TPS61221: The output negative voltage.

Hi Minqiu,

Thank you for your reply.

Can I use Buck DCDC?
It is as low as possible.

Sincerely.
Kengo.

Hi Kengo:

May I know why you prefer a buck DCDC?

 I think BUCK should be also OK with proper design, but I haven't tried it by myself. 

I mean buck IC, not Buck topology. ...

Hi Minqiu,

Thank you for your reply.

Because step-down DCDC(Buck) is lower Iq than LMR70503 or other boost IC.
My customer needs more low Iq device.

Sincerely.
Kengo.

Hi Kengo:

Understand that. 

I'll let my colleague to help you. They are more experienced on BUCK device.

Hi Kengo,

Could you please tell me the specifications (Vin, Vout, Iout, etc) for the buck converter?

Regards,

Febin

Thank you! Minqiu.


Hi Febin,

Thank you for your help.

My customer's specifications are bellow,
Vin=3.3V
Vout=-3.3V(Negative voltage)
Iout=1mA or less.

How about the TPS62745?
It is a super very low Iq.

Sincerely.
Kengo.

Hi Kengo,

Buck Converters need a higher input voltage to operate and we don't have one that provides a negative rail. You could look into Switched Capacitor Inverter but they have a higher Iq.

https://www.ti.com/lit/ds/symlink/lm2776.pdf

Regards,

Febin

Hi Febin,

Thank you for your reply.

Can I refer to this application note(https://www.ti.com/lit/an/slva458b/slva458b.pdf)?

Sincerely.
Kengo.

Hi Kengo,

If you are looking for a solution just by reversing the polarity of the Vout, then you can use any buck converter for this. But we need to make sure that the negative voltage ratings of the FETs are not violated.

Yes, the Application note mentioned can be used as a reference.

Regards,

Febin