8.3.2 TPS2412 vs TPS2413 – MOSFET Control Methods

The TPS2412 control method yields several benefits. First, the low-current GATE driver provides a gentle turnon and turnoff for slowly rising and falling input voltage. Second, it reduces the tendency for on/off cycling of a comparator based solution at light loads. Third, it avoids reverse currents if the fast turnoff threshold is left positive. The drawback to this method is that the MOSFET appears to have a high resistance at light load when the regulation is active. A momentary output voltage droop occurs when a large step load is applied from a light-load condition. The TPS2412 is a better solution for a mid-rail bus that is re-regulated.

The TPS2413 turns the MOSFET on if V_(AC) is greater than 10 mV, and the rapid turnoff is activated at the programmed negative threshold. There is no linear control range and slow turnoff. The disadvantage is that the turnoff threshold must be negative (unless a minimum load is always present) permitting a continuous reverse current. Under a dynamic reverse voltage fault, the lower threshold voltage may permit a higher peak reverse current. There are a number of advantages to this control method. Step loads from a light load condition are handled without a voltage droop beyond I × R. If the redundant converter fails, applications with redundant synchronous converters may permit a small amount of reverse current at light load to assure that the MOSFET is all ready on. The TPS2413 is a better solution for low-voltage buses that are not re-regulated, and that may see large load steps transients.

These applications recommendations are meant as a starting point, with the needs of specific implementations overriding them.