TPS63060-EP: TPS63060

Hi Peter,

Just to make it clear - you want to use one of the switch nodes for a charge pump, like here:

https://e2e.ti.com/blogs_/b/powerhouse/archive/2013/06/13/pumping-milliamps
http://www.ti.com/lit/an/slva398a/slva398a.pdf

but with a negative output circuit like here:

http://www.ti.com/lit/an/slfa002/slfa002.pdf

Or do you have a particular circuit on your mind? We have never tested the above with our buck-boost devices (yet), but it should work. The only limitations I see are:

1. It should be fine if you need a few mA, for larger currents it might affect the internal control and the protection mechanism.
2. Not sure if it would work properly in power-save mode, since the bursts when the device is operating are initiated when the output voltage falls under certain threshold. You would need an additional circuit to detect when the auxiliary negative voltage drops too much. In other words, when there is no load on the main positive output, the negative output might not have any current at all. In forced-PWM mode this is not an issue.
3. The switch nodes L1 and L2 are not always active, you should check your operating conditions to see which nodes you can use. If the TPS63060 is supposed to operate in all three modes, you would need two charge pumps in parallel, each one connected to one of the switch nodes L1 or L2. This is the switch nodes activity, depending on input/output voltages:

1. 1. Vin>Vout: buck mode, L1 switching, L2 = Vout (not switching)
   2. Vin<Vout: boost mode, L1 = Vin (not switching), L2 switching
   3. Vin~Vout: buck-boost mode, both L1 and L2 switching

Best regards,
Milos