TPS54290 / TPS54291: Can it be used to build a 2-phase converter?

Is it possible to generate a 2-phase converter using the TPS54290 or TPS54291 integrated FET converter?

Yes, however there are some things that need to be considered when doing so.

This is possible because the TPS54290/TPS54291 converters meet both of the following requirements:

1. Peak Current Mode Control
2. Transconductance Error Amplifier

2-phase operation is achieved by connecting both channel output voltages to a common node AND connecting both error amplifier output voltages (COMP pins) together.  The feedback pins can be connected together, using a single feedback divider or seperare dividers.  While the later uses less components, it will improve output voltage set-point error distribution by driving to the average of the two dividers.

Since both error amplifiers are driven in parallel, the effective transconductance is doubled.

Since both current mode control channels are driven in parallel, the transconductance of the power stage (Inductor Current / Control Voltage) is also doubled.  Combined, these two effects result in a 4x gain multiplier over the single channel performance.  To design the compensation, follow the design process for a single channel, then multiply the capacitors by 4x and divide the resistor by 4 to obtain the desired closed loop response.

Since Channel 1's current limit is set lower than Channel 2's current limit, this method will work for loads upto 3A (1.5A per channel) as load increases further, channel 1 will being to current limit and only channel 2 will be controlled.  This will reduce the gain of the power-stage by 6dB and prevent current sharing.  While this mode of operation can support transient currents above 3A, it is not recommended for continuous operation.