Datasheet

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    
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SLUS215B − OCTOBER 1998 − REVISED FEBRUARY 2004
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
dropout performance
Referring to the Block Diagram, the dropout voltage of the UCC383 is equal to the minimum voltage drop (V
IN
to V
OUT
) across the N-channel MOSFET. The dropout voltage is dependent on operating conditions such as
load current, input and load voltages, as well as temperature. The UCC383 achieves a low Rds(on) through the
use of an internal charge-pump (V
PUMP
) that drives the MOSFET gate. Figure 2 depicts typical dropout voltages
versus load current for the 3.3-V and 5-V versions of the part, as well as the adjustable version programmed
to 3.0 V.
Figure 3 depicts the typical dropout performance of the adjustable version with various output voltages and load
currents.
Operating temperatures also affect the Rds(on) and dropout voltage of the UCC383. Figure 4 graphs the typical
dropout for the 3.3-V and 5-V versions with a 3-A load over temperature.
Figure 2
0
0.1
0.2
0.3
0.4
0.5
1 1.5 2 2.5 3
I
OUT
(A)
V
IN
−V
OUT
(V)
TYPICAL DROPOUT VOLTAGE
vs.
LOAD CURRENT
V
OUT
= 3.3 V
V
OUT
= 5 V
V
OUT
= 3 V
Figure 3
TYPICAL DROPOUT VOLTAGE
vs.
I
OUT
AND V
OUT
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
3 3.5 4 4.5 5
I
OUT
= 3 A
I
OUT
= 1.5 A
I
OUT
= 1 A
V
OUT
(V)
V
IN
−V
OUT
(V)