Fairchild Semiconductor ML4826-2 Datasheet
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 specifications. The ML4826 includes circuits for the implementation 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
V
CC2
19
VEAO
IEAO
V
FB
I
AC
V
RMS
I
SENSE
RTC
T
OSCILLATOR
OVP
PFC I
LIMIT
UVLO
V
REF
PULSE WIDTH MODULATOR
POWER FACTOR CORRECTOR
2.5V
+
-
-
+
20
2
4
3
7.5V
REFERENCE
18
V
CC
17
V
CCZ
VEA
7
-
+
IEA
1
+
+
-
PFC OUT
15
SRQ
Q
SRQ
Q
2.7V
-1V
RAMP 2
9
PWM 1
13
SRQ
Q
V
DC
6
SS
5
DC I
LIMIT
10
V
CC
DUTY CYCLE
LIMIT
-
+
1V
-
+
2.5V
V
FB
-
+
8V
8V
VIN OK
GAIN
MODULATOR
V
CCZ
3.5kΩ
3.5kΩ
1.5V
50µA
-
+
13.5V
DC I
LIMIT
RAMP 1
8
PWM 2
14
STQ
Q
V
CC2
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
2I
AC
PFC gain control reference input
3I
SENSE
Current sense input to the PFC current limit comparator
4V
RMS
Input for PFC RMS line voltage compensation
5 SS Connection point for the PWM soft start capacitor
6V
DC
PWM voltage feedback input
7R
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
RTC
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 ratings 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 ( θ
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 Ω , 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 µ Ω
Feedback Reference Voltage 2.4 2.5 2.6 V
Input Bias Current Note 2 –0.3 –1.0 µA
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 µA
Sink Current
∆
V
IN
= ±0.5V, V
OUT
= 1.5V 40 80 µA
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 µ Ω
Input Offset Voltage ±3 ±15 mV
Input Bias Current –0.5 –1.0 µA
Ω
Ω
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 µA
Sink Current
∆
V
IN
= ±0.5V, V
OUT
= 1.5V 40 90 µA
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 µA
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
= 100µA, V
RMS
= V
FB
= 0V 0.36 0.55 0.66
I
AC
= 50µA, V
RMS
= 1.2V, V
FB
= 0V 1.20 1.80 2.24
I
AC
= 50µA, V
RMS
= 1.8V, V
FB
= 0V 0.55 0.80 1.01
I
AC
= 100µA, V
RMS
= 3.3V, V
FB
= 0V 0.14 0.20 0.26
Bandwidth IAC = 100µA 10 MHz
Output Voltage I
AC
= 250µA, V
RMS
= 1.15V, V
FB
= 0V 0.72 0.82 0.95 V
Oscillator
Initial Accuracy T
A
= 25°C 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
= 25°C, 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 Ω , 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 IAC 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 TJ = 125˚C, 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, VCC = 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 CL = 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, VCC = 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 CL = 1000pF 50 ns
Supply
Shunt Regulator Voltage
(V
CCZ
)
12.8 13.5 14.2 V
V
CCZ
Load Regulation 25mA < ICC < 55mA ±150 ±300 mV
V
CCZ
Total Variation Load, temp 12.4 14.6 V
Start-up Current VCC = 11.2V, CL = 0 0.7 1.1 mA
Operating Current VCC < V
CCZ
– 0.5V, CL = 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
= RT = 52.3kΩ, C
RAMP1
= CT = 180 pF,
TA = Operating Temperature Range (Note 1)
Symbol Parameter Conditions Min. Typ. Max. Units
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