Datasheet

( )
RLIM,max TOL
LIM,min
201.9
R 1 R
I 0.44
= - ´
+
( )
RLIM,min TOL
LIM,max
201.9
R 1 R
I 0.38
= + ´
-
LIM,max
RLIM,min
201.9
I 0.38
R
= +
LIM,min
RLIM,max
201.9
I 0.44
R
= -
( )
RFLT,max TOL
FAULT,min
185.58
R 1 R
I 0.13
= - ´
+
( )
RFLT,min TOL
FAULT,max
213.68
R 1 R
I 0.13
= + ´
-
FAULT,max
RFLT,min
213.68
I 0.13
R
= +
FAULT,min
RFLT,max
185.58
I 0.13
R
= -
TPS2590
www.ti.com SLUS960F –JULY 2009–REVISED MAY 2013
Programming the Fault (I
FAULT
) and Current-limit (I
LIM
) Thresholds
The I
FAULT
and I
LIM
thresholds are user programmable with an external resistor. The TPS2590 uses an internal
regulation loop to provide a regulated voltage on the IFLT and ILIM pins. The current-limit thresholds are
proportional to the current sourced out of IFLT and ILIM. The recommended 1% resistor range is 49.9kΩ ≤ R
RFLT
≤ 200kΩ and 40.2kΩ ≤ R
RLIM
≤ 100kΩ to ensure the rated accuracy. Many applications require that minimum
fault and current limits are known or that maximum current limit is bounded. It is important to consider the
tolerance of the fault and current limit thresholds, as well as R
RFLT
and R
RLIM
when selecting values. Consult the
Electrical Characteristics table for specific fault and current limit settings.
Using the data for I
FAULT
and I
LIM
from the Electrical Characteristics table, equations can be generated and used
for other set points. Equation 13 and Equation 14 are used to calculate minimum and maximum I
FAULT
where
R
RFLT,max
and R
RFLT,min
include R
RFLT
tolerances. Equation 15 and Equation 16 calculate R
RFLT,max
and R
RFLT,min
where R
TOL
is the 1% resistor tolerance.
(13)
(14)
(15)
(16)
Equation 17 and Equation 18 are used to calculate minimum and maximum I
LIM
where R
RLIM,max
and R
RLIM,min
include R
RLIM
tolerances. Equation 19 and Equation 20 calculate R
RLIM,max
and R
RLIM,min
where R
TOL
is the 1%
resistor tolerance.
(17)
(18)
(19)
(20)
Design Example
A typical design is shown in Figure 18 with the following requirements:
• Nominal input voltage, V
IN
: 12V
• Maximum expected load current, I
OUT
: 3.7A
• Load capacitance, C
LOAD
: 100uF
• Expected resistive load, R
LOAD
during start up: 13Ω
• Current limit, I
LIM, min
: > I
FAULT, max
• Example calculations are shown in the TPS2590 Design Calculator Tool (SLUC398).
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