LTC1697
3
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/C
DIM
(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: I
LAMP(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 I
OVSEN(ON)
, the switch duty cycle will be
0%.
Note 8: At V
DIM
voltages below V
DIM(SHDNON)
the LTC1697 behaves as if
the SHDN pin was pulled low.
Note 9: To minimize I
Q
shutdown, pull the SHDN pin below 0.1V.
Note 10: 2mA ≤ I
LAMP
≤ 5mA.
C
DIM
(Pin 1): Dimming Capacitor. Connect the pin to GND
with a 0.022µF capacitor (nominal). The value of capaci-
tance on the C
DIM
pin determines the dimming PWM
frequency. The transfer function of capacitance to fre-
quency is 5Hz/C
DIM
(µF).
V
DIM
(Pin 2): Dimming Control Pin. The V
DIM
pin controls
the duty cycle of the dimming PWM. It ranges from 0% at
V
DIM
= 1V to 100% at V
DIM
= 2V. If the V
DIM
voltage is
<0.4V the LTC1697 will enter shutdown mode after ≈50ms.
0V
SEN
(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.
V
IN
(Pin 7): Input Supply Pin.
V
C
(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 “V
C
Compensation” for guidelines.
R
PROG
(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.
UU
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PI FU CTIO S
ELECTRICAL CHARACTERISTICS
