SC192IMLTRT Semtech, SC192IMLTRT Datasheet - Page 11

• Manufacturer Part Number: SC192IMLTRT
• Description: IC SYNC BUCK CONV 0.6A 10-MLPD
• Manufacturer: Semtech
• Type: Step-Down (Buck)r

Specifications of SC192IMLTRT

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.75 ~ 5.5 V
• Current - Output: 700mA
• Frequency - Switching: 750kHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MLPD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: SC192IMLTR

Inductor Selection
The inductor values listed in Table 1 will work for nearly
all combinations of output current and output voltages.
After selecting 4.7uH or 10uH for the inductor value two
additional inductor parameters should be considered. The
current rating of the inductor and the DC resistance.
The DC resistance has a great impact on efficiency due
to copper losses. However, small inductors tend to have
higher DC resistance. Therefore a compromise between
size and efficiency will need to be made.
The inductor current must be chosen to prevent the in-
ductor from saturation. The most conservative approach
would be to select an inductor with a saturation current
slightly above the maximum current capability of the
SC192 which is 1.56A peak current for ILIM = Vin or
780mA for ILIM = GND.
A more accurate design of the inductor would be to rate
the inductor for the maximum output current plus the
inductor ripple current that can be calculated as follows:
© 2007 Semtech Corp.
POWER MANAGEMENT
Applications Information Cont.
PSAVE, Cout = 4.7uF, Lout = 4.7uH
I
L(MAX)
Δ
I
L
=
⎛
⎜
⎜
⎜
⎜
⎝
=
- 1
L
I
V
O(MAX
V
•
OUT
f
IN
⎞
⎟
⎟
⎟
⎟
⎠
•
)
+
V
OUT
Δ
2
I
L
11
f = Switching frequency
L = Inductor Value
ΔI
I
V
V
C
I
I
Output Capacitor Selection
Because the SC192 has external compensation avail-
able, low ESR ceramic capacitors can be used. This elimi-
nates the need for bulky tantalum capacitors. Values for
the output capacitors in Table 1 will work for nearly all
combinations of output current and output voltages. The
equation for determining the size of the output capaci-
tor in terms of minimizing the ripple voltage is given as
follows:
Input Capacitor Selection
The input ripple current can be reduced with properly
selecting the input capacitor. Again, values for the input
capacitors in Table 1 will work for nearly all combina-
tions of input current and output voltages. The input ca-
pacitor should be rated for the maximum input ripple
current calculated as:
L
OUT
OUT(MAX)
OUT
IN
OUT
L
= Maximum inductor current
= Peak-to-peak inductor ripple current
= Input voltage
= Output Current
= Output voltage
= Output Capacitance
PWM, Cout = 4.7uF, Lout = 4.7uH
= Maximum DC Output Current
Δ
V
O
=
Δ
I
L
•
⎛
⎜
⎝
8
•
C
1
OUT
•
f
+
ESR
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⎠
SC192