SC120ULTRT Semtech, SC120ULTRT Datasheet - Page 26

• Manufacturer Part Number: SC120ULTRT
• Description: IC BOOST 3.3V/ADJ 6MLPD
• Manufacturer: Semtech
• Type: Step-Up (Boost)r

Specifications of SC120ULTRT

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 1.8 ~ 5 V
• Frequency - Switching: 1.2MHz
• Voltage - Input: 0.7 ~ 4.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 6-MLPD-UT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Other names: SC120ULTR

Applications Information (continued)
formance), will ensure correct mode–switching behavior.
For very low V
nearly-depleted single-cell alkaline battery), a smaller
value of inductance will help to ensure that PWM mode
will switch to PSAVE mode as the load decreases. This
consideration may be of little importance in most applica-
tions, as there is little energy remaining in such a deeply
discharged battery.
The following table lists the manufacturers of recom-
mended inductor options. The specifi cation values shown
are simplifi ed approximations or averages of many device
parameters under various test conditions. See manufac-
turers’ documentation for full performance data.
Capacitor Selection
Input and output capacitors must be chosen carefully to
ensure that they are of the correct value and rating. The
output capacitor requires a minimum capacitance value
of 10μF at the programmed output voltage to ensure sta-
bility over the full operating range, and to ensure positive
mode-switching hysteresis. The DC bias must be included
in capacitor derating to ensure the required effective
capacitance is provided, especially when considering
small package-size capacitors. For example, a 10μF 0805
capacitor may provide suffi cient capacitance at low output
voltages but may be too low at higher output voltages.
Therefore, a higher capacitance value may be required to
provide the minimum of 10μF at these higher output volt-
ages. Additional output capacitance may be required for
V
the PSAVE exit threshold for high V
ity in PWM mode, especially at higher output load
currents.
Low ESR capacitors such as X5R or X7R type ceramic
capacitors are recommended for input bypassing and
output fi ltering. Low-ESR tantalum capacitors are not rec-
ommended due to possible reduction in capacitance seen
Manufacturer/
Part #
Murata
LQM31PN4R7M00
Coilcraft
XFL2006-472
IN
close to V
OUT
Value
IN
(μH)
to reduce ripple in PSAVE mode, to increase
4.7
4.7
(0.7V to 0.8V) such as is obtained with a
DCR
(Ω)
0.3
0.7
Current
Rated
(mA)
700
500
IN
, and to ensure stabil-
Tolerance
(%)
20
20
3.2 x 1.6 x 0.95
Dimensions
2 x 2 x 0.6
LxWxH
(mm)
at the switching frequency of the SC120. Ceramic capaci-
tors of type Y5V are not recommended as their tempera-
ture coeffi cients and large capacitance tolerance make
them unsuitable for this application. The following table
lists recommended capacitors. For smaller values and
smaller packages, it may be necessary to use multiple
devices in parallel, especially for C
PCB Layout Considerations
Poor layout can degrade the performance of the DC-DC
converter and can contribute to EMI problems, ground
bounce, and resistive voltage losses. Poor regulation and
instability can result.
The following simple design rules can be implemented to
ensure good layout:
A layout drawing for the MLP package is shown in Figure 4
and a layout drawing for the SOT23 package is shown in
Figure 5.
Manufacturer/
Part Number
Murata
GRM21BR60J226ME39B
Murata
GRM31CR71A226KE15L
Murata
GRM185R60G475ME15
TDK
C2012X5R1A226M
Taiyo Yuden
JMK212BJ226MG-T
•
•
•
•
Place the inductor and fi lter capacitors as close
to the device as possible and use short wide
traces between the power components.
Route the output voltage feedback path away
from the inductor and LX node to minimize
noise and magnetic interference.
Maximize ground metal on the component side
to improve the return connection and thermal
dissipation. Separation between the LX node
and GND should be maintained to avoid cou-
pling capacitance between the LX node and the
ground plane.
Use a ground plane with several vias connecting
to the component side ground to further reduce
noise interference on sensitive circuit nodes.
Value
(μF)
4.7
22
22
22
22
Rated Volt-
age (VDC)
6.3
10
10
20
4
OUT
.
Type
X5R
X7R
X5R
X5R
X5R
Case
0805
1206
0603
0805
0805
Size
SC120
Height
(mm)
Case
1.25
0.85
1.25
1.6
0.5
26