MAX1724 boost converter does not work with 3V input

Hello guys I am using MAX1724EZK33 boost converter for increasing the voltage from 3V to 3.3V. I am using two 1.5V AA cells. However boost converter doesn't work as i expect. Here is my schematic 2018 04 12 01 33 15 — ImgBB this circuit working with 1.5V input voltage. However i couldn't see any change if i supply with 2.7V. I mean i make high the shutdown pin but boost converter remains close. After i have increased the output capacitor value to 130uF. Now output voltage becomes 2.5V when i pull the shutdown pin to high. When it is low output is 1.8V. Also i hear high frequency voice when boost converter is open. The only thing i havent tried that changing the inductor. I selected 1239AS-H-100M=P2 as a inductor and it has 1A current rating. However i made the prototype in China and i think they might have used a inductor which has lower current rate.

How about arranging the AA batteries in parallel? I know that’s not a fix, but in a pinch…? Also, I don’t see a schematic

ReverseEMF:
How about arranging the AA batteries in parallel? I know that's not a fix, but in a pinch...? Also, I don't see a schematic

Unfortunetly the case of the product is not suitable for parallel connection.

Also any other boost converter suggestions are accepted

Your schematic shows the shut-down pin is floating. PDF says it should be high for normal operation.

Paul

It is connected to an I/O pin of MSP430 however i make shut-down high with an external jumper that supplies 3.3V

Well, your schematic looks correct, so possibilities:

  • From the datasheet: "Low input-to-output voltage differences (i.e. two cells to 3.3V) require higher output capacitor values."
  • Inductor not of proper type or not close enough to the MAX1724EZK33
  • Capacitor ESR too high. Low ESR Ceramic the best, followed by low ESR Tantalum, then Polymar -- NEVER Electrolytic.
  • Power or ground lines not large enough.
  • Input or Output (or both) capacitor(s) not close enough to MAX1724EZK33
  • Not following the PCB Recommendations (see datasheet -- page 11).
  • Maybe the part is bad.
  • Maybe one or both of the batteries are run down enough that their internal resistance is too high [OK, I'm reaching, there :wink: ]

UPDATE: Forgot to mention shorted traces or pads not properly soldered down. This is a very small device. If it was hand soldered, then easily there could be solder bridges or pad not soldered down. [or is this a breakout board?] Also, all of the components should, probably, be SMD -- including the capacitors and inductor.

ReverseEMF:
Well, your schematic looks correct, so possibilities:

  • From the datasheet: "Low input-to-output voltage differences (i.e. two cells to 3.3V) require higher output capacitor values."
  • Inductor not of proper type or not close enough to the MAX1724EZK33
  • Capacitor ESR too high. Low ESR Ceramic the best, followed by low ESR Tantalum, then Polymar -- NEVER Electrolytic.
  • Power or ground lines not large enough.
  • Input or Output (or both) capacitor(s) not close enough to MAX1724EZK33
  • Not following the PCB Recommendations (see datasheet -- page 11).
  • Maybe the part is bad.
  • Maybe one or both of the batteries are run down enough that their internal resistance is too high [OK, I'm reaching, there :wink: ]

UPDATE: Forgot to mention shorted traces or pads not properly soldered down. This is a very small device. If it was hand soldered, then easily there could be solder bridges or pad not soldered down. [or is this a breakout board?] Also, all of the components should, probably, be SMD -- including the capacitors and inductor.

Thanks a lot for your comments here is my layout of boostconverter 2018 04 12 20 28 00 — ImgBB i placed 10uF ceramic capacitor near the Vin and Vout. This circuit worked well when i applied 1.5V to Vin and 3.3V to shut down pin i observed 3.3 Vout. After i applied 2.7V to Vin and circuit has stopped working. I got 1.8V from Vout constantly I mean i could not open the IC while applying high to shut-down. I relaized "Low input-to-output voltage differences (i.e. two cells to 3.3V) require higher output capacitor values" and increased the output capacitor. I have added two 47uF capacitors and one 33uF capacitor parallel. All of them are electrolytics capacitors. After increasing Output capacitor value i have managed to open/close the IC by pulling high/low to shut-down pin. However i got 2.5V on Vout of boost converter. When shut-down is low, i get 1.9V. I still can't get 3.3V at Vout. I kept the input capacitor 10uF. Should i also increase the Cvin ?

caneradiyaman6:
All of them are electrolytics capacitors.

More than likely it's the electrolytics. They are notorious for having a large inductive component ["parasitic Inductance"]. BUt, I Googled "is there such a thing as a low inductance electrolytic", and apparently there is! So, perhaps one of these, if they have a low enough ESR, might work. Otherwise consider ceramic (their cheaper) -- but, pay attention to the tolerance and temperature coefficient. [And consider that the electrolytic's parasitic inductance possibly generated voltage spikes that damaged the IC -- I do believe the datasheet cautions to not use electrolytics]

An article on Capacitor Temperature Coefficient by DigiKey: Understanding Ceramic Capacitor Temp-Coefficients - Support - Engineering and Component Solution Forum - TechForum │ Digi-Key

Then use the formula provided in the datasheet, and choose a value that insures the actual capacitance will be at least as much as the math indicates.

OR

go with X7R [probably a good compromise between temp-co and price] and choose a value that is 15% higher than the computed value. So, if you compute 29µF, then, for a 10% tolerance cap 281.15= 32.2µF. So, let's check the next up standard value of 33µF: 33µF0.9=29.7µF, so that's too low, so the next one up is: 39µF which has a worst case of: 39*0.9=35.1µF, so that's a winner! So, for this example, I would use a 39µF X7R 10% SMD cap! [or you could combine two values in parallel, which would could get you closer to nominal and get the ESR down even lower, but probably not really necessary.

yesterday i solved my problem. I removed all electrolytics capacitors and placed 100uF ceramic capacitors near the Vin and Vout. Output current of boost converter is around 120mA and ESP8266+msp430+rfm43b need more than that. I pulled low enable pin of esp and try to open boost converter. It started to work. i havent tried this before because i thought esp8266 flash is empty. That's why it should not consume so much current. However it came with pre flashed AT firmware of AI THINKER and it was trying to open an AP which needs a lot of power. Thanks a lot for all your effort. I appreciated

caneradiyaman6:
i havent tried this before because i thought esp8266 flash is empty. That's why it should not consume so much current.

My bad for not remembering to ask what the intended load was (i.e. what you are trying to supply power to).

Glad you got it working!