PI2127 Datasheet, PDF (14/19 Pages) Vicor Corporation – 60 Volt, 12 Amp Full-Function Active ORing Solution

Typical Application Example:
Requirement:
Redundant Bus Voltage = 40V ±5V
Maximum Load Current = 9A (assume through each
redundant path)
Maximum Ambient Temperature = 60°C, no air flow
(0LFM)
The current flow parasitic inductance for each ORing
device is 60nH.
Solution:
A single PI2127 for each redundant 40V power source
should be used, configured as shown in the circuit
schematic in Figure 23.
R_PG selection:
35V <V_S-PG <45V
R_PG
=
V_{S min} − V_{S −PGMax}
IC_max + 0.1mA
=
35V − 12.5V
2.1mA
= 10.71kΩ
The closest 1% resistor available is 10.5kΩ
( ) _PdRPG
=
(V_{S −max}
− V_{S −PGMin} ) ²
R _PG
=
45V −11V
10.5kΩ
2
= 110mW
The selected resistor should be capable of supporting
the total power at maximum operating temperature,
60°C. An 0805 (2012) will support the power
requirement.
FT pin:
Connect FT pin to the logic input and to the logic
power supply via a resistor, as required for the proper
input level of the supervisor functions.
Power Dissipation and Junction Temperature:
First use Figure 13 (Junction Temperature vs. Input
Current) to find the final junction temperature for 9A
load current at 60°C ambient temperature. In Figure
13 (illustrated in Figure 22) draw a vertical line from
9A to intersect the 60°C ambient temperature line. At
the intersection draw a horizontal line towards the Y-
axis (Junction Temperature). The Junction
Temperature at maximum load current (9A) and 60°C
ambient is 115°C.
R_DS(on) is 11mΩ maximum at 25°C and will increase as
the Junction temperature increases. From Figure 11,
at 115°C R_DS(on) will increase by 38%, then

R_DS(on) =11mΩ∗1.38 =15.18mΩ maximum at 115°C
Maximum power dissipation is:
Pd_max = Iin² ∗ R_DS(on) = (9A)² ∗15.18mΩ =1.23W
Recalculate T_J:
T_J
max
=
60°C
+
⎜⎛
⎝
45°C
W
∗
(9A)²
∗15.18mΩ⎟⎞
⎠
=
115.3°C
Figure 22: Example 1 final MOSFET junction
temperature at 9A/60°C T_A
Reverse Current Threshold:
The following procedure demonstrates how to
calculate the minimum required reverse current in the
internal MOSFET to generate a reverse fault condition
and turn off the internal MOSFET.
At maximum junction temperature (115°C) and
maximum R_DS(on):
Is.reverse = ^VRVS−TH
R_{DS (on)}
=
− 6mV
15.18mΩ
=
−395mA
Peak current under input short is:
At typical response time:
I _PEAK
= ^{VS * t RVS}
L_PARASITIC
=
45V * 80ns
60nH
= 60A
Picor Corporation • picorpower.com
PI2127
Rev 1.3
Page 14 of 19