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LTC3526EDC-2#TRMPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
LTC3526-2/LTC3526B-2
10
35262b2fc
V
IN
> V
OUT
OPERATION
The LTC3526-2/LTC3526B-2 will maintain voltage regula-
ti
on even when the input voltage is above the desired output
voltage. Note that the efficiency is much lower in this mode,
and the maximum output current capability will be less.
Refer to the Typical Performance Characteristics.
SHORT-CIRCUIT PROTECTION
The LTC3526-2/LTC3526B-2 output disconnect feature
allows output short circuit while maintaining a maximum
internally set current limit. To reduce power dissipation
under short-circuit conditions, the peak switch current
limit is reduced to 400mA (typical).
SCHOTTKY DIODE
Although it is not required, adding a Schottky diode from
SW to V
OUT
will improve efficiency by about 2%. Note
that this defeats the output disconnect and short-circuit
protection features.
PCB LAYOUT GUIDELINES
The high speed operation of the LTC3526-2/LTC3526B-2
demands careful attention to board layout. A careless
layout will result in reduced performance. Figure 2 shows
the recommended component placement. A large ground
pin copper area will help to lower the die temperature. A
multilayer board with a separate ground plane is ideal, but
not absolutely necessary.
COMPONENT SELECTION
Inductor Selection
T
h
e LTC3526-2/LTC3526B-2 can utilize small surface
mount chip inductors due to their fast 2MHz switching
frequency. Inductor values between 1.5µH and 3.3µH are
suitable for most applications. Larger values of inductance
will allow slightly greater output current capability (and
lower the Burst Mode threshold) by reducing the inductor
ripple current. Increasing the inductance above 10µH will
increase size while providing little improvement in output
current capability.
The minimum inductance value is given by:
L
V V V
RIPPLE V
IN MIN OUT MAX IN MIN
OUT MA
>
−
( )
( ) ( ) ( )
(
•
• •2
XX)
where:
Ripple = Allowable inductor current ripple (amps peak-
peak)
V
IN(MIN)
= Minimum input voltage
V
OUT(MAX)
= Maximum output voltage
The inductor current ripple is typically set for 20% to
40% of the maximum inductor current. High frequency
ferrite core inductor materials reduce frequency depen
-
dent power
losses compared to cheaper powdered iron
types, improving efficiency. The inductor should have
low ESR (series resistance of the windings) to reduce the
I
2
R power losses, and must be able to support the peak
Figure 2. Recommended Component Placement for Single Layer Board
+
SW
LTC3526-2
1
GND
MINIMIZE
TRACE ON FB
AND SW
2
V
IN
MULTIPLE VIAS
TO GROUND PLANE
V
IN
V
OUT
FB
SHDN
35262b2 F02
3
6
5
4
ApplicAtions inForMAtion
LTC3526-2/LTC3526B-2
11
35262b2fc
inductor current without saturating. Molded chokes and
some chip inductors usually do not have enough core
area to support the peak inductor currents of 700mA
seen on the LTC3526-2/LTC3526B-2. To minimize radiated
noise, use a shielded inductor. See Table 1 for suggested
components and suppliers.
Table 1. Recommended Inductors
VENDOR PART/STYLE
Coilcraft
(847)
639-6400
www.coilcraft.com
LPO4815
LPS4012, LPS4018
MSS5131
MSS4020
MOS6020
ME3220
DS1605,
DO1608
Coiltronics
www.cooperet.com
SD10,
SD12, SD14, SD18, SD20,
SD52, SD3114, SD3118
FDK
(408)
432-8331
www.fdk.com
MIP3226D4R7M,
MIP3226D3R3M
MIPF2520D4R7
MIPWT3226D3R0
Murata
(714)
852-2001
www.murata.com
LQH43C
LQH32C (-53 series)
301015
Sumida
(847)
956-0666
www.sumida.com
CDRH5D18
CDRH2D14
CDRH3D16
CDRH3D11
CR43
CMD4D06-4R7MC
CMD4D06-3R3MC
Taiyo-Yuden
www.t-yuden.com
NP03SB
NR3015T
NR3012T
TDK
(847)
803-6100
www.component.tdk.com
VLP
VLF, VLCF
Toko
(408)
432-8282
www.tokoam.com
D412C
D518LC
D52LC
D62LCB
Wurth
(201)
785-8800
www.we-online.com
WE-TPC
type S, M
Output and Input Capacitor Selection
Low ESR (equivalent series resistance) 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 4.7µF to 10µF output capacitor is sufficient for most
applications. Larger values up to 22µF 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 LTC3526-2 is de
-
signed 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 (803)
448-9411 www.avxcorp.com
Murata (714)
852-2001 www.murata.com
Taiyo-Yuden (408)
573-4150 www.t-yuden.com
TDK (847)
803-6100 www.component.tdk.com
Samsung (408)
544-5200 www.sem.samsung.com
ApplicAtions inForMAtion
LTC3526-2/LTC3526B-2
12
35262b2fc
1-Cell to 1.8V Converter with <1mm Maximum Height for Low-Noise Applications
1-Cell to 3.3V
2-Cell to 3.3V
SW
V
IN
511k
FDK MIPF2520D2R2
MURATA GRM219R60J475KE19D
*
**
2.2µH*
1M
1µF
4.7µF**
35262b2 T02a
LTC3526B-2
SHDN
V
OUT
FB
V
IN
1V TO 1.6V
V
OUT
1.8V
150mA
OFF ON
GND
SW
V
IN
1.78M
2.7µH*
1M
*TAIYO-YUDEN NP03SB2R7M
1µF
10µF
22pF
35262b2 T04a
LTC3526-2
SHDN
V
OUT
FB
V
IN
1V TO 1.6V
V
OUT
3.3V
75mA
OFF ON
GND
SW
V
IN
1.78M
2.7µH*
1M
*TAIYO-YUDEN NP03SB2R7M
1µF
4.7µF
35262b2 T05a
LTC3526-2
SHDN
V
OUT
FB
V
IN
2V TO 3.2V
V
OUT
3.3V
200mA
OFF ON
GND
LOAD CURRENT (mA)
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 1000
35262b2 TA02b
30
20
10
0
90
100
V
IN
= 1.5V
V
IN
= 1.2V
V
IN
= 0.9V
V
OUT
= 1.8V
LOAD CURRENT (mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 1000
35262b2 TA04b
30
20
10
0
90
100
V
IN
= 1.5V
V
IN
= 1.2V
V
IN
= 0.9V
V
OUT
= 3.3V
LOAD CURRENT (mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 1000
35262b2 TA05b
30
20
10
0
90
100
V
IN
= 3.0V
V
IN
= 2.4V
V
IN
= 1.8V
V
OUT
= 3.3V
typicAl ApplicAtions
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LTC3526EDC-2#TRMPBF

Mfr. #:
Buy LTC3526EDC-2#TRMPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 500mA, 2MHz Synch Step -Up in DFN
Lifecycle:
New from this manufacturer.
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