Fairchild Semiconductor ML4841 Datasheet

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ML4841

Variable Feedforward PFC/PWM Controller Combo

Features

• Internally synchronized PFC and PWM in one IC

• Low total harmonic distortion

• Reduces ripple current in the storage capacitor between
the PFC and PWM sections

• Average current, continuous mode, boost type, leading
edge PFC

• High efficiency trailing edge PWM can be configured for
current mode or voltage mode operation

• Average line voltage compensation with brown-out
control

• PFC overvoltage comparator eliminates output
“runaway” due to load removal

• Current fed multiplier for improved noise immunity

• Overvoltage protection, UVLO, and soft start

Block Diagram

15

2

4

3

8

7

V

FB

2.5V

I

AC

V

RMS

I

SENSE

RAMP 1

RTC

T

VEAO

VEA

-

+

MODULATOR

16

GAIN

3.5kΩ

IEA

-

+

3.5kΩ

IEAO

8V

1

POWER FACTOR CORRECTOR

+

-

OSCILLATOR

General Description

The ML4841 is a controller for power factor corrected,
switched mode power supplies. Power Factor Correction
(PFC) allows the use of smaller, lower cost bulk capacitors,
reduces power line loading and stress on the switching FETs,
and results in a power supply that fully complies with
IEC1000-2-3 specifications. The ML4841 includes circuits
for the implementation of a leading edge, average current,
“boost” type power factor correction, and a trailing edge,
pulse width modulator (PWM).

The PFC frequency of the ML4841 is automatically set at
half that of the PWM frequency generated by the internal
oscillator. This technique allows the user to design with
smaller output 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 input voltage brown-out protection.

13

V

V

OVP

+

2.7V

÷2

-1V

-

+

-

PFC I

LIMIT

CCZ

13.5V

REFERENCE

SRQ

Q

SRQ

Q

CC

7.5V

PFC OUT

V

REF

14

12

RAMP 2

9

V

6

SS

5

DC

DUTY CYCLE

-

+

VIN OK

LIMIT

1V

SRQ

+

-

DC I

LIMIT

V

CCZ

Q

UVLO

PWM OUT

11

8V

1.25V

V

CC

50µA

8V

-

+

-

+

V

FB

2.5V

PULSE WIDTH MODULATOR

REV. 1.0.3 6/13/01

ML4841 PRODUCT SPECIFICATION

Pin Configuration

ML4841

16-Pin PDIP (P16)

Pin Description

PIN NAME FUNCTION

1 IEAO PFC transconductance current error amplifier output

2IACPFC gain control reference input

3I

4V

5SSConnection point for the PWM soft start capacitor

6VDCPWM voltage feedback input

7R

8 RAMP 1 PFC ramp input

9 RAMP 2 PWM ramp current sense input

10 GND Ground

11 PWM OUT PWM driver output

12 PFC OUT PFC driver output

13 V

14 V

15 V

16 VEAO PFC transconductance voltage error amplifier output

SENSE

RMS

TCT

CC

REF

FB

IEAO

I

AC

I

SENSE

V

RMS

SS

V

DC

RT/C

RAMP 1

1

2

3

4

5

6

7

T

8

TOP VIEW

16

15

14

13

12

11

10

9

VEAO

V

FB

V

REF

V

CC

PFC OUT

PWM OUT

GND

RAMP 2

Current sense input to the PFC current limit comparator

Input for PFC RMS line voltage compensation

Connection for oscillator frequency setting components

Positive supply (connected to an internal shunt regulator).

Buffered output for the internal 7.5V reference

PFC transconductance voltage error amplifier input

2 REV. 1.0.3 6/13/01

PRODUCT SPECIFICATION ML4841

Absolute Maximum Ratings

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.

Parameter Min. Max. Units

VCC Shunt Regulator Current 55 mA

I

Voltage on Any Other Pin GND - 0.3 V

I

I

Peak PFC OUT Current, Source or Sink 500 mA

Peak PWM OUT Current, Source or Sink 500 mA

PFC OUT, PWM OUT Energy Per Cycle 1.5 mJ

Junction Temperature 150 °C

Storage Temperature Range –65 150 °C

Lead Temperature (Soldering, 10 sec) 260 °C
Thermal Resistance (θ

Plastic DIP 80 °C/W

Voltage -3 5 V

SENSE

+ 0.3 V

CCZ

REF

Input Current 10 mA

AC

)

JA

20 mA

Operating Conditions

Temperature Range

Parameter Min. Max. Units

ML4841CP 0 70 °C

Electrical Characteristics

Unless otherwise specified, ICC = 25mA, RT = 23kΩ, R
Operating Temperature Range (Note 1)

Symbol Parameter Conditions Min. Typ. Max. Units

Voltage Error Amplifier

Input Voltage Range 0 7 V

Transconductance V

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 0.65 1.0 V
Source Current ∆VIN = ±0.5V, V
Sink Current ∆VIN = ±0.5V, V

Open Loop Gain 60 75 dB

PSRR V

Current Error Amplifier

Input Voltage Range -1.5 2 V

Transconductance V

Input Offset Voltage ±3 ±15 mV

NON INV

CCZ

NON INV

= V

- 3V < VCC < V

= V

= 28.7kΩ, CT = 400pF, C

RAMP1

, VEAO = 3.75V 40 70 100 µ

INV

= 6V -40 -90 µA

OUT

= 1.5V 40 90 µA

OUT

- 0.5V 60 75 dB

CCZ

, VEAO = 3.75V 130 195 310 µ

INV

RAMP1

= 270pF, TA =

Ω

Ω

REV. 1.0.3 6/13/01 3

ML4841 PRODUCT SPECIFICATION

Electrical Characteristics (continued)

