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www.fairchildsemi.com
REV. 1.0.1 6/27/01
Features
Pin-compatible with industry-standard ML4824-1
TriFault DetectTM to conform to UL1950TM requirements
Available in 50% or 74% max duty cycle versions
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 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 gain modulator for improved noise immunity
Overvoltage protection, UVLO, and soft start
General Description
The ML4827 is a controller for power factor corrected,
switched mode power supplies, that includes circuitry
necessary for conformance to the safety requirements of
UL1950. A direct descendent of the industry-standard
ML4824-1, the ML4827 adds a TriFault DetectTM function to
guarantee that no unsafe conditions may result from single
component failure in the PFC. 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. The ML4827 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 device is available in
two versions; the ML4827-1 (Duty Cycle
MAX
= 50%) and
the ML4827-2 (Duty Cycle
MAX
= 74%). The higher
maximum duty cycle of the -2 allows enhanced utilization of
a given transformer core's power handling capacity. 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, and includes a duty cycle limit to prevent
transformer saturation.
Block Diagram
VEAO
IEAO
VFB
IAC
VRMS
ISENSE
RAMP 1
OSCILLATOR
OVP
PFC ILIMIT
UVLO
VREF
PULSE WIDTH MODULATOR
POWER FACTOR CORRECTOR
BROKEN WIRE
COMPARATOR
2.5V
+
+
7.5V
REFERENCE
VCC
VCCZ
VREF
VEA
+
IEA
+
+
+
PFC OUT
S
R
Q
Q
S
R
Q
Q
2.7V
1V
0.5V
2
A
RAMP 2
PWM OUT
S
R
Q
Q
VDC
SS
DC ILIMIT
VCC
DUTY CYCLE
LIMIT
+
1V
+
2.5V
VFB
+
8V
8V
VIN OK
GAIN
MODULATOR
VCCZ
3.5k
3.5k
1.25V
50
A
+
13.5V
DC ILIMIT
14
12
11
GND
10
15
2
4
3
7
8
6
5
9
16
1
13
ML4827
Fault-Protected PFC and PWM Controller Combo
ML4827
PRODUCT SPECIFICATION
2
REV. 1.0.1 6/27/01
Pin Configuration
Pin Description
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.
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
RAMP 1
PFC (master) oscillator input; f
OSC
set by R
T
C
T
8
RAMP 2
When in current mode, this pin functions as as the current sense input; when in
voltage mode, it is the PWM (slave) oscillator input.
9
DC I
LIMIT
PWM current limit comparator input
10
GND
Ground
11
PWM OUT
PWM driver output
12
PFC OUT
PFC driver output
13
V
CC
Positive supply (connected to an internal shunt regulator)
14
V
REF
Buffered output for the internal 7.5V reference
15
V
FB
PFC transconductance voltage error amplifier input, and TriFault Detect input
16
VEAO
PFC transconductance voltage error amplifier output
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
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
IEAO
IAC
ISENSE
VRMS
SS
VDC
RAMP 1
RAMP 2
VEAO
VFB
VREF
VCC
PFC OUT
PWM OUT
GND
DC ILIMIT
TOP VIEW
ML4827
16-Pin PDIP (P16)
16-Pin Wide SOIC (S16W)
PRODUCT SPECIFICATION
ML4827
REV. 1.0.1 6/27/01
3
Operating Conditions
Electrical Characteristics
Unless otherwise specified, I
CC
= 25mA, R
T
= 21.8k
, C
T
= 1000pF, T
A
= Operating Temperature Range (Note 1)
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
J
Junction Temperature
150
C
Storage Temperature Range
65
150
C
Lead Temperature (soldering, 10s)
260
C
Thermal Resistance (
JA
)
Plastic DIP
Plastic SOIC
80
105
C/W
C/W
Parameter
Min.
Max.
Units
Temperature Range
ML4827CP, CS
ML4827IP, IS
0
40
70
85
C
C
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
2.48
2.55
2.62
V
Input Bias Current
Note 2
1
2
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
2
10
17
mV
Input Bias Current
0.5
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
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
ML4827
PRODUCT SPECIFICATION
4
REV. 1.0.1 6/27/01
Tri-Fault Detect
Fault Detect HIGH
2.6
2.7
2.8
V
Time to Fault Detect HIGH
V
FB
= V
FAULT DETECT LOW
to V
FB
=
OPEN 1nF from V
FB
to GND
1
2
ms
Fault Detect LOW
0.4
0.5
0.6
V
PFC I
LIMIT
Comparator
Threshold Voltage
0.8
1.0
1.15
V
(PFC I
LIMIT
V
TH
- 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
2.45
2.55
2.65
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
0.74
0.82
0.90
V
Oscillator
Initial Accuracy
T
A
= 25C
75
80
85
kHz
Voltage Stability
V
CCZ
- 3V < V
CC
< V
CCZ
- 0.5V
1
%
Temperature Stability
2
%
Total Variation
Line, Temp
72
88
kHz
Ramp Valley to Peak Voltage
2.5
V
Dead Time
PFC Only
450
600
750
ns
C
T
Discharge Current
V
RAMP 2
= 0V, V
RAMP 1
= 2.5V
4.5
7.5
9.5
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
Load Regulation
1mA < I(V
REF
) < 20mA
2
15
mV
Temperature Stability
0.4
%
Total Variation
Line, Load, Temp
7.35
7.65
V
Long Term Stability
T
J
= 125C, 1000 Hours
5
25
mV
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
Electrical Characteristics
(Continued)
ML4827
PRODUCT SPECIFICATION
5
REV. 1.0.1 6/27/01
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
GAINMOD
- I
OFFSET
) x I
AC
x (VEAO - 1.5V)
-1
.
PFC
Minimum Duty Cycle
V
IEAO
> 4.0V
0
%
Maximum Duty Cycle
V
IEAO
< 1.2V
90
95
%
Output Low Voltage
I
OUT
= 20mA
0.4
0.8
V
I
OUT
= 100mA
0.8
2.0
V
I
OUT
= 10mA, V
CC
= 8V
0.7
1.5
V
Output High Voltage
I
OUT
= 20mA
10
10.5
V
I
OUT
= 100mA
9.5
10
V
Rise/Fall Time
C
L
= 1000pF
50
ns
PWM
Duty Cycle Range
ML4827-1
0-44
0-47
0-50
%
ML4827-2
0-64
0-70
0-74
%
Output Low Voltage
I
OUT
= -20mA
0.4
0.8
V
I
OUT
= -100mA
0.8
2.0
V
I
OUT
= 10mA, V
CC
= 8V
0.7
1.5
V
Output High Voltage
I
OUT
= 20mA
10
10.5
V
I
OUT
= 100mA
9.5
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
100
300
mV
V
CCZ
Total Variation
Load, Temp
12.4
14.6
V
Start-up Current
V
CC
= 11.8V, C
L
= 0
0.7
1.0
mA
Operating Current
V
CC
< V
CCZ
- 0.5V, C
L
= 0
16
19
mA
Undervoltage Lockout
Threshold
12
13
14
V
Undervoltage Lockout
Hysteresis
2.7
3.0
3.3
V
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
Electrical Characteristics
(Continued)
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