ml4836 Microsemi Corporation, ml4836 Datasheet - Page 8

• Manufacturer Part Number: ml4836
• Description: Compact Fluorescent Electronic Dimming Ballast Controller
• Manufacturer: Microsemi Corporation

ML4836
FUNCTIONAL DESCRIPTION
EOL and the ML4836
The ML4836 uses a circuit that creates a DC voltage
representative of the power supplied to the lamps through
the inverter when use in conjuction with PFC. This voltage
is used by the ML4836 to latch off the ballast when it
exceeds an internal threshold. An external resistor can be
used as the “EOL latch resistor” to set the power level trip
point, as shown in by R9 in Figure 6.
BALLAST OUTPUT SECTION
The IC controls output power to the lamps via frequency
modulation with non-overlapping conduction. This means
8
14
5
7
8
1.20/1.0V
4.65/1.75V
R
INTERRUPT
R
V
T2
X
CC
/C
X
LEA_ENB
R
T2
+
0.625
–
R
+
–
SET
7.5V
Figure 7. Oscillator Block Diagram and Timing
V
V
TH
R
TL
T
= 3.8V
= 1.2V
C
NOTE 1: R
CLOCK
6
T
(Continued)
R
C
T
/C
T
T
I
I
CHG
CHG
SET
SHOULD BE SELECTED SUCH THAT AFTER PREHEAT WITH LEA_ENB "HI",
MUST BE < 0.
IS A UNI-DIRECTIONAL SOURCE CURRENT ONLY.
7.5mA
I
CHG
t
DIS
REF
1
3.8/1.2V
that both ballast output drivers will be low during the
discharging time t
OSCILLATOR
The VCO frequency ranges are controlled by the output
of the LFB amplifier (R
LFB OUT falls in voltage, causing the C
to increase, thereby causing the oscillator frequency to
increase. Since the ballast output network attenuates high
frequencies, the power to the lamp will be decreased. The
oscillator frequency is determined by the following
equations:
+
–
t
CHG
DURING PREHEAT
AFTER PREHEAT
LEA_ENB = HI
LEA_ENB = LOW
I
I
I
CHG =
CHG =
CHG =
DIS
of the oscillator capacitor C
SET
RSET
RSET
RSET
2.5V
5V
5V
). As lamp current decreases,
–
– LEAO
8K±25%
8K±25%
7.5V
T
charging current
T
.