Texas Instruments UCC3857N, UCC3857DWTR, UCC3857DW Datasheet

UCC1857
UCC2857
UCC3857

PRELIMINARY

DESCRIPTION

The UCC3857 provides all of the control functions necessary for an Iso­lated Boost PFC Converter. These converters have the advantage of trans­former isolation between primary and secondary, as well as an output bus
voltage that is lower than the input voltage. By providing both power factor
correction and down conversion in a single power processing stage, the
UCC3857 is ideal for applications which require high efficiency, integration,
and performance.

The UCC3857 brings together the control functions and drivers necessary
to generate overlapping drive signals for external IGBT switches, and pro­vides a separate output to drive an external power MOSFET which pro­vides zero current switching (ZCS) for both the IGBTs. Full programmability
is provided for the MOSFET driver delay time with an external RC network.
ZCS for the IGBT switches alleviates the undesirable turn off losses typi­cally associated with these devices. This allows for higher switching fre­quencies, smaller magnetic components and higher efficiency. The power
factor correction (PFC) portion of the UCC3857 employs the familiar aver­age current control scheme used in previous Unitrode controllers. Internal
circuitry changes, however, have simplified the design of the PFC section
and improved performance.

(continued)

Isolated Boost PFC Preregulator Controller

8 154

VD

13 73

VINCAOCA–MOUTPKLMT

14MOSDRV

16IGDRV1

18IGDRV2

17

PGND

20

CT

6

AGND

19

RT

20

SS

5VREF

12DELAY

11 VAO

10 VA–

2

CRMS

1IAC

REF

REF

Z

V

Z

C

R

S

Q2Q1

T1

FEEDBACK

CKT

OPTO

BIAS

SUPPLY

QA

R

AC

V

OUT

+

–

RECTIFIED
AC INPUT

REF

UCC3857

C

F

TYPICAL APPLICATION CIRCUIT

FEATURES

• PFC With Isolation, V

O

< V

IN

• Single Power Stage

• Zero Current Switched IGBT

• Programmable ZCS Time

• Corrects PF to >0.99

• Fixed Frequency, Average Current

Control

• Improved RMS Feedforward

• Soft Start

• 9V to 18V Supply V Range

• 20-Pin DW, N, J, and L Packages

02/99

UDG-98065

2

UCC1857
UCC2857
UCC3857

ABSOLUTE MAXIMUM RATINGS

Input Supply Voltage (VIN, VD). . . . . . . . . . . . . . . . . . . . . . 18V

General Analog/Logic Inputs

(CRMS, MOUT, CA–, VA–, CT, RT, PKLMT)

(Maximum Forced Voltage). . . . . . . . . . . . . . . . –0.3V to 5V

IAC (Maximum Forced Current) . . . . . . . . . . . . . . . . . . . 300µA

Reference Output Current . . . . . . . . . . . . . . . Internally Limited

Output Current (MOSDRV, IGDRV1, IGDRV2)

Pulsed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A

Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200mA

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

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

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

Unless otherwise indicated, voltages are reference to ground
and currents are positive into, negative out of the specified ter­minal. Pulsed is defined as a less than 10% duty cycle with a
maximum duration of 500 s. Consult Packaging Section of
Databook for thermal limitations and considerations of pack­ages.

3

18
17
16

IAC

122019

15
14

4
5
6
7
8

91110 12 13

CRMS
MOUT

CT
RT

IGDRV2
PGND
IGDRV1
VD
MOSDRV

VIN

VREF

AGND

CA–

CAO

PKLMT
DELAY
VAO

SS

VA–

DESCRIPTION (continued)

Controller improvements include an internal 6 bit A-D
converter for RMS input line voltage detection, a zero
load power circuit, and significantly lower quiescent op­erating current. The A-D converter eliminates an external
2 pole low pass filter for RMS detection.

This simplifies the converter design, eliminates 2nd har­monic ripple from the feedforward component, and pro­vides an approximate 6 times improvement in input line
transient response. The zero load power comparator
prevents energy transfer during open load conditions
without compromising power factor at light loads. Low
startup and operating currents which are achieved
through the use of Unitrode's BCDMOS process simplify
the auxiliary bootstrap supply design.

