LTC3535_15 Datasheet, PDF (13/16 Pages) Linear Technology – Dual Channel 550mA 1MHz Synchronous Step-Up DC/DC Converter

LTC3535
APPLICATIONS INFORMATION
4.7µF to 10µF output capacitor is sufficient for most ap-
plications. Larger values 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.
The internal loop compensation of the LTC3535 is designed
to be stable with output capacitor values of 4.7µF or greater
(without the need for any external series resistor). Although
ceramic capacitors are recommended, low ESR tantalum
capacitors may be used as well.
A small ceramic capacitor in parallel with a larger tantalum
capacitor may be used in demanding applications that have
large load transients. Another method of improving the
transient response is to add a small feed-forward capacitor
across the top resistor of the feedback divider (from V_OUT
to FB). 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, although larger values may be
used without limitations. Table 2 shows a list of several
ceramic capacitor manufacturers. Consult the manufactur-
ers directly for detailed information on their selection of
ceramic capacitors.
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
Samsung
[phone]
www.sem.samsung.com
TYPICAL APPLICATION
Single Cell to 3.3V Converter with 20 Seconds of Holdup with 30mA Load
V_IN
0.8V
TO 1.5V
2.2µF
499k
2.2µF
4.7µH
SW
V_IN1
V_OUT1
SHDN1 V_OUT2
LTC3535
V_IN2
FB1
1.5M
SHDN2
FB2
GND SW2 GND
4.7µH
V_OUT
3.3V
30mA
10µF
V_HOLDUP
+ _CHOLD*
0.47F
1.78M
4.25V
1M
392k
1M
3535 TA02
*POWERSTOR PA-5R0H474-R
V_IN
1V/DIV
V_HOLDUP
2V/DIV
V_OUT
2V/DIV
5s/DIV
3535 TA02b
3535fa
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