ltc3566 Linear Technology Corporation, ltc3566 Datasheet - Page 21

• Manufacturer Part Number: ltc3566
• Description: High Ef?ciency Usb Power Manager Plus 1a Buck-boost Converter
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
V
The style and value of capacitors used with the LTC3566
determine several important parameters such as regulator
control-loop stability and input voltage ripple. Because
the LTC3566 uses a step-down switching power supply
from V
high frequency components. It is strongly recommended
that a low equivalent series resistance (ESR) multilayer
ceramic capacitor be used to bypass V
aluminum capacitors are not recommended because of
their high ESR. The value of the capacitor on V
controls the amount of input voltage ripple for a given load
current. Increasing the size of this capacitor will reduce
the input voltage ripple.
To prevent large V
conditions, it is also recommended that a ceramic capaci-
tor be used to bypass V
in the compensation of the switching regulator. At least
4μF of actual capacitance with low ESR are required on
V
performance and stability.
Multilayer ceramic chip capacitors typically have excep-
tional ESR performance. MLCCs combined with a tight
board layout and an unbroken ground plane will yield very
good performance and low EMI emissions.
There are several types of ceramic capacitors available,
each having considerably different characteristics. For
example, X7R ceramic capacitors have the best voltage
and temperature stability. X5R ceramic capacitors have
apparently higher packing density but poorer performance
over their rated voltage and temperature ranges. Y5V
ceramic capacitors have the highest packing density,
but must be used with caution, because of their extreme
nonlinear characteristic of capacitance vs voltage. The
actual in-circuit capacitance of a ceramic capacitor should
be measured with a small AC signal (ideally less than
200mV) as is expected in-circuit. Many vendors specify
the capacitance vs voltage with a 1V
as a result overstate the capacitance that the capacitor will
present in the application. Using similar operating condi-
tions as the application, the user must measure or request
BUS
OUT
. Additional capacitance will improve load transient
and V
BUS
to V
OUT
OUT
Bypass Capacitors
OUT
, its input current waveform contains
voltage steps during transient load
OUT
. The output capacitor is used
RMS
BUS
AC test signal and
. Tantalum and
BUS
directly
from the vendor the actual capacitance to determine if the
selected capacitor meets the minimum capacitance that
the application requires.
Buck-Boost Regulator Input/Output Capacitor
Selection
Low ESR MLCC capacitors should be used at both the
buck-boost regulator output (V
regulator input supply (V
capacitors should be used because they retain their ca-
pacitance over wider voltage and temperature ranges than
other ceramic types. A 22μF output capacitor is suffi cient
for most applications. The buck-boost regulator input sup-
ply should be bypassed with a 2.2μF capacitor. Consult
with capacitor manufacturers for detailed information on
their selection and specifi cations of ceramic capacitors.
Many manufacturers now offer very thin (<1mm tall)
ceramic capacitors ideal for use in height restricted de-
signs. Table 6 shows a list of several ceramic capacitor
manufacturers.
Table 6. Recommended Ceramic Capacitor Manufacturers
Over-Programming the Battery Charger
The USB high power specifi cation allows for up to 2.5W to
be drawn from the USB port (5V x 500mA). The PowerPath
switching regulator transforms the voltage at V
above the voltage at BAT with high effi ciency, while limiting
power to less than the amount programmed at CLPROG.
In some cases the battery charger may be programmed
(with the PROG pin) to deliver the maximum safe charging
current without regard to the USB specifi cations. If there
is insuffi cient current available to charge the battery at the
programmed rate, the PowerPath regulator will reduce
charge current until the system load on V
MANUFACTURER
Vishay Siliconix
Taiyo Yuden
Murata
AVX
TDK
IN1
). Only X5R or X7R ceramic
OUT1
www.avxcorp.com
www.t-yuden.com
) and the buck-boost
www.murata.com
www.vishay.com
www.tdk.com
WEBSITE
LTC3566
OUT
is satisfi ed
BUS
21
to just
3566p