LM22680EVAL/NOPB National Semiconductor, LM22680EVAL/NOPB Datasheet - Page 2

• Manufacturer Part Number: LM22680EVAL/NOPB
• Description: BOARD EVAL FOR LM22680
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM22680EVAL/NOPB

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.3V
• Current - Output: 500mA
• Voltage - Input: 4.5 ~ 42 V
• Regulator Topology: Buck
• Frequency - Switching: 500kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM22680
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: LM22680EVAL; LM22680EVAL

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Evaluation Board Setup
Before applying power to the LM22680 evaluation board, all
external connections should be verified. The external power
supply must be turned off and connected with proper polarity
to the VIN and GND posts. A load resistor or electronic load
should be connected between the VOUT and GND. Both the
VIN and VOUT connections should use the closest GND
posts respective to VIN or VOUT. The output voltage can be
monitored with a multi-meter or oscilloscope at the VOUT
post.
Once all connections to the evaluation board have been ver-
ified, input power can be applied. A load resistor or electronic
load does not require connection during startup. If the EN test
point is left floating, the output voltage will ramp up when an
input voltage is applied. Make sure that the external power
supply (input voltage power source) is capable of providing
enough current so that the adjusted output voltage can be
obtained. Keep in mind that the startup current will be greater
than the steady state current.
Synchronization and Adjustable
Frequency
A SYNC test point is provided to allow synchronization of the
LM22680 to an external clock signal. Space for a frequency
adjust resistor, R3, is also provided. Refer to the LM22680
datasheet for more details about the synchronizing and ad-
justable frequency features.
Precision Enable
The EN test point provided on the LM22680 evaluation board
can be used to shut down the LM22680 when connecting this
test point to ground.
Ref #
C1
C2
C3
C4
C5
C6
D1
R1
R2
R3
U1
L1
TABLE 1. LM22680EVAL Bill of Materials for VOUT = 3.3V, Designed for 2A output current
12 µH 3.91A WE-PD L
22 µF 63V electrolytic
120 µF 6.3V 24mohm
6.8 µF 50V ceramic
60V 5A CMSH5-60
10 nF 50V ceramic
Not populated
Not populated
Not populated
1.54 kΩ 1%
976Ω 1%
Value
2
National Semiconductor
Central Semiconductor
Nippon Chemi-Con
Component Selection
Before changing the default components refer to the
LM22680 datasheet for information regarding component se-
lection. The WEBENCH® designer online circuit simulation
tool is also available at www.national.com.
The output voltage is adjustable with resistors R1 and R2
shown in the schematic. Any changes to these evaluation
board feedback resistors may require changes to the inductor
and output capacitor values. It is especially important to
change the output capacitor, C4, if the output voltages are
adjusted higher than 5V. The Schottky diode, D1, has a volt-
age rating of 60V to allow for a 42V maximum input voltage.
If the input voltage is below 38V, a 40V Schottky diode may
be used with a lower forward voltage to improve efficiency.
For improved heat dissipation, a Schottky diode in a D2PAK
package may be selected for higher efficiency. The input ca-
pacitor, C2, is not always required. This capacitor is placed
on the evaluation board to make the application robust and
minimize input voltage ringing if power is suddenly applied.
Capacitor C2 also helps stabilize the transfer function of the
converter loop. The input capacitor C1 provides the main
contribution to the switch current. Both capacitors are select-
ed with appropriate values intended only for the evaluation of
the LM22680. For production designs, the impedance of the
power source as well as the ripple current rating of the se-
lected input capacitors need to be taken into consideration
and modified accordingly. See the LM22680 datasheet for
more information.
Output capacitor C5 is not populated but space is provided to
add a second output capacitor. This second output capacitor
may be used to further reduce output voltage ripple.
Panasonic
Supplier
Coilcraft
Wurth
TDK
TDK
-
-
-
-
-
APXE6R3ARA121ME61G
CRCW0603976RFKEA
CRCW06031K54FKEA
C4532X7R1H685K
C1608X7R1H103K
LM22680MR-ADJ
MSS1260-123ML
EEEFK1J220XP
Part Number
CMSH5-60
744771112