ML4835
FUNCTIONAL DESCRIPTION
The ML4835 consists of peak or average current
controlled continuous boost power factor front end section
with a flexible ballast control section. Start-up and lamp-
out retry timing are controlled by the selection of external
timing components, allowing for control of a wide variety
of different lamp types. The ballast section controls the
lamp power using frequency modulation (FM) with
additional programmability provided to adjust the VCO
frequency range. This allows for the IC to be used with a
variety of different output networks. Figure 1 depicts a
detailed block diagram of ML4835.
The ML4835 provides several safety features. See the
corresponding sections for more details:
• End-of-lamp life detection to detect EOL and shut-off
lamps; See End Of Life Section.
• Thermal shutdown for temperature sensing extremes;
See IC Bias, Under-Voltage Lockout and Thermal
Shutdown Section.
• Relamping starting with anti-flash for programmable
restart for lamp out conditions while minimizing
“flashing” when powering from full power to dimming
levels; See Starting, Re-Start, Preheat and Interrupt
Section
REF
20
19
14
VCC
AGND
REF
6.75V
+
–
REF_OK
THERMAL SHUTDOWN
TEMP
130ºC/100ºC
OUT A
17
+
–
OUT B
16
PGND
–
Q
UVLO
Q
R
PWDET
S
+
–
15
12
1.0V
14V
+
13
1
CRAMP
PREHEAT
PVFB/OVP
–
+
+
COMP
V
TO
2.5V
PEAO
2
PIFBO
4
PIFB
3
PFC OUT
18
+
I
4.75V/
1.75V
Q
Q
S
R
1.25V/1V
INTERRUPT
10
–
–
–
+
–
RX/CX
6.75V/1.25V
R
S
Q
Q
CLK1
Q
T
Q
÷2
+
RT2
8
+
–1V
2.75V
PVFB
RX/CX
+
–
–
R
ILIM
S
Q
Q
PFC CONTROLLER
CLK
OSCILLATOR
RT/CT
9
OVP
LEAO
6
LAMP FB
–
11
7
V
TO
I
RSET
+
5
2.5V
V
TO
I
Figure 1. Detailed Block Diagram
6
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
