Enpirion
®
Power Evaluation Board User Guide
EP53A8xQI PowerSoC
Using the External Voltage Divider
The EP53A8xQI evaluation board is designed to provide a great deal of flexibility
in evaluating the performance of the Altera Enpirion DC/DC module.
Pre-tinned pads are provided to place 0805 sized resistors on the board to
implement an external resistor divider for the EP53A8LQI to choose an output
voltage other than one of the pre-set voltages available on the VID. See Figure 3
for the basic circuit.
V
IN
V
Sense
V
S0
V
S2
E
P
5
3
A
8
L
10
µ
F
0805
4.7uF
0603
V
OUT
V
OUT
AGND
ENABLE
Ra
Rb
V
FB
V
S1
PGND
AVIN
PVIN
100
Ohms
Figure 3. External divider schematic for the EP53A8LQI
The output voltage is selected by the following formula:
(
)
Rb
Ra
OUT
V
V
+
=
1
6
.
0
R
a
must be chosen as 237k
Ω
to maintain control loop stability. Then R
b
is given
as:
Ω
−
=
6
.
0
10
2
.
142
3
2
OUT
V
x
R
The external voltage divider option is chosen by setting the jumpers VS0 – VS3
to logic “high”.
Page 5 of 7
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