LM3677TL-1.8EV National Semiconductor, LM3677TL-1.8EV Datasheet - Page 2

• 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
LM3677TL-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 well
below 16 µA quiescent current level (PFM mode) but large
enough that it is not susceptible to noise. If R
given the V
feedback network will be 2.5 µA. The output voltage of the
adjustable parts ranges from 1.2V to 3.3V. The output voltage
formula is:
V
Powering the LM3677 for Bench
Measurements
When powering the LM3677 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
V
: output voltage (V)
OUT
1.2
1.3
1.5
1.6
1.8
2.5
2.8
3.3
(V)
FB
is 0.5V, then the current through the resistor
R
1
280
320
357
442
464
402
464
562
(kΩ )
TABLE 1. LM3677-ADJ Configurations for Various V
R
2
200
200
178
200
178
100
100
100
(kΩ )
2
is 200 kΩ, and
C
2
) should be
1
8.2
8.2
6.8
5.6
5.6
6.0
5.6
5.6
(pF)
OUT
C
none
none
none
none
none
none
2
2
24
24
(pF)
V
R
R
For the fixed output voltage parts the feedback resistors are
internal and R
The bypass capacitors C
uation Board) in parallel with the feedback resistors are cho-
sen for increased stability. 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 given to 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.
FB
1
2
2
: feedback resistor from V
: feedback resistor from FB to GND (Ω)
.
: feedback voltage (0.5V typical)
L (µH)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
out
1
(Circuit of Figure 2)
is 0Ω.
C
1
IN
and C
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
(µF)
OUT
2
to FB(Ω )
(labeled C
C
3
OUT
and C
10
10
10
10
10
10
10
10
(µF)
4
on Eval-
1
and