LX1689 Ver la hoja de datos (PDF) - Microsemi Corporation

Número de pieza

componentes Descripción

Fabricante

LX1689

Third Generation CCFL Controller

Microsemi Corporation 

LX1689

TM

®

Third Generation CCFL Controller

PRODUCTION DATA SHEET

PIN NAME

BRITE_C

EA_IN

BRITE_R

EA_OUT

BRITE_IN

BRITE_OUT

ENABLE

I_R

FUNCTIONAL PIN DESCRIPTION (CONTINUED)

DESCRIPTION

BRITE Filter Capacitor and FAULT Output. Used to convert higher frequency digital PWM inputs to proportional

DC currents at the BRITE_OUT pin. The capacitor forms a low pass filter with an internal 200K resistor. This

pin will be driven to VDD_A if a lamp fault is detected by the LX1689. If no fault is present the voltage at this pin

will vary from 50mV to 1.05V as BRITE_IN varies from 0 to 2V. A CMOS gate may be connected to this pin to

sense the fault condition. TTL gates or other low impedance (less than 20 megohm) must not be connected to

this node as their DC resistance will load the internal 200K resistor and create error in the BRITE_OUT current

level.

Error Amp Inverting Input. Frequency Compensation input for the Error Amplifier. See EA_OUT below. A

100K, negative TC on chip resistor connected between the inverting input of the error amplifier and the output of

the I_SNS full wave rectifier is the resistor in an R/C loop compensation network.

Dedicated Bias resistor for BRITE_OUT current source.

Error Amp Output. Error amplifier is a GM type and does not require a external capacitor for stability. An

external capacitor is connected from this pin to EA_IN to adjust the loop response of the inverter module. This

capacitor value can vary from 100pF to 5000pF in various applications. This capacitor may also be connected

from the EA_OUT to ground.

Brightness Control Input. The input signal can be a DC voltage, a low frequency pulse width modulated digital

signal, or a high frequency pulse width modulated digital signal. Active DC voltage range is 0.5 to 2.0V. Signals

above 2V are clipped and signals below 0.5V make output current from the BRITE_OUT pin near zero. Low

frequency digital PWM signals up to 500Hz can be applied to affect Digital Dimming. Higher frequency PWM

signals, up to 100KHz are filtered to an equivalent DC current at the BRITE_OUT pin by adding a capacitor at

the BRITE_C pin. On chip signal conditioning amplifiers clip inputs above 2V so that lamp current amplitude is

not sensitive to the voltage level variations of a digital PWM input signal.

Brightness Reference Current Output. This variable current source is the mirror of BRITE_R current multiplied

by the voltage at BRITE_C (0 to 1.0V) when analog dimming is selected, or by 1.0V when digital dimming is

selected. It becomes the reference voltage to the lamp current error amplifier when applied to an external

precision resistor connected from the BRITE_OUT pin to ground. BRITE_OUT current:

IBRITE_OUT = IBRITE_R × 1.0 (Digital Dimming Mode)

IBRITE_OUT = IBRITE_R × VBRITE_C (Analog Dimming Mode)

VBRITE_OUT = IBRITE_R × RBRITE_OUT

1.00V

IBRITE_R =

RBRITE_R

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

V_BATT pin, disabling all functions. Logic threshold is about 1.2V. Maximum current into V_BATT when

ENABLE < 0.3V, V_BATT <28V, is 28 µA. ENABLE may be connected to V_BATT through a series resistor if

the disable function is not used. Resistor tolerance is ± 10%; and R value is:

R

=

[V_BATTMIN − 1.5V]

30x10−6 Amp

The Enable pin can be connected directly to 3.3/5V logic.

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 10K to

150K Ohms.

1.00V

II_R =

RI_R

Copyright © 2000

Rev. 1.1, 2006-02-27

Microsemi

Integrated Products

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

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