MC33260DG ON Semiconductor, MC33260DG Datasheet - Page 11

• 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

This equation shows that the maximum on- -time is inversely
proportional to the squared output voltage. This property is
used for follower boost operation (refer to Follower Boost
section).
CURRENT SENSE BLOCK
inserting a ground referenced resistor (R
input diodes bridge (and the input filtering capacitor).
Therefore a negative voltage proportional to the inductor
current is built:
where:
through a resistor R
negative clamp (- -0.7 V) that prevents substrate injection.
Current Sense comparator resets the PWM latch to force the
gate drive signal low state. In that condition, the power
MOSFET cannot be on.
overcurrent limitation while it serves the zero current
detection during the off time.
The inductor current is converted into a voltage by
The negative signal V
As long as the Pin 4 voltage is lower than (- -60 mV), the
During the on- -time, the Pin 4 information is used for the
I
R
V
L
cs
cs
An overcurrent is detected if V
is the inductor current,
is the current sense resistor,
is the measured R
Figure 27. Current Sensing
during the Power Switch on state
V cs = --
OCP
V
OCP
. The pin is internally protected by a
cs
cs
= R
pin4
voltage.
is applied to the current sense
OCP

R cs × I
crosses the threshold (--60 mV)
¢ I
OCP
Pin Numbers are Relevant to the PDIP- -8 Version
Zero Current Detection
L

cs
) in series with the
--60 mV
V
OCP
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Time
11
Zero Current Detection
MOSFET cannot turn on as long as the inductor current
hasn’t reached zero (discontinuous mode).
threshold so that as long as V
the circuit gate drive signal is kept in low state.
Consequently, no power MOSFET turn on is possible until
the inductor current is measured as smaller than (60 mV/R
that is, the inductor current nearly equals zero.
Overcurrent Protection
Drive Pin voltage is high), a current source is applied to the
Pin 4. A voltage drop V
resistor R
and the Current Sense Pin (refer to Figure 28). So, instead
of V
the maximum permissible current is the solution of the
following equation:
where:
where:
and the precedent equation can be simplified. The maximum
current is then given by the following equation:
whatever the R
choice of R
R
The Zero Current Detection function guarantees that the
The Pin 4 voltage is simply compared to the (- -60 mV)
During the power switch conduction (i.e. when the Gate
The overcurrent threshold is then:
Practically, the V
Consequently, the R
cs
Ipk
R
R
I
D1...D4
OCP
cs
cs
OCP
, the sum (V
max
is the sensing resistor.
Ipk max =
R
V
is the current supplied by the Current Sense Pin
--
OCP
OCP
sensing resistor (R
when the gate drive signal is high (power switch
conduction phase). I
is the resistor connected between the pin and the

OCP
R cs × Ipk max
is maximum allowed current,
Ipk max ≈
cs
Figure 28. Current Sense Block
. In particular, the inrush resistor can be utilized.
4
that is connected between the sense resistor
cs
1
value is. This gives a high freedom in the
cs

R
OCP
+ V
OCP
OCP
0
R
I
(Output_Ctrl Low <=> Gate Drive in Low State)
ocp
Output_Ctrl
OCP
R cs ( Ω )
OCP
offset is high compared to 60 mV
(205 mA)

OCP
resistor can program the OCP level
+ V
× I
LEB
cs
) is compared to (- -60 mV) and
( kΩ )
OCP
cs
),
is then generated across the
OCP
--60 mV
OCP
is lower than this threshold,
R cs
To Output Buffer
equals 205 mA typically.
× 0.205 ( A )

+
--
= --60 mV
+ 60 × 10 --3
S
R
R
PWM
Latch
Q
Output_Ctrl
cs
)