Texas Instruments UC3872DWTR, UC3872DW, UC3872QTR, UC3872Q, UC3872N Datasheet

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UC1872

UC2872

UC3872

Resonant Lamp Ballast Controller

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

•1 A 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 resonant power stage develops a sinusoidal lamp drive voltage, and minimizes 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 1 A when disabled.

Soft start and open lamp detect circuitry have been incorporated to minimize component stresses. Open lamp detection is enabled at the completion 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.

BLOCK DIAGRAM

VCC	10		UVLO	3.0V
				REF
REF	9
ENBL	(HIGH=ENABLE)						PUSH PULL
	11						OUTPUTS
					0.1V	+	N-CHANNEL
COMP	4					–
INV	6		–		OPEN		TOGGLE
					LAMP
			EA
		20 A	+		DETECT		T
			1.5V			PWM
SS	5					–
						– 1
				200	A	+
					0.2V		R
CT	7				+		S
			OSCILLATOR
	ZERO DETECT		SENSE
			OUT
ZD	8						BUCK DRIVE
		–	SYNC
	0.5V	+					P-CHANNEL
					14
					GND

Note: Pin numbers shown are for DIP package.

3	VC
2	AOUT
50k
1	BOUT
50k
50k
12	COUT
13	PGND
UDG-99112

07/99

ABSOLUTE MAXIMUM RATINGS

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.3 to +10V VCC, VC Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +24V ZD Input Current

High Impedance Source . . . . . . . . . . . . . . . . . . . . . . +10mA ZD Input Voltage

Low Impedance Source . . . . . . . . . . . . . . . . . . . . . . . . +24V Power Dissipation at TA = 25° C . . . . . . . . . . . . . . . . . . . . . . 1W Storage Temperature . . . . . . . . . . . . . . . . . . . −65° C to +150° C Lead Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300° C

Note 1: Currents are positive into, negative out of the specified terminal.

Note 2: Consult Packaging Section of Databook for thermal limitations and considerations of package.

UC1872

UC2872

UC3872

CONNECTION DIAGRAMS

SOIC-16, SSOP-16 (TOP VIEW)

DW, M Package

DIL-14 (TOP VIEW)

N Package

PLCC-20 (Top View)

Q Package

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these parameters apply for TJ = −55° C to +125°C for the UC1872, –40° C to +85° C for the UC2872, −0°C to +70°C for the UC3872; VCC= 5V, VC = 15V, VENBL = 5V, CT = 1nF, ZD = 1V.

PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNITS
Reference Section
Output Voltage	TJ = 25° C	2.963	3.000	3.037	V
	Over Temperature	2.940	3.000	3.060	V
Line Regulation	VCC = 4.75V to 18V			10	mV
Load Regulation	IO = 0 to −5mA			10	mV
Oscillator Section
Free Running Frequency	TJ = 25° C	57	68	78	kHz
Maximum Synchronization Frequency	TJ = 25° C	160	200	240	kHz
Charge Current	VCT = 1.5V	180	200	220	µ A
Voltage Stability				2	%
Temperature Stability			4	8	%
Zero Detect Threshold		0.46	0.5	0.56	V
Error Amp Section
Input Voltage	VO = 2V	1.445	1.475	1.505	V
Input Bias Current			−0.4	−2	µ A
Open Loop Gain	VO = 0.5 to 3V	65	90		dB
Output High	VINV = 1.3V	3.1	3.5	3.9	V

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UC1872

UC2872

UC3872

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these parameters apply for TJ = −55° C to +125°C for the UC1872, –40° C to +85° C for the UC2872, −0°C to +70°C for the UC3872; VCC= 5V, VC = 15V, VENBL = 5V, CT = 1nF, ZD = 1V.

PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNITS
Error Amp Section (cont.)
Output Low	VINV = 1.7V		0.1	0.2	V
Output Source Current	VINV = 1.3V, VO = 2V	–350	–500		A
Output Sink Current	VINV = 1.7V, VO = 2V	10	20		mA
Common Mode Range		0		VIN-1V	V
Unity Gain Bandwidth	TJ = 25° C (Note 4)		1		MHz
Open Lamp Detect Section
Soft Start Threshold	VINV = 0V	2.9	3.4	3.8	V
Open Lamp Detect Threshold	VSS = 4.2V	0.6	1.0	1.4	V
Soft Start Current	VSS = 2V	10	20	40	µ A
Output Section
Output Low Level	IOUT = 0, Outputs A and B		0.05	0.2	V
	IOUT = 10mA		0.1	0.4	V
	IOUT = 100mA		1.5	2.2	V
Output High Level	IOUT = 0, Output C	13.9	14.9		V
	IOUT = −10mA	13.5	14.3		V
	IOUT = −100mA	12.5	13.5		V
Rise Time	TJ = 25° C, Cl = 1nF (Note 4)		30	80	ns
Fall Time	TJ = 25° C, Cl = 1nF (Note 4)		30	80	ns
Output Dynamics
Out A and B Duty Cycle		48	49.9	50	%
Out C Max Duty Cycle	VINV = 1V	100			%
Out C Min Duty Cycle	VINV = 2V			0	%
Under Voltage Lockout Section
Startup Threshold Voltage		3.7	4.2	4.5	V
Hysteresis		120	200	280	mV
Enable Section
Input High Threshold		2			V
Input Low Threshold				0.8	V
Input Current	VENBL = 5V		150	400	µ A
Supply Current Section
VCC Supply Current	VCC = 24V		6	14	mA
VC Supply Current	VC = 24V		5	12	mA
ICC Disabled	VCC = 24V, VENBL = 0V		1	10	µ A

Note 3: Unless otherwise specified, all voltages are with respect to ground. Currents are positive into, and negative out of the specified terminal.

Note 4: Guaranteed by design. Not 100% tested in production.

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