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LX1691A

Enhanced Multi-Mode CCFL Controller

Microsemi Corporation 

LX1691A

TM

®

Enhanced Multi-Mode CCFL Controller

PRODUCTION DATA SHEET

FUNCTIONAL PIN DESCRIPTION (CONTINUED)

PIN NAME

DESCRIPTION

DIM_MODE*

Dimming Mode Input. This three state input pin places the IC in Analog Dimming Mode, internal Digital Dimming

Mode, or external Digital Dimming Mode. If the input is left open or forced to VDDA / 2, Analog mode is selected.

If connected to VDDA, Digital Dimming mode with an external clock from the DD_CLK input controls the burst

timing generator. Burst frequency is the external clock frequency divided by 512. If DIM_MODE is connected

to Ground, Digital Dimming with an internal clock is selected. Burst frequency in internal clock mode is lamp

current frequency divided by 512, and burst duty cycle is directly proportional to the voltage at BRITE_IN.

OP_SNS

Over Voltage & Over Current Sense. This input pin combines the functionality of OV_SNS and OC_SNS in the

LX1691. The OP_SNS input signal is a full wave AC voltage centered around ground that is proportional to

lamp voltage. The OP_SNS input will be full wave rectified, then applied to a digital comparator with a 2V

reference to cause peak voltage greater than 2V to digitally reset the PWM logic on a pulse by pulse basis.

Frequency range of the input signal is 10Khz to 500KHz. Normal operating voltage is less than ± 2V, and

abnormal voltage can operate continuously as high as ±7V peak under load fault conditions. Transients under

fault conditions can reach ± 10VPK. Input voltage greater than ± 3V peak but less than ± 10V peak may cause

saturation but will not cause malfunction, phase reversal, or reliability issues with the IC.

VIN_SNS

Input Voltage Sense. This input pin senses power supply amplitude and automatically adjusts the maximum

pulse width of AOUT and BOUT to improve line transient response and regulation. An external resistor divider

from the input power supply drives this pin. Maximum duty cycle is indirectly proportional to input voltage.

Maximum duty cycle versus VIN slope can be varied by selection of external resistor values and ratios. See

Application note for equations and design examples.

I_SNS

Current Sense Input. A full wave AC voltage input centered around ground that is proportional to lamp current.

The I_SNS input is full wave rectified and amplified, then presented to the inverting input of the current error

amplifier. During the strike mode the current sense input will regulate to 1V regardless of BRITE_IN setting.

Frequency range of the input signal is 10 KHz to 500KHz. Normal operating voltage is less than ± 2V, and

abnormal voltage can operate continuously as high as ± 7V peak under load fault conditions. Transient under

fault conditions can reach ± 10VPK. Input voltages of up to ± 3V peak are linearly rectified. Input voltage above

± 3V peak but less than ±10V peak may cause saturation but do not cause malfunction, phase reversal, or

reliability issues with the IC.

EA_OUT

Error Amp Output. An external capacitor is connected from this pin to GND to adjust loop response of the

inverter module. This capacitor value can vary from 10pF to 5000pF in various applications.

BRITE_IN

Brightness Control Input. The input signal should be a DC voltage or a filtered high frequency pulse width

modulated digital signal. Active DC voltage range is 0.0 to 2.0V. On chip signal conditioning amplifiers clip

inputs above 2V.

ENABLE

I_R

Chip Enable Input. If logic high, all functions are enabled. If logic low, internal power is disconnected from the

VDDP pin, disabling all functions. Maximum current into VDDP when ENABLE < 0.3V, VDDP<5V, is 10µA. ENABLE

may be connected directly to VDDP if the disable function is not used.

Current Reference Resistor Input. Connects to an external resistor that determines the magnitude of internal

bias currents. The nominal lamp frequency can be adjusted by varying this resistor value in the range of 40K to

100K Ohms.

1.00V

II_R =

RI_R

*See dimming mode truth table for a summary of dimming operation with respect to DD_CLK & DIM_MODE inputs.

Copyright © 2003

Rev. 1.0, 8/31/2004

Microsemi

Integrated Products

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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