Fairchild Semiconductor ML4800CP Datasheet

March 2001

PRELIMINARY

ML4800

Power Factor Correction and PWM Controller Combo

GENERAL DESCRIPTION

The ML4800 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 IEC1000-3-2 specification. Intended as a BiCMOS
version of the industry-standard ML4824, the ML4800
includes circuits for the implementation of leading edge,
average current, “boost” type power factor correction and
a trailing edge, pulse width modulator (PWM). It also
includes a TriFault Detect™ function to help ensure that no
unsafe conditions will result from single component failure
in the PFC. Gate-drivers with 1A capabilities minimize the
need for external driver circuits. Low power requirements
improve efficiency and reduce component costs.

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
brownout protection. The PWM section can be operated in
current or voltage mode, at up to 250kHz, and includes an
accurate 50% duty cycle limit to prevent transformer
saturation.

FEATURES

■ Internally synchronized leading-edge PFC and trailing-

edge PWM in one IC

■ TriFault Detect™ for UL1950 compliance and

enhanced safety

■ Slew rate enhanced transconductance error amplifier

for ultra-fast PFC response

■ Low power: 200µA startup current, 5.5mA operating

current

■ Low total harmonic distortion, high PF

■ Reduced ripple current in storage capacitor between

PFC and PWM sections

■ Average current, continuous boost leading edge PFC

■ PWM configurable for current-mode or voltage mode

operation

■ Current fed gain modulator for improved noise immunity

■ Overvoltage and brown-out protection, UVLO, and soft

start

BLOCK DIAGRAM

VEAO

15

2

4

3

7

8

6

5

9

V

2.5V

I

AC

V

I

SENSE

RAMP 1

RAMP 2

V

SS

DC I

FB

RMS

DC

V

CC

LIMIT

VEA

-

+

25µA

MODULATOR

1.25V

V

REF

16

GAIN

1.6kΩ

1.6kΩ

1

IEAO

IEA

+

-

-

+

-

+

POWER FACTOR CORRECTOR

0.5V

+

-

+

-

OSCILLATOR

V

-

FB

2.45V

+

PULSE WIDTH MODULATOR

TRI-FAULT

DUTY CYCLE

VIN OK

LIMIT

2.75V

1.0V

-1V

PFC I

-

+

OVP

+

-

+

-

LIMIT

DC I

LIMIT

V

CC

V

CC

17V

SRQ

SRQ

SRQ

UVLO

13

7.5V

REFERENCE

Q

Q

Q

V

CC

V

PFC OUT

PWM OUT

REF

14

12

11

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ML4800

PIN CONFIGURATION

ML4800

16-Pin PDIP (P16)

16-Pin Narrow SOIC (S16N)

PIN DESCRIPTION

PIN NAME FUNCTION

1 IEAO Slew rate enhanced PFC

transconductance error amplifier output

2I

AC

3I

SENSE

PFC AC line reference input to Gain
Modulator

Current sense input to the PFC Gain
Modulator

IEAO

I

AC

I

SENSE

V

RMS

V

DC

RAMP 1

RAMP 2

SS

1

2

3

4

5

6

7

8

TOP VIEW

16

VEAO

15

V

FB

14

V

REF

13

V

CC

12

PFC OUT

11

PWM OUT

10

GND

9

DC I

LIMIT

PIN NAME FUNCTION

9 DC I

LIMIT

PWM cycle-by-cycle current limit
comparator input

10 GND Ground

11 PWM OUT PWM driver output

12 PFC OUT PFC driver output

4V

RMS

PFC Gain Modulator RMS line voltage
compensation input

5 SS Connection point for the PWM soft start

capacitor

6V

DC

PWM voltage feedback input

7 RAMP 1 Oscillator timing node; timing set

by R

TCT

8 RAMP 2 When in current mode, this pin

functions as the current sense input;
when in voltage mode, it is the PWM
modulation ramp input.

13 V

14 V

CC

REF

Positive supply

Buffered output for the internal

7.5V reference

15 V

FB

PFC transconductance voltage
error amplifier input

16 VEAO PFC transconductance voltage

error amplifier output

2 REV. 1.0.2 3/7/2001

ABSOLUTE MAXIMUM RATINGS

ML4800

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.

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

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

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

Thermal Resistance (θ

)

JA

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

V

..............................................................................................

CC

Voltage ................................................. -5V to 0.7V

I

SENSE

Voltage on Any Other Pin ...... GND - 0.3V to V

I

...........................................................................................

