NCP1207DR2 ON Semiconductor, NCP1207DR2 Datasheet - Page 12

• Manufacturer Part Number: NCP1207DR2
• Description: IC CTRLR PWM CM OVP OCP HV 8SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1207DR2

• Output Isolation: Isolated
• Voltage - Input: 10.6 ~ 16 V
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: NCP1207DR2OSTR

Latching Off the NCP1207
shut down permanently the NCP1207 via a dedicated signal,
e.g. coming from a temperature sensor. The reset occurs
when the user unplugs the power supply from the mains
outlet. To trigger the latchoff, a CTN (Figure 25) or a simple
NPN transistor (Figure 26) can do the work.
Shutting Off the NCP1207
NPN bipolar transistor as depicted by Figure 27. When OFF,
Q1 is transparent to the operation. When forward biased, the
transistor pulls the FB pin to ground (V
permanently disables the IC. A small time constant on the
transistor base will avoid false triggering (Figure 27).
ON/OFF
ON/OFF
In certain cases, it can be very convenient to externally
Shutdown can easily be implemented through a simple
soon as the temperature exceeds a given setpoint
Figure 26. A simple transistor arrangement allows
Figure 25. A simple CTN triggers the latchoff as
Figure 27. A simple bipolar transistor totally
to trigger the latchoff by an external signal
3
10 k
1
2
3
4
disables the IC
NCP1207
10 nF
CTN
2
Q1
1
2
3
4
8
7
6
5
NCP1207
1
CE(sat)
Aux
1
2
3
4
NCP1207
8
7
6
5
200 mV) and
Aux
http://onsemi.com
8
7
6
5
NCP1207
12
Power Dissipation
through the internal DSS circuitry. The DSS being an
auto−adaptive circuit (e.g. the ON/OFF Duty Cycle adjusts
itself depending on the current demand), the current flowing
through the DSS is therefore the direct image of the
NCP1207 current consumption. The total power dissipation
can be evaluated using:
operate the device on a 250 Vac rail, the maximum rectified
voltage can go up to 350 Vdc. As a result, the worse case
dissipation occurs at the maximum switching frequency and
the highest line. The dissipation is actually given by the
internal consumption of the NCP1207 when driving the
selected MOSFET. The best method to evaluate this total
consumption is probably to run the final circuit from a
50 Vdc source applied to pin 8 and measure the average
current flowing into this pin. Suppose that we find 2.0 mA,
meaning that the DSS Duty Cycle will be 2.0/7.0 = 28.6%.
From the 350 Vdc rail, the part will dissipate:
will drop at higher operating junction temperatures).
A DIP8 package offers a junction−to−ambient thermal
resistance R
dissipation can thus be computed knowing the maximum
operating ambient temperature (e.g. 70 C) together with
the maximum allowable junction temperature (125 C):
do not reach the worse consumption budget imposed by the
operating conditions. Several solutions exist to cure this
trouble:
350 V @ 2.0 mA + 700 mW
P max +
The NCP1207 is directly supplied from the DC rail
The first one consists in adding some copper area around
the NCP1207 DIP8 footprint. By adding a min pad area
of 80 mm
75 C/W. Maximum power then grows up to 730 mW.
A resistor Rdrop needs to be inserted with pin 8 to
a) avoid negative spikes at turn−off (see below)
b) split the power budget between this resistor and the
package. The resistor is calculated by leaving at least 50 V
on pin 8 at minimum input voltage (suppose 100 Vdc in
our case):
power dissipated by the resistor is thus:
P drop + V dropRMS
Please refer to the application note AND8069 available
from www.onsemi.com/pub/ncp1200.
+
+
T Jmax * T Amax
2
7.0 mA @ 7.1 kW @ 0.286
I DSS @ R drop @ DSS duty * cycle
qJA
of 35 mm copper (1 oz.) R
R drop v
R qJA
of 100 C/W. The maximum power
7.1 kW
2
V bulkmin * 50 V
R drop
(V HVDC * 11 V) @ I CC2
t 550 mW
R drop
(however this 2.0 mA number
7.0 mA
. As we can see, we
2
qJA
+ 99.5 mW
t 7.1 kW
drops to about
2
. If we
. The