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ML4821CS

P1-P3P4-P6P7-P9P10-P12
ML4821 PRODUCT SPECIFICATION
4
REV. 1.0.2 6/19/01
Voltage Error Amplifier
Input Offset Voltage 0 –15 mV
Input Bias Current –50 –800 nA
Open Loop Gain 2 < EA OUT < 6V 60 75 dB
PSRR 12V < V
CC
< 24V 70 100 dB
Output Sink Current EA OUT = 4V, INV = 5.5V 300 500 µA
Output Source Current EA OUT
= 4.0V, INV
= 4.8V –10 –30 mA
Output High Voltage I
PIN6
= –5mA, V
PIN7
= 4.8V 7.0 7.5 V
Output Low Voltage I
PIN6
= 0, EA– = 5.5V 0 0.5 V
Unity Gain Bandwidth 1.0 MHz
Soft Start Charge Current V
PIN9
= 4V –22 –38 –50 µA
Current Error Amplifier
Input Offset Voltage –50 5mV
Input Bias Current –0.15 –1µA
Input Offset Current 400 nA
Open Loop Gain 2 < EA OUT < 7V 80 100 dB
PSRR 12V < V
CC
< 24V 65 85 dB
Output Voltage Low I
OL
= 300µA 0 0.5 V
Output Voltage High I
OH
= –10mA 7.0 7.5 V
Input Common Mode Range –0.3 2.5 V
Gain Modulator
Gain V
INV
= 4.8V, V
RMS
= 0V
V
INV
= 4.8V, V
RMS
= 1.75V
V
INV
= 4.8V, V
RMS
= 2.6V
V
INV
= 4.8V, V
RMS
= 5.2V
0.75
3.1
1.25
0.22
1.2
3.88
1.75
0.38
1.3
4.5
2.15
0.50
Output Current V
INV
= 5.2V, V
RMS
= 5.2V –2 –4µA
Output Current Limit V
INV
= 4.8V, I
SINE
= 500
µ
A,
V
RMS
= 1.75V
360 395 420 µA
I
LIM
Comparator
Input Offset Voltage +15 mV
Input Bias Current –100 –200 µA
OVP Comparator
Input Offset Voltage Output Off –25 5 mV
Hysteresis Output On 85 105 130 mV
Input Bias Current –0.3 –3µA
Propagation Delay 150 ns
Shutdown Threshold 0.4 0.7 1.0 V
PWM Comparator
Input Common Mode Range 0 8 V
Propagation Delay 150 ns
Electrical Characteristics
(continued)
Unless otherwise specified, R
T
= 6.2k
Ω
, C
T
= 720pF, T
A
= Operating Temperature Range, V
CC
= 15V (Notes 1 & 2).
Parameter Conditions Min. Typ. Max. Units
PRODUCT SPECIFICATION ML4821
REV. 1.0.2 6/19/01
5
Notes:
1. Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions.
2. V
CC
is raised above the start-up threshold first to activate the IC, then returned to 15V
3. Gain Modulator gain is defined as:
Output
Output Voltage Low I
OUT
= 20mA
I
OUT
= 200mA
0.1
1.6
0.4
2.4
V
V
Output Voltage High I
OUT
= –20mA
I
OUT
= –200mA
13
12
13.5
13.4
V
V
Output Voltage Low in UVLO I
OUT
= –5mA, V
CC
= 8V 0.1 0.8 V
Output Rise/Fall Time C
L
= 1000pF 50 ns
Undervoltage Lockout
Start-up Threshold 14.5 16.5 V
Shut-Down Threshold 8.5 11.0 V
V
REF
Good Threshold 4.4 V
Supply
Supply Current Start-up, V
CC
= 14V, T
A
= 25°C
Operating, T
A
= 25°C
0.6
26
1.2
32
mA
mA
Internal Shunt Zener Voltage I
CC
= 35mA 25 27 35 V
Electrical Characteristics
(continued)
Unless otherwise specified, R
T
= 6.2k
Ω
, C
T
= 720pF, T
A
= Operating Temperature Range, V
CC
= 15V (Notes 1 & 2).
Parameter Conditions Min. Typ. Max. Units
I
OUTIA+
I
INEAOUT
------------------------
ML4821 PRODUCT SPECIFICATION
6 REV. 1.0.2 6/19/01
Functional Description
Oscillator
The ML4821 oscillator charges the external capacitor
connected to C
T
with a current equal to 2.5/R
T
. When the
capacitor voltage reaches the upper threshold, the compara-
tor changes state and the capacitor discharges to the lower
threshold through Q1.
The oscillator period can be described by the following
relationship:
T
OSC
= T
RAMP
+ T
DISCHARGE
where:
T
RAMP
= C(Ramp Valley to Peak) ÷ (I
RT
/2)
and:
T
DISCHARGE
= C(Ramp Valley to Pk) ÷ (8.4mA – I
RT
/2)
The ML4821 oscillator includes a SYNC input for synchro-
nizing to an external frequency source. A positive pulse on
this pin of 2V (typ) resets the oscillators comparator and
initiates a discharge cycle for C
T
. The R
T
and C
T
component
values which set the ML4821 oscillator frequency should be
selected to produce a lower frequency than the external
frequency source.
VOLTAGE and Current ERROR Amplifiers
The ML4821 voltage error amplifier is a high open loop
gain, wide bandwidth amplifier with a class A output. The
soft start circuit controls the input to this amplifier for closed
loop soft start operation.
The current error amplifier (IA) is similar to the voltage error
amplifier but is designed for very low offsets to allow the
selection of a low value resistor for R
SENSE
.
Output Driver Stage
The ML4821 Output Driver is a 1A peak output high speed
totem pole circuit designed to quickly drive capacitive loads,
such as power MOSFET gates. The driver circuit’s output
voltage is internally limited to 17V.
Gain Modulator
The ML4821 gain modulator responds linearly to current
injected into the I
SINE
pin, and in an inverse-square fashion
to voltage on the V
RMS
pin. At very low voltages on the V
RMS
pin, the gain modulator enforces a power limit, or ”brown-
out protection”, upon the overall PFC circuit (Figures 6 and
7). The rectified line input sine wave is converted to a current
for the I
SINE
input via a dropping resistor. In this way, most
ground noise produces an insignificant effect on the refer-
ence to the PWM comparator. This gives the ML4821 a high
degree of immunity to the disturbances common in high-
power switching circuits.
CLOCK
t
D
C
T
RAMP PEAK
RAMP VALLEY
Figure 1. Oscillator Block Diagram
Figure 2. Oscillator Timing Resistance vs. Frequency
R
T
+
–
R
T
C
T
C
T
V
REF
8.4mA
Q1
Q2
1kΩ
2kΩ
SYNC
I
R
T
2
I
R
T
1000
100
10
01020
1nF
30 40
50
R
T
(kΩ)
FREQUENCY (kHz)
680pF
470pF
330pF
150pF
P1-P3P4-P6P7-P9P10-P12

ML4821CS

Mfr. #:
Buy ML4821CS
Manufacturer:
ON Semiconductor / Fairchild
Description:
Power Factor Correction - PFC PFC Controller
Lifecycle:
New from this manufacturer.
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