PI2123 Datasheet, PDF (15/20 Pages) Vicor Corporation – 15 Volt, 15 Amp Full-Function Active ORing Solution

curves versus conducted current at given ambient
temperatures and air flow.
OV/UV resistor selection:
The UV and OV comparator inputs are used to
monitor the input voltage and will indicate a fault
condition when this voltage is out of range. The UV
& OV pins can be configured in two different ways,
either with a divider on each pin, or with a three-
resistor divider to the same node, enabling the
elimination of one resistor. Under-voltage is
monitored by the UV pin input and over-voltage is
monitored with the OV pin input.
The Fault pin ( FT ) will indicate a fault (active low)
when the UV pin is below the threshold or when the
OV pin is above the threshold. The threshold is
0.50V typical with 25mV hysteresis and the input
current is less than ±1µA. It is important to consider
the maximum current that will flow in the resistor
divider and maximum error due to UV and OV input
current. Set the resistor current to 100µA or higher
to maintain better than 1% accuracy for UV and OV
due to the bias current.
The three-resistor voltage divider configuration for
both UV and OV to monitor the same voltage node
is shown in Figure 19:
Figure 19: UV & OV three-resistor divider
configuration
Ra = ^{V (OVTH )}
I _Ra
Set Ra value based on system allowable current
I _Ra
Rb
=
Ra_{⎜⎜⎝⎛}
V
V
(OV
(UV
)
)
− 1_{⎟⎟⎠⎞}
Rc
=
(Ra
+
Rb
)_{⎜⎜⎝⎛}
V (UV )
V (UV_TH
)
− 1_{⎟⎟⎠⎞}
Where:
V (UV_TH )
V (OV_TH )
V (UV )
I _Ra
: UV threshold voltage at Vin.
: OV threshold voltage at Vin.
: UV voltage set
: Ra current.
Alternatively, a two-resistor voltage divider
configuration can be used and is shown in Figure
20.
Figure 20: UV & OV 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.
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PI2123
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