LM3673TL-ADJEV National Semiconductor, LM3673TL-ADJEV Datasheet - Page 2

• Manufacturer Part Number: LM3673TL-ADJEV
• Description: BOARD EVALUATION LM3673TL-ADJ
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3673TL-ADJEV

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.1 ~ 3.3V
• Current - Output: 350mA
• Voltage - Input: 2.7 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 2MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM3673
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

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Output Voltage Selection for
LM3673MF-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
200kΩ to keep the current drawn through this network small,
but large enough that it is not susceptible to noise. If R
200kΩ, and given the V
the resistor feedback network will be 2.5µA. The output volt-
age formula is:
V
V
Powering the LM3673 for Bench
Measurements
When powering the LM3673 with a bench power supply, it is
recommended to place a 100µF 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
1
200
191
280
357
442
432
464
523
402
464
562
(kΩ )
FB
TABLE 1. LM3673-ADJ Configurations for Various V
is 0.5V, then the current through
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)
OUT
2
is
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 also be looked at the enable pin of the
device. The enable should never be taken high, until minimum
guaranteed 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