stays the same. I would understand if the PWM does something strange like goes into many MHz and the transistor can "keep up" but the PWM is the nearly identical to when there is no load. (Down to the scope measurement noise level).Any ideas what I'm doing wrong?Best regards,Marko
MCP23017 basic input protection - Page 1
Forum section: electronics / projects

author: John B
author_rank: Frequent Contributor
timestamp: January 16, 2021, 03:48:56 am
content: Does anyone know if the I/O pins on the MCP23017 have any ESD protection diodes? I am designing a system where the IO pins are connected to a pin header which is connected to separate boards. Those boards will have their own ESD and voltage protection which will protect the MCP23017 chips, but sometimes the IO pins would be left unconnected and open circuit.Is there a benefit to adding some series resistors to limit current to any protection diodes in this case? A single resistor is doable and may even help with trace routing, but any further diode protection will be impractical as there's 128 channels.

author: Ian.M
author_rank: Super Contributor
timestamp: January 16, 2021, 04:39:20 am
content: The datasheet electrical specs say: "Input clamp current, IIK(VI< 0 or VI> VDD)....±20 mA", so what do *YOU* think?Yes, series resistors would be helpful, if only to make sure your external ESD/overvoltage protection takes the brunt of any 'hit'. Can your design tolerate 10K series resistors?N.B. there have been problems with input transitions on bit 7 of a MCP23017 port corrupting the state of other input pins! Seehttps://www.microchip.com/forums/m831656.aspx
MCP23017 / MCP23S17 smaller alternatives with less IOS - Page 1
Forum section: electronics / projects

author: mairo
author_rank: Unknown
timestamp: June 27, 2023, 04:12:14 am
content: I am looking for a physically smaller package (smaller than the available MCP23xxx QFN) alternative of MCP23017 / MCP23S17 IO extenders.The alternative part does not need to have 16 IOs, between 6-8 is sufficient.It must be available in both I2C, or SPI versions, or have them both at the same time.It must have at least 3 available user selectable I2C address pins.3.3V operation for power and IOs, although 5V might be considered as well.I know NXP has some similar parts, but I was not able to find what I need.Thank you!

author: mairo
author_rank: Unknown
timestamp: June 27, 2023, 05:49:01 am
content: NXP PCA9502 seems like possible replacement, but also open for other options.

author: avaqsemi
author_rank: Newbie
timestamp: June 27, 2023, 07:02:46 am
content: One alternative that meets your requirements is the PCA953x series of IO expanders from Texas Instruments. The PCA953x series for examplehttps://www.avaq.com/chip/pca9538pwrPCA9538PWR offers smaller package options and a range of IO counts while supporting both I2C and SPI interfaces.

author: fchk
author_rank: Frequent Contributor
timestamp: June 27, 2023, 08:08:45 am
content: Quote from: mairo on June 27, 2023, 04:12:14 amTHe 8 bit version of MCP23?017 is MCP23?08 (MCP23008 and MCP23S08). Works exctly the same.fchk

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 27, 2023, 09:46:25 am
content: If you reallyreallywant to save on component size maybe take a look at SPLDs (for example SLG46855) and make your own glue logic. Your requirement for dual SPI/I2C really torpedoes almost all newer and fancier IO expander offerings.

author: mairo
author_rank: Unknown
timestamp: June 27, 2023, 11:57:39 pm
content: Now I feel embarrassed, MCP23008/MCP23S08 seems what I am looking for as it is the closest physically smaller replacement with very minimal changes in the routing and the firmware.NXP PCA9502 is the best in terms of being able to handle both I2C and SPI in a single package, but I will need to see how more complex the routing need to be and will it actually achieve any space savings. The use case is for an auxiliary board that can either communicate via I2C, or via SPI and it can be as two separate parts, although one universal part could be better if can be done within the other design constrains.SLG46855 defiantly looks interesting, it is available in a very small size and also seems the cheapest when you look at the hardware only. Will need to investigate further to see can it be done and what resources will take.TI PCA953x seems not suitable as it does no have SPI option (maybe in a different drop of replacement model?) and also the I2C part only has 2 address pins.
MCP23S17 SPI extender - it works but not totally satisfied - Page 1
Forum section: electronics / projects

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 15, 2013, 04:14:44 pm
content: HiI've got an Arduino project where it drives an SPI version of the MCP23S17 bus extender (http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf). It's just a POC before I hook it up to a microprocessor to drive the buses.I was originally using the MC23S17 Class (http://playground.arduino.cc/Main/MCP23S17) but prefer to run my own code, for a better understanding.So, to see how little programming the MC23S17 needed, I sniffed the bus while sending a value to the output pins and this is what I got from the library version and the raw SPI library version (which is a set of SPI transfers based on what I saw in the class version of the capture).The only obvious difference in function is that the class version sends one value (1) to the outputs and the library sends another (5), for clarity. LEDs confirm this.However, when looking at the SPI captures, there are a couple of things that seem odd.Firstly, while it looks like the 64 0 0 0 sets up ports to be outputs, and the 64 18 x x writes the data to the output pins, it's not clear what the 64 10 8 does. I'mthinkingthat it's updating the IOCON.HAEN flag to say use the user specified hardware address but the MCP23S17 has all the address pins pulled low. This command sequence is definitely needed as the SPI library version of the code does not work without it.Secondly, the class version of the data shows 64 18 1 0 while the SPI library version shows 64 18 0 5. Why would it be that if the last two bytes are not reversed in the second example, it doesn't work (three LEDs all off, as if we're seeing the 0 and not the 5) ?Thanks

author: tszaboo
author_rank: Super Contributor
timestamp: October 15, 2013, 05:47:27 pm
content: OK. You have the datasheet. You also have a source code, it is in the library, the *.CPP file. Open it, read it. It has comments like every single line, which are longer than the Lord of the Rings. Why do you need us, and the logic analyzer?

