Datasheet

0
I
LIMIT
12VNRS = 1
12xCL[3:0] = 0111B
T
I
MAX
.6I
MAX
0
T
FAULT
0
I
LIMIT
12VNRS = 0
12xCL[3:0] = 0111B
T
I
MAX
.6I
MAX
0
T
FAULT
0
I
LIMIT
12VNRS = X
12xCL[3:0] = 1111B
T
I
MAX
.6I
MAX
0
T
FAULT
If 12xCL[3:0] = 1111B,
12VNRS has no effect
CBA
TPS2359
www.ti.com SLUS792H –FEBRUARY 2008–REVISED MAY 2013
Redundant vs Non-Redundant Inrush Current Limiting
The TPS2359 can support either redundant or non-redundant systems. Redundant systems generally use a
single fixed current limit, as described above. Non-redundant systems can benefit from a higher current limit
during inrush to compensate for the lack of a redundant supply. The MicroTCA™ standard allows up to 19.4 A
for up to 200 ms in non-redundant systems, while limiting individual supplies in redundant systems to 9.1 A at all
times. One can optimize the performance of the system for either application by properly setting the 12VNRS bit
that controls inrush limiting. The ability to change the inrush profile using 12VNRS makes it possible to
reconfigure a controller for redundant or non-redundant operation with a single bit. This is particularly useful for
MicroTCA Power Modules which may be deployed in redundant or non-redundamnt systems.
The 12VNRS bit affects the value of the 12xCL bits during inrush. Setting 12VNRS causes the current limit
threshold and fast trip threshold to behave as if 12xCL = 1111B during inrush. Once the current flowing through
the channel falls below the current limit threshold, the current limit threshold and fast trip threshold correspond to
the actual values of the 12xCL bits.
Figure 24 helps illustrate the behavior of the 12VNRS bit. Figure 24A shows that setting the 12xCL bits to 1111B
results in a current limit equal to IMAX. Figure 24B shows how the 12xCL bits affect the current limit when the
12VNRS bit is cleared. Setting 12xCL = 0111B reduces the current limit to 60% of I
MAX
. Figure 24C shows how
the 12xCL bits affect the current limit when the 12VNRS bit is set. The current limit initially equals I
MAX
, but as
soon as the current drops below this level, the current limit resets to 60% of I
MAX
and remains there so long as
the channel remains enabled.
Figure 24. Current Limits in Redundant and Non-Redundant Systems
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