Description

This reference design demonstrates two methods that connect two TPS61288 devices in parallel to support high-output power. One method is to connect the VIN, VOUT, FB and COMP pin together directly. Because the two devices share the same voltage on the COMP pin, the inductor peak current of the two devices is closed at the typical condition. However, considering the process variation at the worst condition, the output current of one device can only be 50% of the other device. Thus, the maximum average power of this method is approximately 30 W from 3.3-V to 4.2-V input, but the peak output power can be 60 W for dozens of milliseconds. The other method uses an amplifier and two current-sensing resistors to maintain the current balance between two ICs. The amplifier compares the output voltage differential of two ICs, and then adjusts the voltage of one device to keep the two VOUT pins similar. The current of the two ICs is closed to each other. See the Power Sharing Between Two Parallel, Four-Switch Buck-Boost Converters application report for the details of this method. The average output power can be up to 40 W using this method.

Bench test results of these two solutions are found in this test report. Detailed schematics, layouts, and BOMs are found the in the reference design folder.