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 15, 2013, 05:58:05 pm
content: Because I didn't realise that the source code was in there ?That should do it thanks.

author: free_electron
author_rank: Super Contributor
timestamp: October 15, 2013, 06:10:21 pm
content: Quote from: netdudeuk on October 15, 2013, 05:58:05 pmIsn't that the whole point of 'open source' ?

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 15, 2013, 06:16:04 pm
content: Quote from: free_electron on October 15, 2013, 06:10:21 pmSurely better to not reply than to be negative ?
MCP3008 and MCP23017 experiments - first project verification - Page 1
Forum section: electronics / projects

author: novice_electronic
author_rank: Newbie
timestamp: April 23, 2024, 11:39:43 pm
content: Hello there! I'm Karol, and I've embarked on the journey of automating my gardening beyond mere experimentation. I've drafted a PCB design, although I must confess, it's a tad messy. Before investing in components and PCB fabrication, I'm seeking validation that I'm on the right path.The PCB integrates two MCP3008 and MCP23017 chips. The MCP3008 manages temperature sensors, while the MCP23017 controls servos/relays. Both chips are powered by an external 5V supply. I've included TVS diodes on both the external 5V line and the internal Raspberry Pi line, although I suspect the latter may be redundant. Additionally, I've added resistors to drop the supplied voltage to the chips to 3.3V, even though they can function at 5V, which might be unnecessary. To stabilize the 5V external line, I've inserted a few 100nF capacitors, albeit without extensive research. Zener diodes have also been added for extra stability.Does this layout and design make sense? I'm open to any feedback or suggestions before I proceed further.I have included ZIP file containing KiCad project

author: moffy
author_rank: Super Contributor
timestamp: April 24, 2024, 12:49:01 am
content: Quote from: novice_electronic on April 23, 2024, 11:39:43 pmJust an FYI, not everyone uses or has Kicad, if you want a broader input, if you post your schematics etc as JPEG or PDF no one will need specialist software to view what you post. Secondly resistors make poor voltage drops because their voltage linearly depends on current which can vary. If you want to drop from 5V to near 3.3V, use a couple of series diodes, they'll drop between 1.2V to 1.5V in normal operation, this is not a comment on whether it is desirable or not.
MCP3201 not talking to ESP32-S3 - Page 1
Forum section: electronics / projects

author: robzy
author_rank: Regular Contributor
timestamp: October 15, 2024, 11:55:34 pm
content: I've spent hours trying to debug this but can't solve it.I have anMCP3201connected to an ESP32-S3 (SuperMini on AliExpress) on a custom PCB. JLCPCB made and assembled the PCB.Problem: The MCP3201 refuses to actually send out any data on its DOUT pin. It has an SPI-like interface with a CS, CLK, and DOUT/MISO signal.Connections: I have connected the GPIO8 to DOUT, GPIO9 to CLK, and GPIO10 to CS. For the MCP3201 I've connected Vref to VDD and IN- to GND. Both of these should be valid according to the datasheet.Software debugging: I have using an MCP3201 Arduino library, the SPI Arduino library, and even raw bitbanging to the MCP3201, and still nothing.Hardware debugging: I have used a logic analyser to maake sure that the CS and CLK signals are coming through as expected. And I have confirmed the MCP3201 is getting 3.3V. I've double checked that the IC is an MCP3201 and that it's in the correct orientation.Possibly a clue: When the ESP32-S3 SuperMini board itself is unplugged from the PCB the GPIO8 pin remains at ground regardless of whether I touch GPIO8 or not. When the ESP32-S3 SuperMini board is plugged into the PCB the GPIO8/DOUT pin seems to be semi-floating, because when I touch the pins the firmware reads different values.Any ideas about next steps?I'm grasping at straws, but is it possible that JLCPCB accidentally sourced fake MCP3201s?<-- I was totally wrong

author: JLCPCB Official
author_rank: Regular Contributor
timestamp: October 16, 2024, 08:37:40 am
content: hello , we purchase parts only from original manufacturers, their authorized distributors, or reliable suppliers.We want to assure you that the quality is of utmost importance to us.Every single part for assembly from JLCPCB is guaranteed to be authentic and traceable to the original manufacturer. For any problem, you can also contact support@jlcpcb.com ~

author: robzy
author_rank: Regular Contributor
timestamp: October 16, 2024, 10:03:50 am
content: I am sorry. I shouldn't have said that without thinking.I should say that I've made dozens of orders with JLCPCB, including assembly services, and I've always had a good experience.I did some more investigation on my board - revised my bitbanging code - and now the MCP3201 is working perfectly. More investigation needs to be done to work out why the other code isn't working - but I've now proved 100% that the MCP3201 is working perfectly.
MCP3208 alternative with VRef > VDD - Page 1
Forum section: electronics / projects

author: LukeW
author_rank: Frequent Contributor
timestamp: December 20, 2015, 04:27:54 pm
content: I'm looking for an 8-input, 12-bit ADC. I've got some MCP3208s, but they don't like having a reference that is above VDD. I'm looking to take the reference voltage greater than Vdd - say about 4.096V or 5V on VRef(and corresponding upper voltages on the analog inputs) with a Vdd (at least for the digital I/O levels) which is lower than that, at about 2.7 or 3.3V.Any recommendations for a device that will support that?

