www.fairchildsemi.com
ML4801
Variable Feedforward PFC/PWM Controller Combo
Features
•
•
•
•
•
•
•
•
•
Internally synchronized PFC and PWM in one IC
Low start-up current (200µA typ.)
Low operating current (5.5mA typ.)
Low total harmonic distortion
Reduces ripple current in the storage capacitor between
the PFC and PWM sections
Average current continuous boost leading edge PFC
High efficiency trailing edge PWM optimized for current
mode operation
Current fed gain modulator for improved noise immunity
Brown-out control, overvoltage protection, UVLO, and
soft start
General Description
The ML4801 is a controller for power factor corrected,
switched mode power supplies. Key features of this
combined PFC and PWM controller are low start-up and
operating currents. 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
specifications. The ML4801 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 ML4801 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 compara-
tor 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.
Block Diagram
16
VEAO
VFB
15
2.5V
IAC
2
VRMS
4
ISENSE
3
RAMP 1
8
RTCT
7
RAMP 2
9
8V
VDC
6
VCC
SS
5
8V
25µA
1.25V
-
+
-
+
1
IEAO
POWER FACTOR CORRECTOR
OVP
+
+
–
-
13
VCC
VCC
7.5V
REFERENCE
S
-1V
+
-
VEA
-
+
VREF
14
1.6kΩ
IEA
+
2.75V
-
Q
GAIN
MODULATOR
1.6kΩ
R
S
Q
PFC OUT
Q
12
PFC ILIMIT
R
Q
OSCILLATOR
÷2
DUTY CYCLE
LIMIT
PWM OUT
S
VFB
2.5V
-
+
Q
VIN OK
+
11
R
DC ILIMIT
Q
GND
10
1.5V
-
PULSE WIDTH MODULATOR
VCC
UVLO
REV. 1.2 3/27/01
ML4801
PRODUCT SPECIFICATION
Pin Configuration
ML4801
16-Pin PDIP (P16)
16-Pin Narrow SOIC (S16N)
IEAO 1
IAC 2
ISENSE 3
VRMS 4
SS 5
VDC 6
RTCT 7
RAMP 1 8
16 VEAO
15 VFB
14 VREF
13 VCC
12 PFC OUT
11 PWM OUT
10 GND
9
RAMP 2
TOP VIEW
Pin Description
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Name
IEAO
I
AC
I
SENSE
V
RMS
SS
V
DC
R
T
C
T
RAMP 1
RAMP 2
GND
PWM OUT
PFC OUT
V
CC
V
REF
V
FB
VEAO
PFC gain control reference input
Current sense input to the PFC current limit comparator
Input for PFC RMS line voltage compensation
Connection point for the PWM soft start capacitor
PWM voltage feedback input
Connection for oscillator frequency setting components
PFC ramp input
PWM ramp current sense input
Ground
PWM driver output
PFC driver output
Positive supply (connected to an internal shunt regulator).
Buffered output for the internal 7.5V reference
PFC transconductance voltage error amplifier input
PFC transconductance voltage error amplifier output
Function
PFC transconductance current error amplifier output
2
REV. 1.2 3/27/01
PRODUCT SPECIFICATION
ML4801
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
V
CC
I
SENSE
Voltage
Voltage on Any Other Pin
I
REF
I
AC
Input Current
Peak PFC OUT Current, Source or Sink
Peak PWM OUT Current, Source or Sink
PFC OUT, PWM OUT Energy Per Cycle
Junction Temperature
Storage Temperature Range
Lead Temperature (Soldering, 10 sec)
Thermal Resistance (
θ
JA
)
Plastic DIP
Plastic SOIC
–65
-3
GND - 0.3
Min.
Max.
18
5
V
CC
+ 0.3
20
10
500
500
1.5
150
150
260
80
105
Units
V
V
V
mA
mA
mA
mA
µJ
°C
°C
°C
°C/W
°C/W
Operating Conditions
Temperature Range
ML4801CX
ML4801IX
Min.
0
-40
Max.
70
85
Units
°C
°C
Electrical Characteristics
Unless otherwise specified, V
CC
= 15V, R
T
= 29.4k
Ω
, R
RAMP1
= 15.4k
Ω
, CT = 270pF, C
RAMP1
= 620pF,
T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Input Voltage Range
Transconductance
Feedback Reference Voltage
Input Bias Current
Output High Voltage
Output Low Voltage
Source Current
Sink Current
Open Loop Gain
PSRR
Current Error Amplifier
Input Voltage Range
Transconductance
Input Offset Voltage
REV. 1.2 3/27/01
Conditions
Min.
0
Typ.
