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參數(shù)資料
| 型號： | LX1689CPWT |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | FLUORESCENT LIGHT CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | PLASTIC, TSSOP-20 |
| 文件頁數(shù)： | 4/14頁 |
| 文件大?。?/td> | 491K |
| 代理商： | LX1689CPWT |
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 12
Copyright
2000
Rev. 1.0c, 2004-02-23
WWW
.Microse
m
i
.CO
M
LX1689
Third Generation CCFL Controller
PRODUCTION DATA SHEET
I N T E GRA T ED
PR ODUC T S
DESCRIPTION (CONTINUED)
LX1689 OPERATION
Four operating modes: Power On Delay, Strike, Run, and Fault
modes are employed by the LX1689. Upon power up or ENABLE
going true, Power On Delay is automatically invoked.
Immediately after termination of Power On Delay, or ENABLE
going true, strike mode is entered. After a successful strike, e.g.
lamp is ignited, run mode is entered. If ignition is unsuccessful, or
if the lamp extinguishes while running, Fault mode is entered.
Lamp ignition is determined by monitoring the lamp current
feedback voltage at pin I_SNS. Lamp current cycles are counted
from the beginning of Strike mode. If 8 or more complete cycles
occur the lamp is declared ignited. If less than 8, the lamp is
considered not ignited and Strike mode continues until ignition is
detected or strike time out is reached.
After run mode is entered lamp current cycles are sampled every
8192 x 1/fO to determine that the lamp has not inadvertently
extinguished. If at least 8 lamp current pulses are counted in each
sample, Run mode is maintained.
Otherwise, Fault mode is
entered. Strike mode can be entered only once for each on/off cycle
of either V_BATT or ENABLE.
This insures that even
intermittent lamp failures cannot cause the module to continuously
output maximum strike voltage.
Power ON Delay Mode
All functions are activated except that AOUT and BOUT are
inhibited. Delay is 16384 x 1/fO determined by counting Ramp
clocks. The first of 16 sweeps is decoded as the power on delay
period. The subsequent 15 sweeps are used for controlling the
Ramp generator during Strike Mode. Power on delay is activated
at every V_BATT power up sequence and ENABLE sequence.
Strike Mode
Entered from Power On Delay, or upon an ENABLE sequence.
Control of the Ramp Generator frequency is switched to a DAC
output. Frequency is increased in a saw tooth fashion from normal
run value to as high as five times that value, for up to 15 sweeps.
If while strike frequency is ramping up, the over voltage set point
at OV_SNS is detected, strike frequency will freeze at that value
until either the lamp strikes or the timeout is reached. Strike Mode
is terminated by reaching 15 sweep counts or by detecting lamp
ignition. If strike is successful, Run Mode is entered.
If
unsuccessful, Fault mode is entered, a fault is declared and the A &
B outputs are shut off.
The purpose of sweeping lamp frequency up during strike is to
operate at the unloaded resonant frequency of the transformer and
lamp load. This generates the high lamp striking voltage required,
since at resonance, output voltage from the transformer will
increase to any value needed to cause ignition. A capacitive
voltage divider provides output voltage feedback to the OV_SNS
pin, which freezes Strike Frequency to limit maximum output
voltage to a safe value.
Since strike frequency is held constant once the LX1689 senses
maximum safe output voltage, maximum strike potential is
continuously impressed across the lamp for the entire strike period.
Because strike frequency is ramped up rather than simply
stepped, the entire range of possible self-resonant frequencies is
covered. Transformer manufacturing is simplified and parasitic
panel capacitance values are no longer critical. The 5:1 strike
frequency range easily covers the self-resonant frequency of all
practical lamp assembly and transformer combinations.
The only way to re-initiate the strike process is to either cycle
V_BATT or ENABLE off and on.
If ignition is successful, ramp frequency immediately returns to
its normal run value.
Run Mode
Entered only by detection of a successful Strike. Ramp generator
frequency control is immediately switched from DAC output to a
fixed reference that sets the normal run frequency. During Run
mode, the Fault Detect Counter is reset approximately every 8192 x
1/fO. The lamp current cycle counter is monitored to insure at least
8 current cycles received during each period. If less than 8, the
lamp is considered extinguished and the Fault Mode is entered.
Fault Mode
Fault Mode may be entered from either Strike or Run Mode as
described above. In Fault Mode, the A & B output drivers are
forced low and the BRITE_C pin is driven to VDD_A to indicate
the fault condition.
Fault mode may be cleared by cycling
ENABLE off then on, or by removing and applying V_BATT.
External load on the BRITE_C pin is limited to a filter capacitor and
single CMOS gate input.
DESIGN PROCEDURE
Selecting the I_R resistor value
This resistor determines the frequency of the on chip oscillator.
The output of the oscillator, RAMP_C, controls all timing functions.
It must be chosen first, and will be in the range of 10K to 150K
ohms.
The output frequency approximated by the following
formula : RI_R = 5.24E
9 / FLAMPOUT(Hz)
RAMP_C frequency is twice lamp output current frequency.
Driving the BRITE_IN Input
BRITE_IN can be a DC voltage, a low frequency PWM signal
that produces direct digital dimming, or a higher frequency PWM
signal that is converted to a proportional DC level by adding a filter
capacitor at the BRITE_C pin. 100% duty cycle corresponds to 1.1
volt, and 0% duty cycle corresponds to zero volts at the BRITE_C
pin. Maximum BRITE_IN input frequency for PWM inputs is 100
KHz, but when converting frequencies above 25 KHz to DC, some
accuracy is lost. The BRITE_IN input circuitry includes on-chip
active voltage clamps that ignore input voltage greater than 2.0V
and less than 0.5V. This allows the use of digital PWM input
signals where brightness is dependent only on duty cycle, with no
contribution
DD
EE
SSCC
RR
IIPP
TT
IIOO
NN
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| LX1689CPW-TR | 制造商:Microsemi Corporation 功能描述:CCFL DRVR 28V 20TSSOP - Tape and Reel 制造商:Microsemi Corporation 功能描述:DIRECT DRIVE CONTROLLER |
| LX1689IPW | 功能描述:IC CTLR CCFL BACKLIGHT 20-TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 照明，鎮(zhèn)流器控制器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:CCFL 控制器 頻率:40 ~ 80 kHz 電流 - 電源:5mA 電流 - 輸出:- 電源電壓:4.5 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 封裝/外殼:16-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC 包裝:帶卷 (TR) 其它名稱:90-3991V+V01 |
| LX1689IPWTR | 制造商:Microsemi Corporation 功能描述:CCFL Controller 3.3V/5V/9V/12V/15V/18V/24V 20-Pin TSSOP T/R |
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| LX1691 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:Enhanced Multi-Mode CCFL Controller |
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