LTC3524_15 Datasheet, PDF (12/16 Pages) Linear Technology – Adjustable TFT Bias Supply with WLED Driver

LTC3524
APPLICATIONS INFORMATION
Inductor Selection
3.3μH to 15μH inductors are recommended for use with
the LTC3524’s two boost converters. The synchronous
LCD bias boost inductor should have a saturation current
(I_SAT) rating of at least 150mA, where the nonsynchronous
white LED boost inductor should have a rating of at least
600mA. In most applications, the inductor value for the
LCD bias will be larger (10μH to 15μH) to prevent opera-
tion in deep discontinuous mode. The inductor value for
the white LED can be smaller (3.3μH to 6.8μH), since it
operates at higher currents. Ferrite core materials are
strongly recommended for their superior high frequency
performance characteristics. Inductors meeting these
requirements are listed in Table 1. The maximum current
and DCR ranges in the table correspond to the respec-
tive Inductance range (for example, the 3.3μH inductor
will have the highest maximum current and lowest DCR).
Shielded inductor series parts are in bold text.
The V_IN input capacitor should be an X5R type of at least
2.2μF using a low impedance connection to the battery.
The VLED output capacitor should be X5R type and at least
1μF for analog dimming and 4.7μF for PWM dimming.
The V_OUT capacitor should also be an X5R type between
2.2μF and 10μF. A larger capacitor (10μF) should be used
if lower output ripple is desired or the output load required
is close to the 25mA maximum.
The charge pumps require flying capacitors (C2⁺ to C2^–,
CN⁺, and CH⁺ to CH^–) that should be at least 0.1μF to obtain
specified performance. Ceramic X5R types are strongly
recommended for their low ESR and ESL and capacitance
vs bias voltage stability. The filter capacitors on V2x, VN,
Table 1. Recommended Inductors
PART
ME3220
LP03010
MSS4020
SD3112
L
(μH)
3.3-15
3.3-10
3.3-15
3.3-15
MIP3226D
3-10
LQH32CN
LQH2MC
CDRH3D16
CDRH2D14
NR3010
NR3015
4.7-15
4.7-15
3.3-15
3.3-12
3.3-15
3.3-15
MAXIMUM
CURRENT
(mA)
1300-700
950-570
1100-440
970-405
1000-200
650-300
300-200
1100-520
820-420
750-400
1200-560
DCR (Ω)
0.14-0.52
0.2-0.52
0.09-0.33
0.16-0.65
0.1-0.16
0.15-0.58
0.8-1.6
0.09-0.41
0.12-0.32
0.16-0.74
0.1-0.36
DIMENSIONS
(mm)
(L × W × H)
3.2 × 2.5 × 2.0
3.0 × 3.0 × 1.0
4.0 × 4.0 × 2.0
3.1 × 3.1 × 1.2
3.2 × 2.6 × 1.0
3.2 × 2.5 × 1.5
2 × 1.6 × 0.9
3.8 × 3.8 × 1.8
3.2 × 3.2 × 1.5
3.0 × 3.0 × 1.0
3.0 × 3.0 × 1.5
MANUFACTURER
Coil Craft
www.coilcraft.com
Cooper
www.cooperet.com
FDK
www.fdk.com
Murata
www.murata.com
Sumida
www.sumida.com
Taiyo Yuden
www.t-yuden.com
3524f
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