MC33260DG ON Semiconductor, MC33260DG Datasheet - Page 10

• Manufacturer Part Number: MC33260DG
• Description: IC PFC CONTROLLER DCM 8SOIC
• Manufacturer: ON Semiconductor
• Series: GreenLine™r

Specifications of MC33260DG

• Mode: Discontinuous Conduction (DCM)
• Current - Startup: 100µA
• Voltage - Supply: 11 V ~ 16 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Maximum Operating Temperature: + 105 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

equation can be simplified as follows (I
replaced by its typical value 200 mA
through a 300 kΩ resistor. The Pin 2 voltage (V
compared to the oscillator sawtooth for PWM control.
and ground, for external loop compensation. The bandwidth
is typically set below 20 Hz so that the regulation block
output should be relatively constant over a given ac line
cycle. This integration that results in a constant on- -time over
the ac line period, prevents the mains frequency output
ripple from distorting the ac line current.
OSCILLATOR SECTION
current (I
where:
voltage level as follows:
Consequently:
In practice, V
The regulation block output is connected to the Pin 2
An external capacitor must be connected between Pin 2
The oscillator consists of three phases:
The oscillator charge current is dependent on the feedback
So, the oscillator charge current is linked to the output
 Charge Phase: The oscillator capacitor voltage grows
 Discharge Phase: The oscillator capacitor is abruptly
 Waiting Phase: At the end of the discharge sequence,
I
I
I
charge
o
ref
is the feedback current (drawn by Pin 1),
up linearly from its bottom value (ground) until it
exceeds V
that moment, the PWM latch output gets low and the
oscillator discharge sequence is set.
discharged down to its valley value (0 V).
the oscillator voltage is maintained in a low state until
the PWM latch is set again.
is the internal reference current (200 mA
o
is the oscillator charge current,
). In effect
CT
3
I
charge
R o ≈ 5 ×
pin1
control
R o =
1
Figure 26. Oscillator
I
is small compared to (V
charge
=
(regulation block output voltage). At

V o
0
2 ×
I
charge


V o
regH
= 2 ×

I
= 2 ¢ I
15 pF
R 2 o × I
regH

V o − V
regH
− V
o
I
Pin Numbers are Relevant to the PDIP- -8 Version
I 2 o
ref
¢ I
( kΩ )
ref
pin1
pin1
1
o
/ I
ref

regH
Output_Ctrl
2
o
)
0
regH
being also
control
and this
http://onsemi.com
) is
10
where:
compared to V
neglecting V
an internal capacitance (C
voltage. Over the oscillator swing, its average value
typically equals 15 pF (min 10 pF, max 20 pF).
and external capacitors.
PWM LATCH SECTION
block output (V
oscillator sawtooth so that the gate drive signal (Pin 7) is
high until the oscillator ramp exceeds V
where:
the Oscillator Section:
(preconverter output voltage) and that the on- -time is
maximum when Vcontrol is maximum (1.5 V typically).
the following equation:
Refer to Electrical Characteristics, Oscillator Section.
Then:
In practice, V
It must be noticed that the oscillator terminal (Pin 3) has
The total oscillator capacitor is then the sum of the internal
The MC33260 operates in voltage mode: the regulation
The on- -time is then given by the following equation:
Consequently, replacing I
One can notice that the on- -time depends on V
At a given V
This equation can be simplified replacing
V
R
V
t
C
I
V
on
charge

o
o
pin3
pin1
control
t on
is the output voltage,
is the feedback resistor,
is the on- -time,

internal and external capacitor),
is the total oscillator capacitor (sum of the
is the Pin 1 clamp voltage.
max =
is the oscillator charge current (Pin 3 current),
t on =
is the Pin 2 voltage (regulation block output).
pin1

o
[( V control ) max * I ref ]
o
, the maximum on- -time is then expressed by
pin1
control
. The equation can then be simplified by
:

C
t on =
R 2 o × I
t on
pin3
I
C
that is in the range of 2.5 V, is very small
charge

pin3
max =
- - Pin 2 voltage) is compared to the
× R 2 o × I
C
2
ref
pin3
= C
int
≈
charge
× C
) that varies versus the Pin 3
2 × V 2 o
C
R 2 o × I
K osc × V 2 o
× V
T
2 × V 2 o
I
pin3
2 × V 2 o
ch
pin3
+ C
by the expression given in
ref
control

× R 2 o
×
× V
int
ref
by K osc

control
V
control
control
.

max
o