author: kripton2035
author_rank: Super Contributor
timestamp: December 20, 2015, 04:59:34 pm
content: would be easier to insert a voltage divider with two resistors on the ADC input ?

author: langwadt
author_rank: Super Contributor
timestamp: December 20, 2015, 05:04:14 pm
content: Quote from: LukeW on December 20, 2015, 04:27:54 pmyou are unlikely to find an ADC that can handle anything above the supply on any input, but something like an AD7091 has a separate supply for the interface

author: LukeW
author_rank: Frequent Contributor
timestamp: December 20, 2015, 05:22:20 pm
content: I don't really care about having a Vcc on the analog side that is at 5 volts, it would just simplify things if the digital interface side could be powered separately without level translation.

author: nctnico
author_rank: Super Contributor
timestamp: December 20, 2015, 08:54:31 pm
content: Then look for an ADC with workable logic levels when powered from 5V (IOW: anything but Microchip).
MCP3425 input voltage range - Page 1
Forum section: electronics / projects

author: madwolfe
author_rank: Contributor
timestamp: June 03, 2019, 01:17:53 pm
content: I'm having difficulties understanding the input voltage range for the MCP3425. I'm needing to measure a 0->3.3v range.From the datasheet (description at top):QuoteBut also from the datasheet:QuoteWhere PGA is the gain (which would = 1).I feel like it should be capable of measuring the voltage correctly, or would a voltage divider be necessary? (As the output is calibrated, the accuracy of the voltage divider wouldn't be important but the stability would be, so this could be an option).Thanks

author: madwolfe
author_rank: Contributor
timestamp: June 03, 2019, 01:42:34 pm
content: And of course, I forgot the link to the datasheet:http://ww1.microchip.com/downloads/en/DeviceDoc/22072b.pdf

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 03, 2019, 01:49:06 pm
content: As the internal reference is 2.048V and the internal PGA min gain is 1, there is no way you can measure a 0-3.3V input range without attenuating it first...You can safely apply an input up to VDD but the ADC will saturate at 2.048V.A quick suggestion would be to use an LTC2453 instead (similar specs and price).

author: madwolfe
author_rank: Contributor
timestamp: June 03, 2019, 08:03:34 pm
content: Brilliant, thanks for that. The LTC2453 looks like it will be good, and better than using a voltage divider.
MCP4725, CLK ripple at output - Page 1
Forum section: electronics / projects

author: Jan80
author_rank: Newbie
timestamp: March 02, 2019, 03:52:41 am
content: Hi, I'm considering usage of popular MCP4725 for a project, but I'm facing an issue which I couldn't find described anywhere on forums.It appears that CLK signal of the microprocessor causes a ripple at the output of the DAC.I already tried basic stuff like blocking caps, various runs of GND, different values of I2C pull-ups, different Arduino boards, different power supplies, but without affect on the DAC output.My test setup consists of MCP4725 breakout board, arduino nano supplied of 12V battery pack(Vin) for the lowest possible noise. DAC uses 5V of arduino linear regulator.Toppicture shows the output signal while alternating DAC by 1bit in the middle of the output range. 1bit represents cca 1.2mV and the pp-ripple is about 30mV which is way too high to accept.Middlepicture shows Vcc of DAC and the output. As you can see there is just very little noise at Vcc, nothing what would explain the issue.Bottompicture shows correlation of i2C CLK and output signals.Can anyone confirm my findings? Any idea how to get rid of the ripple or is this a feature of MCP4725 ( can't tell if it's genuine). thanks
MCP73123 & TPS61200 shutdown problem - Page 1
Forum section: electronics / projects

author: zaphod5
author_rank: Contributor
timestamp: February 07, 2019, 01:30:49 am
content: Hi everyone I'm having a problem with a generic implementation of the MCP73123 usb charging IC which feeds to a LifePo4 battery and provides 3.2v-2.6v to a TPS61200 boost converter IC outputting 5v. Both IC's are laid out according to their datasheets and work fine in every way, except once I connect and disconnect a usb charger the boost converter shuts down. Short of adding a p-mosfet to disconnect the power going to the boost IC while the usb charger is connected (gate to usb 5v, also to 10k pull down resistor), what can be done? Ideas are most welcome, TIA.

author: nsrmagazin
author_rank: Regular Contributor
timestamp: February 07, 2019, 06:57:05 am
content: Post a circuit please, this looks like a case of a bad connection. Do you have to separate the ICs during charging and discharging?

