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Step-up converter TPS61107 startup under load

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Andy_123

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Just looking for some ideas:

Using TPS61107 step up converter from TI

according to the datasheet it should give me at least 400mA at 3.3V output with battery voltage 2.4V
https://www.electro-tech-online.com/custompdfs/2009/04/tps61107.pdf


if I start it with low load (100mA or less), it starts normally and I can increase load at this point up to 280mA(or may be higher) and it will keep stable and clean 3.3V

if I start it with load 200mA or higher, it never goes above battery voltage (2.1-2.4V) and if I keep it for few seconds kills chip permanently.

Schematics as shown in the datasheet (see attached), except:
- input capacitor is 22uF ceramic
- LDO is not used and not connected
- LBI is not connected

Any ideas?
 

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I've no idea why it's having the problem you described.

On the datasheet it looks like it takes a while for the converter Vo to reach it's target voltage. So just let it start up before you draw current. There's a PGOOD output that goes high when Vo is where it should be; try using this output to enable your load.
 
In this specific application I should not have any problems to sequence load: I can start PIC18F first, and it can turn LCD backlight and Ethernet module once PGOOD is set.
But I would like to have this design for future appliactions where I may need to have 200mA load on power up.

Just looking for ideas.
 
What is the current rating on the inductor you are using? (saturation current and DC current)
 
Below is inductor information for inductor I have now.

I actually tried few different SMD inductors as well with 10Amp rating - same result
 

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