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

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 STA TUS 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

UC1901 SIMPLIFIED SCHEMATIC

11/98

UDG-98080

2

UC1901
UC2901
UC3901

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.

CONNECTION DIAGRAMS

DIL-14, SOIC-14 (TOP VIEW)
J or N Package, D Package

PLCC-20, LCC-20 (TOP VIEW)
Q, L Packages

SOIC-16 Wide (TOP VIEW)
DW Package

TEMPERATURE

RANGE

AVAILABLE

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

TEMPERATURE AND PACKAGE SELECTION
GUIDE

3

UC1901
UC2901
UC3901

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, these specifications apply for VIN= 10V, RT= 10kΩ, CT=

820pF, TA= T

J

.

PARAMETER TEST CONDITIONS UC1901/UC2901 UC3901 UNITS

MIN TYP MAX MIN TYP MAX

Reference Section

Output Voltage T

J

= 25°C 1.485 1.5 1.515 1.47 1.5 1.53 V

T

MIN

≤ TJ≤ T

MAX

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 I

OUT

= 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 V

CM

= 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 V

CM

= 0.5 to 7.5V 60 80 60 80 dB
PSRR VIN= 2 to 25V 80 100 80 100 dB
Output Swing, ∆ V

O 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 T

J

= 25°C 140 150 160 130 150 170 kHz

T

MIN

≤ TJ≤ T

MAX

130 170 120 180 kHz

Line Sensitivity V

IN

= 5 to 35V .15 .35 .15 .60 %/V
Maximum Frequency RT= 10k, CT= 10pF 5 5 MHz
Ext. Clock Low Threshold Pin 1 (CT) = V

IN

0.5 0.5 V

Ext. Clock High Threshold Pin 1 (CT) = V

IN

1.6 1.6 V

Status Indicator Section

Input Voltage Window @ E/A Inputs, V

CM

= 1.5V

±

135±150±165±130±150±170 mV

Saturation Voltage E/A∆ Input = 0V, I

SINK

= 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 V

IN

= 35V 5 8 5 10 mA

UVLO Section

Drivers Enabled Threshold At Input Supply V

IN

3.9 4.5 3.9 4.5 V

Status Output Enabled
Threshold

At Input Supply V

IN

3.9 4.5 3.9 4.5 V

Change in Reference Output When VINReaches UVLO

Threshold

–2 –30 –2 –30 mV