Fairchild Semiconductor ML4812CQ Datasheet
www.fairchildsemi.com
ML4812
Power Factor Controller
Features
• Precision buffered 5V reference (±0.5%)
• Current-input gain modulator reduces external
components and improves noise immunity
• Programmable ramp compensation circuit
• 1A peak current totem-pole output drive
• Overvoltage comparator helps prevent output voltage
“runaway”
• Wide common mode range in current sense comparators
for better noise immunity
• Large oscillator amplitude for better noise immunity
Block Diagram
(Pin Configuration Shown is for DIP Version)
OVP
5
I
SENSE
1
GM OUT
2
EA OUT
3
EA–
4
5V
5V
5V
+
–
+
–
+
–
–
ERROR
AMP
I
EA
Description
The ML4812 is designed to optimally facilitate a peak
current control boost type power factor correction system.
Special care has been taken in the design of the ML4812 to
increase system noise immunity. The circuit includes a
precision reference, gain modulator, error amplifier, overvoltage protection, ramp compensation, as well as a high
current output. In addition, start-up is simplified by an undervoltage lockout circuit with 6V hysteresis.
In a typical application, the ML4812 functions as a current
mode regulator . The current which is necessary to terminate
the cycle is a product of the sinusoidal line voltage times the
output of the error amplifier which is regulating the output
DC voltage. Ramp compensation is programmable with an
external resistor, to provide stable operation when the duty
cycle exceeds 50%.
SHDN
V
32V
OUT
REF
V
CC
10
12
11
14
13
SRQ
V
CC
Q
PWR GND
UNDER
VOLTAGE
LOCKOUT
I
SINE
6
RAMP COMP
7
C
T
16
R
T
8
GAIN MODULATOR
OSC
5V
1kΩ
GND
15
CLOCK
9
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ML4812 PRODUCT SPECIFICATION
Pin Configuration
ML4812
20-Pin PLCC (Q20)
SENSE
GM OUT
I
NC
CTGND
3212019
NC
SHDN
CLOCK
18
17
16
15
14
4
5
6
7
8
910111213
T
R
RAMP COMP
Top View
V
REF
V
CC
NC
OUT
PWR GND
16-Pin PDIP (P16)
I
SENSE
GM OUT
EA OUT
EA–
OVP
I
SINE
RAMP COMP
R
T
ML4812
1
2
3
4
5
6
7
8
Top View
16
15
14
13
12
11
10
9
C
T
GND
V
REF
V
CC
OUT
PWR GND
SHDN
CLOCK
EA OUT
EA–
NC
OVP
I
SINE
Pin Description
Number Name Function
1 I
SENSE
2 GM OUT Output of gain modulator. A resistor to ground on this pin converts the current to a
3 EA OUT Output of error amplifier.
4EA– Inverting input to error amplifier.
5 OVP Input to over voltage comparator.
6 I
SINE
7 RAMP
COMP
8R
T
9 CLOCK Digital clock output.
10 SHDN A TTL compatible low level on this pin turns off the output.
11 PWR
GND
12 OUT High current totem pole output.
13 V
14 V
CC
REF
15 GND Analog signal ground.
16 C
T
Input from the current sense transformer to the non-inverting input of the PWM
comparator.
voltage. This pin is clamped to 5V and tied to the inverting input of the PWM comparator.
Current gain modulator input.
Buffered output from the oscillator ramp (C
is internally subtracted from the product of I
). A resistor to ground sets the current which
T
SINE
and I
in the gain modulator.
EA
Oscillator timing resistor pin. A 5V source sets a current in the external resistor which is
mirrored to charge C
.
T
Return for the high current totem pole output.
Positive Supply for the IC.
Buffered output for the 5V voltage reference.
Timing capacitor for the oscillator.
