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Step-up converter TPS61107 startup under load

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Andy_123

Member
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
http://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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dougy83

Well-Known Member
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.
 

Andy_123

Member
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.
 

ronsimpson

Well-Known Member
Most Helpful Member
What is the current rating on the inductor you are using? (saturation current and DC current)
 

Andy_123

Member
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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