Datasheet

SHORT _ min
1.037
ILIMx
48000
I
R
=
SHORT _ max
0.962
ILIMx
48000
I
R
=
0
750
3000
3250
I
SHORT
- Current Limit - mA
1250
2000
0 20 40 120 140 180 200
R
ILIM
- Current Limit Resistance - kW
10080 220
2750
2500
2250
1750
1500
1000
500
250
16060
I
SHORT_min
I
SHORT_max
500
1250
I
SHORT
- Current Limit - mA
1750
2500
10 15 20 35 40 50 55
R
ILIM
- Current Limit Resistance - kW
30 60
3250
3000
2750
2250
2000
1500
1000
750
4525
I
SHORT_min
I
SHORT_max
TPS2540, TPS2540A
TPS2541, TPS2541A
SLVSAG2C –OCTOBER 2010– REVISED OCTOBER 2011 www.ti.com
APPLICATION INFORMATION
Programming the Current Limit Threshold
There are two overcurrent thresholds, which are user programmable via R
ILIM0
and R
ILIM1
. The
TPS2540/40A/41/41A uses an internal regulation loop to provide a regulated voltage on the ILIM0 and ILIM1
pins. The current-limit thresholds are proportional to the current sourced out of ILIM0 and ILIM1. The
recommended 1% resistor range for R
ILIM0
and R
ILIM1
are 16.9 kΩ ≤ R
ILIM
≤ 750 kΩ to ensure stability of the
internal regulation loop, although not exceeding 210 kΩ results in a better accuracy. Many applications require
that the minimum current limit is above a certain current level or that the maximum current limit is below a certain
current level, so it is important to consider the tolerance of the overcurrent threshold when selecting a value for
R
ILIMx
. The following equations calculates the resulting overcurrent threshold for a given external resistor value
(R
ILIMx
). The traces routing the R
ILIMx
resistors to the TPS2540/40A/41/41A should be as short as possible to
reduce parasitic effects on the current-limit accuracy.
The equations and the graph below can be used to estimate the minimum and maximum variation of the current
limit threshold for a predefined resistor value. This variation is an approximation only and does not take into
account the resistor tolerance or the variation of ILIM. For exact variation of ILIM, refer to the current limit section
of the electrical specification table.
(4)
(5)
Current Limit Threshold Current Limit Threshold
vs vs
Current Limit Resistance Current Limit Resistance
Figure 40. Figure 41.
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