Fairchild Semiconductor ML4821 Datasheet

www.fairchildsemi.com

ML4821

Power Factor Controller

Features

• Average current sensing for lowest possible harmonic
distortion

• Average line compensation with brown-out control

• Precision buffered 5V reference

• 1A peak current totem-pole output drive

• Overvoltage comparator eliminates output “runaway” due
to load removal

• Wide common mode range in current sense comparators
for better noise immunity

• Large oscillator amplitude for better noise immunity

• Output driver internally limited to 17V

• “Sleep mode” shutdown input

Block Diagram

General Description

The ML4821 provides complete control for a “boost” type
power factor correction system using the average current
sensing method. Special care has been taken in the design of
the ML4821 to increase system noise immunity. The circuit
includes a precision reference, gain modulator, average
current error amplifier, output error amplifier, over-voltage
protection comparator, shutdown logic, as well as a high
current output. In addition, start-up is simplified by an under­voltage lockout circuit.

In a typical application, the ML4821 controls the AC input
current by adjusting the pulse width of the output MOSFET.
This modulates the line current so that its shape conforms to
the shape of the input voltage. The reference for the current
regulator is a product of the sinusoidal line voltage times the
output of the error amplifier which is regulating the output
DC voltage. Average line voltage compensation is provided
in the gain modulator to ensure constant loop gain over a
wide input voltage range. This compensation includes a
special “brown-out” control which reduces output power
below 90V RMS input.

OVP

11

I

LIM

1

IA OUT

2

IA–

3

IA+

4

I

SINE

5

V

RMS

8

EA OUT

6

EA–

7

SOFT START

9

+

V

REF

–

+

–

+

OUT

GAIN

MODULATOR

–

V

REF

+

–

–

+

V

REF

0.7V

+

–

R

S

Q

OSC

SLEEP

UNDER
VOLTAGE
LOCKOUT

V

LIMIT

17V

V

REF

GND

V

OUT

PGND

SYNC

16

18

CC

15

14

13

R

T

12

10

C

T

17

REV. 1.0.2 6/19/01

ML4821 PRODUCT SPECIFICATION

Pin Connection

18-Pin PDIP (P18) 20-Pin SOIC (S20)

SOFT START

Pin Description

Pin Number

11I

2 2 IA OUT Output and compensation node of the average current error amplifier

33IA– Inverting input of the average current error amplifier

4 4 IA+ Non-Inverting input of the average current error amplifier and output of the

55I

6 6 EA OUT Output of output voltage error amplifier

7 7 INV Inverting input to error amplifier

88V

9 9 SOFT

10 12 SYNC Oscillator synchronization input

11 13 OVP Inhibits output pulses when the voltage at this pin exceeds 5V. Also,

12 14 R

13 15 PWR

14 16 OUT High current totem pole output

15 17 V

16 18 V

17 19 C

18 20 GND Analog signal ground

I

LIM

IA OUT

IA–

IA+

I

SINE

EA OUT

EA–

V

RMS

1

2

3

4

5

6

7

8

9

TOP VIEW

Name Function18-Pin DIP 20-Pin SOIC

LIM

SINE

RMS

START

GND

CC

REF

18

GND

17

C

T

V

16

REF

V

15

CC

OUT

14

13

PGND

12

R

T

OVP

11

10

SYNC

I

LIM

IA OUT

IA–

IA+

I

SINE

EA OUT

EA–

V

RMS

SOFT START

N/C

1

2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

GND

C

T

V

REF

V

CC

OUT

PGND

R

T

OVP

SYNC

N/C

TOP VIEW

Peak cycle-by-cycle current limit input

gain modulator

Gain modulator input

Input for average line voltage compensation

Normally connected to soft start capacitor

when the voltage at this pin is less than 0.7V, the IC goes into low current
shut-down mode.

Timing resistor for the oscillator

T

Return for the high current totem pole output

Positive supply for the IC

Buffered output for the 5V voltage reference

Timing capacitor for the oscillator.

