3 How to improve the loop characteristic of TPS2583x-Q1

Usually, 45° phase margin is enough to ensure the stable of system, but some customer want to have higher phase margin. To improve the phase margin, there two options:

• Reducing the power inductor is a specific way to improve the phase margin, but as we all know that reduce the power inductor will increase the inductor current ripple, customer need trade off those two performance. When the inductor decreases to a certain extent, we need to increase the frequency to keep low current ripple of the inductance. Table 2 is the loop test result of different inductor under 400 kHz and 2.2 MHz of TPS2583x-Q1 without cable compensation.

Table 2. Loop Result vs Inductor

Vin(V)	I_load(A)	Cout (µF)	Fsw (kHz)	Inductor(uH)	Fcross(kHz)	Phase Margin(°C)	Gain Margin(dB)
13.5	3	66	400	10	39.3	44.9	-13.52
				8.2	41.9	50.4	-14.22
				6.8	38.9	53.2	-14.65
			2200	2.2	37.25	67.923	-16.868

• Increasing output capacitance. According to our test results, the phase margin of TPS2583x system can be increased by appropriately increasing the capacitance.
• Table 3 is the test result of different output capacitance values.