REF

I

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

AC

CCZ

18V

+ 0.3V

10mA

Peak PFC OUT Current, Source or Sink ....................... 1A

Peak PWM OUT Current, Source or Sink .................... 1A

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

OPERATING CONDITIONS

Temperature Range

ML4800CX.................................................... 0°C to 70°C

ML4800IX .................................................. -40°C to 85°C

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

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, VCC = 15V, RT = 52.3kΩ, CT = 470pF, TA = Operating Temperature Range (Note 1)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VOLTAGE ERROR AMPLIFIER

Input Voltage Range 0 5 V

Transconductance V

Feedback Reference Voltage 2.43 2.5 2.57 V

NON INV

= V

, VEAO = 3.75V 30 65 90 µ

INV

Ω

Input Bias Current Note 2 -0.5 -1.0 µA

Output High Voltage 6.0 6.7 V

Output Low Voltage 0.1 0.4 V

Source Current VIN = ±0.5V, V

Sink Current VIN = ±0.5V, V

Open Loop Gain 50 60 dB

Power Supply Rejection Ratio 11V < VCC < 16.5V 50 60 dB

CURRENT ERROR AMPLIFIER

Input Voltage Range -1.5 2 V

Transconductance V

Input Offset Voltage 0 4 15 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, V

Sink Current VIN = ±0.5V, V

Open Loop Gain 60 70 dB

Power Supply Rejection Ratio 11V < VCC < 16.5V 60 75 dB

OVP COMPARATOR

NON INV

= 6V -40 -140 µA

OUT

= 1.5V 40 140 µA

OUT

= V

, VEAO = 3.75V 50 100 150 µ

INV

= 6V -40 -104 µA

OUT

= 1.5V 40 160 µA

OUT

Ω

Threshold Voltage 2.65 2.75 2.85 V

Hysteresis 175 250 325 mV

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ML4800

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

TRI-FAULT DETECT

Fault Detect HIGH 2.65 2.75 2.85 V

Time to Fault Detect HIGH V

= V

FB

FAULT DETECT LOW

OPEN. 470pF from VFB to GND

Fault Detect LOW 0.4 0.5 0.6 V

to VFB =24ms

PFC I

COMPARATOR

LIMIT

Threshold Voltage -0.9 -1.0 -1.1 V

(PFC I

LIMIT VTH

Delay to Output 150 300 ns

DC I

COMPARATOR

LIMIT

Threshold Voltage 0.95 1.0 1.05 V

Input Bias Current ±0.3 ±1 µA

Delay to Output 150 300 ns

VIN OK COMPARATOR

Threshold Voltage 2.35 2.45 2.55 V

Hysteresis 0.8 1.0 1.2 V

GAIN MODULATOR

Gain (Note 3) IAC = 100µA, V

Bandwidth IAC = 100µA 10 MHz

Output Voltage I

- Gain Modulator Output) 120 220 mV

= VFB = 0V 0.60 0.80 1.05

RMS

IAC = 50µA, V

IAC = 50µA, V

IAC = 100µA, V

= 350µA, V

AC

= 1.2V, VFB = 0V 1.8 2.0 2.40

RMS

= 1.8V, VFB = 0V 0.85 1.0 1.25

RMS

= 3.3V, VFB = 0V 0.20 0.30 0.40

RMS

= 1V, 0.60 0.75 0.9 V

RMS

VFB = 0V

OSCILLATOR

Initial Accuracy TA = 25°C 717681kHz

Voltage Stability 11V < VCC < 16.5V 1 %

Temperature Stability 2%

Total Variation Line, Temp 68 84 kHz

Ramp Valley to Peak Voltage 2.5 V

PFC Dead Time 250 330 ns

CT Discharge Current V

RAMP 2

= 0V, V

= 2.5V 3.5 5.5 7.5 mA

RAMP 1

4 REV. 1.0.2 3/7/2001

ML4800

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

REFERENCE

PFC

PWM

Output Voltage TA = 25°C, I(V

) = 1mA 7.4 7.5 7.6 V

REF

Line Regulation 11V <VCC <16.5V 10 25 mV

Load Regulation 0mA <I(V

) <10mA;

REF

TA = 0ºC to 70ºC 10 20 mV

0mA < I(V

) < 5mA;

REF

TA = –40ºC to 85ºC 10 20 mV

Temperature Stability 0.4 %

Total Variation Line, Load, Temp 7.35 7.65 V

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

Minimum Duty Cycle V

Maximum Duty Cycle V

Output Low Voltage I

Output High Voltage I

> 4.0V 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 = 9V 0.4 0.8 V

OUT

= 20mA V

OUT

I

= 100mA V

OUT

– 0.8V V

CC

- 2V V

CC

Rise/Fall Time CL = 1000pF 50 ns

Duty Cycle Range 0-44 0-47 0-49 %

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 = 9V 0.4 0.8 V

OUT

= 20mA V

OUT

I

= 100mA V

OUT

Rise/Fall Time CL = 1000pF 50 ns

SUPPLY

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

Operating Current 14V, CL = 0 5.5 7 mA

Undervoltage Lockout Threshold 12.4 13 13.6 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 V

Note 3: Gain = K x 5.3V; K = (I

GAINMOD

- I

) x [IAC (VEAO - 0.625)]-1; VEAO

OFFSET

pin.

FB

MAX

=5V.

– 0.8V V

CC

- 2V V

CC

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