lx1996 Microsemi Corporation, lx1996 Datasheet - Page 13

• Manufacturer Part Number: lx1996
• Description: Multi-string Led Back-light Controller
• Manufacturer: Microsemi Corporation

Copyright © 2007
Rev. 1.0, 2007-12-14
A
The internal dimming oscillator can be synchronized to an
external clock on the PWM input. A PLL loop filter capacitor
must be connected between CLF and GND pins for
synchronization. Use 0.1uF for 200Hz, 0.001uF for 20KHz.
The RT, CT and CLF pins can be left open if both the internal
dimming and ultrasonic pulse skipping modes are not used.
D
In this mode, a DC voltage on the DI pin is used to vary the
reference voltage at the PRG pin. The PRG pin reference
voltage, in conjunction with the resistor connected between the
PRG pin and ground, sets the LED current. The ratio of DI
input voltage to PRG pin voltage is 1:1, up to 2V input. The DI
input voltage range is 0V to 5V, however, the voltage at PRG
pin is limited to 0.2V to 2V with an internal voltage clamp.
Thus the dimming ratio is limited to 10:1. A higher dimming
ratio is obtained in the Combined Analog and Digital Dimming
mode.
NALOG TO
IRECT
A
NALOG
TM
D
IGITAL
D
IMMING
D
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
IMMING WITH EXTERNAL SYNC
O P E R A T I O N T H E O R Y
Analog Mixed Signal Group
Microsemi
®
The table below summarizes the dimming modes.
Multi-string LED Back-light Controller
DSEL1
Open
Open
Low
Low
Hi
Hi
P
RODUCTION
Table 1 - Dimming Modes
DSEL2
Low
Low
Low
Hi
Hi
Hi
D
ATASHEET
Direct Digital Dimming
Combined Analog and
Digital Dimming Modes
Direct Analog Dimming
Direct Analog Dimming
with Ultrasonic Pulse
Skipping (USPS)
Analog to Digital dimming
with internal clock
Analog to Digital dimming
with external clock
synchronization.
Dimming Method
LX1996
Page 13