2
REV. 1.0.4 5/31/01
ML4812 PRODUCT SPECIFICATION
Absolute Maximum Ratings
Supply Current (I
) 30mA
CC
1
Output Current Source or Sink (OUT) DC 1.0A
Output Energy (capacitive load per cycle) 5µJ
Gain Modulator I
SINE
Input (I
) 1.2mA
SINE
Error Amp Sink Current (EA OUT) 10mA
Oscillator Charge Current 2mA
Analog Inputs (I
, EA–, OVP) –0.3V to 5.5V
SENSE
Junction Temperature 150°C
Storage Temperature Range –65°C to 150°C
Lead Temperature (soldering 10 sec.) 260°C
Thermal Resistance ( θ
20-Pin PLCC
16-Pin PDIP
Note:
1. 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.
JA
)
60°C/W
65°C/W
Operating Conditions
Temperature Range
ML4812CX 0°C to 70°C
3
REV. 1.0.4 5/31/01
PRODUCT SPECIFICATION ML4812
Electrical Characteristics
Unless otherwise specified, V
Parameter Conditions Min. Typ. Max. Units
Oscillator
Initial Accuracy T
Voltage Stability 12V < V
Temperature Stability 2 %
Total Variation Line, temperature 90 108 kHz
Ramp Valley to Peak 3.3 V
R
Voltage 4.8 5.0 5.2 V
T
Discharge Current (R
open) T
T
Clock Out Voltage Low RL = 16k Ω
Clock Out Voltage High RL = 16k Ω
Reference
Output Voltage T
Line Regulation 12V < V
Load Regulation 1mA < IO < 20mA 2 20 mV
Temperature Stability 0.4 %
Total Variation Line, load, temp. 4.9 5.1 V
Output Noise Voltage 10Hz to 10kHz 50 µV
Long Term Stability T
Short Circuit Current V
Error Amplifier
Input Offset Voltage ±15 mV
Input Bias Current –0.1 –1.0 µA
Open Loop Gain 1 < V
PSRR 12V < V
Output Sink Current V
Output Source Current V
Output High Voltage I
Output Low Voltage I
Unity Gain Bandwidth 1.0 MHz
Gain Modulator
I
Input Voltage I
SINE
Output Current (GM OUT) I
Bandwidth 200 kHz
PSRR 12V < V
= 15V , R
CC
= 14k Ω , C
T
= 25°C 91 98 105 kHz
J
< 18V 0.3 %
CC
= 25°C, V
J
V
= 2V 7.3 8.4 9.3 mA
CT
= 1000pF, T
T
= 2V 7.8 8.4 9.0 mA
CT
= Operating Temperature Range (Notes 1, 2).
A
0.2 0.5 V
3.0 3.5 V
= 25°C, I
J
= 125°C, 1000 hours 5 25 mV
J
= 0V –30 –85 –180 mA
REF
EA OUT
EA OUT
EA OUT
EA OUT
EA OUT
= 500µA 0.4 0.7 0.9 V
SINE
= 500µA, EA– = V
SINE
I
= 500µA, EA– = V
SINE
I
= 1mA, EA– = V
SINE
I
= 500µA, EA– = V
SINE
I
RAMP COMP
= 1mA 4.95 5.00 5.05 V
O
< 25V 2 20 mV
CC
< 5V 60 75 dB
< 25V 60 75 dB
CC
= 1.1V, V
= 5.0V, V
= –0.5mA, V
= 1mA, V
= 6.2V 2 12 mA
EA–
– = 4.8V –0.5 –1.0 mA
EA
– = 4.8V 5.3 5.5 V
EA
– = 6.2V 0.5 1.0 V
EA
– 20mV 430 470 510 µA
REF
+ 20mV 3 10 µA
REF
– 20mV 860 940 1020 µA
REF
REF
– 20mV,
455 µA
= 50µA
< 25V 70 dB
CC
REV. 1.0.4 5/31/01
4
ML4812 PRODUCT SPECIFICATION
Electrical Characteristics
Unless otherwise specified, V
CC
(Continued)
= 15V , R
= 14k Ω , C
T
= 1000pF, T
T
= Operating Temperature Range (Notes 1, 2).
