I designed the circuit as follows. I used a 2.2uH inductor with a 19mohm DCR and a 4.9A Isat, and added a 220pF capacitor to the feed forward path for stability. However, it cannot provide a 5V, 1A output at a 2.7V input; the output drops to zero. It can only output a maximum of 800mA, which is significantly lower than the efficiency shown in the datasheet. The output capacitor is 100uF, and it's all integrated into the IC, making it difficult to debug. Please help me figure out what the problem might be.
Furthermore, when I gradually increase the load at a 2V input (around 400mA), it switches at 1MHz initially but then drops to 700kHz, and again the output falls to zero. Please help me.