Texas Instruments UC3847J, UC3847DWTR, UC3847DW, UC3846QTR, UC3846Q Datasheet

UC1846/7

UC2846/7

UC3846/7

Current Mode PWM Controller

FEATURES

∙Automatic Feed Forward Compensation

∙Programmable Pulse-by-Pulse Current Limiting

∙Automatic Symmetry Correction in Push-pull Configuration

∙Enhanced Load Response Characteristics

∙Parallel Operation Capability for Modular Power Systems

∙Differential Current Sense Amplifier with Wide Common Mode Range

∙Double Pulse Suppression

∙500mA (Peak) Totem-pole Outputs

∙±1% Bandgap Reference

∙Under-voltage Lockout

∙Soft Start Capability

∙Shutdown Terminal

∙500kHZ Operation

DESCRIPTION

The UC1846/7 family of control ICs provides all of the necessary features to implement fixed frequency, current mode control schemes while maintaining a minimum external parts count. The superior performance of this technique can be measured in improved line regulation, enhanced load response characteristics, and a simpler, easier-to-design control loop. Topological advantages include inherent pulse-by-pulse current limiting capability, automatic symmetry correction for push-pull converters, and the ability to parallel “power modules" while maintaining equal current sharing.

Protection circuitry includes built-in under-voltage lockout and programmable current limit in addition to soft start capability. A shutdown function is also available which can initiate either a complete shutdown with automatic restart or latch the supply off.

Other features include fully latched operation, double pulse suppression, deadline adjust capability, and a ±1% trimmed bandgap reference.

The UC1846 features low outputs in the OFF state, while the UC1847 features high outputs in the OFF state.

BLOCK DIAGRAM

1/97

UC1846/7

UC2846/7

UC3846/7

ABSOLUTE MAXIMUM RATINGS (Note 1)

Supply Voltage (Pin 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V

Collector Supply Voltage (Pin 13). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V Output Current, Source or Sink (Pins 11, 14). . . . . . . . . . . . . . . . . . . . . . . . 500mA Analog Inputs (Pins 3, 4, 5, 6, 16) . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +VIN Reference Output Current (Pin 2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30mA Sync Output Current (Pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5mA Error Amplifier Output Current (Pin 7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5mA Soft Start Sink Current (Pin 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA Oscillator Charging Current (Pin 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA Power Dissipation at TA=25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW Power Dissipation at TC=25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000mW Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65°C to +150°C Lead Temperature (soldering, 10 seconds. . . . . . . . . . . . . . . . . . . . . . . . . +300°C

Note 1. All voltages are with respect to Ground, Pin 13. Currents are positive into, negative out of the speficied terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages. Pin numbers refer to DIL and SOIC packages only.

CONNECTION DIAGRAMS

	DIL-16, SOIC-16	PLCC-20, LCC-20	PACKAGE PIN FUNCTION
	(TOP VIEW)	(TOP VIEW)
			FUNCTION	PIN
	J or N Package, DW Package	Q, L Packages	N/C	1
			C/L SS	2
			VREF	3
			C/S-	4
			C/S+	5
			N/C	6
			E/A+	7
			E/A-	8
			Comp	9
			CT	10
			N/C	11
			RT	12
			Sync	13
			A Out	14
			Gnd	15
			N/C	16
			VC	17
			B Out	18
			VIN	19
			Shutdown	20

ELECTRICAL CHARACTERISTICS (Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7;

VIN=15V, RT=10k, CT=4.7nF, TA=TJ.)

		UC1846/UC1847			UC3846/UC3847
PARAMETER	TEST CONDITIONS	UC2846/UC2847
		MIN.	TYP.	MAX.	MIN.	TYP.	MAX.	UNITS
Reference Section
Output Voltage	TJ=25°C, I O=1mA	5.05	5.10	5.15	5.00	5.10	5.20	V
Line Regulation	VIN=8V to 40V		5	20		5	20	mV
Load Regulation	IL=1mA to 10mA		3	15		3	15	mV
Temperature Stability	Over Operating Range, (Note 2)		0.4			0.4		mV/°C
Total Output Variation	Line, Load, and Temperature (Note 2)	5.00		5.20	4.95		5.25	V
Output Noise Voltage	10Hz≤ f ≤10kHz, TJ=25°C (Note 2)		100			100		μV
Long Term Stability	TJ=125°C, 1000 Hrs. (Note 2)		5			5		mV
Short Circuit Output Current	VREF=0V	-10	-45		-10	-45		mA

2

ELECTRICAL

CHARACTERISTICS (cont.)

