LX1801
PRODUCTION DATA SHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
Copyright
2005
Rev. 1.0, 5/4/2006
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SMBus to Analog & Digital System Interface
TM
FUNCTIONAL PIN DESCRIPTION
Name
Description
VDD
Power Supply Input: 4.5V to 5.5V
VSS
Ground (2 Pins)
SCL
Digital Input. SMBus Clock – 10 to 100 KHz capable
SDA
Digital I/O. SMBus Data – SMBus Data line
ADR0
SMBus Address strap input – The address for the LX1801 is determined by the state of this pin (see table 1).
ALS_IN
Analog input. Ambient light sensor input. Zero to VREF_IN range.
PWM_IN
A digital input from the system controller whose duty cycle determines lamp brightness when in PWM mode,
and multiplies lamp brightness by a fractional value equal to its duty cycle when in DPST mode.
VREF_IN
Analog Input reference voltage for ADC and DAC. Operating range is 1.5 to 3 Vdc. Nominal input is 2.040V.
Input impedance is greater than 10M.
V_BOT
An analog voltage input whose value determines the minimum output voltage of BRITE_OUT after the effect
of the PWM input when in DPST mode and at all times in other modes.
BRITE_OUT
Analog output voltage that is equal to desired BRITE_OUT voltage after modulation by the PWM input and
offset by the voltage at the V_BOT input. An R/C filter at this pin to low pass filters the signal and determines
response time when in PWM and DPST modes. In PWM and DPST modes, the output voltage is modulated
on and off at the duty cycle and frequency of PWM_IN. The R/C filter is comprised of an internal 100K
resistor and an external capacitor to ground.
LMP_C
Lamp Capacitor. A capacitor, typically 10nF and a resistor, typically 1M, are connected in parallel from
this pin to ground. They filter a peak voltage detector with the LMP_ON input.
OVR_CUR
Analog / Digital input to comparator and latch. Used for over current status input in M07 application. 1.2V
threshold. If OVR_CUR > 1.2VDC, a “1” is latched and written to bit 0 (FAULT) and bit 2(OV_CURR) of the
fault status register (Register 0x02). The latched bits can only be cleared by a write byte command to
register 0x01 to make the LAMP_CTL bit true. If bit 0 or bit 2 of register 0x02 is set, this will reset the
LAMP_CTL bit in register 0x01, causing the enable output to the CCFL controller (EN_OUT) to go low and
turn off the inverter. Zero to VDD input voltage range.
LMP_ON
Digital input. Approximately 1V threshold. When LMP_ON is “1” it charges the capacitor at pin LMP_C to
VDD, indicating the lamp is turned on. This pin is normally connected to the A_OUT pin of the LX1692 / 93
controller, and will cause internal circuitry to report the lamp is on if there are pulses on A_OUT. If these
pulses stop long enough for the voltage at LMP_C to decrease below 1.2 V, the lamp is reported off at bit
03 of the FLT/STAT register (0x02). . If LAMP_CTL transitions to high, requesting the inverter to turn on, and
LMP_C does not go above 1.2V before the FLT_DLY pin reaches 2.5V, an open lamp error signal is
produced and is stored, along with other error conditions, to bit zero of the FLT STATUS register 0x02. An
Open lamp fault will cause EN_OUT to go low. See FLT_DLY description. Zero to VDD input voltage range
FLT_DLY
Analog / Digital input to the open lamp comparator and latch. This input provides for a time out before
LMP_ON is sensed for an open lamp fault. The comparator has a 2.5V threshold. The comparator output is
latched when 2.5V is exceeded. The latch is reset at power on and when EN_OUT transitions to high. This
pin is normally connected to the C_TO pin of the LX1692 or 1693 CCFL controller.
EN_OUT
Digital Output. Enable output to CCFL controller. TTL voltage and current levels. EN_OUT is made high or
low by a write byte command to register 0x01. It is also reset by bit zero of register 0x02 going high.
PP
AA
CC
KK
AA
GG
EE
DD
AA
TT
AA