author: zaphod5
author_rank: Contributor
timestamp: February 07, 2019, 08:42:03 am
content: Hi nsrmagazin, thanks for your reply. I broke down and built a pnp circuit (didn't have p-mosfets on hand) and it's working perfectly now. It's late here, but tomorrow I'll post the circuit in hope there's a simpler solution.

author: zaphod5
author_rank: Contributor
timestamp: February 08, 2019, 12:29:26 am
content: Here are the schematics for the two circuits, I look forward to your reply.
MCP73213 IC status out is varying (NEED HELP PLEASE) - Page 1
Forum section: electronics / projects

author: Sai teja
author_rank: Regular Contributor
timestamp: September 23, 2017, 02:20:38 pm
content: Hello,I am using MCP73213 IC for my charging application. IC is working great. But I have an issue with status pin of MCP73213.As per datasheet, status pin should gives HighZ(High impedence) on charge completion and 0 volts during charge cycle.Datasheet of MCP73213 IC :http://ww1.microchip.com/downloads/en/DeviceDoc/20002190C.pdfHere are my observations: On charge completion it is giving 6.5 volts. And on charge completion it is giving 0 volts.Later on, I have added n-channel mosfet to status pin for attaining switching functionality depending upon output of status pin.Mosfet is connected as shown in the figure.Gate of mosfet is attached to status pin of MCP73213 IC.Drain is connected to GPIO and also pulled up to 3.3 volts with 12 k resistorsource is grounded.On doing so the HighZ (High Impedence) voltage is reducing to 4.5 volts.I am really confused why is this happening.Please help me in this regard.

author: viperidae
author_rank: Frequent Contributor
timestamp: September 24, 2017, 08:56:13 am
content: The chip might have ESD protection diodes on the pin, pulling down any voltage higher than its supply

author: hcglitte
author_rank: Regular Contributor
timestamp: September 24, 2017, 09:37:36 am
content: Do you have a pull-up resistor from the charger status pin to your MCU positive power rail? This should work.If your MCU positive power rail is higher than charger VDD (unlikely) by 0.3V there will flow a small current through theESD diode of the charger pin when HighZ.HC

author: Sai teja
author_rank: Regular Contributor
timestamp: September 25, 2017, 04:36:15 am
content: Datasheet says status output is High Z on charge completion.But that voltage is not mentioned. What might be the value of High Z of MCP73213 datasheet?

author: sleemanj
author_rank: Super Contributor
timestamp: September 25, 2017, 05:48:11 am
content: Hi-Z means high impedance, effectively like having a switch turned off, or a wire hanging in mid-air, it does not make a lot of sense to talk about what voltage is found on an open-drain pin (either not connected (open) or ground (drain)) when it is open.You need to pull it up to ensure that the output is a known state when open. Indeed even the datasheet says this on page 13..."Alternatively, a pull-up resistor can be applied for interfacing to a host microcontroller. "
MCP73831/2: Strange Issue - Page 1
Forum section: electronics / projects

author: NikhilRockssss
author_rank: Newbie
timestamp: July 17, 2017, 01:41:15 pm
content: Hey EEVBloggers,I'm having an issue with MCP73831/2. It's part of this wearable I've been designing, and so far it's been working great when I was working on it on the development board. Then I integrated it into a case, and there is this one very strange issue.We are charging a LiPo with 220mah with a RPROG of 4.7K. VDD and VBAT are both bypassed by a 4.7uF (According to the DS). Now, once this is done, it works flawlessly for days and weeks, but suddenly, it blows up, even when it's not charging. We open up the body, and find that VBAT and GND have been short circuited internally in the IC.We initially thought it was due to high junction temperature, but the fact that it blows up even when there's no charge across it, is worryingPlease help. I've attached a pic of the circuit we're using for your reference.Thanks!Nikhil G.

author: phenol
author_rank: Regular Contributor
timestamp: July 18, 2017, 03:05:58 am
content: I had this chip blow up on me mysteriously a number of times until i found out that it is rather intolerant to voltage transients on its input due to ringing caused by the low esr mlcc and cable inductance. A small tvs on the input solved the problem.
MCP73832 charger - safely reading STAT pin from MCU - Page 1
Forum section: electronics / projects

author: argintviu
author_rank: Contributor
timestamp: October 19, 2019, 12:33:18 pm
content: Hi all,I want to design a small project and make it portable. It uses an 18650 li-ion battery and I thought it'd be nice to also incorporate a cheap little MCP73832 IC to be able to charge the unit from the USB port. I have been researching for a way to read the STAT pin from the MCU so that I know in the software when the battery is being charged.Since the USB delivers 5V and the MCU will be powered by the battery - as low as 3.1V, I can't read the STAT pin directly from the MCU because no input should be higher than its VCC. To avoid this issue, I used 2 transistors as a sort of level shifter to interface between the 3V and 5V parts and also light up a "charging" LED (simplified schematic attached).Is there anything wrong with this way of reading the STAT pin?

author: KL27x
author_rank: Super Contributor
timestamp: October 19, 2019, 12:49:16 pm
content: QuoteYeah, there's 1 thing. It's unnecessarily complicated.QuoteSee that pullup between 5V and the STAT pin? Instead of connecting it to the 5V rail, put it on your micro's Vdd rail. That's one of the main reasons we have open drain outputs.

