LP8720TLE NSC [National Semiconductor], LP8720TLE Datasheet - Page 15

• Manufacturer Part Number: LP8720TLE
• Description: One Step-Down DC/DC and Five Linear Regulators with I2C Compatible Interface
• Manufacturer: NSC [National Semiconductor]

Output Voltage Selection Using External Resistor Divider
Buck1 output voltage can be programmed via the selection of
the external feedback resistor network.
V
The resistor from FB to ground R
kΩ to keep the current drawn through the resistor network to
a minimum but large enough that it is not susceptible to noise.
With R
resistor feedback network will be 2.5 µA.
OUT
will be adjusted to make the voltage at FB equal to 0.5V.
FB2
=200 kΩ and V
FB
at 0.5V, the current through the
FB2
should be around 200
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The formula for output voltage selection is
V
V
For any out voltage greater than or equal to 0.8V a transfer
function zero should be added by the addition of a capacitor
C1. The formula for calculation of C1 is:
For recommended component values see the table below.
V
OUT
FB
OUT
1.85
1.0
1.2
1.4
1.5
1.6
– feedback voltage (0.5V)
– output voltage
[V] R
FB1
200
280
360
360
440
540
[kΩ] R
FB2
200
200
200
180
200
200
[kΩ] C1 [pF] L [µH] C
8.2
6.8
18
12
10
10
2.2
2.2
2.2
2.2
2.2
2.2
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OUT
10
10
10
10
10
10
[µF]