LM2679-5.0EVAL National Semiconductor, LM2679-5.0EVAL Datasheet - Page 10

• Manufacturer Part Number: LM2679-5.0EVAL
• Description: EVALUATION BOARD FOR LM2679-5.0
• Manufacturer: National Semiconductor
• Series: SIMPLE SWITCHER®r

Specifications of LM2679-5.0EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 5V
• Current - Output: 5A
• Voltage - Input: 14 ~ 28V
• Regulator Topology: Buck
• Frequency - Switching: 260kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM2679
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: *LM2679-5.0EVAL; LM2679-5.0-EVAL; LM2679-5.0-EVAL

www.national.com
A: OUTPUT RESPONSE: 1V/DIV
B: LOAD CURRENT: I
Operating the Evaluation Boards
SETUP
The LM2673S-5_EVAL and LM2679S-5_EVAL evaluation
boards come ready to be tested. The only setup needed is
connecting the input voltage to the VIN and GND posts. The
output can be taken from the VOUT post. The other signals
of interest, switch output (SW out) and softstart (C_SS) posts,
are clearly marked for use in checking the signal integrity. The
softstart post has an ON/OFF input when this feature is being
used.
FIGURE 15. Output Response to 0
LOAD
= 1A/DIV
∼
5A Transient Load
10114522
10
OPERATING CONDITIONS
The input source for the LM267x family of regulators must be
8V or greater for proper setup and operation. The input volt-
age range for LM2673S-5_EVAL evaluation board is from 8V
to 12V and the range for LM2679S-5_EVAL is from 14V to
28V. The maximum voltage rating of the LM267x family of
regulators is 40V.
Load can be applied from 0A to the maximum for the design.
Higher current above the design current limit will result in ac-
tivation of the design current limit circuit. It is advisable to have
a minimal load of (at least 10 mA) during startup when the
input to output differential voltage is greater than 10V to pre-
vent output ramping beyond desired value.
PCB LAYOUT OPTIMIZATION
As in any switching regulator, layout is very important. Rapidly
switching currents associated with wiring inductance can gen-
erate voltage transients which can cause problems. For min-
imal inductance and ground loops, the printed circuit traces
should be as wide and short as possible on the PCB. For best
results, external components should be located as close to
the switcher IC as possible using ground plane construction
or single point grounding.
If open core inductors are used, special care must be taken
as to the location and positioning of this type of inductor. Al-
lowing the inductor flux to intersect sensitive feedback, IC
groundpath and C
When using the adjustable version, special care must be tak-
en as to the location of the feedback resistors and associated
wiring. Physically locate both resistors near the IC, and route
the wiring away from the inductor, especially an open core
type of inductor.
OUT
wiring can cause problems.