PI2001 Datasheet, PDF (15/23 Pages) Vicor Corporation – Universal Active ORing Controller IC

Ra = ^{V (OVTH )}
I _Ra
Set Ra value based on system allowable current
I _Ra
Ra = ^{V (OVTH )}
I _Ra
Rb
=
Ra_{⎜⎜⎝⎛}
V
V
(OV
(UV
)
)
−
1_{⎟⎟⎠⎞}
Rc
=
(Ra
+
Rb)_{⎜⎜⎝⎛}
V (UV
V_TH
)
− 1_{⎟⎟⎠⎞}
Where:
V (UV_TH ) : UV threshold voltage
V (OV_TH ) : OV threshold voltage
V(UV) : UV voltage
I _Ra
: Ra current.
Alternatively, a two-resistor voltage divider
configuration can be used and is shown in (Figure 14).
Figure 14: Two-resistor divider configuration
The UV resistor voltage divider can be obtained from
the following equations:
R1_UV
= ^{V (UVTH )}
I _RUV
Set R1_UV value based on system allowable current
I _RUV ≥ 100μA
R 2_UV
=
R1_UV
⎜⎜⎝⎛
V (UV )
V (UV_TH
)
− 1_{⎟⎟⎠⎞}
Where:
V (UV_TH ) : UV threshold voltage
I _RUV
: R1_UV current
R1_UV
= ^{V (UVTH )}
I _RUV
Set R1_OV value based on system allowable current
I _RUV ≥ 100μA
R 2 _OV
=
R1_OV
⎜⎜⎝⎛
V (OV )
V (OV_TH
)
−1_{⎟⎟⎠⎞}
Where:
V (OV_TH ) : OV threshold voltage
I _ROV
: R1_OV current
Typical application Example 1:
Requirement:
Redundant Bus Voltage = 3.3V
Load Current = 15A (assume through each redundant
path)
Maximum Ambient Temperature = 75°C
Auxiliary Voltage = 12V (11V to 13V)
Solution:
1. A single PI2001 with suitable external MOSFET
for each redundant 3.3V power source should be
used, configured as shown in the circuit schematic
in figure 15
2. Select a suitable N-Channel MOSFET: Most
industry standard MOSFETs have a Vgs rating of
+/-12V or higher. Select an N-Channel MOSFET
with a low Rds(on) which is capable of supporting
the full load current with some margin, so a
MOSFET capable of at least 18A in steady state
is reasonable. An exemplary MOSFET having
these characteristic is FDS6162N7 from Fairchild.
From FDS6162N7 datasheet:
• N-Channel MOSFET
• V_DS= 20V
• I_D = 23A continuous drain current
• VGS(MAX)= ± 12V
• R_θJA= 40°C/W
• R_DS(on)=2.9mΩ typical at I_D=23A, V_GS≥4.5V,
T_J=25°C
Reverse current threshold is:
Is.reverse = ^Vth.reverse = ^{− 6mV} = −2.07 A
Rds(on) 2.9mΩ
Power dissipation:
Rds(on) is 3.5mΩ maximum at 25°C & 4.5Vgs and will
increase as the temperature increases. Add 25°C to
maximum ambient temperature to compensate for the
temperature rise due to power dissipation. At 100°C
(75°C + 25°C) Rds(on) will increase by 28%.
Rds(on) = 3.5mΩ∗1.28 = 4.48mΩ maximum at 100°C
Trise= Rth_JA ∗ Is² ∗ Rds(on)
Maximum Junction temperature
T_{J max} = T_A +Trise
T_J
max
=
75°C
+
⎜⎛
⎝
40°C
W
∗
(15A)²
∗
4.48mΩ⎟⎞
⎠
=
115°C
Picor Corporation • picorpower.com
PI2001
Rev 1.0 Page 15 of 23