LM3674MF-ADJEV National Semiconductor, LM3674MF-ADJEV Datasheet - Page 2

• Manufacturer Part Number: LM3674MF-ADJEV
• Description: BOARD EVALUATION LM3674MF-ADJ
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3674MF-ADJEV

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1 ~ 3.3V
• Current - Output: 600mA
• Voltage - Input: 2.7 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 2MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM3674
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

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Output Voltage Selection for
LM3674MF-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 from FB to GND (R
200 kΩ to keep the current drawn through this network small,
but large enough that it is not susceptible to noise. If R
kΩ, and given the V
resistor feedback network will be 2.5 µA. The output voltage
formula is:
V
V
Powering the LM3674 for Bench
Measurement
When powering the LM3674 with a bench power supply, it is
recommended to place a 100 µF tantalum capacitor across
the VIN and GND supply terminals of the bench power supply.
This capacitor will reduce the input spike caused by the power
OUT
FB
: feedback voltage (0.5V typical)
V
: output voltage (V)
1.875
OUT
1.0
1.1
1.2
1.5
1.6
1.7
1.8
2.5
2.8
3.3
(V)
R
FB
1
200
191
280
357
442
432
464
523
402
464
562
(kΩ )
is 0.5V, then the current through the
TABLE 1. LM3674-ADJ Configurations for Various V
R
2
200
158
200
178
200
178
178
191
100
100
100
(kΩ )
C
2
) should be
1
8.2
8.2
8.2
6.8
8.2
8.2
6.8
18
18
12
10
(pF)
2
is 200
OUT
C
None
None
None
None
None
None
None
None
None
2
2
33
33
(pF)
R
R
For the fixed output voltage parts the feedback resistors are
internal. Place a 0Ω resistor for R
The bypass capacitors C
uation Board) in parallel with the feedback resistors are cho-
sen for stable operation. Below are the formulas for C
C
supply and long power cables. The combination of the power
supply and inductance within the power cables produce a
large voltage spike that may damage the device. In addition,
consideration must be given to the enable pin of the device.
The enable should never be taken high, until minimum guar-
anteed operating voltage of 2.7V is reached. The enable pin
should also never exceed the input voltage.
1
2
2
: feedback resistor from V
: feedback resistor from FB to GND (Ω)
.
L (µH)
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
out
(Circuit of Figure 2)
C
1
IN
and C
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
(µF)
OUT
2
to FB(Ω )
(labeled C
1
.
C
3
OUT
and C
10
10
10
10
10
10
10
10
10
10
10
(µF)
4
on Eval-
1
and