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Unitrode

UCC2972 Datasheet Preview

UCC2972 Datasheet

BiCMOS Cold Cathode Fluorescent Lamp Driver Controller

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UCC1972/3
UCC2972/3
UCC3972/3
BiCMOS Cold Cathode Fluorescent Lamp Driver Controller
FEATURES
1mA Typical Supply Current
Accurate Lamp Current Control
Analog or Low Frequency Dimming
Capability
Open Lamp Protection
Programmable Startup Delay
4.5V to 25V Operation
PWM Frequency Synchronized to
External Resonant Tank
8 Pin TSSOP and SOIC Packages
Available
Internal Voltage Clamp Protects
Transformer from Over-voltage
(UCC3973)
TYPICAL APPLICATION CIRCUIT
DESCRIPTION
Design goals for a Cold Cathode Fluorescent Lamp (CCFL) converter used
in a notebook computer or portable application include small size, high effi-
ciency, and low cost. The UCC3972/3 CCFL controllers provide the neces-
sary circuit blocks to implement a highly efficient CCFL backlight power
supply in a small footprint 8 pin TSSOP package. The BiCMOS controllers
typically consume less than 1mA of operating current, improving overall
system efficiency when compared to bipolar controllers requiring 5mA to
10mA of operating current.
External parts count is minimized and system cost is reduced by integrating
such features as a feedback controlled PWM driver stage, open lamp pro-
tection, startup delay and synchronization circuitry between the buck and
push-pull stages. The UCC3972/3 include an internal shunt regulator, al-
lowing the part to operate with input voltages from 4.5V up to 25V. The part
supports both analog and externally generated low frequency dimming
modes of operation.
The UCC3973 adds a programmable voltage clamp at the BUCK pin. This
feature can be used to protect the transformer from overvoltage during
startup or when an open lamp occurs. Transformer voltage is controlled by
reducing duty cycle when an over-voltage is detected.
UCC3972 NO INTERNAL VOLTAGE CLAMP
UCC3973
INTERNAL VOLTAGE CLAMP LIMITS TRANS FORMER
VOLTAGE AT S TART-UP OR DURING FAULT
C6 27pF
T1
S YS TEM VOLTAGE
(4.5V TO 25V)
R2 1k
C1
6.8µF
R1
1kUCC3972/3
8 VDD
C2
1µF
VBAT 2
6 GND
BUCK 1
5 MODE
C3
1µF 3 COMP
OUT 7
FB 4
C4 33nF
D1
C7
0.1µF
R10
Q2
R11
C5 0.1µF
Q3
R6 75
L1
68µH
R3 68k
LOW FREQUENCY DIMMING
DLFD RLFD 68k
D2
LAMP
HV
LAMP
LV
ANALOG
DIMMING
R5 10k
R4 750
0V-5V LOW FREQUENCY CONTROL S IGNAL
SLUS252C - OCTOBER 1998 - REVISED MARCH 2005
UDG-99154




Unitrode

UCC2972 Datasheet Preview

UCC2972 Datasheet

BiCMOS Cold Cathode Fluorescent Lamp Driver Controller

No Preview Available !

ABSOLUTE MAXIMUM RATINGS
VBAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +27V
VDD Maximum Forced Current . . . . . . . . . . . . . . . . . . . . 30mA
Maximum Forced Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 17V
BUCK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –5V to VBAT
MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to 4.0V
MODE Maximum Forced Current . . . . . . . . . . . . . . . . . . 300mA
Operating Junction Temperature . . . . . . . . . . –55°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Unless otherwise indicated, currents are positive into, negative
out of the specified terminal. Pulse is defined as less than 10%
duty cycle with a maximum duration of 500ms. Consult Pack-
aging Section of Databook for thermal limitations and consider-
ations of packages. All voltages are referenced to GND.
CONNECTION DIAGRAMS
TSSOP-8 (TOP VIEW)
PW Package
BUCK 1
VBAT 2
COMP 3
FB 4
UCC1972/3
UCC2972/3
UCC3972/3
8 VDD
7 OUT
6 GND
5 MODE
DIL-8 (TOP VIEW)
J, N Packages
OUT 1
VDD 2
BUCK 3
VBAT 4
8 GND
7 MODE
6 FB
5 COMP
ELECTRICAL CHARACTERISTICS:Unless otherwise specified these specifications hold for TA=0°C to +70°C for the
UC3972/3, –40°C to +85°C for the UC2972/3, and –55°C to +125°C for the UC1972/3; TA=TJ; VDD=VBAT=VBUCK=12V;
MODE=OPEN. For any tests with VBAT>17V, place a 1k resistor from VBAT to VDD.
PARAMETER
TEST CONDITIONS
MIN TYP MAX UNITS
Input supply
VDD Supply Current
VDD = 12V
1 1.5 mA
VBAT = 25V
7 10.5 mA
VBAT Supply Current
VBAT = 12V
30 60 mA
VBAT = 25V
70 140 mA
VDD Regulator Turn-on Voltage
ISOURCE = 2mA to 10mA
17 18 19
V
VDD UVLO Threshold
Low to high
3.6 4 4.4 V
UVLO Threshold Hysteresis
100 200 300 mV
Output Section
Pull Down Resistance
Pull Up Resistance
ISINK = 10mA to 100mA
ISOURCE = 10mA to 100mA
25 50
25 50
W
W
Output Clamp Voltage
VBAT = 25V, Shunt Regulator on
16 18
V
Output Low
MODE = 0.5V, ISINK = 1mA
0.05 0.2
V
Rise Time
CL = 1nF, Note 1
200 ns
Fall Time
CL = 1nF, Note 1
200 ns
2


Part Number UCC2972
Description BiCMOS Cold Cathode Fluorescent Lamp Driver Controller
Maker Unitrode
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