Datasheet

TPS2410 vs TPS2411 – MOSFET CONTROL METHODS
TPS2410
TPS2411
www.ti.com .................................................................................................................................................. SLVS727C – NOVEMBER 2006 – REVISED JUNE 2009
The operation of the two parts is summarized in Table 2 .
Table 2. Operation as a Function of V
AC
Turnoff Threshold
(1)
≤ V
AC
≤ 10 mV
V
(AC)
≤ Turnoff Threshold
(1)
V
(AC)
> 10 mV
(MOSFET
V
(AC)
Forced < 10 mV
r
DS(on)
× I
LOAD
) ≤ 10 mV
Weak GATE pull-down
TPS2410 Strong GATE pull-down (OFF) V
(AC)
regulated to 10 mV GATE pulled high (ON)
(OFF)
TPS2411 Strong GATE pull-down (OFF) Depends on previous state GATE pulled high (ON)
(Hysteresis region)
(1) Turnoff threshold is established by the value of RSET.
The TPS2410 control method yields several benefits. First, the low current GATE driver provides a gentle turn-on
and turn-off 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 turn-off 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 TPS2410 is a better solution for a mid-rail bus that will be re-regulated.
The TPS2411 turns the MOSFET on if V
(AC)
is greater than 10 mV, and hard off when V
(AC)
is less than the
RSET programmed threshold. There is no linear control range and slow turn-off. The disadvantage is that the
turn-off threshold must be negative (unless a specified 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 in order to assure that the
MOSFET is all ready on. The TPS2411 is a better solution for low-voltage busses that will not be 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
over-riding them.
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