UNITRODE UCC1839, UCC2839, UCC3839 Technical data

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Secondary Side Average Current Mode Controller

UCC1839
UCC2839
UCC3839

FEATURES

• Practical Secondary Side Control of
Isolated Power Supplies

• Provides a Self Regulating Bias
Supply From a High Input Voltage
Using an External N-Channel
Depletion Mode FET

• Onboard Precision, Fixed Gain,
Differential Current Sense Amplifier

• Wide Bandwidth Current Error
Amplifier

• 5V Reference

• High Current, Programmable Gm

Amplifier Optimized to Drive
Opto-couplers

DESCRIPTION

The UCC3839 provides the control functions for secondary side average
current mode control in isolated power supplies. Start up, pulse width
modulation and MOSFET drive must be accomplished independently on
the primary side. Communication from secondary to primary side is antici­pated through an opto-isolator.

Accordingly, the UCC3839 contains a fixed gain current sense amplifier,
voltage and current error amplifiers, and a Gm type buffer/driver amplifier
for the opto-isolator. Additional housekeeping functions include a precision
5V reference and a bias supply regulator.

Power for the UCC3839 can be generated by peak rectifying the voltage of
the secondary winding of the isolation transformer. From this unregulated
voltage, the UCC3839’s bias supply regulator will generate its own 7.5V
bias supply using an external, N-channel, depletion mode FET.

The UCC3839 can be configured for traditional average current mode con­trol where the output of the voltage error amplifier commands the current
error amplifier. It can also be configured for output voltage regulation with
average current mode short circuit current limiting, employing two parallel
control loops regulating the output voltage and output current independ­ently.

BLOCK DIAGRAM

04/99

UDG-97011

ABSOLUTE MAXIMUM RATINGS

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V

Supply Current

(LED not connected) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2mA

(LED connected) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14mA

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to 15V

Power Dissipation at TA = 60°C

(LED not connected). . . . . . . . . . . . . . . . . . . . . . . . . . 20mW

(LED connected). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55mW

Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C

Junction Temperature. . . . . . . . . . . . . . . . . . . –55°C to +150°C

Lead Temperature (Soldering, 10sec.) . . . . . . . . . . . . . +300°C

Currents are positive into, negative out of the specified terminal.
Consult Packaging Section of Databook for thermal limitations
and considerations of package.

UCC1839
UCC2839
UCC3839

CONNECTION DIAGRAMS

DIL-14, SOIC-14 (Top View)
J or N Package, D Package

ELECTRICAL CHARACTERISTICS:

UCC2839 and –55°C to 125°C for the UCC1839. V

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Current Error Amplifier

VIO 10 mV

AVOL 60 dB

CMRR V

PSRR VLINE = 10V to 20V 60 dB

CAO High CA– = 1V, CA+ = 1.1V, ICAO = –100µA 4.8 7 V

ICAO CA– = 1V, CA+ = 1.1V, CAO = 0.5V –500 –250 µA

CAO Low CA– = 1V, CA+ = 0.9V, ICAO = 500µA 0.2 0.4 V

GBW F = 100kHz, TA = 25°C 3 5 MHz

Voltage Error Amplifier

VA– 1.475 1.5 1.525 V

AVOL 60 dB

PSRR V

VAO High IVAO = –100µA to 100µA 4.8 5 5.2 V

IVAO VA– = 1.45V, VAO = 0.5V –500 –250 µA

VAO Low VA– = 1.55V, VAO = 0.5V, IVAO = 500µA 0.2 0.4 V

GBW (Note 1) 3 5 MHz

Current Sense Amplifier

CSO Zero CS+ = CS– = –0.3V to 5.5V, I

AV CS+ = 0, CS– = 0mV to –200mV 7.8 8 8.2 V/V

Current Sense Amplifier (cont.)

Slew Rate CS+ = 0, CS– = 0mV to –0.5V 2 4 V/µs

CSO CS+ = –200mV, CS– = –700mV 4.8 5 5.2 V

LED Driver

I

LED LED = 5.5V, CA– = 1V, CA+ = 1.1V, RG = 400 0 10 µA

Gm LED = 5.5V, CAO = 1V to 3V, RG = 400 2.25 2.5 2.75 mS

Slew Rate CAO = 2V to 2.5V, LED = 400Ω to 5.5V, RG = 400 2 4 V/µs

CM = 0.5V to 5.5V 60 dB

LINE = 10V to 20V 60 dB

LED = 5.5V, CA– = 1V, CA+ = 0.9V, RG = 400 9 10 11 mA

Unless otherwise specified, 0°C to 70°C for the UCC3839, –40°C to 85° for the

= 10V, RG = 400Ω. TA=TJ.

LINE

CSO = –100µA to 100µA 0.95 1 1.05 V

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