LTC1697 Datasheet, PDF (1/8 Pages) Linear Technology – High Efficiency Low Power 1W CCFL Switching Regulator

LTC1697
High Efficiency Low Power
1W CCFL Switching Regulator
FEATURES
■ _{Operates from Single Li-Ion Battery}
■ _{2.8V to 5.5V Input Voltage Range}
■ _{Very Low Shutdown Current: <2µA}
■ _{Synchronous Buck Architecture for High Efficiency}
■ _{PWM Dimming Frequency Adjustable with a Single}
Capacitor
■ _{Accurate Lamp Current Maximizes Lamp Lifetime}
■ _{Fixed Frequency Operation at 300kHz}
■ _{Internal or External PWM Dimming}
■ _{Small 10-Pin MSOP Package}
U
APPLICATIO S
■ _PDAs
■ _{Handheld Computers}
■ _{Portable Instruments}
■ _{Handheld GPS with Map Display}
■ _{Handheld TV/Video Monitor}
DESCRIPTIO
The LTC^®1697 is designed to control a single 1W cold
cathode fluorescent lamp (CCFL). An internal PWM dim-
ming system maximizes efficiency and dimming range.
Accurate lamp currents can be set with a single external
resistor.
The LTC1697 includes a synchronous current mode PWM
controller with internal 1A MOSFET switches. It contains
a 300kHz oscillator, 0.8V reference, and internal current
sense. It operates from a 2.8V to 5.5V input voltage. The
LTC1697 also has a thermal limit and a shutdown that
reduces supply current to <2µA.
The LTC1697 is available in the MSOP-10 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Protected by U.S. Patent 6522116.
TYPICAL APPLICATIO
6
5
27pF
1kV
1
10 2 3 4
V_IN
2.8V TO 5.5V
330Ω
0.15µF
CCFL
LAMP
+
Li-Ion
CELL
33µH
200k
10µF
OFF ON
DIMMING INPUT
1V(0%) – 2V(100%)
0.022µF
V_IN SW 0V_SEN
SHDN
LTC1697
V_{DIM LAMP}
C_DIM
R_PROG
V_C
GND
8.25k
0.1µF
1697 TA01
I_CCFL vs R_PROG
10
9
8
7
6
5
4
3
2
4k
6k 8k 10k
R_PROG (Ω)
20k
1967 TA01b
1697f
1