SC1563ISK-1.8TR Semtech, SC1563ISK-1.8TR Datasheet - Page 6

• Manufacturer Part Number: SC1563ISK-1.8TR
• Description: IC, LDO VOLT REG, 1.8V, 0.5A, 5-SOT-23
• Manufacturer: Semtech

Specifications of SC1563ISK-1.8TR

• Primary Input Voltage: 6.5V
• Output Voltage Fixed: 1.8V
• Dropout Voltage Vdo: 350mV
• No. Of Pins: 5
• Output Current: 500mA
• Operating Temperature Range: -40°C To +85°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Introduction
The SC1563 is intended for applications such as
graphics cards where high current capability and very low
dropout voltage are required. It provides a very simple,
low cost solution that uses little pcb real estate.
Additional features include a shutdown pin to allow for a
very low power consumption standby mode, and a fully
adjustable output.
Component Selection
Input capacitor - a 1µF ceramic capacitor is
recommended. This allows for the device being some
distance from any bulk capacitance on the rail.
Additionally, input droop due to load transients is reduced,
improving load transient response. Additional capacitance
may be added if required by the application.
Output capacitor - a minimum bulk capacitance of 1µF,
along with a 0.1µF ceramic decoupling capacitor is
recommended. Increasing the bulk capacitance will
improve the overall transient response. The use of
multiple lower value ceramic capacitors in parallel to
achieve the desired bulk capacitance will not cause
stability issues. Although designed for use with ceramic
output capacitors, the SC1563 is extremely tolerant of
output capacitor ESR values and thus will also work
comfortably with tantalum output capacitors.
Noise immunity - in very electrically noisy environments,
it is recommended that 0.1µF ceramic capacitors be
placed from IN to GND and OUT to GND as close to the
device pins as possible.
External voltage selection resistors - the use of 1%
resistors, and designing for a current flow
recommended to ensure a well regulated output (thus
R2
POWER MANAGEMENT
Applications Information
2006 Semtech Corp.
120k ).
10µA is
6
Thermal Considerations
The power dissipation in the SC1563 is approximately
equal to the product of the output current and the input
to output voltage differential:
The absolute worst-case dissipation is given by:
For a typical scenario, V
I
V
V
I
Thus P
Using this figure, and assuming T
calculate the maximum thermal impedance allowable to
maintain T
This should be achievable with the SOT-23-5 package
using pcb copper area to aid in conducting the heat away
from the device. Internal ground/power planes and air
flow will also assist in removing heat.
P
P
R
OUT
Q(MAX)
IN(MAX)
OUT(MIN)
D
D
TH
(
MAX
J (
= 500mA, therefore:
V
)
A
= 150µA,
)(
= 3.465V,
D(MAX)
IN
MAX
= 2.450V and
V
)
V
J
IN
OUT
(
= 0.508W.
MAX
150°C:
T
)
( J
MAX
I
OUT
V
P
D
OUT
)
(
MAX
(
T
MIN
A
)
IN
(
MAX
)
= 3.3V ± 5%, V
)
I
OUT
(
MAX
150
. 0
)
A(MAX)
508
V
70
IN
= 70°C, we can
(
MAX
SC1563
www.semtech.com
OUT
157
)
= 2.5V and
I
Q
(
MAX
C
/
W
)