LX1691
Enhanced Multi-Mode CCFL Controller
®
TM
PRODUCTION DATA SHEET
FUNCTIONAL PIN DESCRIPTION (CONTINUED)
DESCRIPTION
PIN NAME
Brightness Reference Current Output. This variable current source is the mirror of BRITE_R current multiplied
by the BRITE_IN signal and becomes the reference voltage to the error amplifier when DIM_MODE is open or
½ VDDA. Connecting an additional resistor to VDDA determines minimum lamp current in order to prevent fault
condition. A light sensor (LX1970) may be used in conjunction with BRITE_OUT to change amplitude of lamp
current in response to ambient light intensity.
BRITE_OUT
VBRITE_OUT = VBRITE_IN X BRITE_OUT/BRITE_R (When DD_CLK is connected to VDDA
)
VBRITE_OUT = (2-VBRITE_IN) X BRITE_OUT/BRITE_R (When DD_CLK is connected to GND)
When DIM_MODE is GND or VDDA, then BRITE_OUT has to be biased with an external resistor.
Dedicated bias resistor for BRITE_OUT current source when DIM_MODE is open or ½ VDDA. Connecting an
additional resistor to VDDA determines minimum Burst Duty Cycle in digital dimming. A light sensor (LX1970)
may be used in conjunction with BRITE_R to change Burst Duty Cycle in response to ambient light intensity.
BRITE_R
DIMMING TABLE
DIM_
MODE
DD_
CLK
DESCRIPTION
CONDITIONS
Reversed Internal Digital
Dimming
Internally Clocked PWM
Burst Generator, External
Input to BRITE_IN
Voltage at BRITE_IN controls lamp current burst duty cycle. Duty cycle is inversely
proportional to voltage at BRITE_IN. Burst period is LX1691 oscillator frequency
divided by 1024 (lamp current frequency divided by 512). An external voltage
connected to the BRITE_OUT pin sets lamp current amplitude.
Low
0V
Conventional Internal
Digital Dimming
Voltage at BRITE_IN controls lamp current burst duty cycle. Duty cycle is directly
proportional to voltage at BRITE_IN. Burst period is LX1691 oscillator frequency
divided by 1024 (lamp current frequency divided by 512). An external voltage
connected to the BRITE_OUT pin sets lamp current amplitude
Internally clocked PWM
Burst Generator, External
Input to BRITE_IN
High
Conventional External
Digital Dimming
Externally clocked PWM
burst generator, external
input to BRITE_IN
Voltage at BRITE_IN controls lamp current burst duty cycle. Duty cycle is directly
proportional to voltage at BRITE_IN. Burst period is DD_CLK input divided by 512. An
external voltage connected to the BRITE_OUT pin sets lamp current amplitude.
VDDA
Pulse
Reversed Analog
Voltage at BRITE_IN controls lamp current amplitude. Amplitude is inversely
proportional to voltage at BRITE_IN.
Voltage at BRITE_IN controls lamp current amplitude. Amplitude is directly proportional
to voltage at BRITE_IN.
Low
Amplitude Dimming
Conventional Analog
Amplitude Dimming
High
Voltage at BRITE_IN controls lamp current amplitude. Amplitude is directly proportional
to voltage at BRITE_IN.
½
VDDA
or open
Conventional Analog
Amplitude Dimming with
External Direct PWM
Control
Burst period and duty cycle are directly proportional to signal at DD_CLK input pin. If
held low, duty cycle is 0% (Zero duty will cause a fault shut down. Minimum duty to
prevent fault shut down is lamp and temperature dependent. User must characterize
lamp to determine minimum duty cycle.). If held high, duty cycle is 100% (full
brightness).
Pulse
Copyright © 2003
Rev. 1.0, 7/16/2004
Microsemi
Page 4
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
MICROSEMI [ Microsemi ]
