Fairchild Semiconductor ML4802CP Datasheet

December 2000

PRELIMINARY

ML4802

PFC/PWM Controller Combo with Green Mode

GENERAL DESCRIPTION

The ML 4802 is a controller for power factor corrected, switched mode power supplies that offers Green Mode operation and reduced start-up and operating currents. Green Mode is an efficiency improving circuit feature which operates automatically in low power situations. This feature helps meet the demands of Energy Star™ programs.

Power Factor Correction (PFC) offers the use of lower cost bulk capacitors, reduces power line loading and stress on the switching FETs. The ML4802 includes circuits for the implementation of a leading edge, average current, “boost” type power factor corrector and a trailing edge Pulse Width Modulator (PWM).

The PFC frequency of the ML4802 is automatically synchronized to be one half that of the PWM. This technique allows the user to design with smaller PWM components while maintaining the optimum operating frequency for the PFC. An over-voltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting and brown-out protection.

FEATURES

■ Internally synchronized PFC and PWM in one IC

■ Green Mode maximizes efficiency during low power

standby operation

■ Low supply current

(Start-up 200µA typ., operating 5.5mA typ.)

■ Average current continuous boost leading edge PFC

■ High efficiency trailing edge PWM can be configured

for current mode operation

■ Reduced ripple current in the storage capacitor

between the PFC and PWM sections

■ PFC overvoltage comparator eliminates output

“runaway” due to load removal

■ Current fed gain modulator for improved noise

immunity

■ Overvoltage protection, UVLO, and soft start

BLOCK DIAGRAM

VEAO IEAO

2.5V

VEA

MODULATOR

VCC

25µA

VFB

IAC

VRMS

ISENSE

RAMP 1

RT/CT

RAMP 2

VDC

16 1 13

GAIN

1.25V

1.8kΩ

IEA

–

POWER FACTOR CORRECTOR

PFC

CONTROLLER

÷2

OSCILLATOR

DC LIMIT

VFB

2.43V

PULSE WIDTH MODULATOR

VIN OK

1.5V

2.75V

-1V

VFB

VDC

OVP

PFC I

LIMIT

DC ILIMIT

GREEN MODE

CONTROLLER

REFERENCE

PFC

OUTPUT

DRIVER

PWM

OUTPUT

DRIVER

VCC

7.5V

GREEN MODE

VREF

PFC OUT

PWM OUT

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ML4802

PIN CONFIGURATION

ML4802

16-Pin PDIP (P16)

16-Pin Narrow SOIC (S16N)

IEAO

IAC

ISENSE

VRMS

VDC

RT/CT

RAMP 1

PIN DESCRIPTION

PIN NAME FUNCTION

1 IEAO PFC current error amplifier output

2 IAC PFC gain control reference input

3 ISENSE Current sense input to the PFC current

limit comparator

TOP VIEW

VEAO

VFB

VREF

VCC

PFC OUT

PWM OUT

GND

RAMP 2

PIN NAME FUNCTION

9 RAMP 2 PWM current feedback/overcurrent

limit input

10 GND Ground

11 PWM OUT PWM driver output

4 VRMS Input for PFC RMS line voltage

12 PFC OUT PFC driver output

compensation

13 VCC Positive supply input

5 SS Connection point for the PWM soft start

capacitor

14 VREF Buffered output for the internal 7.5V

reference

6 VDC PWM feedback voltage input

15 VFB PFC voltage error amplifier input

7 RT/CT Connection for master (PWM) oscillator

frequency setting components

16 VEAO PFC voltage error amplifier output

8 RAMP 1 PFC ramp input

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ABSOLUTE MAXIMUM RATINGS

ML4802

Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied.

VCC ...........................................................................18V

Lead Temperature (Soldering, 10 sec)..................... 260°C

Thermal Resistance (θja)

Plastic DIP ....................................................... 80°C/W

Plastic SOIC ................................................... 105°C/W

OPERATING CONDITIONS

ISENSE Voltage ................................................ –3V to 5V

Voltage on Any Other Pin ..... GND – 0.3V to VCC + 0.3V

IREF ........................................................................20mA

IAC Input Current ....................................................10mA

Temperature Range

ML4802CX ................................................ 0°C to 70°C

ML4802IX .............................................. –40°C to 85°C

PeakCurrent, Source or Sink

PFC OUT, PWM OUT ........................................500mA

PFC OUT, PWM OUT Energy Per Cycle................... 1.5µJ

Junction Temperature ............................................. 150°C

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

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, VCC = 15V, RT = 29.4kΩ, RRAMP1 = 15.4kΩ, CT = 270pF, CRAMP1 = 620pF, TA = Operating Temperature Range (Note 1)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VOLTAGE ERROR AMPLIFIER

Input Voltage Range 0 5 V Transconductance VNON INV = VINV, VEAO = 3.75V 20 35 50 µ

