LM3668SD-2833 NSC [National Semiconductor], LM3668SD-2833 Datasheet - Page 16

• Manufacturer Part Number: LM3668SD-2833
• Description: 1A, High Efficiency Dual Mode Single Inductor Buck-Boost DC/DC Converter
• Manufacturer: NSC [National Semiconductor]

www.national.com
10 µF for C
LMK212 BJ106MG (+/-20%)
22 µF for C
LMK212 BJ106KG (+/-10%)
tion regarding capacitance verses case size. Table 1 lists
several capacitor suppliers.
The output filter capacitor smooths out current flow from the
inductor to the load, helps maintain a steady output voltage
during transient load changes and reduces output voltage
ripple. These capacitors must be selected with sufficient ca-
pacitance and sufficiently low ESR to perform these functions.
Layout Considerations
As for any high frequency switcher, it is important to place the
external components as close as possible to the IC to maxi-
mize device performance. Below are some layout recommen-
dations:
1) Place input filter and output filter capacitors close to the IC
to minimize copper trace resistance which will directly effect
the overall ripple voltage.
2) Route noise sensitive trace away from noisy power com-
ponents. Separate power GND (Noisy GND) and Signal GND
GRM21BR60J106K
C2012X5R0J106K
JMK212BJ226MG
LMK212BJ226MG
JMK212BJ106K
Model
IN
OUT
(For 4.5/5V option, use 10V or higher rating capacitor)
(For 4.5/5V option, use 10V or higher rating capacitor)
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Type
TABLE 1. Suggested Capacitors and Suppliers
Taiyon-Yuden
Taiyon-Yuden
Taiyo-Yuden
Taiyo-Yuden
Taiyo-Yuden
Vendor
Murata
TDK
16
Note that the output voltage ripple is dependent on the induc-
tor current ripple and the equivalent series resistance of the
output capacitor (R
The R
dependent); make sure the value used for calculations is at
the switching frequency of the part.
(quiet GND) and star GND them at a single point on the PCB
preferably close to the device GND pin.
3) Connect the ground pins and filter capacitors together via
a ground plane to prevent switching current circulating
through the ground plane. Additional layout consideration re-
garding the LLP package can be found in Application AN
1187.
ESR
is frequency dependent (as well as temperature
Voltage Rating
ESR
6.3V
6.3V
6.3V
6.3V
10V
10V
10V
).
0805 (2012)
0805 (2012)
0805 (2012)
0805 (2012)
0805 (2012)
0806(2012)
0805(2012)
Case Size
Inch (mm)