LM2682: Output voltage when input is floating or connected to GDN

Hi Esa,

I will look into this and get back to you. I don't have LM2682 samples right now but I ordered them.


Regards,

Juha

Hi Esa,

Assuming you have 10kohm pull-up resistor between  output and ground, the output will be pulled to 0V in both cases. (Vin floating or tied to GND)
Without pull-up, output capacitor is holding the output voltage unless it is discharged to somewhere.(Self-discharge if nothing else)

Regards,

Juha

Hi Juha,

Many thanks for your reply! I assume that if the pull-up resistor is between the output and 5V, the output will be pulled to 5V in both cases. Is this correct?

Regards,
Esa

Esa,

I will check tomorrow if pull-up to +5V is possible. Some inverting charge pumps don't tolerate positive voltage in output. Can you tell what kind of load the LM2682 is driving?

Regards,
Juha

Hi Juha,

Thanks in advance for checking. The load is a LCD display - I'm sorry I do not have further details.

Regards,
Esa

Hi Esa,

Unfortunately it seems that LM2682 starts sinking current when output is pulled higher than 0V. 10kohm pull-up resistor pulls Vout only to 0.5 V.

Regards,
Juha

Thanks Juha.

Is this valid for both cases, i.e. when the input is floating and when it is connected to GND?

Regards,
Esa

Esa,

Yes. 

Regards,

Juha