LTC1697 datasheet(3/8 Pages) LINER

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LTC1697

1697f

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: All voltages specified with respect to GND pin.

Note 3: The dimming PWM frequency is set by the equation 5Hz/CDIM(µF).

Note 4: Actual operating current will be higher due to lamp operating

current.

Note 5: The LTC1697 is guaranteed to meet performance specifications

from 0°C to 70°C. Specifications over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process controls.

Note 6: ILAMP(AVG) = the average of the magnitude (absolute value) of the

positive and negative lamp current flowing into and out of the LAMP pin.

Note 7: For currents at or above IOVSEN(ON), the switch duty cycle will be

0%.

Note 8: At VDIM voltages below VDIM(SHDNON) the LTC1697 behaves as if

the SHDN pin was pulled low.

Note 9: To minimize IQ shutdown, pull the SHDN pin below 0.1V.

Note 10: 2mA ≤ ILAMP ≤ 5mA.

CDIM (Pin 1): Dimming Capacitor. Connect the pin to GND

with a 0.022µF capacitor (nominal). The value of capaci-

tance on the CDIM pin determines the dimming PWM

frequency. The transfer function of capacitance to fre-

quency is 5Hz/CDIM(µF).

VDIM (Pin 2): Dimming Control Pin. The VDIM pin controls

the duty cycle of the dimming PWM. It ranges from 0% at

VDIM = 1V to 100% at VDIM = 2V. If the VDIM voltage is

<0.4V the LTC1697 will enter shutdown mode after ≈50ms.

0VSEN (Pin 3): Overvoltage Sense Pin. Protects the high-

voltage transformer from the overvoltage condition that

occurs when the lamp is open or not present. This pin is

connected through a resistor to the emitters of the drive

transistors of the Royer oscillator.

SW (Pin 4): Switch Pin. Connect the inductor and optional

Schottky diode here. Minimize trace length to keep EMI

and high frequency ringing down.

GND (Pin 5): Signal and Power Ground for the LTC1697.

LAMP (Pin 6): Lamp Current Feedback Pin. Connect this

pin to the CCFL lamp.

VIN (Pin 7): Input Supply Pin.

VC (PIN 8): Compensation Node. Connect this pin to GND

through a 0.1µF capacitor. See Application Information

section. A frequency compensation network is connected

to this pin to compensate the loop. See the section “VC

Compensation” for guidelines.

RPROG (Pin 9): Lamp Current Programming. Connect this

pin to GND with a 6.4k 1% resistor (nominal). See Appli-

cation Information section for resistor selection.

SHDN (Pin 10): Shutdown. Grounding this pin shuts down

the LTC1697. Tie to >1V to enable.

PI FU CTIO S

ELECTRICAL CHARACTERISTICS

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