UCC3839DG4 - Texas Instruments

UCC2839

UCC3839

SLUS179A - APRIL 1999 - REVISED NOVEMBER 2001

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

Secondary Side Average Current Mode Controller

BLOCK DIAGRAM

UDG-97011

DESCRIPTION

The UCC3839 provides the control functions for secondary side average

current mode control in isolated power supplies. Start up, pulse width mod-

ulation and MOSFET drive must be accomplished independently on the

primary side. Communication from secondary to primary side is antici-

pated 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 con-

trol 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 independ-

ently.

UCC2839

UCC3839

CONNECTION DIAGRAMS

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

UCC2839. VLINE = 10V, RG = 400Ω. TA=T

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Current Error Amplifier

VIO 10 mV

AVOL 60 dB

CMRR VCM = 0.5V to 5.5V 60 dB

PSRR VLINE = 10V to 20V 60 dB

CAO High CA– = 1V, CA+ = 1.1V, ICAO = –100 A 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– 1.46 1.5 1.525 V

AVOL 60 dB

PSRR VLINE = 10V to 20V 60 dB

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, ICSO = –100µA to 100µA 0.85 1 1.15 V

AV CS+ = 0, CS– = 0mV to –200mV 7.75 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 4.75 5 5.2 V

LED Driver

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

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

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 = 400Ωto 5.5V, RG = 400 1 4 V/µs

DIL-14, SOIC-14 (Top View)

D or N Package

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.

UCC2839

UCC3839

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

UCC2839. VLINE = 10V, RG = 400Ω. TA=T

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Precision Reference

REF TJ= 25°C 4.94 5 5.06 V

IREF = 0mA to 1mA, VLINE = 10V to 20V 4.9 5.1 V

VA+/REF 0.298 0.3 0.302 V/V

VDD Regulator

VDD IDD = 0mA to –15mA, VLINE = 10V to 40V 7 7.5 8 V

IVDD VLINE = 10V to 40V, CA– = 0V, CA+ = 1V, VA– = 2.9V, CS+

= CS– = 0, IREF = 0

1.3 2 mA

Note 1: Ensured by design. Not 100% tested in production.

CA–: Current Error Amplifier Negative Input.

CAO: Current Error Amplifier Output. Output source cur-

rent is limited, and output sink current is guaranteed to

be greater than the VAO output source current. Current

loop compensation components are generally connected

to CAO and CA–.

CA+: Current Error Amplifier Positive Input.

CS–: Current Sense Amplifier Negative Input.

CSO: Current Sense Amplifier Output. Internally set gain

VOUT/VIN = 8 VIN = 0V results in CSO = 1V.

CS+: Current Sense Amplifier Positive Input.

GM: Gm (transconductance) Programming Pin. Resistor

RGM = 400Ωto GND.

GND: Chip Ground.

LED: Output of LED Driver. Connect LED from VDD pin

to LED.

REF: 5V Precision Reference Buffer Output. Minimum

Decoupling Capacitance = 0.01µF

VA–: Voltage Error Amplifier Negative Input. Voltage Er-

ror Amplifier is internally referenced to 1.5V

VAO: Voltage Error Amplifier Output. In a two loop aver-

age current mode control configuration, VAO is con-

nected to CA+ and is the current command signal. VAO

is internally clamped not to exceed 5V for short circuit

control. In a single loop voltage mode control configura-

tion with a parallel average short circuit current control

loop, VAO is connected directly to CAO. Output source

current is limited, and output sink current is guaranteed

to be greater than the CAO output source current.

VDD: 7.5V Regulator output. Supply for most of the chip.

Minimum Decoupling Capacitance = 0.01µF

VGATE: External FET Gate Control Voltage.

PIN DESCRIPTIONS

Fig. 1 shows a typical secondary side average current

mode controller configuration using the UCC3839. In this

configuration, output voltage is sensed and regulated by

the voltage error amplifier. Its output, VAO provides the

reference for the current error amplifier at the CA+ pin.

VAO can be connected to CA+ directly or through a re-

sistive divider depending on the particular application re-

quirements.

Average current mode control needs accurate output cur-

rent information which is provided by a low value current

sense resistor. The voltage proportional to the con-

verter’s output current is sensed and amplified by the

precision current sense amplifier of the chip. The

onboard current sense amplifier has a gain of 8 and is in-

tended for differential sensing of the shunt voltage with a

common mode voltage range from 0V up to 5V. The out-

put of the current sense amplifier, CSO is 1V for zero in-

put which guarantees that the circuit can control currents

down to 0A.

The CSO signal is fed to the CA– input of the current er-

ror amplifier through a resistor. The current error amplifier

takes the VAO and CSO signals and generates the error

signal for the pulse width modulator.

APPLICATION INFORMATION

UCC2839

UCC3839

Figure 1. Secondary side average current mode controller.

UDG-97012

Since the PWM function is located on the primary side of

the power converter the CAO signal must be sent across

the safety isolation boundary. The UCC3839 anticipates

an opto-coupler to provide isolation between primary and

secondary. Therefore, CAO drives a transconductance

amplifier that controls LED current in an opto-isolator.

During start up and when CAO exceeds 4V, the current

in the LED drops to zero. Maximum LED current is ob-

tained during normal operation as CAO reaches its low-

est potential. Its value is determined by the programming

resistor value from the GM pin to circuit GND.

An alternative secondary side controller configuration is

introduced in Fig. 2. In this circuit, the voltage and current

control loops of the UCC3839 are connected parallel. It

can be achieved by connecting the VAO and CAO pins

together. The error amplifier with the lower output voltage

controls the current in the opto-coupler providing the

feedback signal for the PWM section on the primary side.

Voltage regulation is still maintained by the voltage error

amplifier until a user programmable output current is

reached. At this time CAO will take control over the Gm

amplifier and the output current of the converter will be

regulated while the output voltage falls below its nominal

value. This current level is set at the CA+ input by a re-

sistive divider from the 5V reference of the chip.

Since the chip is powered from a peak rectifier which

maintains the bias supply for the UCC3839 even under

short circuit conditions, both of these techniques can be

used to eliminate the short circuit runaway problem in

isolated power supplies using peak current mode control

on the primary side.

APPLICATION INFORMATION (cont.)

UCC2839

UCC3839

Figure 3. Typical primary side circuit for use with secondary side average current mode controller.

UDG-97014

Figure 2. Voltage mode with average current short circuit limit.

APPLICATION INFORMATION (cont.)

UDG-97014

PACKAGING INFORMATION

Orderable Device Status (1) Package

Type Package

Drawing Pins Package

Qty Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)

UCC2839D ACTIVE SOIC D 14 50 Green (RoHS &

no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR

UCC2839DTR ACTIVE SOIC D 14 2500 Green (RoHS &

no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR

UCC2839DTRG4 ACTIVE SOIC D 14 2500 Green (RoHS &

no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR

UCC2839N ACTIVE PDIP N 14 25 Green (RoHS &

no Sb/Br) CU NIPDAU N / A for Pkg Type

UCC2839NG4 ACTIVE PDIP N 14 25 Green (RoHS &

no Sb/Br) CU NIPDAU N / A for Pkg Type

UCC3839D ACTIVE SOIC D 14 50 Green (RoHS &

no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in

a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check

http://www.ti.com/productcontent for the latest availability information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements

for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered

at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and

package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS

compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame

retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)

(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder

temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is

provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the

accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take

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incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited

information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI

to Customer on an annual basis.

PACKAGE OPTION ADDENDUM

www.ti.com 15-Sep-2006

Addendum-Page 1