LM3677LE-1.8EV National Semiconductor, LM3677LE-1.8EV Datasheet - Page 18
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LM3677LE-1.8EV
Manufacturer Part Number
LM3677LE-1.8EV
Description
BOARD EVAL FOR LM3677LE-1.8
Manufacturer
National Semiconductor
Series
PowerWise®r
Specifications of LM3677LE-1.8EV
Main Purpose
DC/DC, Step Down
Outputs And Type
1, Non-Isolated
Voltage - Output
1.8V
Current - Output
600mA
Voltage - Input
2.7 ~ 5.5V
Regulator Topology
Buck
Frequency - Switching
3MHz
Board Type
Fully Populated
Utilized Ic / Part
LM3677
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Power - Output
-
www.national.com
OUTPUT VOLTAGE SELECTION FOR LM3677-ADJ
The output voltage of the adjustable parts can be pro-
grammed through the resistor network connected from V
to FB to GND. The resistor and FB to GND (R
kΩ to keep the current drawn through this network well below
16 µA quiescent current level (PFM mode) but large enough
that it is not susceptible to noise. If R
the V
network will be 2.5 µA. The output voltage of the adjustable
parts ranges from 1.2V and 3.3V. The output voltage formula
is:
V
V
OUT
FB
: feedback voltage (0.5V typical)
V
: output voltage (V)
FB
OUT
1.2
1.3
1.5
1.6
1.8
2.5
2.8
3.3
is 0.5V, then the current through the resistor feedback
(V)
R
1
TABLE 3. LM3677–ADJ Configurations for Various V
280
320
357
442
464
402
464
562
(kΩ )
30008406
2
R
is 200 kΩ, and given
2
200
200
178
200
178
100
100
100
(kΩ )
2
) should be 200
C
1
8.2
8.2
6.8
5.6
5.6
6.0
5.6
5.6
(pF)
OUT
18
R
R
For the fixed output voltage parts the feedback resistors are
internal and R
The bypass capacitors C
Evaluation Board) in parallel with the feedback resistors are
chosen for increased stability. Below are the formulas for C
and C
C
none
none
none
none
none
none
1
2
2
: feedback resistor from V
: feedback resistor from to FB to GND (Ω)
24
24
(pF)
2
:
OUT
1
is 0Ω.
(Circuit of Figure 2)
L (µH)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1
and C
OUT
C
to FB (Ω)
IN
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
2
(µF)
(labeled C3 and C4 on
30008404
30008405
C
OUT
10
10
10
10
10
10
10
10
(µF)
1