LINEAR dn417f Data Sheet
Summary
This documentation details the LT3489, a miniature, high-frequency DC-DC converter engineered for demanding electronic applications. The device provides multiple regulated outputs (such as 8V, 23V, and -8V) from a single wide input range, making it ideal for power-hungry systems like large TFT-LCD panels or portable devices. The manual covers detailed circuit designs and technical specifications, helping engineers integrate reliable, space-saving power solutions into complex electronics requiring high power density and efficiency.
Page 1 Text Content
Drive Large TFT-LCD Displays with a Space-Saving Triple-Output Regulator – Design Note 417 Jesus Rosales
Introduction switching frequency, and it is also pin compatible with
The power appetite of large TFT-LCDs appears to be the popular LT1946. The design process with the LT3489 insatiable. Power supplies must feed increasing numbers is easy and predictable.
of transistors and improved display resolutions, and do
The circuit in Figure 2 operates as a SEPIC converter,
so without taking much space.
allowing the output to be higher or lower than the input.
The triple output supply shown in Figure 1 shows a com- Pulling the ⎯S⎯H ⎯D⎯N pin to ground sets the output at 0V even
pact design based on the LT3489, which is optimized for while the voltage source is connected to the input.
driving large TFT panel displays. The main output provides
Both applications take full advantage of the soft-start
8V at 600m A while the 23V and –8V outputs provide 10m A
feature in which a single capacitor programs the voltage
and 20m A respectively, all from a 3.3V input. Even though
ramp rate of the output at startup. The 2MHz switching
TFT converters generally run from a regulated 3.3V or
frequency makes possible the use of small surface mount
5V source, this converter can operate seamlessly from
inductors and ceramic capacitors, which reduce the total
a Lithium-Ion battery, delivering 5W when the battery is
footprint of the design. Figure 3 shows how small the
drained to 3.3V and 8W when it is at 4.2V.
triple-output TFT circuit in Figure 1 can be.
The LT3489 squeezes a 2.5A, 0.12Ω, 40V switch into a
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology tiny 3mm × 3mm MS8E footprint. It offers external or Corporation. All other trademarks are the property of their respective owners.
internal compensation, an internal soft-start, a 2MHz
D1 D2 BAT54S BAT54S VON
2.2μH AVDD
3.3V TO 5V
VIN SW DFLS220L R3
LT3489 SS VOFF
FB –8V
VC GND D5
BAT54S
DN417 F01
L1: COOPER ELECTRONICS; SD25-2R2
Figure 1. A 3.3V Input, Triple-Output—8V, 23V and –8V—2MHz, TFT Converter
Page Summary Contents For LINEAR dn417f Data Sheet
Manual Details
| Brand | Linear |
|---|---|
| Pages | 2 |
| File Size | 126.82 KB |
| Published | May 31, 2026 |
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Frequently Asked Questions
What kind of circuit is shown in Figure 2?
Figure 2 illustrates a converter that operates from a 3V to 10V input, providing an 8V output with current capacity between 400mA and 900mA.
Does the LT3489 support different operating modes and flexibility?
Yes, it offers external or internal compensation, an internal soft-start, a fixed frequency, and flexible compensation for improved performance.
What is the size of the LT3489's switch package?
The rugged 2.5A, 0.12Ω, 40V internal switch fits remarkably well into a tiny 3mm × 3mm MS8E footprint.
Can the triple-output circuit be used with different power sources?
Yes, it can operate seamlessly from a 3.3V input down to 5V source or even a Lithium-Ion battery.