Texas Instruments UC3901QTR, UC3901Q, UC3901N, UC3901J, UC3901DWTR Datasheet

UC1901

UC2901

UC3901

Isolated Feedback Generator

FEATURES

∙An Amplitude-Modulation System for Transformer Coupling an Isolated Feedback Error Signal

∙Low-Cost Alternative to Optical Couplers

∙Internal 1% Reference and Error Amplifier

∙Internal Carrier Oscillator Usable to 5MHz

∙Modulator Synchronizable to an External Clock

∙Loop Status Monitor

UC1901 SIMPLIFIED SCHEMATIC

DESCRIPTION

The UC1901 family is designed to solve many of the problems associated with closing a feedback control loop across a voltage isolation boundary. As a stable and reliable alternative to an optical coupler, these devices feature an amplitude modulation system which allows a loop error signal to be coupled with a small RF transformer or capacitor.

The programmable, high-frequency oscillator within the UC1901 series permits the use of smaller, less expensive transformers which can readily be built to meet the isolation requirements of today's line-operated power systems. As an alternative to RF operation, the external clock input to these devices allows synchronization to a system clock or to the switching frequency of a SMPS.

An additional feature is a status monitoring circuit which provides an activelow output when the sensed error voltage is within ±10% of the reference. The DRIVERA output, DRIVERB output, and STATUS output are disabled until the input supply has reached a sufficient level to allow proper operation of the device.

Since these devices can also be used as a DC driver for optical couplers, the benefits of 4.5 to 40V supply operation, a 1% accurate reference, and a high gain general purpose amplifier offer advantages even though an AC system may not be desired.

μ	μ
	μ
	UDG-98080
11/98

ABSOLUTE MAXIMUM RATINGS (Note 1)

Input Supply Voltage, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Reference Output Current . . . . . . . . . . . . . . . . . . . . . . . –10mA Driver Output Currents . . . . . . . . . . . . . . . . . . . . . . . . . . –35mA Status Indicator Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Status Indicator Current . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA Ext. Clock Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Error Amplifier Inputs . . . . . . . . . . . . . . . . . . . . . –0.5V to +35V Power Dissipation at TA = 25°C. . . . . . . . . . . . . . . . . . 1000mW Power Dissipation at TC = 25°C . . . . . . . . . . . . . . . . . 2000mW Operating Junction Temperature . . . . . . . . . . –55°C to +150°C Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C Lead Temperature (Soldering, 10 seconds) . . . . . . . . . . 300°C

Note 1: Voltages are referenced to ground, Pin 7. Currents are positive into, negative out of the specified terminal.

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

UC1901

UC2901

UC3901

CONNECTION DIAGRAMS

DIL-14, SOIC-14 (TOP VIEW)

J or N Package, D Package

SOIC-16 Wide (TOP VIEW)

DW Package

TEMPERATURE AND PACKAGE SELECTION GUIDE

	TEMPERATURE	AVAILABLE
	RANGE	PACKAGES
UC1901	–55°C to +125°C	J, L
UC2901	–40°C to +85°C	D, DW, J, N, Q
UC3901	0°C to +70°C	D, DW, J, N, Q

PLCC-20, LCC-20 (TOP VIEW)

Q, L Packages

2

UC1901

UC2901

UC3901

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for VIN = 10V, RT = 10kΩ, CT = 820pF, TA = TJ.

PARAMETER	TEST CONDITIONS		UC1901/UC2901				UC3901		UNITS
			MIN	TYP	MAX	MIN	TYP	MAX
Reference Section
Output Voltage	TJ = 25°C		1.485	1.5	1.515	1.47	1.5	1.53	V
	TMIN ≤ TJ ≤ TMAX		1.470	1.5	1.530	1.455	1.5	1.545
Line Regulation	VIN = 4.5 to 35V			2	10		2	15	mV
Load Regulation	IOUT = 0 to 5mA			4	10		4	15	mV
Short Circuit Current	TJ = 25°C			–35	–55		–35	–55	mV
Error Amplifier Section (To Compensation Terminal)
Input Offset Voltage	VCM = 1.5V			1	4		1	8	mV
Input Bias Current	VCM = 1.5V			–1	–3		–1	–6	μA
Input Offset Current	VCM = 1.5V			0.1	1		0.1	2	μA
Small Signal Open Loop Gain			40	60		40	60		dB
CMRR	VCM = 0.5 to 7.5V		60	80		60	80		dB
PSRR	VIN = 2 to 25V		80	100		80	100		dB
Output Swing, VO			0.4	0.7		0.4	0.7		V
Maximum Sink Current			90	150		90	150		μA
Maximum Source Current			–2	–3		–2	–3		mA
Gain Band Width Product				1			1		MHz
Slew Rate				0.3			0.3		V/μS
Modulators/Drivers Section (From Compensation Terminal)
Voltage Gain			11	12	13	10	12	14	dB
Output Swing			±1.6	±2.8		±1.6	±2.8		V
Driver Sink Current			500	700		500	700		μA
Driver Source Current			–15	–35		–15	–35		mA
Gain Band Width Product				25			25		MHz
Oscillator Section
Initial Accuracy	TJ = 25°C		140	150	160	130	150	170	kHz
	TMIN ≤ TJ ≤ TMAX		130		170	120		180	kHz
Line Sensitivity	VIN = 5 to 35V			.15	.35		.15	.60	%/V
Maximum Frequency	RT = 10k, CT = 10pF			5			5		MHz
Ext. Clock Low Threshold	Pin 1 (CT) = VIN		0.5			0.5			V
Ext. Clock High Threshold	Pin 1 (CT) = VIN				1.6			1.6	V
Status Indicator Section
Input Voltage Window	@ E/A Inputs, VCM = 1.5V		±135	±150	±165	±130	±150	±170	mV
Saturation Voltage	E/A Input = 0V, ISINK = 1.6mA				0.45			0.45	V
Max. Output Current	Pin 13 = 3V, E/A	Input = 0.0V	8	15		8	15		mA
Leakage Current	Pin 13 = 40V, E/A	Input = 0.2V		.05	1		.05	5	μA
Supply Current	VIN = 35V			5	8		5	10	mA
UVLO Section
Drivers Enabled Threshold	At Input Supply VIN			3.9	4.5		3.9	4.5	V
Status Output Enabled	At Input Supply VIN			3.9	4.5		3.9	4.5	V
Threshold
Change in Reference Output	When VIN Reaches UVLO			–2	–30		–2	–30	mV
	Threshold

3