UC1846/7

UC2846/7

UC3846/7

(Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; V IN=15V, RT=10k, CT=4.7nF, TA=TJ.)

		UC1846/UC1847			UC3846/UC3847
PARAMETER	TEST CONDITIONS	UC2846/UC2847
		MIN.	TYP.	MAX.	MIN.	TYP.	MAX.	UNITS
Oscillator Section
Initial Accuracy	TJ=25°C	39	43	47	39	43	47	kHz
Voltage Stability	VIN=8V to 40V		-1	2		-1	2	%
Temperature Stability	Over Operating Range (Note 2)		-1			-1		%
Sync Output High Level		3.9	4.35		3.9	4.35		V
Sync Output Low Level			2.3	2.5		2.3	2.5	V
Sync Input High Level	Pin 8=0V	3.9			3.9			V
Sync Input Low Level	Pin 8=0V			2.5			2.5	V
Sync Input Current	Sync Voltage=3.9V, Pin 8=0V		1.3	1.5		1.3	1.5	mA
Error Amp Section
Input Offset Voltage			0.5	5		0.5	10	mV
Input Bias Current			-0.6	-1		-0.6	-2	μA
Input Offset Current			40	250		40	250	nA
Common Mode Range	VIN=8V to 40V	0		VIN-2V	0		VIN-2V	V
Open Loop Voltage Gain	VO=1.2 to 3V, VCM=2V	80	105		80	105		dB
Unity Gain Bandwidth	TJ=25°C (Note 2)	0.7	1.0		0.7	1.0		MHz
CMRR	VCM=0V to 38V, VIN=40V	75	100		75	100		dB
PSRR	VIN=8V to 40V	80	105		80	105		dB
Output Sink Current	VID=-15mV to -5V, VPIN 7=1.2V	2	6		2	6		mA
Output Source Current	VID=15mV to 5V, VPIN 7=2.5V	-0.4	-0.5		-0.4	-0.5		mA
High Level Output Voltage	RL=(Pin 7) 15kΩ	4.3	4.6		4.3	4.6		V
Low Level Output Voltage			0.7	1		0.7	1	V
Current Sense Amplifier Section
Amplifier Gain	VPIN 3=0V, Pin 1 Open (Notes 3 & 4)	2.5	2.75	3.0	2.5	2.75	3.0	V
Maximum Differential Input	Pin 1 Open (Note 3)
Signal (VPIN 4-VPIN 3)	RL (Pin 7)=15kW	1.1	1.2		1.1	1.2		V
Input Offset Voltage	VPIN 1=0.5V, Pin 7 Open (Note 3)		5	25		5	25	mV
CMRR	VCM=1V to 12V	60	83		60	83		dB
PSRR	VIN=8V to 40V	60	84		60	84		dB
Input Bias Current	VPIN 1=0.5V, Pin 7 Open (Note 3)		-2.5	-10		-2.5	-10	μA
Input Offset Current	VPIN 1=0.5V, Pin 7 Open (Note 3)		0.08	1		0.08	1	μA
Input Common Mode Range		0		VIN-3	0		VIN-3	V
Delay to Outputs	TJ=25°C, (Note 2)		200	500		200	500	ns
Current Limit Adjust Section
Current Limit Offset	VPIN 3=0V, VPIN 4=0V, Pin 7 Open
	(Note 3)	0.45	0.5	0.55	0.45	0.5	0.55	V
Input Bias Current	VPIN 5=VREF, VPIN 6=0V		-10	-30		-10	-30	μA
Shutdown Terminal Section
Threshold Voltage		250	350	400	250	350	400	mV
Input Voltage Range		0		VIN	0		VIN	V
Minimum Latching Current	(Note 6)
(IPIN 1)		3.0	1.5		3.0	1.5		mA

3