author: argintviu
author_rank: Contributor
timestamp: October 19, 2019, 01:28:57 pm
content: There's one issue though, if the LED gets its power from the battery, the charging might never finish. In any case, I'll test your idea and also add a load sharing mechanism like here:https://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing/. That should mitigate any issues.Thanks for the input!

author: KL27x
author_rank: Super Contributor
timestamp: October 19, 2019, 01:40:54 pm
content: ^ The variant with the lowest cutoff is 5% typical, 3.75% minimum. If you were using 500mA current limit, that would be 18.75mA minimum.You can buy variants that cutout at up to 20%, typical. See electrical specifications and product identification page for the codes/suffixes.QuoteGood idea.
MCP73837 Li-ion USB charging - Page 1
Forum section: electronics / projects

author: zerosignal
author_rank: Newbie
timestamp: March 10, 2017, 08:03:54 pm
content: Hi there!First post here - great channel and forum. I would be grateful if someone more experienced could give me some guidance on a circuit I am designing.I am basing a design on the MCP73837 dual input lithium ion battery charger IC. There is already a great reference design in the A1149 application notehttp://ww1.microchip.com/downloads/en/AppNotes/01149c.pdfalthough I am not quite sure how best to set the PROG2 input to select the 500mA USB charging mode without the use of an additional MCU.I understand that the pin can be driven logic low to select 100mA mode, and that this could be achieved by tieing the input to ground but for a logic high to select 500mA operation can I just tie this input to the power rail at the top of the attached diagram or is this just totally wrong?The design I am working on is a battery powered Raspberry Pi Zero project for which I rather not have to use a GPIO pin and additional software to drive this input on the charging IC high. I'm reasonably comfortable with the operation of the rest of the design detailed in the application note however.Any advice on how best to proceed would be greatly appreciated.Thanks!

author: trophosphere
author_rank: Frequent Contributor
timestamp: March 11, 2017, 05:47:53 am
content: Tie PROG2 to the positive rail of your USB charging port. Per the datasheet on page 5, the input voltage needs to be at least 0.8Vdd for Vdd = VUSB when input power source is from USB-port.

author: zerosignal
author_rank: Newbie
timestamp: March 11, 2017, 08:30:34 am
content: Cool thanks for the response.I had seen the minimum value and the Vdd changes between Vac and Vusb depending on which sources were present but was unsure on where to tie into this.There are plenty of designs floating about that tie the input low but none I can see that use the high mode. Simply leaving it low would take days to chatge the a 3000mah battery!Thanks again.
MCP73871 and TPS61090 Troubleshooting - Page 1
Forum section: electronics / projects

author: HermesTheNurse
author_rank: Newbie
timestamp: August 19, 2024, 06:55:53 am
content: I apologize in advance if I violate any forum conventions here. If that happens I will adapt postings accordingly moving forward.Context:I have been working on a PCB design that incorporates the TPS61090 (Boost converter) and MCP73871 (Charge controller) of Adafruit's Powerboost1000C, as seen here:https://learn.adafruit.com/adafruit-powerboost-1000c-load-share-usb-charge-boost/downloads.I've checked the Powerboost1000C circuit diagrams and Eagle PCB board files provided by Adafruit, and pretty meticulously matched everything to spec. However, when I plug this in, the boost converter chip (TPS61090) gets extremely hot, and yes, eventually starts smoking.Circuit:For power, I will be switching between a +5V USB and a 3.7V-4.2V Lipo battery supply. The power circuit is the portion highlighted in Yellow, where the microUSB port feeds USB power from the Teensy's VUSB pin (#1) to a MCP73871 charge controller (U2, #2). Directly below this are two terminals (Orange) where the battery joins the circuit. Both power sources then feed into the TPS61090RSAR boost converter (U1, #3). If the battery is discharging, the 3.7V-4.2V will be stepped up to +5V here. Finally, power is delivered back into the Teensy through the +5V "VIN" pin (#4).TPS61090(Boost Converter):MCP73871(Charge Controller):Physical Board:Additional Project Files:Herehttps://github.com/ColbyDAllen/Wearable-Drum-Machine/tree/main/Version%201/Hardware/E-CAD/Gerber_Drillare the Gerber/Drill files that I used to have this board fabricated.Herehttps://drive.google.com/file/d/1sePkgNdDCUta4Hd3auVm2ioGn66iGeJi/viewis the full schematic of the board. For some reason, the resolution when zooming is much better on the mobile app (You can even read the text on the datasheet pinouts).2 Questions:Having read elsewhere that the passives (Capacitors, resistors, etc.) might need to be placed closer to their respective ICs, I have two questions:1. Could I be missing decoupling capacitors; 10 or 100nF caps, placed close to all power inputs?2. I'm thinking a board revision is the best plan of action moving forward. Are there any steps that I might want to take before that?

