TI-UC3872.pdf
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UC1872
UC2872
UC3872
07/99
FEATURES
•
Controls Different Types of Lamps:
Cold Cathode Fluorescent, Neon, and
Gas Discharge
•
Zero Voltage Switching (ZVS) of
Push-Pull Drivers
•
Accurate Control of Lamp Current
•
Variable Lamp Intensity Control
•
1µA Disable Current
•
4.5V to 24V Operation
•
Open Lamp Detection Circuitry
DESCRIPTION
The UC3872 is a resonant lamp ballast controller optimized for driving
cold cathode fluorescent, neon, and other gas discharge lamps. The res
-
onant power stage develops a sinusoidal lamp drive voltage, and mini
-
mizes switching loss and EMI generation. Lamp intensity adjustment is
accomplished with a buck regulator, which is synchronized to the external
power stage’s resonant frequency. Suitable for automotive and battery
powered applications, the UC3872 draws only 1µA when disabled.
Soft start and open lamp detect circuitry have been incorporated to mini
-
mize component stresses. Open lamp detection is enabled at the comple
-
tion of a soft start cycle. The chip is optimized for smooth duty cycle
control to 100%.
Other features include a precision 1.2% reference, undervoltage lockout,
and accurate minimum and maximum frequency control.
Resonant Lamp Ballast Controller
4
6
5
3
2
12
13
1
14
7
8
+
–
0.5V
SYNC
OUT
SENSE
OSCILLATOR
GND
+
–
–
+
OPEN
LAMP
DETECT
+
–
+
–
UVLO
3.0V
REF
10
9
11
R
S
T
TOGGLE
50k
50k
50k
PUSH PULL
OUTPUTS
N-CHANNEL
VC
AOUT
BOUT
COUT
PGND
0.1V
PWM
1
0.2V
200µA
ZERO DETECT
ZD
CT
SS
INV
COMP
ENBL
REF
VCC
1.5V
20µA
(HIGH=ENABLE)
BUCK DRIVE
P-CHANNEL
EA
BLOCK DIAGRAM
UDG-99112
Note: Pin numbers shown are for DIP package.
application
INFO
available
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