Datasheet
10 20 30 40 50 60 70 80 90 100
Current Limit Programming Resistor of ILIM_SET - kW
3.6
3
2.4
1.8
1.2
0.6
0
OUT Short Circuit Current Limit - A
V = 5 V
IN
I
OS_MAX
I
OS_TYP
I
OS_MIN
100 200 300 400 500 600 700
Current Limit Programming Resistor of ILIM_SET - kW
600m
OUT Short Circuit Current Limit - A
I
OS_MAX
I
OS_TYP
I
OS_MIN
V = 5 V
IN
500m
400m
300m
200m
100m
0
0.967OS_MAX
ILIM
51228
I
R
=
1.030OS_ MIN
ILIM
51228
I
R
=
TPS2511
www.ti.com
SLUSB18 –JUNE 2012
APPLICATION INFORMATION
Programming the Current Limit Threshold
The user-programmable R
ILIM
resistor on the ILIMIT_SET pin sets the current limit. The TPS2511 uses an
internal regulation loop to provide a regulated voltage on the ILIM_SET pin. The current-limiting threshold is
proportional to the current sourced out of the ILIM_SET pin. The recommended 1% resistor range for R
ILIM
is
between 16.9 kΩ and 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 remain above a certain
current level or that the maximum current limit remain below a certain current level, so it is important to consider
the tolerance of the overcurrent threshold when selecting a value for R
ILIM
. The Equation 2 and Equation 3
calculate the resulting overcurrent thresholds for a given external resistor value (R
ILIM
). The traces routing the
R
ILIM
resistor to the TPS2511 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 disregards the inaccuracy of the resistor
itself.
where
• I
OS_MIN
is in mA
• R
ILIM
is in kΩ (2)
xxxxxx
where
• I
OS_MAX
is in mA
• R
ILIM
is in kΩ (3)
Figure 31. Current Limit Threshold vs Current Figure 32. Current Limit Threshold vs Current
Limit Resistance Limit Resistance
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