LT3595AEUHH-PBF Просмотр технического описания (PDF) - Linear Technology
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LT3595AEUHH-PBF Datasheet PDF : 16 Pages
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OPERATION
Discontinuous Current Mode
The LT3595A can drive a 10-LED string at 15mA LED
current operating in continuous conduction mode using
the recommended external components shown in the ap-
plication circuit on page 1 of this data sheet. As current
is further reduced, the regulator enters discontinuous
conduction mode. The photo in Figure 1 details circuit
operation driving ten LEDs at 10mA load. The inductor
current reaches zero during the discharge phase and the
SW pin exhibits ringing. The ringing is due to the LC tank
circuit formed by the inductor in combination with the
switch and diode capacitance. This ringing is not harmful;
far less spectral energy is contained in the ringing than in
the switch transitions.
LT3595A
VSW
20V/DIV
IL
20mA/DIV
400ns/DIV
VIN = 45V
10 LEDS AT 10mA
3595A F01
Figure 1. Switching Waveforms
APPLICATIONS INFORMATION
Inductor Selection
A 100μH inductor is recommended for most LT3595A
applications. Although small size and high efficiency are
major concerns, the inductor should have low core losses
at 2MHz and low DCR (copper wire resistance). Some
inductors that meet these criteria are listed in Table 1. An
efficiency comparison of different inductors is shown in
Figure 2.
100
COILCRAFT 1812FS-104KLB
COILCRAFT LPS4012-104MLB
TOKO A915AY-101M
TDK VLCF4020T-101MR26
COILTRONICS SD3812-101
95
COILTRONICS SD52-101
90
Table 1. Inductor Manufacturers
VENDOR
PART
SERIES
INDUCTANCE
RANGE (μH)
RELEVANT TO
LT3595A
Coilcraft
www.coilcraft.com
DO1605
LPS4012
1812FS
MSS5131
100 to 680
100 to 680
100 to 680
100 to 390
Sumida
www.sumida.com
CDC4D20 100 to 680
Toko
www.tokoam.com
D53LC
100 to 680
TDK
www.component.
tdk.com
VLCF4020T 100 to 330
Coiltronics
www.cooperet.com
SD3812
SD52
100 to 330
100 to 330
Murata
www.murata.com
LQH32M
LQH43M
100 to 560
100 to 680
DIMENSIONS
(mm)
5.4 × 4.2 × 1.8
4 × 4 × 1.2
5.8 × 4.9 × 3.8
5.1 × 5.1 × 3.1
4.8 × 4.8 × 2
5.2 × 5.4 × 3
4×4×2
4 × 4 × 1.2
5.6 × 5.2 × 2
3.2 × 2.5 × 2
4.5 × 3.2 × 2
85
10
20
30
ILED (mA)*
VIN = 45V L = 100μH
10 LEDS
*ILED ADJUSTED WITH RSET
40
50
3595A F02
Figure 2. Efficiency Comparison of Different Inductors
Capacitor Selection
The small size of ceramic capacitors make them ideal for
LT3595A applications. Only X5R and X7R types should
be used because they retain their capacitance over wider
voltage and temperature ranges than other types such as
Y5V or Z5U. Typically, 10μF capacitors on VIN and VCC
are sufficient. The output capacitor used across the LED
3595af
9
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