Max. Units
5
V
µ
Ω
V
µA
V
0.4
-150
150
V
µA
µA
dB
dB
2
V
µ
Ω
mV
3
Voltage Error Amplifier
V
NON INV
= V
INV
, VEAO = 3.75V
Note 2
6.0
∆
V
IN
= ±0.5V, V
OUT
= 6V
∆
V
IN
= ±0.5V, V
OUT
= 1.5V
11V < V
CC
< 16.5V
-40
40
60
60
-1.5
V
NON INV
= V
INV
, VEAO = 3.75V
60
0
100
8
40
2.43
65
2.50
-0.5
6.7
0.1
-70
70
70
70
80
2.57
-1.0
120
15
ML4801
PRODUCT SPECIFICATION
Electrical Characteristics(Continued)
Unless otherwise specified, V
CC
= 15V, R
T
= 29.4k
Ω
, R
RAMP1
= 15.4k
Ω
, CT = 270pF, C
RAMP1
= 620pF,
T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Input Bias Current
Output High Voltage
Output Low Voltage
Source Current
Sink Current
Open Loop Gain
PSRR
OVP Comparator
Threshold Voltage
Hysteresis
PFC I
LIMIT
Comparator
Threshold Voltage
∆
PFC I
LIMIT
Threshold - Gain
Modulator Output
Delay to Output
DC I
LIMIT
Comparator
Threshold Voltage
Input Bias Current
Delay to Output
V
IN
OK Comparator
Threshold Voltage
Hysteresis
GAIN MODULATOR
Gain (Note 3)
I
AC
= 100µA, V
RMS
= V
FB
= 0V
I
AC
= 50µA, V
RMS
= 1V, V
FB
= 0V
I
AC
= 50µA, V
RMS
= 1.8V, V
FB
= 0V
I
AC
= 100µA, V
RMS
= 3.3V, V
FB
= 0V
Bandwidth
Output Voltage
Oscillator
Initial Accuracy
Voltage Stability
Temperature Stability
Total Variation
Ramp Valley to Peak Voltage
PFC Dead Time
C
T
Discharge Current
Reference
Output Voltage
Line Regulation
4
Conditions
Min.
6.0
Typ.
-0.5
6.7
0.65
Max. Units
-1.0
1.0
-150
150
µA
V
V
µA
µA
dB
dB
2.85
325
-1.1
V
mV
V
mV
300
1.6
±1
300
2.6
1.2
1.05
2.40
1.25
0.40
MHz
0.85
212
V
kHz
%
%
218
kHz
V
600
7.5
7.6
25
ns
mA
V
mV
ns
V
µA
ns
V
V
∆
V
IN
= ±0.5V, V
OUT
= 6V
∆
V
IN
= ±0.5V, V
OUT
= 1.5V
11V < V
CC
< 16.5V
-40
40
55
60
2.65
175
-0.9
120
-70
70
65
75
2.75
250
-1.0
220
150
1.4
1.5
±0.3
150
2.4
0.8
0.65
1.90
0.90
0.20
0.65
188
2.5
1.0
0.85
2.20
1.05
0.30
10
0.75
200
1
2
I
AC
= 100µA
I
AC
= 350µA, V
RMS
= 1V, V
FB
= 0V
T
A
= 25°C
11V < V
CC
< 16.5V
Over Line and Temp
182
2.5
350
V
RAMP 2
= 0V, V
RAMP 1
= 2.5V
T
A
= 25°C, I(V
REF
) = 1mA
11V < V
CC
< 16.5V
3.5
7.4
470
5.5
7.5
10
REV. 1.2 3/27/01
PRODUCT SPECIFICATION
ML4801
Electrical Characteristics(Continued)
Unless otherwise specified, V
CC
= 15V, R
T
= 29.4kΩ, R
RAMP1
= 15.4kΩ, CT = 270pF, C
RAMP1
= 620pF,
T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Load Regulation
Temperature Stability
Total Variation
Long Term Stability
PFC
Minimum Duty Cycle
Maximum Duty Cycle
Output Low Voltage
V
IEAO
> 6.7V
V
IEAO
< 1.2V
I
OUT
= -20mA
I
OUT
= -100mA
I
OUT
= -10mA, V
CC
= 9V
Output High Voltage
Rise/Fall Time
PWM
DC
V
OL
Duty Cycle Range
Output Low Voltage
I
OUT
= -20mA
I
OUT
= -100mA
I
OUT
= -10mA, V
CC
= 9V
V
OH
Output High Voltage
Rise/Fall Time
Supply
Start-up Current
Operating Current
Undervoltage Lockout
Threshold
Undervoltage Lockout
Hysteresis
V
CC
= 12V, C
L
= 0
V
CC
= 14V, C
L
= 0
12.4
2.7
200
5.5
13.0
3.0
350
7.0
13.6
3.3
µA
mA
V
V
I
OUT
= 20mA
I
OUT
= 100mA
C
L
= 1000pF
V
CC
- 0. 8
V
CC
- 2.0
50
0-44
0-47
0.4
0.7
0.4
0-50
0.8
2.0
0.8
%
V
V
V
V
V
ns
I
OUT
= 20mA
I
OUT
= 100mA
C
L
= 1000pF
V
CC
- 0.8
V
CC
- 2.0
50
90
95
0.4
0.7
0.4
0.8
2.0
0.8
0
%
%
V
V
V
V
V
ns
Line, Load, Temp
T
J
= 125°C, 1000 Hours
7.35
5
Conditions
1mA < I(V
REF
) < 10mA
Min.
Typ.
10
0.4
7.65
25
Max. Units
20
mV
%
V
mV
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
FB
pin.
3. Gain = K x 5.3V; K = (I
MULO
- I
OFFSET
) x I
AC
x (VEAO - 0.625V)
-1
.
REV. 1.2 3/27/01
5
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