T

2

REV. 1.0.2 6/19/01

PRODUCT SPECIFICATION ML4821

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

Supply Current (I

OUT Current, Source or Sink 1.0 A

Output Energy (capacitive load per cycle) 5 µJ

I

Input Current 1.2 mA

SINE

EA OUT Source Current 50 mA

Oscillator Charge Current 2 mA

Input Voltage GND –0.3V 5.5 V

Junction Temperature 150 °C

Storage Temperature Range –65 150 °C

Lead Temperature (Soldering 10 sec.) 260 °C

Thermal Resistance ( θ
Plastic DIP
Plastic SOIC

) 35 mA

CC

)

JA

75
95

°C/W
°C/W

Operating Conditions

Temperature Range Min Max Units

ML4821CX 0 70 °C

Electrical Characteristics

Unless otherwise specified, R

Parameter Conditions Min. Typ. Max. Units

Oscillator

Initial accuracy T

Voltage stability 12V < V

Temperature stability 2 %

Total Variation Line, Temperature 85 115 kHz

Ramp Valley to Peak 4.7 5.2 5.6 V

R

Voltage 4.8 5.0 5.2 V

T

Discharge Current C

SYNC Input Threshold 1.5 2.0 3.0 V

Reference

Output Voltage T

Line regulation 12V < V

Load regulation 1mA < I

Temperature stability .4 %

Total Variation line, load, temp 4.9 5.1 V

Output Noise Voltage 10Hz to 10kHz 50 µV

Long Term Stability T

Short Circuit Current V

= 6.2k Ω , C

T

= 720pF, T

T

= 25°C 90 100 110 kHz

A

CC

= 2V, R

T

= 25°C, I

A

CC

O

= 125°C, 1000 hrs 5 25 mV

A

= 0V –30 –85 –180 mA

REF

= Operating Temperature Range, V

A

< 18V 1 %

= Open 7.8 8.4 9.3 mA

T

= 1mA 4.95 5.00 5.05 V

O

< 24V 2 10 mV

< 20mA 2 15 mV

= 15V (Notes 1 & 2).

CC

REV. 1.0.2 6/19/01

3

ML4821 PRODUCT SPECIFICATION

Electrical Characteristics

Unless otherwise specified, R

= 6.2k Ω , C

T

(continued)

= 720pF, T

T

= Operating Temperature Range, V

A

= 15V (Notes 1 & 2).

CC

Parameter Conditions Min. Typ. Max. Units

Voltage Error Amplifier

Input Offset Voltage 0 –15 mV

Input Bias Current –50 –800 nA

Open Loop Gain 2 < EA OUT < 6V 60 75 dB

PSRR 12V < V

< 24V 70 100 dB

CC

Output Sink Current EA OUT = 4V, INV = 5.5V 300 500 µA

Output Source Current EA OUT

Output High Voltage I

Output Low Voltage I

PIN6

PIN6

= 4.0V, INV

= –5mA, V

= 4.8V –10 –30 mA

= 4.8V 7.0 7.5 V

PIN7

= 0, EA– = 5.5V 0 0.5 V

Unity Gain Bandwidth 1.0 MHz

Soft Start Charge Current V

= 4V –22 –38 –50 µA

PIN9

Current Error Amplifier

Input Offset Voltage –50 5mV

Input Bias Current –0.15 –1µA

Input Offset Current 400 nA

Open Loop Gain 2 < EA OUT < 7V 80 100 dB

PSRR 12V < V

Output Voltage Low I

Output Voltage High I

= 300µA 0 0.5 V

OL

= –10mA 7.0 7.5 V

OH

< 24V 65 85 dB

CC

Input Common Mode Range –0.3 2.5 V

Gain Modulator

Gain V

Output Current V

Output Current Limit V

I

Comparator

LIM

INV

V

INV

V

INV

V

INV

INV

INV

V

RMS

= 4.8V, V
= 4.8V, V
= 4.8V, V
= 4.8V, V

= 5.2V, V

= 4.8V, I

= 1.75V

= 0V

RMS

= 1.75V

RMS

= 2.6V

RMS

= 5.2V

RMS

= 5.2V –2 –4µA

RMS

= 500 µ A,

SINE

0.75

3.1

1.25

0.22

1.2

3.88

1.75

0.38

1.3

4.5

2.15

0.50

360 395 420 µA

Input Offset Voltage +15 mV

Input Bias Current –100 –200 µA

OVP Comparator

Input Offset Voltage Output Off –25 5 mV

Hysteresis Output On 85 105 130 mV

Input Bias Current –0.3 –3µA

Propagation Delay 150 ns

Shutdown Threshold 0.4 0.7 1.0 V

PWM Comparator

Input Common Mode Range 0 8 V

Propagation Delay 150 ns

4

REV. 1.0.2 6/19/01