author: ArdWar
author_rank: Frequent Contributor
timestamp: August 19, 2024, 09:47:47 am
content: For a boost converter it's the output capacitor that is critical. Your layout is reasonable (C5 is close, C4 could be closer), but your routing may need improvement. Try to put the output capacitor loop (pin1,15,16 -> C4 -> pin5,6,7) in single layer with nice wide trace/polygon. Or at least put more than one via if you have to change layers.As for your design, I don't see anything wrong with the circuit. Are you sure there weren't any solder bridges underneath the IC? You got enough caps already, and bad layout alone rarely result in such catastrophic failure.Quote from: HermesTheNurse on August 19, 2024, 06:55:53 amYou did cut the VUSB-VIN jumper tie on the teensyright?
MCP73871 - Will this work when only a battery is connected ? - Page 1
Forum section: electronics / projects

author: freeflyer
author_rank: Contributor
timestamp: July 22, 2025, 05:17:28 pm
content: I have designed a PCB that uses the MCP73871.I just want to confirm that this will work with only a battery connected (i.e. no USB)?Below is my schematic, VBUS comes from a USB connector and +BATT is connected to the battery terminal.I am hopiing that power from the battery will be provided on the OUT pin when only the battery is connected (to VBAT & VBAT_SENSE pins) even when VBUS is not connected.

author: thm_w
author_rank: Super Contributor
timestamp: July 22, 2025, 11:09:51 pm
content: "The MCP73871 is capable of autonomous power source selection between input or battery."yesSomething is wrong with your schematic symbol, its missing pins 11, 15, 19, 20

author: freeflyer
author_rank: Contributor
timestamp: July 23, 2025, 08:23:30 am
content: Quote from: thm_w on July 22, 2025, 11:09:51 pmThanks thm_wGood spot with the schematic symbol, the pins are missing on the symbol I downloaded but in kicad there is a pinpoint table which has those missing pin numbers so when it’s transferred to the pcb the pins are properly connected. Not sure why the symbol was created like that but it is correct on the pcb and pin out table
MCU controllable switch regulator - Page 1
Forum section: electronics / projects

author: Philfreeze
author_rank: Regular Contributor
timestamp: September 07, 2015, 09:32:45 pm
content: Hi guysI am new here and I hope this is not a repost, if it is then you can just link to the old post and I will read it. I don't mind reading.I am currently planning a project where the goal is to make a portable programmer and mini PSU for different other projects.For this I would like to have a controllable output voltage which would allow me to use it for 5V and 3.3V projects (maybe 2.5 and 1.8V projects down the road, you never know...).These are the specs I would like to achieve:Vout from 1.8V to 12V regulated.Iout @ 5V should be arround 1AVin can vary from arround 3V up to 5.5VI have evaluated two differnt solutions. One is to directly control a buck-boost converter with the MCU and the other is to build a regulator with a normal chip and then bias the feedback pin with a DAC which is controlled by my MCU.I really can't decide which of this solutions would be better. I tend to try the first one because it is cheaper and I have full control over the regulater rather than just passively changing the output voltage.Which one would you choose and why?If you need additional information just ask and I will provide it.

author: mariush
author_rank: Super Contributor
timestamp: September 07, 2015, 10:06:28 pm
content: Another simple way would be to use a digital potentiometer instead of a resistor in the voltage regulator's feedback.There's plenty of regulators that can be controlled through i2c protocol, just search google for "i2c controlled switching regulator". Linear, Micrel, Semtech are just a few that have them.To get such wide range of output voltages you'd probably be looking at SEPIC configuration (buck and boost) not just buck regulator, and that makes it a bit more complicated.

author: ajb
author_rank: Super Contributor
timestamp: September 07, 2015, 10:11:11 pm
content: Using a dedicated controller and biasing its feedback would be simpler to get right. Directly controlling the switching stage(s) of a buck-boost converter with an MCU is certainly doable, but will take some care to create a stable and robust solution. A dedicated controller IC pretty much has that taken care of.So I'd say unless you're interested in building an MCU-based switching converter as a project unto itself, just use a controller IC.

author: Philfreeze
author_rank: Regular Contributor
timestamp: September 15, 2015, 11:46:27 am
content: Thanks you both.I have a SEPIC or a buck-boost configuration planed. SEPIC would be easier to control with a MCU but the buck-boost is more common, I think.The digital potentiometer is a nice idea, I will have to look into the precision and stability of it but it sounds good.Since you both recommend to change the feedback I will go for this solution first, thanks!

author: 0xPIT
author_rank: Regular Contributor
timestamp: September 15, 2015, 09:05:52 pm
content: Maybe you can try a MAX1620, it's a programmable LCD bias controllers, which is basically a switch mode controller.
MCU controlled battery charger - Page 1
Forum section: electronics / projects

author: Rendo
author_rank: Newbie
timestamp: November 27, 2019, 09:08:43 pm
content: Hello everyone. I tried the following on an buck converter. I cut the connection of the bottom feedback resistor to ground and hooked it up to a DAC controlled by an Arduino. I was also measuring the current and voltage of the output with an ADC. It worked and I was able to accurately control the voltage and current.My question is that if this design is stable or will I mess the feedback control loop on the long run? I want to modify a SMPS (probably a cheap Chinese one, 24V, 20A) to charge a lead acid battery and I was wondering if this design could work and not suddenly lose control of the voltage/current and damage the battery while I'm away.Does this design also work on a voltage divider connected to a TL431 instead of the feedback pin on an control IC?
Mcu controlled Pfc - Page 1
Forum section: electronics / projects