A
Parameter Conditions Min. Typ. Max. Units
OVP Comparator
Input Offset Voltage Output Off –25 +5 mV
Hysteresis Output On 95 105 115 mV
Input Bias Current –0.3 –3µA
Propagation Delay 150 ns
PWM Comparator: I
SENSE
Input Offset Voltage ±15 mV
Input Offset Current ±1 µA
Input Common Mode Range –0.2 5.5 V
Input Bias Current –2 –10 µA
Propagation Delay 150 ns
I
Trip Point V
LIMIT
GM OUT
= 5.5V 4.8 5 5.2 V
Output
Output Voltage Low I
Output Voltage High I
Output Voltage Low in UVLO I
Output Rise/Fall Time C
Shutdown V
= –20mA 0.1 0.4 V
OUT
I
= –200mA 1.6 2.2 V
OUT
= 20mA 13 13.5 V
OUT
I
= 200mA 12 13.4 V
OUT
= –5mA, V
OUT
= 1000pF 50 ns
L
IH
V
IL
I
, V
IL
IIH, V
= 0V –1.5 mA
SHDN
= 5V 10 µA
SHDN
= 8V 0.1 0.8 V
CC
2.0 V
0.8 V
Under-Voltage Lockout
Startup Threshold 15 16 17 V
Shutdown Threshold 9 10 11 V
V
Good Threshold 4.4 V
REF
Supply
Supply Current Start-Up, V
Operating, T
Internal Shunt Zener Voltage I
Notes:
1. Limits are guaranteed by 100% testing, sampling, or correlation with worst-case test conditions.
2. V
is raised above the Startup Threshold first to activate the IC, then returned to 15V.
CC
= 30mA 25 30 34 V
CC
= 14V, T
CC
= 25°C2025mA
J
= 25°C 0.8 1.2 mA
J
5
REV. 1.0.4 5/31/01
ML4812 PRODUCT SPECIFICATION
Functional Description
Oscillator
The ML4812 oscillator charges the external capacitor (CT)
with a current (I
voltage reaches the upper threshold, the comparator changes
state and the capacitor discharges to the lower threshold
through Q1. While the capacitor is discharging, Q2 provides
a high pulse.
EXTERNAL
CLOCK
C
SYNC
R
SYNC
) equal to 5/R
SET
I
SET
R
T
C
T
10
9
16
. When the capacitor
SET
SYNC
R
T
I
T
8.4mA
SET
5.6V
C
Q
2
+
-
The Oscillator period can be described by the following
relationship:
T
OSCTRAMPTDEADTIME
+=
where:
OUT
--------------------=
1D
–
ON
V
V
IN
and:
CTV
×
T
DEADTIME
10
8
5
(kΩ)
T
R
3
2
1
10 100 1000
5nF 2nF
10nF
20nF
OSCILLATOR FREQUENCY (kHz)
RAMPVALLEYTOPEAK
-------------------------------------------------------------------------=
8.4mA I
1nF
–
SET
90%
85%
80%
70%
MAXIMUM DUTY CYCLE (%)
RAMP PEAK
RAMP VALLEY
6
Q
1
CLOCK
t
D
V(CT)
Figure 1. Oscillator Block Diagram
Figure 2. Oscillator Timing Resistance vs. Frequency
15
V
CC
14
13
SOURCE SATURATION
LOAD TO GROUND
SINK SATURATION
LOAD TO V
3
2
1
OUTPUT SATURATION VOLTAGE (V)
0
0 200 400 800
CC
OUTPUT CURRENT (mA)
VCC = 15V
80µs PULSED LOAD
120Hz RATE
GND
600
Figure 3. Output Saturation Voltage vs. Output Current
REV. 1.0.4 5/31/01
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