Additional features include: under voltage lockout for reli­able off-line startup, a programmable over current shut­down, an auxiliary shutdown port, a precision 7.5V
reference, a high amplitude oscillator ramp for improved
noise immunity, softstart, and a low offset analog square,
multiple and divide circuit. Like previous Unitrode PFC
controllers, worldwide operation without range switches
is easily implemented.

IGDRV2

RT

CT

PGND

IGDRV1

MOSDRV

VD

PKLMT

1

2

3

4

5

6

7

8

20

19

18

17

16

15

14

13

CRMS

IAC

CAO

AGND

CA–

MOUT

VIN

VREF

9

10VA–

SS DELAY

VAO

12

11

CONNECTION DIAGRAMS

DIL-20, SOIC- 20 (Top View)
J, N and DW Packages

PLCC-20 (Top View)
L Package

3

UCC1857
UCC2857
UCC3857

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated, these specifications apply for TA= 0°C to 70°C for the

UCC3857, –40°C to +85°C for the UCC2857, and –55°C to +125°C for the UCC1857, V

VIN

, VVD= 12V, RT= 19.2K, CT= 680pF.

TA= TJ.

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Input Supply

Supply Current, Active No Load on Outputs, V

VD

= V

VIN

3.5 5 mA

Supply Current, Startup No Load on Outputs, V

VD

= V

VIN

60 TBD µA
VIN UVLO Threshold 13.75 15.5 V
UVLO Threshold Hysteresis 3 3.75 TBD V

Reference

Output Voltage (V

VREF

)T

J

= 25°C, I

REF

= 1mA 7.387 7.5 7.613 V
Over Temperature, UCC3857 7.368 7.5 7.631 V
Over Temperature, UCC1857, UCC2857 7.313 7.5 7.687 V

Load Regulation I

REF

= 1mA to 10mA 2 10 mV

Line Regulation V

VIN

= VVD= 12V to 16V 2 15 mV

Short Circuit Current V

VREF

= 0V –55 –30 mA

Current Amplifier

Input Offset Voltage (Note 1) –3 0 3 mV
Input Bias Current (Note 1) –50 nA
Input Offset Current (Note 1) 25 nA
CMRR V

CM

= 0V to 1.5V, V

CAO

= 3V 80 dB

AVOL VCM= 0V, V

CAO

= 2V to 5V 65 85 dB

VOH Load on CAO = 50µA, V

MOUT

= 1V, V

CA–

= 0V 6 7 V

VOL Load on CAO = 50µA, V

MOUT

= 0V, VCA– = 1V 0.2 V

Maximum Output Current Source : V

CA–

= 0V, V

MOUT

= 1V, V

CAO

= 3V –150 µA

Sink : V

CA–

= 1V, V

MOUT

= 0V, V

CAO

= 3V 5 30 50 mA

Gain Bandwidth Product fIN= 100kHz, 10mV p – p 3 5 MHz

Voltage Amplifier

Input Voltage Measured on V

VA–

,

V

VAO

= 3V 2.9 3 3.1 V

Input Bias Current Measured on V

VA–

,

V

VAO

= 3V –50 nA

AVOL V

VAO

= 1V to 5V 75 dB

VOH Load on V

VAO

= –50µA, V

VA–

= 2.8V 5.3 5.55 5.7 V

VOL Load on V

VAO

= 50µA, V

VA–

= 3.2V 0.1 0.45 V

Maximum Output Current Source: V

VA–

= 2.8V, V

VAO

= 3V –20 –12 –5 mA

Sink: V

VA–

= 3.2V, V

VAO

= 3V 5 20 30 mA

Oscillator

Initial Accuracy T

J

= 25°C 42.5 50 57.5 kHz

40 50 60 kHz

Voltage Stability V

VIN

= 12V to 18V 1 %
CT Ramp Peak-Valley Amplitude 4 4.5 5 V
CT Ramp Valley Voltage 1.5 V

Output Drivers

VOH IL = –100mA 9 10 V
VOL IL = 100mA 0.1 0.5 V
Rise Time C

LOAD

= 1nF 25 TBD ns

Fall Time C

LOAD

= 1nF 10 TBD ns

Trailing Edge Delay

Delay Time R

D

= 12k, CD= 200pF, V

VAO

= 4V 1.6 2 2.4 µs