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LTC3526LEDC-2#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
LTC3526L-2/LTC3526LB-2
10
3526lb2fa
V
IN
> V
OUT
OPERATION
The LTC3526L-2/LTC3526LB-2 will maintain voltage regu-
lation 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.
S
HOR
T-CIRCUIT PROTECTION
The LTC3526L-2/LTC3526LB-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).
S
CHOTTKY DIODE
Although not recommended, 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
LA
YOUT GUIDELINES
The high speed operation of the LTC3526L-2/LTC3526LB-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
The LTC3526L-2/LTC3526LB-2 can utilize small surface
mount chip inductors due to their fast 2MHz switching
frequency. Inductor values between 1.5µH and 4.7µH 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 6.8µH will
increase component 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
OU
>
( )
( ) ( ) ( )
• –
• •2
TT MAX( )
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
LTC3526L-2
1
GND
MINIMIZE
TRACE ON FB
AND SW
2
V
IN
MULTIPLE VIAS
TO GROUND PLANE
V
IN
V
OUT
FB
SHDN
3526lb2 F02
3
6
5
4
applicaTions inForMaTion
LTC3526L-2/LTC3526LB-2
11
3526lb2fa
inductor current without saturating. Molded chokes and
some chip inductors usually do not have enough core
area to support the peak inductor current of 750mA seen
on the LTC3526L-2
/LTC3526LB-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,
LPS3314
MSS4020
ME3220
Coiltronics
www.cooperet.com
SD10, SD12, SD3114, SD3118
FDK
(408) 432-8331
www.fdk.com
MIP3226D
MIPF2520D
MIPWT3226D
MIPSZ2012D
MIPS2520D
Murata
(714) 852-2001
www.murata.com
LQH3NP
LQH32P
LQM2MPN
Sumida
(847) 956-0666
www.sumida.com
CDRH2D14
CDRH2D11
CDRH3D11
Taiyo-Yuden
www.t-yuden.com
NR3010T
NR3015T
NR3012T
TDK
(847) 803-6100
www.component.tdk.com
VLP
VLF, VLCF
Toko
(408) 432-8282
www.tokoam.com
D412C
Würth
(201) 785-8800
www.we-online.com
WE-TPC type S, M, TH, XS
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 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 LTC3526L-2/
LTC3526LB-2 are designed to be stable with output ca-
pacitor 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
LTC3526L-2/LTC3526LB-2
12
3526lb2fa
1-Cell to 1.8V Converter with <1mm Maximum Height
Fixed Frequency 1-Cell to 2.85V Low Noise Converter
1-Cell to 3.3V
SW
V
IN
511k
FDK MIPWT3226D2R2
MURATA GRM219R60J106KE19D
*
**
1M
2.2µH*
1µF
10µF**
68pF
3526lb2 TA02a
LTC3526L-2
SHDN
V
OUT
FB
V
IN
0.8V TO 1.6V
V
OUT
1.8V
150mA
OFF ON
GND
SW
V
IN
1.4M
1M
*SUMIDA CDRH2D11NP-2R2N
3526lb2 TA03a
LTC3526LB-2
SHDN
V
OUT
FB
V
IN
0.8V TO 1.6V
V
OUT
2.85V
100mA
OFF ON
GND
2.2µH*
1µF
4.7µF
SW
V
IN
1.78M
1M
*TAIYO-YUDEN NR3015T2R2M
33pF
3526lb2 TA04a
LTC3526L-2
SHDN
V
OUT
FB
V
IN
0.8V TO 1.6V
V
OUT
3.3V
75mA
OFF ON
GND
2.2µH*
1µF
10µF
LOAD CURRENT (mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 1000
3526lb2 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
3526lb2 TA03b
30
20
10
0
90
100
V
IN
= 1.5V
V
IN
= 1.2V
V
IN
= 0.9V
V
OUT
= 2.85V
LOAD CURRENT (mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 1000
3526lb2 TA04b
30
20
10
0
90
100
V
IN
= 1.5V
V
IN
= 1.2V
V
IN
= 0.9V
V
OUT
= 3.3V
Typical applicaTions
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LTC3526LEDC-2#TRPBF

Mfr. #:
Buy LTC3526LEDC-2#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 550mA, 2MHz Synchronous Step-Up DC/DC Converters in 2mm x 2mm DFN
Lifecycle:
New from this manufacturer.
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