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www.fairchildsemi.com
REV. 1.0.5 2/14/02
Features
Internally synchronized PFC and PWM in one IC
Low total harmonic distortion
Low ripple current in the storage capacitor between the
PFC and PWM sections
Average current, continuous boost, leading edge PFC
High efficiency trailing edge PWM with dual totem-pole
outputs
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
General Description
The ML4826 is a high power controller for power factor
corrected, switched mode power supplies. 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 specifi-
cations. The ML4826 includes circuits for the implementa-
tion of a leading edge, average current "boost" type power
factor correction and a trailing edge, pulse width modulator
(PWM) with dual totem-pole outputs.
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. The PWM section can be operated in current or
voltage mode at up to 250kHz and includes a duty cycle limit
to prevent transformer saturation.
Block Diagram
VCC2
19
VEAO
IEAO
VFB
IAC
VRMS
ISENSE
RTCT
OSCILLATOR
OVP
PFC ILIMIT
UVLO
VREF
PULSE WIDTH MODULATOR
POWER FACTOR CORRECTOR
2.5V
+
-
-
+
20
2
4
3
7.5V
REFERENCE
18
VCC
17
VCCZ
VEA
7
-
+
IEA
1
+
-
+
-
PFC OUT
15
S
R
Q
Q
S
R
Q
Q
2.7V
-1V
RAMP 2
9
PWM 1
13
S
R
Q
Q
VDC
6
SS
5
DC ILIMIT
10
VCC
DUTY CYCLE
LIMIT
-
+
1V
-
+
2.5V
VFB
-
+
8V
8V
VIN OK
GAIN
MODULATOR
VCCZ
3.5k
3.5k
1.5V
50
A
-
+
13.5V
DC ILIMIT
RAMP 1
8
PWM 2
14
S
T
Q
Q
VCC2
PGND
16
PGND
12
AGND
11
8V
ML4826
PFC and Dual Output PWM Controller Combo
ML4826
PRODUCT SPECIFICATION
2
REV. 1.0.5 2/14/02
Pin Configuration
Pin Description
PIN NAME
FUNCTION
1
IEAO
PFC transconductance current error amplifier output
2
I
AC
PFC gain control reference input
3
I
SENSE
Current sense input to the PFC current limit comparator
4
V
RMS
Input for PFC RMS line voltage compensation
5
SS
Connection point for the PWM soft start capacitor
6
V
DC
PWM voltage feedback input
7
R
T
C
T
Connection for oscillator frequency setting components
8
RAMP 1
PFC ramp input
9
RAMP 2
When in current mode, this pin functions as the current sense input; when in voltage mode,
it is the PWM input from the PFC output (feedforward ramp)
10
DC I
LIMIT
PWM current limit comparator input
11
AGND
Analog signal ground
12
PGND
Return for the PWM totem-pole outputs
13
PWM 2
PWM driver 2 output
14
PWM 1
PWM drive 1 output
15
PFC OUT
PFC driver output
16
V
CC2
Positive supply for the PWM drive outputs
17
V
CC1
Positive supply (connected to an internal shunt regulator).
18
V
REF
Buffered output for the internal 7.5V reference
19
V
FB
PFC transconductance voltage error amplifier input
20
VEAO
PFC transconductance voltage error amplifier output
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
IEAO
I
AC
I
SENSE
V
RMS
SS
V
DC
R
T
C
T
RAMP 1
RAMP 2
DC I
LIMIT
VEAO
V
FB
V
REF
V
CC2
V
CC1
PFC OUT
PWM 1
PWM 2
PGND
AGND
TOP VIEW
ML4826
20-Pin PDIP (P20)
PRODUCT SPECIFICATION
ML4826
REV. 1.0.5 2/14/02
3
Absolute Maximum Ratings
Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum rat-
ings are stress ratings only and functional device operation is not implied.
Operating Conditions
Parameter
Min
Max.
Units
V
CC
Shunt Regulator Current
55
mA
I
SENSE
Voltage
3
5
V
Voltage on Any Other Pin
GND 0.3
V
CCZ
+ 0.3
V
I
REF
20
mA
I
AC
Input Current
10
mA
Peak PFC OUT Current, Source or Sink
500
mA
Peak PWM OUT Current, Source or Sink
500
mA
PFC OUT, PWM 1, PWM 2 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 (
JA
)
Plastic DIP
67
C/W
Parameter
Min.
Max.
