SC1566 查看數據表（PDF） - Semtech Corporation
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SC1566 Datasheet PDF : 12 Pages
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SC1566
POWER MANAGEMENT
Typical Characteristics (Cont.)
Quiescent Current vs.
Junction Temperature
700
VIN = 3.3V
690
680
670
660
650
640
630
620
610
600
-50 -25
0
25
50
75
TJ (°C)
100 125 150
Off-State Quiescent Current vs.
Junction Temperature
12
VIN = 5.5V
10
8
6
4
2
0
-50
-25
0
25
50
75
100 125 150
TJ (°C)
Applications Information
Introduction
The SC1566 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 very little pcb real estate and
typically does not require a heatsink. Additional features
include an enable pin to allow for a very low power
consumption standby mode, and a fully adjustable
output (5-pin versions).
Component Selection
to choose an appropriate output capacitor for a given
stability requirement.
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 (5-pin parts): the
use of 1% resistors, and designing for a current flow
≥ 10µµA is recommended to ensure a well regulated
output (thus R2 ≤ 120kΩ).
Input capacitor: a 4.7µF or 10µF ceramic capacitor is Thermal Considerations
recommended. This allows for the device being some
distance from any bulk capacitance on the rail. The power dissipation in the SC1566 is approximately
Additionally, input droop due to load transients is reduced, equal to the product of the output current and the input
improving load transient response. Additional capacitance to output voltage differential:
may be added if required by the application.
PD ≈ (VIN − VOUT )• IO
Output capacitor: a minimum bulk capacitance of 2.2µF,
along with a 0.1µF ceramic decoupling capacitor is The absolute worst-case dissipation is given by:
recommended. Increasing the bulk capacitance will
( ) improve the overall transient response. The use of PD(MAX ) = VIN (MAX ) − VOUT (MIN ) • IO(MAX ) + VIN (MAX ) • IQ (MAX )
multiple lower value ceramic capacitors in parallel to
achieve the desired bulk capacitance will not cause For a typical scenario, V = 3.3V ± 5%, V = 2.8V and
stability issues. Although designed for use with ceramic
output capacitors, the SC1566 is extremely tolerant of
IO = 2.5A, therefore:
IN
OUT
output capacitor ESR values and thus will also work
comfortably with tantalum output capacitors. For refer-
VIN(MAX) = 3.465V, VOUT(MIN) = 2.744V and IQ(MAX) = 1.75mA,
ence, the phase-margin contour of Figure 1. can be used Thus PD(MAX) = 1.81W.
2005 Semtech Corp.
7
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