Unless otherwise specified, I

= 25mA, RT = 23kΩ, R

CC

Operating Temperature Range (Note 1)

Symbol Parameter Conditions Min. Typ. Max. Units

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, V
Sink Current ∆V

= ±0.5V, V

IN

Open Loop Gain 60 75 dB

PSRR V

- 3V < VCC < V

CCZ

OVP Comparator

Threshold Voltage 2.6 2.7 2.8 V

Hysteresis 70 95 125 mV

PFC I

Comparator

LIMIT

Threshold Voltage -0.8 -1.0 -1.15 V
∆(PFC I

LIMIT VTH

- Gain

Modulator Output)

Delay to Output 150 300 ns

DC I

Comparator

LIMIT

Threshold Voltage 0.9 1.0 1.1 V

Input Bias Current ±0.3 ±1 µA

Delay to Output 150 300 ns

VIN OK Comparator

Threshold Voltage 2.4 2.5 2.6 V

Hysteresis 0.8 1.0 1.2 V

Gain Modulator

Gain (Note 3) IAC = 100µA, V

IAC = 50µA, V

IAC = 50µA, V

= 100µA, V

I

AC

Bandwidth IAC = 100µA 10 MHz

Output Voltage I

= 250µA, V

AC

VFB = 0V

Oscillator

Initial Accuracy TA = 25°C 188 200 212 kHz

Voltage Stability V

- 3V < VCC < V

CCZ

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 V

RAMP 2

= 0V, V

= 28.7kΩ, CT = 400pF, C

RAMP1

OUT

OUT

= 6V -40 -90 µA

= 1.5V 40 90 µA

- 0.5V 60 75 dB

CCZ

RAMP1

100 190 mV

= VFB = 0V 0.35 0.50 0.65

RMS

= 1.2V, VFB = 0V 1.15 1.65 2.15

RMS

= 1.8V, VFB = 0V 0.52 0.74 0.96

RMS

= 3.3V, VFB = 0V 0.14 0.20 0.26

RMS

RMS

RAMP 1

= 1.15V,

- 0.5V 1 %

CCZ

= 2.5V 4.5 7.5 9.5 mA

0.74 0.82 0.90 V

= 270pF, TA =

4 REV. 1.0.3 6/13/01

PRODUCT SPECIFICATION ML4841

Electrical Characteristics (continued)

Unless otherwise specified, I

= 25mA, RT = 23kΩ, R

CC

Operating Temperature Range (Note 1)

Symbol Parameter Conditions Min. Typ. Max. Units

Reference

Output Voltage TA = 25°C, I(V

Line Regulation V

Load Regulation 1mA < I(V

- 3V < VCC < V

CCZ

REF

Temperature Stability 0.4 %

Total Variation Line, Load, Temp 7.25 7.65 V

Long Term Stability T

= 125°C, 1000 Hours 5 25 mV

J

PFC

Minimum Duty Cycle V

Maximum Duty Cycle V

Output Low Voltage I

Output High Voltage I

> 6.7V 0 %

IEAO

< 1.2V 90 95 %

IEAO

= -20mA 0.4 0.8 V

OUT

I

= -100mA 0.7 2.0 V

OUT

I

= 10mA, VCC = 8V 0.8 1.5 V

OUT

= 20mA 10 10.5 V

OUT

I

= 100mA 9.5 10 V

OUT

Rise/Fall Time CL = 1000pF 50 ns

PWM

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

V

OL

V

OH

Output Low Voltage I

Output High Voltage I

= -20mA 0.4 0.8 V

OUT

I

= -100mA 0.7 2.0 V

OUT

I

= 10mA, VCC = 8V 0.8 1.5 V

OUT

= 20mA 10 10.5 V

OUT

I

= 100mA 9.5 10 V

OUT

Rise/Fall Time CL = 1000pF 50 ns

Supply

V

CCZ

Shunt Regulator Voltage 12.8 13.5 14.2 V

V

Load Regulation 25mA < ICC < 55mA ±100 ±200 mV

CCZ

V

Total Variation Load, Temp 12.4 14.6 V

CCZ

Start-up Current VCC = 11.2V, CL = 0 0.7 1.0 mA

Operating Current VCC < V

CCZ

Undervoltage Lockout
Threshold

Undervoltage Lockout
Hysteresis

Notes

1. Limits are guaranteed by 100% testing, sampling, or correlation with worst-case test conditions.

2. Includes all bias currents to other circuits connected to the V

3. Gain = K x 5.3V; K = (I

GAINMOD

- I

OFFSET

) x IAC x (VEAO - 1.5V)-1.

= 28.7kΩ, CT = 400pF, C

RAMP1

) = 1mA 7.4 7.5 7.6 V

REF

- 0.5V 2 10 mV

CCZ

RAMP1

= 270pF, TA =

) < 20mA 2 15 mV

- 0.5V, CL = 0 17 21 mA

V

-

V

-

V

CCZ

1.0

CCZ

0.7

CCZ

0.4

-

2.7 3.0 3.3 V

pin.

FB

V

REV. 1.0.3 6/13/01 5