author: mirbagheri1122
author_rank: Contributor
timestamp: April 23, 2017, 12:20:43 pm
content: hiI designed a 500w pfc that is been controlled with mcu pwm.now i selected my pid coefficient with refer to transfer function of a boost smps of course intuitively.please help me to choose them properly.
MCU crystal oscillator PCB layout confusion - Page 1
Forum section: electronics / projects

author: shadewind
author_rank: Frequent Contributor
timestamp: August 17, 2019, 05:22:50 pm
content: I'm laying out a board with an STM32F302C8 MCU and am currently looking at the ST Micro application note regarding crystal oscillators:https://www.st.com/content/ccc/resource/technical/document/application_note/c6/eb/5e/11/e3/69/43/eb/CD00221665.pdf/files/CD00221665.pdf/jcr:content/translations/en.CD00221665.pdfI've also looked into the equivalent Atmel (Microchip) app note and there are some commonalities that I don't quite understand as well as some differences that confuse me:http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8128-Best-Practices-for-the-PCB-Layout-of-Oscillators_ApplicationNote_AVR186.pdfI was hoping someone could shine some light on some of these points:Both recommend a local ground plane only connected at the MCU pin. Since this is a four layer board, I've just made a split in the ground plane that is a snip that goes to the closest MCU ground pin and connected it to this ground plane through a via (screenshot attached) and it seems to be approximately how the STM app note is doing it. Is this correct? Also, I've never done anything like this before and not really had any problems so I'm wondering, how important is this really? I'm assuming that the reason is two-fold, to prevent the EMI from radiating out from the oscillator into the application ground plane but also to prevent digital noise from the ground plane radiating in and bothering the osciallator?Both app notes show crystal traces running through the load caps on the way to the crystal, how important is this? By running the traces directly to the crystal and then the caps, the trace length between the MCU and the crystal would be shorter.Microchip recommends grounding the crystal while ST Micro recommends not doing so. Datasheet for my ABM3B crystal says "GND" on the shield pads so it seems like it was actually made to be grounded but I don't know. It seems to be that it would be wise to shield emissions from the crystal by shunt the shield to ground.Both recommend guard traces around the crystal but I don't really have space for it and I don't see most people bother with it. How much does this matter?Thanks in advance.
MCU Crystal Resonator Placement in Reference to RF Module - Page 1
Forum section: electronics / projects

author: kml183
author_rank: Contributor
timestamp: July 02, 2023, 10:19:36 am
content: Hello!I want to place a crystal resonator (CSTNE16M0V53) and a MCU (atmega328p) on the top layer of a 4-layer pcb where directly underneath on the bottom layer I will have an RF34463F30 1W 433Mhz transciever module.https://www.tindie.com/products/nicerf/rf4463f30-1w-wireless-transceiver-module/?pt=ac_prod_search.Attached is the rough idea of the placement. I am going to be using a controlled impedance stackup from JLCPCB. My signals for each layer from top to bottom will be signal/power, gnd, gnd, rf.I want to do this because I have a width constraint for this project and i want to make the PCB basically the size of the RF module.Am I going to run into EMI issues with the resonator or with any other signals from the MCU like an i2c, uart or icsp port?

author: ArdWar
author_rank: Frequent Contributor
timestamp: July 02, 2023, 03:28:49 pm
content: Should be fine with what I assume two solid ground plane. Although I'd prefer to rotate the whole MCU block so XTAL is away from ANT pin as precaution.On a side note, do you even really need the XTAL?I've seen people adding 16MHz to their 328 board for no particular reason. I don't think anyone need 0.5% jitter UART.

author: kml183
author_rank: Contributor
timestamp: July 02, 2023, 06:17:11 pm
content: Quote from: ArdWar on July 02, 2023, 03:28:49 pmYa good point I was just following the reference design for a nano.Thanks! Ya the antenna is on the top left so I should be good.

author: DIYGUY Chris
author_rank: Contributor
timestamp: July 03, 2023, 09:38:55 am
content: I recommend keeping the antenna away from any grounded surfaces or objects to ensure optimal performance.
MCU & DB File - Page 1
Forum section: electronics / projects

author: cwmadhan
author_rank: Newbie
timestamp: April 19, 2025, 02:20:22 pm
content: Hello,I have developed a datalogger with SD card and FatFs which is working fine. Am able to create a file and log data. Now i have different requirement that i need to open and read a database file (sqlite). This will be read only and no write/table creation or editing the datas. All i need to do is read the db file and access all the table datas properly and process further. I know its not a simple task but does anyone ever worked on this? Any inputs will be highly useful. Thanks in advance.Regards,Madhan.

author: voltsandjolts
author_rank: Unknown
timestamp: April 19, 2025, 02:49:43 pm
content: Segger supports (at least a subset of) sqlite in emFile.Also search for "arduino sqlite" maybe something there.

