LM3677TL-1.8EV National Semiconductor, LM3677TL-1.8EV Datasheet - Page 18

• Manufacturer Part Number: LM3677TL-1.8EV
• Description: BOARD EVALUATION LM3677TL-1.8
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3677TL-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: -

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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