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Электронный компонент: ML4800

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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 DetectTM 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
I
Internally synchronized leading-edge PFC and trailing-
edge PWM in one IC
I
TriFault DetectTM for UL1950 compliance and
enhanced safety
I
Slew rate enhanced transconductance error amplifier
for ultra-fast PFC response
I
Low power: 200
A startup current, 5.5mA operating
current
I
Low total harmonic distortion, high PF
I
Reduced ripple current in storage capacitor between
PFC and PWM sections
I
Average current, continuous boost leading edge PFC
I
PWM configurable for current-mode or voltage mode
operation
I
Current fed gain modulator for improved noise immunity
I
Overvoltage and brown-out protection, UVLO, and soft
start
BLOCK DIAGRAM
15
VEAO
IEAO
VFB
IAC
VRMS
ISENSE
RAMP 1
OSCILLATOR
OVP
PFC ILIMIT
UVLO
VREF
PULSE WIDTH MODULATOR
POWER FACTOR CORRECTOR
TRI-FAULT
2.5V
+
-
-
+
16
2
4
3
7.5V
REFERENCE
14
VCC
13
VCC
VEA
7
-
+
IEA
1
+
-
+
-
+
-
PFC OUT
12
S
R
Q
Q
S
R
Q
Q
2.75V
0.5V
-1V
RAMP 2
8
PWM OUT
11
S
R
Q
Q
VDC
6
SS
5
DC ILIMIT
9
VCC
DUTY CYCLE
LIMIT
-
+
1.0V
-
+
2.45V
VFB
-
+
VREF
VIN OK
GAIN
MODULATOR
VCC
1.6k
1.6k
1.25V
25A
-
+
DC ILIMIT
17V
REV. 1.0.2 3/7/2001
ML4800
2
REV. 1.0.2 3/7/2001
PIN CONFIGURATION
PIN DESCRIPTION
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
13
V
CC
Positive supply
14
V
REF
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
PIN
NAME
FUNCTION
1
IEAO
Slew rate enhanced PFC
transconductance error amplifier output
2
I
AC
PFC AC line reference input to Gain
Modulator
3
I
SENSE
Current sense input to the PFC Gain
Modulator
4
V
RMS
PFC Gain Modulator RMS line voltage
compensation input
5
SS
Connection point for the PWM soft start
capacitor
6
V
DC
PWM voltage feedback input
7
RAMP 1
Oscillator timing node; timing set
by R
T
C
T
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.
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
ML4800
16-Pin PDIP (P16)
16-Pin Narrow SOIC (S16N)
ML4800
REV. 1.0.2 3/7/2001
3
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, V
CC
= 15V, R
T
= 52.3k
, C
T
= 470pF, T
A
= Operating Temperature Range (Note 1)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VOLTAGE ERROR AMPLIFIER
Input Voltage Range
0
5
V
Transconductance
V
NON INV
= V
INV
, VEAO = 3.75V
30
65
90
Feedback Reference Voltage
2.43
2.5
2.57
V
Input Bias Current
Note 2
-0.5
-1.0
A
Output High Voltage
6.0
6.7
V
Output Low Voltage
0.1
0.4
V
Source Current
V
IN
=
0.5V, V
OUT
= 6V
-40
-140
A
Sink Current
V
IN
=
0.5V, V
OUT
= 1.5V
40
140
A
Open Loop Gain
50
60
dB
Power Supply Rejection Ratio
11V < V
CC
< 16.5V
50
60
dB
CURRENT ERROR AMPLIFIER
Input Voltage Range
-1.5
2
V
Transconductance
V
NON INV
= V
INV
, VEAO = 3.75V
50
100
150
Input Offset Voltage
0
4
15
mV
Input Bias Current
-0.5
-1.0
A
Output High Voltage
6.0
6.7
V
Output Low Voltage
0.65
1.0
V
Source Current
V
IN
=
0.5V, V
OUT
= 6V
-40
-104
A
Sink Current
V
IN
=
0.5V, V
OUT
= 1.5V
40
160
A
Open Loop Gain
60
70
dB
Power Supply Rejection Ratio
11V < V
CC
< 16.5V
60
75
dB
OVP COMPARATOR
Threshold Voltage
2.65
2.75
2.85
V
Hysteresis
175
250
325
mV
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.
V
CC ..............................................................................................
18V
I
SENSE
Voltage ................................................. -5V to 0.7V
Voltage on Any Other Pin ...... GND - 0.3V to V
CCZ
+ 0.3V
I
REF ...........................................................................................