Units
Temperature Range
ML4826CP2
0
70
C
Electrical Characteristics
Unless otherwise specified, I
CC
= 25mA, R
RAMP 1
= R
T
= 52.3k
, C
RAMP1
= C
T
= 180 pF,
T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
Voltage Error Amplifier
Input Voltage Range
0
7
V
Transconductance
V
NON INV
= V
INV
, VEAO = 3.75V
50
85
120
Feedback Reference Voltage
2.4
2.5
2.6
V
Input Bias Current
Note 2
0.3
1.0
A
Output High Voltage
6.0
6.7
V
Output Low Voltage
0.6
1.0
V
Source Current
V
IN
= 0.5V, V
OUT
= 6V
40
80
A
Sink Current
V
IN
= 0.5V, V
OUT
= 1.5V
40
80
A
Open Loop Gain
60
75
dB
Power Supply Rejection Ratio
V
CCZ
3V < V
CC
< V
CCZ
0.5V
60
75
dB
Current Error Amplifier
Input Voltage Range
-1.5
2
V
Transconductance
V
NON INV
= V
INV
, VEAO = 3.75V
130
195
310
Input Offset Voltage
3
15
mV
Input Bias Current
0.5
1.0
A
ML4826
PRODUCT SPECIFICATION
4
REV. 1.0.5 2/14/02
Output High Voltage
6.0
6.7
V
Output Low Voltage
0.6
1.0
V
Source Current
V
IN
= 0.5V, V
OUT
= 6V
40
90
A
Sink Current
V
IN
= 0.5V, V
OUT
= 1.5V
40
90
A
Open Loop Gain
60
75
dB
Power Supply Rejection Ratio
V
CCZ
3V < V
CC
< V
CCZ
0.5V
60
75
dB
OVP Comparator
Threshold Voltage
2.6
2.7
2.8
V
Hysteresis
80
115
150
mV
PFC I
LIMIT
Comparator
Threshold Voltage
0.8
1.0
1.15
V
(
PFC I
LIMIT
- Gain Modulator
Output)
100
190
mV
Delay to Output
150
300
ns
DC I
LIMIT
comparator
Threshold Voltage
0.9
1.0
1.1
V
Input Bias Current
0.3
1
A
Delay to Output
150
300
ns
V
IN
OK Comparator
Threshold Voltage
2.4
2.5
2.6
V
Hysteresis
0.8
1.0
1.2
V
Gain Modulator
Gain (Note 3)
I
AC
= 100A, V
RMS
= V
FB
= 0V
0.36
0.55
0.66
I
AC
= 50A, V
RMS
= 1.2V, V
FB
= 0V
1.20
1.80
2.24
I
AC
= 50A, V
RMS
= 1.8V, V
FB
= 0V
0.55
0.80
1.01
I
AC
= 100A, V
RMS
= 3.3V, V
FB
= 0V
0.14
0.20
0.26
Bandwidth
IAC = 100A
10
MHz
Output Voltage
I
AC
= 250A, V
RMS
= 1.15V, V
FB
= 0V
0.72
0.82
0.95
V
Oscillator
Initial Accuracy
T
A
= 25C
180
190
200
kHz
Voltage Stability
V
CCZ
3V < V
CC
< V
CCZ
0.5V
1
%
Temperature Stability
2
%
Total Variation
Line, Temp
170
210
kHz
Ramp Valley to Peak Voltage
2.5
V
Dead Time
PFC Only
250
500
ns
C
T
Discharge Current
V
RAMP 1
= 0V, V(R
T
C
T
) = 2.5V
4.5
7.5
9.5
mA
RAMP 1 Discharge Current
5
mA
Reference
Output Voltage
T
A
= 25C, I(V
REF
) = 1mA
7.4
7.5
7.6
V
Line Regulation
V
CCZ
3V < V
CC
< V
CCZ
0.5V
2
10
mV
Electrical Characteristics
(continued)
Unless otherwise specified, I
CC
= 25mA, R
RAMP 1
= R
T
= 52.3k
, C
RAMP1
= C
T
= 180 pF,
T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
PRODUCT SPECIFICATION
ML4826
REV. 1.0.5 2/14/02
5
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 VFB pin.
3. Gain = K x 5.3V; K = (I
GAINMOD
- I
OFFSET
) x I
AC
x (VEAO - 1.5V)
-1
.
Load Regulation
1mA < I(V
REF
) < 20mA
7
20
mV
Total Variation
Line, Load, Temp
7.25
7.65
V
Long Term Stability
T
J
= 125C, 1000 Hours
5
25
mV
PFC
Minimum Duty Cycle
ML4826-2, V
IEAO
> 5.7V
0
%
Maximum Duty Cycle
V
IEAO
< 1.2V
90
95
%
Output Low Voltage
I
OUT
= 20mA
0.4
0.8
V
I
OUT
= 50mA
0.6
3.0
V
I
OUT
= 10mA, V
CC
= 8V
0.7
1.5
V
Output High Voltage
I
OUT
= 20mA
9.5
10.5
V
I
OUT
= 50mA
9.0
10
V
Rise/Fall Time
C
L
= 1000pF
50
ns
PWM
Duty Cycle Range
0-47
0-48
0-50
%
Output Low Voltage
I
OUT
= 20mA
0.4
0.8
V
I
OUT
= 50mA
0.6
3.0
V
I
OUT
= 10mA, V
CC
= 8V
0.7
1.5
V
Output High Voltage
I
OUT
= 20mA
9.5
10.5
V
I
OUT
= 50mA
9.0
10
V
Rise/Fall Time
C
L
= 1000pF
50
ns
Supply
Shunt Regulator Voltage
(V
CCZ
)
12.8
13.5
14.2
V
V
CCZ
Load Regulation
25mA < I
CC
< 55mA
150
300
mV
V
CCZ
Total Variation
Load, temp
12.4
14.6
V
Start-up Current
V
CC
= 11.2V, C
L
= 0
0.7
1.1
mA
Operating Current
V
CC
< V
CCZ
0.5V, C
L
= 0
22
28
mA
Undervoltage Lockout
Threshold
12
13
14
V
Undervoltage Lockout
Hysteresis
2.65
3.0
3.35
V
Electrical Characteristics
(continued)
Unless otherwise specified, I
CC
= 25mA, R
RAMP 1
= R
T
= 52.3k
, C
RAMP1
= C
T
= 180 pF,
T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
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