Technical Reference Note
Trim Characteristics
Rev.09.30.14_#1.0
AVO250-48S28B
Page 20
Connecting an external resistor between Trim pin and Vo- pin will decrease the output voltage. While connecting it
between Trim and Vo+ will increase the output voltage. The following equations determine the external resistance to obtain
the trimmed output voltage.
100%
Radj _ down = (
− 2)kΩ
∆%
Vo (100% + ∆%)
1.225× ∆%
100% + 2× ∆%
∆%
Radj _ up = (
−
)kΩ
△:Output e rate against nominal output voltage.
100×(Vnom −Vo )
∆ =
Vnom
Vnom: Nominal output voltage.
For example, to get 32.5V output, the trimmingresistor is
100 × (Vnom −Vo )
100 × (32.5 − 28)
∆ =
=
=16.07
Vnom
28
32.5(100 +16.07
1.225×16.07
)
100% + 2×16.07%
Radj−up
=
−
= 189.6(KΩ)
16.07%
For 1% adjustment resistor, the trimed output voltageis guaranteed within ±2%.
When trimmingup, the output current should be decreased accordingly so as not to exceed the maximum output power.
Vo+
S+
Vo+
S+
Load
Load
R
trim _down
Trim
Trim
Rtrim _up
C
out
C
out
S-
S-
Vo-
Vo-
Figure 17 Trim up
Figure 18 Trim down
For AVO250-48S28B, if the sense compensate function is not necessary, connect S+ to Vo+ and S- to Vo- directly.
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