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
REF_OK
20
+
VCC
19
REF 6.75V –
AGND
14
THERMAL SHUTDOWN
TEMP
130ºC/100ºC
–
14V
+
UVLO
CRAMP
13
PVFB/OVP
1
–
V
TO
2.5V +
I
PEAO
2
PIFBO
4
PIFB
3
PFC OUT
18
–1V
2.75V +
PVFB –
+
–
ILIM
OVP
RX/CX
11
RSET
7
+
RQ
–
SQ
4.75V/
1.75V
PREHEAT
+
–
CLK1
÷2
RQ
SQ
PFC CONTROLLER
V TO I
QR
QS
QS
QR
Q
T
Q
CLK
OSCILLATOR
OUT A
17
OUT B
16
PGND
15
PWDET
12
1.0V
COMP
1.25V/1V
INTERRUPT
10
RX/CX
6.75V/1.25V
RT2
8
V TO I
RT/CT
9
LEAO
6
LAMP FB
5
2.5V
Figure 1. Detailed Block Diagram
6