Typical Application Example 2:
Requirement:
Redundant Bus Voltage = 1.2V
Load Current = 100A (assume through each
redundant path)
Auxiliary Voltage = 12V
Solution:
Five PI2121’s for each redundant 1.2V power source
should be used, configured in a master / slave
configuration as shown in the circuit schematic in
Figure 23.
Vaux: Since the Vaux voltage does not exceed the
VC pin clamp voltage, connect the Vaux directly to
each PI2121 VC pin.
SP and SN pins: For each specific PI2121, connect
each SP pin to the respective S pins and each SN
pin to the respective D pins. The master unit will
perform the sensing function.
BK pin: Connect the Master PI2121 BK pin directly
to ground to achieve the minimum reverse current
response time, and connect the BK pin of the slaved
PI2121’s to the respective local VC pin.
Figure 22: Two PI2121 in High Side ORing
configuration
SL pin: For each set of parallel PI2121’s connect
the SL pins together.
pin: Connect the
pin of the Master PI2121
FT
FT
to a logic input and to the logic power supply via a
10KΩ resistor.
Program UV and OV of the Master PI2121 to
monitor Input Voltage:
Program UV at 1.1V and OV at 1.3V
Use the three-resistor divider configuration:
IRa = 200μA
500mV
or 2.49kΩ 1%
Ra =
= 2.5kΩ
200μA
1.3V
1.1V
⎛
⎝
⎞
⎠
or 453Ω 1%
Rb = 2.49kΩ
−1 = 452Ω
⎜
⎟
1.1V
⎛
⎝
⎞
⎠
Rc =
(
2.49kΩ + 453Ω
)
−1 = 3.53.kΩ
⎜
⎟
500mV
or 3.57kΩ 1%
Picor Corporation • picorpower.com
PI2121
Rev. 1.0 Page 17 of 21
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