Feedback Reference Voltage 2.4 2.5 2.6 V Input Bias Current Note 2 -0.5 -1.0 µA

Output High Voltage 6.0 6.7 V

Output Low Voltage 0.2 0.5 V Source Current ∆VIN = ±0.5V, VOUT = 6V –1 –2.5 –4 µA Sink Current ∆VIN = ±0.5V, VOUT = 1.5V –1 –2.5 –4 µA

Open Loop Gain 50 60 dB

PSRR 11V < VCC < 16.5V 50 60 dB

CURRENT ERROR AMPLIFIER

Input Voltage Range -1.5 2 V Transconductance VNON INV = VINV, VEAO = 3.75V 50 100 150 µ

Input Offset Voltage –5 3 10 mV Input Bias Current -0.5 -1.0 µA

Output High Voltage 6.0 6.7 V

Output Low Voltage 0.65 1.0 V Source Current ∆VIN = ±0.5V, VOUT = 6V -40 -70 -150 µA Sink Current ∆VIN = ±0.5V, VOUT = 1.5V 40 70 150 µA

Open Loop Gain 60 75 dB

PSRR 11V < VCC < 16.5V 60 75 dB

Ω

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ML4802

ELECTRICAL CHARACTERISTICS (Continued)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

OVP COMPARATOR

Threshold Voltage 2.65 2.75 2.85 V

Hysteresis 175 250 325 mV

PFC ILIMIT COMPARATOR

Threshold Voltage –0.9 –1 –1.1 V

∆PFC ILIMIT Threshold - Gain Modulator Output 120 220 mV

Delay to Output 150 300 ns

DC ILIMIT COMPARATOR

Threshold Voltage 1.4 1.5 1.6 V Input Bias Current ±0.3 ± 1 µA

Delay to Output 150 300 ns

VIN OK COMPARATOR

Threshold Voltage 2.33 2.43 2.55 V

Hysteresis 0.8 1.0 1.2 V

GAIN MODULATOR

Gain (Note 3) IAC = 100µA, VRMS = VFB = 0V 0.6 0.8 1.05

IAC = 50µA, VRMS = 1.2V, VFB = 0V 1.8 2 2.80 IAC = 50µA, VRMS = 1.8V, VFB = 0V 0.8 1 1.25

IAC = 100µA, VRMS = 3.3V, VFB = 0V 0.2 0.3 0.4 Bandwidth IAC = 100µA 10 MHz Output Voltage IAC = 250µA, VRMS = 1.15V, 0.6 0.75 0.9 V

VFB = 0V

OSCILLATOR

Initial Accuracy TA = 25ºC 188 200 212 kHz

Voltage Stability 11V < VCC < 16.5V 1 %

Temperature Stability 2%

Total Variation Line, Temp 182 218 kHz

Ramp Valley to Peak Voltage 2.5 V

Dead Time PFC Only 260 400 ns

CT Discharge Current VRAMP 2 = 0V, VRAMP 1 = 2.5V 3.5 5.5 7.5 mA

GREEN MODE

VGMT-L Green Mode Threshold Low VGMT = VDC –VLS 70 275 mV

VGMT-H Green Mode Threshold High VGMT = VDC –VLS 360 580 mV

VLS Level Shift 1.25 V

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ML4802

ELECTRICAL CHARACTERISTICS (Continued)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

REFERENCE

Output Voltage TA = 25ºC, I(VREF) = 1mA 7.4 7.5 7.6 V

Line Regulation 11V < VCC < 16.5V 2 30 mV

Load Regulation 1mA < I(VREF) < 10mA 2 20 mV

Temperature Stability 0.4 %

Total Variation Line, Load, Temp 7.35 7.65 V

Long Term Stability TJ = 125ºC, 1000 Hours 5 25 mV

PFC

Minimum Duty Cycle VIEAO > 4.0V 0 %

Maximum Duty Cycle VIEAO < 1.2V 85 90 %

Output Low Voltage IOUT = –20mA 0.4 0.8 V

IOUT = –100mA 0.7 2.0 V

IOUT = –10mA, VCC = 11V 0.8 1.5 V

Output High Voltage IOUT = 20mA VCC - 0.8 V

IOUT = 100mA VCC - 2.0 V

Rise/Fall Time CL = 1000pF 50 ns

PWM

DC Duty Cycle Range 0-44 0-47 0-50 %

VOL Output Low Voltage IOUT = –20mA 0.4 0.8 V

IOUT = –100mA 0.7 2.0 V

IOUT = –10mA, VCC = 11V 0.8 1.5 V

VOH Output High Voltage IOUT = 20mA VCC - 0. 8 V

IOUT = 100mA VCC - 2.0 V

Rise/Fall Time CL = 1000pF 50 ns

SUPPLY

Start-up Current VCC = 12V, CL = 0 200 350 µA

Operating Current VCC = 14V, CL = 0 5 7 mA

Undervoltage Lockout Threshold 12 13 14 V

Undervoltage Lockout Hysteresis 2.5 2.8 3.1 V

Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst-case test conditions. Note 2: Includes all bias currents to other circuits connected to the VFB pin. Note 3: Gain = K x 5.3V; K = (IMULO - IOFFSET) x IAC x (VEAO - 1.5V)

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