NCP1379DR2G ON Semiconductor, NCP1379DR2G Datasheet - Page 20

• Manufacturer Part Number: NCP1379DR2G
• Description: IC CTLR QUASI CURRENT MODE 8SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1379DR2G

• Output Isolation: Isolated
• Voltage - Input: 9 ~ 28 V
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Duty Cycle (max): 6.7 %
• Mounting Style: SMD/SMT
• Switching Frequency: 65 KHz
• Operating Supply Voltage: 8.3 V to 12.3 V
• Supply Current: 1.7 mA
• Maximum Operating Temperature: + 125 C
• Fall Time: 25 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 40 ns
• Synchronous Pin: No
• Topology: Quasi-Resonant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Where:
N
/ N
V
V
using Equation 2. While selecting the value for R
must be careful not choosing a too low value for this resistor
in order to have enough voltage for zero−crossing detection
during the off−time. We recommend having at least 8 V on
ZCD pin, the maximum voltage being 10 V.
follows:
R
Design example:
on the pin Fault.
voltage condition, the pin 7 permanently monitors a fraction
of the bulk voltage through a voltage divider. When this
image of bulk voltage is below the V
controller stops switching. When the bulk voltage comes
back within safe limits, the circuit restarts pulsing. The
hysteresis for the brown−out function is implemented with
a high side current source sinking 10 mA when the
brown−out comparator is high (V
HV−BULK
p,aux
IN
OPP
zcd
By selecting a value for R
During the off−time, ZCD pin voltage can be expressed as
We can thus deduce the relationship between R
NCP1379 combine brown−out and overvoltage detection
In order to protect the power supply against low input
p
:
is the DC input voltage
Rbou
is the negative OPP voltage
Rbol
is the auxiliary to primary turn ration: N
VCC
R
V
R
R
zcd
ZCD
ZCD
OVP/BO
opl
Dz
R
) R
opl
+
+
7
R
opu
V
ZCD
aux
+ −
Rc l a mp
Vclamp
R
* V
) Ropl
opl
V
opl
N
ZCD
VOVP
d
p,aux
, we can easily deduce R
VDD
* V
bulk
OVERVOLTAGE PROTECTION / BROWN−OUT
Figure 36. Brown−out and Overvoltage Protection
V
V
V
ZCD
IBO
IN
auz
OPP
VBO
> V
* V
* V
+
−
−
BO
+
bulk(on)
OPP
d
threshold, the
p,aux
)
opl
opl
(eq. 2)
= N
(eq. 3)
(eq. 4)
http://onsemi.com
noi s e de l a y
noi s e de l a y
, we
and
opu
aux
20
•
•
•
If we want at least 8 V on ZCD pin, we have:
We can choose: R
peak current by 37.5% at high line (370 Vdc). The
corresponding OPP voltage is:
Using Equation 2, we have:
Thus,
bulk voltage is high, an internal clamp limits the voltage.
conduct and inject current inside the internal clamp resistor
R
voltage reaches V
latched. The controller will be reset if V
V
R
R
clamp
CC(reset)
For the over power compensation, we need to decrease the
In order to avoid having a too high voltage on pin 7 if the
In case of over voltage, the zener diode will start to
R
V
V
N
R
ZCD
ZCD
opl
aux
opu
d
p,aux
grand
reset
= 0.6 V
R
BO reset
thus causing pin 7 voltage to increase. When this
= 18 V
+
) R
+ 221
opl
= 0.18
or if a brown−out occurs (Figure 37).
V
V
opu
aux
OPP
Ropl
* V
+ −
+
R
V
S
+ 0.375
zcd
OVP
−0.18
* R
ZCD
d
N
Q
Q
* V
= 1 kW and R
p,aux
, the controller latches−off and stays
ZCD
ZCD
V
V
( −0.3 )
370 * ( −0.3 )
+ 221
IN
OPP
V
+
* V
ILIM
18 * 0.6 * 8
La tc h
OPP
CS c omp
opl
+ −300 mV
1k * 1k + 220 kW
= 1 kW.
8
+ 221
CC
R
S
falls bellow
+ 1.2
Q
Q
(eq. 5)
(eq. 6)
(eq. 7)
(eq. 8)
DRV