LTC3539 Datasheet, PDF (10/12 Pages) Linear Technology – 2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters

LTC3539/LTC3539-2
APPLICATIONS INFORMATION
Table 1. Representative Inductors
VENDOR
PART/STYLE
Coilcraft
[phone]
www.coilcraft.com
MSS5131
LPS4018-222
MSS6132
MOS6020
Murata
www.murata.com
LQH55D
LQH66S
Sumida
[phone]
www.sumida.com
CDRH4D22
CDRH4D28C
CDRH5D28
CDR6D23
TDK
[phone]
www.component.tdk.com
VLF5014ST
Toko
[phone]
www.tokoam.com
D53LC
D63LCB
Wurth
[phone]
www.we-online.com
WE-TPC Type LH, X
WE-PD Type XS
Output and Input Capacitor Selection
The internal loop compensation of the LTC3539 is designed
to be stable with output capacitor values of 10μF or greater.
Although ceramic capacitors are recommended, low ESR
(equivalent series resistance) tantalum capacitors may be
used as well.
Low ESR capacitors should be used to minimize the
output voltage ripple. Multilayer ceramic capacitors are
an excellent choice as they have extremely low ESR and
are available in small footprints. A 22μF to 47μF output
capacitor is sufficient for output voltages of 3V or greater.
An output capacitor of up to 100μF is required at lower
output voltages. Even with V_OUT greater than 3V, larger
values up to 100μF may be used to obtain extremely low
output voltage ripple and improve transient response. X5R
and X7R dielectric materials are preferred for their ability
to maintain capacitance over wide voltage and temperature
ranges. Y5V types should not be used.
A small ceramic capacitor in parallel with a larger tantalum
capacitor may be used in demanding applications which
have large load transients. A feedforward capacitor across
the top resistor of the feedback divider (from V_OUT to FB)
is usually required to improve transient response. A typical
value of 22pF will generally suffice.
Low ESR input capacitors reduce input switching noise and
reduce the peak current drawn from the battery. It follows
that ceramic capacitors are also a good choice for input
decoupling and should be located as close as possible to
the device. A 2.2μF input capacitor is sufficient for most
applications. Larger values may be used without limita-
tions. Table 2 shows a list of several ceramic capacitor
manufacturers. Consult the manufacturers directly for
detailed information on their selection of ceramic parts.
Table 2. Capacitor Vendor Information
SUPPLIER PHONE
WEBSITE
AVX
[phone]
www.avxcorp.com
Murata
[phone]
www.murata.com
Taiyo-Yuden [phone]
www.t-yuden.com
TDK
[phone]
www.component.tdk.com
TYPICAL APPLICATIONS
1 Cell to 1.8V
1 Cell to 3.3V
V_IN
1V TO 1.6V
2.2μF
2.2μH
V_IN
0.9V TO 1.6V
2.2μF
2.2μH
V_IN
SW
LTC3539
PWM BURST MODE V_OUT
1M
22pF
V_IN
SW
LTC3539
V_OUT
1.8V
PWM BURST MODE V_OUT
500mA
1M
OFF ON
SHDN FB
GND PGND
1.91M
22μF*
x5
OFF ON SHDN FB
GND PGND
562k
*AT HIGH LOAD CURRENTS, A
TANTALUM CAPACITOR WILL
IMPROVE PERFORMANCE.
3539 TA02
10
Li-Ion Cell to 5V
V_IN
3V TO 4.5V
2.2μF
2.2μH
22pF
V_IN
SW
LTC3539-2
V_OUT
3.3V
PWM BURST MODE V_OUT
350mA
1M
22μF
OFF ON
SHDN FB
x2
GND PGND
309k
3539 TA03
22pF
V_OUT
5V
750mA
22μF
3539 TA04
3539f