SC198AMLTRT Semtech, SC198AMLTRT Datasheet - Page 12

• Manufacturer Part Number: SC198AMLTRT
• Description: IC DUAL DC-DC BUCK CONV 20-MLPQ
• Manufacturer: Semtech
• Type: Step-Down (Buck)r

Specifications of SC198AMLTRT

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: Programmable
• Current - Output: 800mA
• Frequency - Switching: 1MHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-MLPQ
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: SC198AMLTR

Applications Information (continued)
Inductor Selection
The SC198A was designed for optimum performance
when using a 4.7μH inductor. The magnitude of the
inductor current ripple is dependent on the inductor value
and is determined by the equation
This equation demonstrates the relationship between
input voltage, output voltage, and inductor ripple current.
The inductor should also have a low DCR to minimize the
conduction losses and maximize effi ciency. The minimum
DC current rating of the inductor should be equal to the
maximum load current plus half of the inductor current
ripple as shown by the equation
Final inductor selection will depend on various design
considerations such as effi ciency, EMI, size, and cost. Table
2 lists some manufacturers of practical inductor options.
Capacitor Selection
Input Capacitor
The source input current to a buck converter is non-con-
tinuous. To prevent large input voltage ripple a low ESR
ceramic capacitor is required. A minimum value of 4.7μF
should be used for suffi cient input voltage fi ltering and a
22μF MLCC may be used for optimum input voltage
fi ltering.
Manufacturer/
Part No.
Coilcraft
LPO6610-472ML
Coilcraft
1812PS-472KLB
Coilcraft
D01608C-472ML
I
L(Peak)
I
L
L
Table 2 — Recommended Inductors
V
I
OUT
OUT(MAX)
f
osc
Value
(μH)
4.7
4.7
4.7
1
0.20
0.11
0.09
V
DCR
(Ω)
V
OUT
2
I
IN
L
Current
2.10
Rate
1.1
1.5
(A)
Tolerance
(+%)
±20
±20
±20
6.60 × 5.50 × 1.10
5.87 × 4.89 × 3.81
6.60 × 4.50 × 13.0
Dimensions
LxWxH
(mm)
Output Capacitor
Output voltage ripple is dominated by the fi lter capaci-
tance ESR as shown in the equation
Capacitors with X7R or X5R ceramic dielectric are strongly
recommended for their low ESR and superior temperature
and voltage characteristics. Y5V capacitors should not be
used as their temperature coeffi cients make them unsuit-
able for this application.
When selecting capacitors for the application, fi rst con-
sider the DC voltage characteristic of the capacitor. The
capacitance value at the DC operating voltage may be
considerably lower than the rated value. Table 3 lists rec-
ommended capacitor values which have been chosen to
minimize the impact of this limitation. A 10μF ceramic
capacitor is the minimum recommended value for the
output fi lter capacitor. It is important to ensure the capaci-
tor value does not drop below 9μF for the operating range
of the application.
Manufacturer/
Part No.
Murata
GRM21BR60J226ME39
Murata
GRM188R60J106ME47
Murata
GRM21BR60J106KE01B
V
OUT(P-P)
Table 3 — Recommended Capacitors
= DI
L
× ESR
COUT
Value
(μF)
22
10
10
Voltage
Rated
(VDC)
6.3
6.3
6.3
Type
X5R
X5R
X5R
SC198A
Case
0805
0603
0805
Size
12