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Q: TPS62200 vs. TPS62220 by 3276
comparison between TPS62200 and TPS62220, 300mA vs. 400mA.
* Both parts have an 85C power rating of 160mW and the same Rdson for the P and N channel FETs. Because of the higher switching frequency, the 220 shows a few % lower efficiency than the 200. So what is the basis for the 100mA higher output current in the 220? A larger die?
* Also, what sets the true current limit? If I have 300mA at 1.2V output, that's 360mW output power, and at 85% efficiency, only 54mW of dissipation. If the limit is 160mW, can the part actually run closer to the P-Ch current limit?
* For the 62200, can you expand on the conditions that set the 380/480/670mA P-Ch limit? And that limit is cycle-by-cycle peak current limiting only?
A: Re: TPS62200 vs. TPS62220 by 1090425
The rated output current is simply what the part was designed/characterized/tested for. Across all/almost all operating conditions (Vin, Vout, L, etc) of the part, it can provide the rated current. You can operate the part at higher currents than this as long as you remain within the thermal limits of the IC and stay below current limit. Typically, at some operating points, you might get around 10-30% more current than the rated current without hitting current limit.
The current limit and thermal limit are independent parameters. Either could limit the IC.
Also look at newer ICs, such as the TPS62230 and TPS62240 which provide much better performance and much smaller solution size.
A: Re: TPS62200 vs. TPS62220 by 8433
The peak current is measured while the p-FET is on. If the minimum current limit is reached some ICs will turn off the p-FET immediately, resulting in reduced duty cycle and therefore lower output voltage/power.
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