LTC3524_15 Datasheet, PDF (1/16 Pages) Linear Technology – Adjustable TFT Bias Supply with WLED Driver

FEATURES
■ _{Generates Three Adjustable, Low Noise Rails for}
Small/Medium TFT Displays
■ _{Drives Up to Ten White LEDs}
■ _{LED Dimming and Open-Circuit Protection}
■ _{Controlled Power-Up/Power-Down Sequencing}
■ _{1.5MHz Fixed Frequency, Low Noise Operation}
■ _{VIN Range 2.5V to 6V, VOUT Range 3V to 6V}
■ _{TFT Supply Efficiency Up to 90%}
■ _{LED Supply Efficiency Up to 78%}
■ _{Two Independantly Enabled LED Strings}
■ _{200 to 1 True Color PWM}^TM _Dimming
■ _{Tiny External Solution}
■ _{24-Lead QFN Package (4mm × 4mm × 0.75mm)}
APPLICATIONS
■ _{PDAs, Palmtop Computers}
■ _{Digital Still and Video Cameras}
■ _{Handheld GPS}
■ _{Portable Instrument Displays}
■ _{Portable Media Players}
LTC3524
Adjustable TFT Bias Supply
with WLED Driver
DESCRIPTION
The LTC^®3524 is an integrated BIAS and white LED power
converter solution for small/medium-sized polysilicon thin
film transistor (TFT) liquid crystal (LCD) display panels.
The device operates from a single Lithium-Ion/polymer
battery or any voltage source between 2.5V and 6V.
A 1.5MHz synchronous boost converter generates a pro-
grammable low noise, high efficiency 25mA TFT supply
of up to 6.0V. Regulated, low ripple charge pumps are
used to generate up to +20V and –20V at 2mA. Output
sequencing is internally controlled to insure proper
initialization and rapid discharge of the LCD panel in
shutdown.
A second 1.5MHz boost converter powers one or two LED
strings with up to five series elements each. LED current
and display brightness can be controlled over a wide range
using analog or digital means up to 25mA.
The LTC3524 is offered in the 4mm × 4mm 24-pin QFN
package, minimizing the total solution footprint.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
True Color PWM is a registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
+5V, –7.5V, +12.5V, 8 LED Power Supply
+
–
+5V
25mA
+12.5V
2mA
Li-Ion
2.2μF
10μH 3.3μH
SW1
V_IN
SW2
VLED
10μF _324k
+10V
0.47μF
0.47μF _220k
V_OUT
1M
LED2
0.1μF
FBVO
VNIN
V2x
C2⁺
C2^–
VH
LTC3524
LED1
PROG
ELED2
ELED1
ELCD
FBN
2M
FBH
VN
CH⁺ CH^– GND CN⁺
0.1μF
0.1μF
10μF
100k for 20mA
470k
1M
V_IN
V_OUT
–7.5V
2mA
0.47μF
3524 TA01a
LCD Bias and LED Efficiency
V_IN = 3.6V, V_OUT = 5V, 8 LEDs
100
V_IN = 3.6V
90
LCD
80
LED
70
60
5
10
15
20
25
V_OUT OR LED STRING CURRENT (mA)
3524 TA01b
3524f
1