author: gerbay
author_rank: Regular Contributor
timestamp: April 19, 2025, 02:54:48 pm
content: https://github.com/luismeruje/SQLite-STM32stm32h7 port
MCU IO drive strength vs reliable max output frequency - Page 1
Forum section: electronics / projects

author: Psi
author_rank: Super Contributor
timestamp: May 17, 2022, 08:34:34 am
content: I've been looking for a rule of thumb or table showing what sort of output frequencies you can do reliably with different IO drive currents. But I've not really found anything useful.Anyone know for a 1 master 1 slave I2C/SPI comms setup, what's a good rule of thumb for clock limits on a 4mA drive IO vs a 20mA IO drive pin?Assuming the I2C/SPI device is relatively close to the MCU on the PCB (inch or 2)

author: Siwastaja
author_rank: Super Contributor
timestamp: May 17, 2022, 08:49:52 am
content: Just go back to physics:Q = I*tQ = C*dV,where C is the sum of pin capacitances (see datasheets) plus trace capacitance (use an online calculator, or ignore if short).This will give you the ballpark. The problem is, "4mA drive strength" does not actually mean 4mA constant current driver. At the end of the day, measurements are needed.You can also calculate equivalent R_io from given "drive strength", then treat it as an RC circuit.You will very quickly develop your own rule-of-thumb by just setting up a test. Change the drive strength and look at the oscillosscope: see the rise/fall times.I would use 4mA maybe up to 5MHz SPI, and 20mA above that (up to 20MHz). 33-47ohm series resistors at drivers significantly reduce ringing and EMI by series terminating the line. This explicit resistor will be way more controlled than the drive strength setting. Above 20MHz, I would seriously start considering signal integrity. But note that even 0.000001Hz SPI still spews out with the same edge rate and is subject to false clocking.I2C is totally different because the pullup resistor dominates over the IO drive strength, making it colossally slow anyway. Lot of appnotes about I2C pullup value. I just use 4.7kOhm for low-power, low-speed use cases (below 100kHz) and 1.5kOhm for high-speed stuff (up to 400kHz).
mcu pulling clock amplitude down? - Page 1
Forum section: electronics / projects

author: ftransform
author_rank: Frequent Contributor
timestamp: May 18, 2013, 02:00:57 am
content: So i have a PIC16 MCU receiving a SPI clock signal.For some reason the clock signal is being pulled down in amplitude (from 5V to 2.5V when it is connected.I thought that there was maybe not enough drive current, so I put two 74HC04 inverters in series to make a buffer and I passed my signal through it. When connected to the MCU the signal was even lower, like 1V.Is there some kind of mis-configuration that can lead to this problem or is the chip fucked? Why would giving it a higher current drive the signal voltage down even lower? wtf!

author: Rerouter
author_rank: Super Contributor
timestamp: May 18, 2013, 02:09:18 am
content: how are you measuring the signals?do you have some glitch in your code forcing it to output low?also as those buffers can sink 25mA, what can your chip supplying the clock feed supply?

author: ejeffrey
author_rank: Super Contributor
timestamp: May 18, 2013, 02:11:39 am
content: Are you sure the SPI clock is configured as an input rather than an output?Are you sure the wiring is right? Are you using a solderless breadboard? If so, check for bad contacts, especially to the supply voltage.Probe other points in the circuit. Does the supply pin of the inverter chip drop to 1 V? Are the ground pins actually at 0V?Typically when building a circuit for the first time, guessing a chip is bad should be your last resort unless you know you have done something to destroy it (like reverse the supply polarity). It is always far more likely that you have made a mistake.

author: ftransform
author_rank: Frequent Contributor
timestamp: May 18, 2013, 02:18:32 am
content: oh stupid me, i think it was set in master modei need to take up medidation or something electronics make me so angry i cant think

author: glatocha
author_rank: Regular Contributor
timestamp: May 18, 2013, 04:24:02 am
content: I have a simple working solution. When you stuck, go for a jog. I will reduce the tension and might bring you the solution.

author: ftransform
author_rank: Frequent Contributor
timestamp: May 18, 2013, 09:04:53 am
content: Quote from: glatocha on May 18, 2013, 04:24:02 amlol, ice cream
MCU read ADC LVDS output - Page 1
Forum section: electronics / projects

author: arul
author_rank: Regular Contributor
timestamp: October 20, 2020, 07:28:54 am
content: Hi All,I need some advise regarding ADC interface with Microcontroller.Here, that ADC(Analog to Digital Converter) output is serial LVDS(Low Voltage Differential Signal). How to read the ADC value using microcontroller(MCU)?I have been come across with that attached block diagram.In this block diagram, I read analog value using ADC. That ADC output configuration is LVDS(Low Voltage Differential Signal), so that LVDS is converted into TTL level. After that ADC value is passed to Microcontroller. The level shifter is added in between MCU and LVDS-TTL converter, if needed only because of MCU operating logic level.Is it correct? Please give more suggestion and recommend which MCU, ADC are suitable for that.Thanks all

author: mjkuwp
author_rank: Unknown
timestamp: October 20, 2020, 06:12:01 pm
content: there isn't enough information here.First you should try to use an ADC that communicates via SPI or else i2c. in that case you can directly connect it to the mcu.if you use an ADC with the LVDS output then you should try to find a transceiver that works at the logic level of your micro - example 3.3V.

author: daqq
author_rank: Super Contributor
timestamp: October 20, 2020, 08:24:31 pm
content: QuoteI think you have your design route backwards. You first select your ADC and MCU (or FPGA, since pretty much all of the ADCs that use LVDS as an output interface are very fast), then worry about all of the rest. Why fixate on using LVDS when the rest of your system is not chosen?