MP1048 – FULL BRIDGE CCFL CONTROLLER
Table 1—Function Modes
Function
ABRT
Pin Connection
DBRT BRS
Ratio
3:1
10:1
Set by
Customer
30:1
Set by
Customer
Analog Mode 0 – 1.2V
V
CC
V
CC
Burst Mode
R6
V
CC
0 – 1.2V
with DC
C7
Input Voltage
Burst Mode
V
CC
PWM
V
CC
with External
Source
R6
Analog and
0 – 1.2V 0 – 1.2V
C7
Burst Mode
Analog and
Burst Mode
0 – 1.2V PWM
V
CC
with External
Source
Fault Timer: The timing for the fault timer will
depend on the sourcing current as described
above and the capacitor C2 on the FT pin. The
user can program the time for the voltage to
rise after the chip detects a “real” fault. When a
fault is triggered, the internal voltage (V
CC
) will
collapse from 6V to 0V. If no fault is detected a
1µA current sink will keep FT to 0V.
Startup
For reliable ignition of the lamp, the operating
frequency is swept temporarily toward the
unloaded resonant frequency of the tank during
startup. This guarantees the strike voltage of
the lamp at any temperature due to a resonant
topology for switching the outputs and
eliminates the need for external ramp timing
circuits to ensure startup. Once the strike
voltage is achieved, the switching frequency is
gradually adjusted to the preset fixed value.
The operating frequency before the lamp strikes
can be swept as much as 160% of the preset
frequency value.
Chip Enable
The chip has an ON/OFF function, which is
controlled by the EN pin (#13). The enable
signal goes directly to a Schmitt trigger. The
chip will turn ON with an EN = High and OFF
with an EN = Low.
Brightness Polarity
Burst: 100% duty cycle is at 1.2V
Analog: 1.2V is for maximum brightness
Fault Protection
Open Lamp: The LV pin (#3) is used to detect
whether an open lamp condition has occurred.
If the voltage at LV exceeds +1.2V, a pulse of
current will pull down on the COMP pin to
regulate the lamp voltage. The Fault Timer will
be started with a 1µA current source injecting
into C2 at the FT pin, while the fault condition
persists. If the voltage at the FT pin exceeds
1.2V, then the chip will shutdown.
Excessive Secondary Current (Shorted Lamp):
The SI pin (#1) is used to detect whether
excessive secondary current has occurred. If a
fault condition occurs that increases the
secondary current, then the voltage at SI will be
greater than 1.2V. A pulse of current will pull
down on the COMP pin to regulate the
secondary current. The Fault Timer will be
started with a 65µA current source injecting into
C2 at the FT pin while the fault condition
persists.
If the voltage at the FT pin exceeds 1.2V, then
the chip will shutdown and need to be enabled
again.
MP1048 Rev. 0.9
9/24/2007
www.MonolithicPower.com
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© 2007 MPS. All Rights Reserved.
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