New chip from National LM Hi again wayne, When you experience the highest power heating of the ic chip, what is the input voltage to the ic chip? Have rebuilt the circuit using your pcb not the mine and it works just fine. An Rds of 0. Can i use through hole components on a new pcb for all the parts except the lm of course? It’s going to take a week to digest this varying duty cycle feature aspect. When starting up the circuit, you may wish to adjust BOOT to 2 volts, and then slowly bring it up to the required test voltage of either 3v, 4v, or 7v instead of leaving it on constantly.

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Most standard flashlights draw maybe ler but only at about 2. On the plus side, the higher output voltage means the ratio of the diode drop to the output voltage is half, meaning overall it eats less eff.

Ok, that does sound a little high, but maybe it doesnt last long.

No wonder it gets hot. For that output current, you probably need a completely new design with different IC.

This is almost twice what the data sheet shows. Image resizer by SevenSkins.

Also, does anything ‘shut down’ as it’s suppose to with that chip when it goes into overload? When i finished breadboarding the circuit lee put an input voltage of 6 volts the output was 6 volts too. Since this converter could be run in many different configurations it would be impossible to say what voltage it actually heats up.


No National LM samples. As I recall I saw it rise to.

2 Cell – Battery to 5V Step Up DC-DC Converter Using LM2623

The time now is What do you read when you do this and get the overheating? Current probe inserted to monitor current into pin 8. Voltage supply connected to pin 7 BOOT that varies from 3v to 7v lm262 least. However, now that we have established that the Vdd pin is bootstrapped, that ALMOST eliminates the problems associated with Vin possibly causing the heating problems.

New chip from National LM

This draws ma at over 6 volts, which is pretty high. Having looked at the circuit again though shows that perhaps this is normal for such high output currents and voltages or the inductor has too much current for it’s size.

A single 1W LS at mA would then hit the magic point somewhere around 3. At least I have one design that has been though layout and has been etched. Im asking questions because im trying to understand where the circuit is operating when it seems to get hot.

Does it provide lde continously even when the input is 2. Midpoint on the time axis of the ‘on’ part of the waveform 3.


To make things easier I think I’ll start a web page with my scope pictures and such. Then, R3 can be selected using Equation 1. This lled exists or gets worse as Vin ln2623 farther away from Vout going down.

This test has a total of three results, depending on BOOT voltage setting.

As soon as you can get the tests in, we can go from there. So, when Vin is near Vout the average inductor current is near equal to Iout.

2.4V to 5V Step Up DC-DC Converter

Leave a Reply Cancel reply. That would occur at different Vin depending on if you drove a single LS at. I have not been able to get close to this with standard batteries or even Lithium batteries since I believe the internal impedance and chemical compositition affect the input power that can be drawn. Looks very similar to the LM New chip from National LM Hi again Wayne and Rene, and hi Vic, I was interested in this circuit because of the low vin and possible higher output current.