SC1548CSK-1.8 TRT Semtech, SC1548CSK-1.8 TRT Datasheet - Page 12

• Manufacturer Part Number: SC1548CSK-1.8 TRT
• Manufacturer: Semtech

Specifications of SC1548CSK-1.8 TRT

• Lead Free Status / RoHS Status: Compliant

It is possible to adjust the output voltage of the fixed
voltage options, by applying an external resistor divider
to the sense pin (please refer to Figure 1 below). Since
the sense pin sinks a nominal 100µA, the resistor
values should be selected to allow 10mA to flow through
the divider. This will ensure that variations in this current
do not adversely affect output voltage regulation. Thus a
target value for R2 (maximum) can be calculated:
Adjustable Output Voltage Option
The adjustable output voltage option does not have an
internal resistor divider. The adjust pin connects directly
to the inverting input of the error amplifier, and the
output voltage is set using external resistors (please
refer to Figure 2 above). In this case, the adjust pin
sources a nominal 0.5µA, so the resistor values should
be selected to allow 50µA to flow through the divider.
POWER MANAGEMENT
Applications Infomation (Cont.)
2004 Semtech Corp.
VOUT
VOUT
Figure 2: Setting The Output Voltage of the Adjustable Output Voltage Option
Figure 1: Adjusting The Output Voltage of Fixed Output Voltage Options
R1
R2
R1
R2
+
+
C1
100uF
C1
100uF
+
+
C2
100uF
C2
100uF
Q1
Q1
12
+
The output voltage can only be adjusted upwards from the fixed
output voltage, and can be calculated using the
following equation:
+
Again, a target value for R2 (maximum) can be
calculated:
The output voltage can be calculated as follows:
R
R
V
V
2
OUT
2
OUT
C3
22uF
C3
22uF
(
ADJUSTED
. 1
V
50
OUT
. 1
263
10
263
mA
(
A
FIXED
V
)
)
1
2
3
1
SC1548CSK-X.X
V
1
2
3
OUT
SNS
GND
DRV
SC1548CSK
U1
R
R
VPWR
VPWR
ADJ
GND
DRV
U1
(
1
2
FIXED
EN
IN
EN
IN
)
0
5 .
5
4
5
4
1
A
R
R
12V IN
R
1
2
12V IN
1
C4
0.1uF
R
C4
0.1uF
1
ENABLE
100
ENABLE
SC1548
www.semtech.com
A
Volts