10mA
I
AC
Input Current .................................................... 10mA
Peak PFC OUT Current, Source or Sink ....................... 1A
Peak PWM OUT Current, Source or Sink .................... 1A
PFC OUT, PWM OUT Energy Per Cycle ................... 1.5
J
Junction Temperature .............................................. 150
C
Storage Temperature Range ...................... -65
C to 150C
Lead Temperature (Soldering, 10 sec) ..................... 260
C
Thermal Resistance (
JA
)
Plastic DIP .......................................................... 80
C/W
Plastic SOIC ...................................................... 105
C/W
OPERATING CONDITIONS
Temperature Range
ML4800CX .................................................... 0
C to 70C
ML4800IX .................................................. -40
C to 85C
ML4800
4
REV. 1.0.2 3/7/2001
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
FB
= V
FAULT DETECT LOW
to V
FB
=
2
4
ms
OPEN.
470pF from V
FB
to GND
Fault Detect LOW
0.4
0.5
0.6
V
PFC I
LIMIT
COMPARATOR
Threshold Voltage
-0.9
-1.0
-1.1
V
(PFC I
LIMIT
V
TH
- Gain Modulator Output)
120
220
mV
Delay to Output
150
300
ns
DC I
LIMIT
COMPARATOR
Threshold Voltage
0.95
1.0
1.05
V
Input Bias Current
0.3
1
A
Delay to Output
150
300
ns
V
IN
OK COMPARATOR
Threshold Voltage
2.35
2.45
2.55
V
Hysteresis
0.8
1.0
1.2
V
GAIN MODULATOR
Gain (Note 3)
I
AC
= 100
A, V
RMS
= V
FB
= 0V
0.60
0.80
1.05
I
AC
= 50
A, V
RMS
= 1.2V, V
FB
= 0V
1.8
2.0
2.40
I
AC
= 50
A, V
RMS
= 1.8V, V
FB
= 0V
0.85
1.0
1.25
I
AC
= 100
A, V
RMS
= 3.3V, V
FB
= 0V
0.20
0.30
0.40
Bandwidth
I
AC
= 100
A
10
MHz
Output Voltage
I
AC
= 350
A, V
RMS
= 1V,
0.60
0.75
0.9
V
V
FB
= 0V
OSCILLATOR
Initial Accuracy
T
A
= 25
C
71
76
81
kHz
Voltage Stability
11V < V
CC
< 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
C
T
Discharge Current
V
RAMP 2
= 0V, V
RAMP 1
= 2.5V
3.5
5.5
7.5
mA
ML4800
REV. 1.0.2 3/7/2001
5
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
REFERENCE
Output Voltage
T
A
= 25
C, I(V
REF
) = 1mA
7.4
7.5
7.6
V
Line Regulation
11V <V
CC
<16.5V
10
25
mV
Load Regulation
0mA <I(V
REF
) <10mA;
T
A
= 0C to 70C
10
20
mV
0mA < I(V
REF
) < 5mA;
T
A
= 40C to 85C
10
20
mV
Temperature Stability
0.4
%
Total Variation
Line, Load, Temp
7.35
7.65
V
Long Term Stability
T
J
= 125
C, 1000 Hours
5
25
mV
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
0.7
2.0
V
I
OUT
= 10mA, V
CC
= 9V
0.4
0.8
V
Output High Voltage
I
OUT
= 20mA
V
CC
0.8V
V
I
OUT
= 100mA
V
CC
- 2V
V
Rise/Fall Time
C
L
= 1000pF
50
ns
PWM
Duty Cycle Range
0-44
0-47
0-49
%
Output Low Voltage
I
OUT
= -20mA
0.4
0.8
V
I
OUT
= -100mA
0.7
2.0
V
I
OUT
= 10mA, V
CC
= 9V
0.4
0.8
V
Output High Voltage
I
OUT
= 20mA
V
CC
0.8V
V
I
OUT
= 100mA
V
CC
- 2V
V
Rise/Fall Time
C
L
= 1000pF
50
ns
SUPPLY
Start-up Current
V
CC
= 12V, C
L
= 0
200
350
A
Operating Current
14V, C
L
= 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
FB
pin.
Note 3: Gain = K x 5.3V; K = (I
GAINMOD
- I
OFFSET
) x [I
AC
(VEAO - 0.625)]
-1
; VEAO
MAX
=5V.