NCP1271P65G ON Semiconductor, NCP1271P65G Datasheet - Page 15

• Manufacturer Part Number: NCP1271P65G
• Description: IC CTRLR PWM CM OVP OTP HV 7DIP
• Manufacturer: ON Semiconductor
• Series: Soft-Skip™r

Specifications of NCP1271P65G

• Output Isolation: Either
• Frequency Range: 55 ~ 69kHz
• Voltage - Input: 9.1 ~ 20 V
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 8-DIP (0.300", 7.62mm), 7 Leads
• Number Of Outputs: 1
• Duty Cycle (max): 80 %
• Output Voltage: - 0.3 V to + 20 V
• Output Current: 800 mA
• Mounting Style: Through Hole
• Switching Frequency: 65 KHz
• Maximum Operating Temperature: + 150 C
• Fall Time: 20 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 30 ns
• Synchronous Pin: No
• Topology: Flyback
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

also enters fault condition when V
(9.1 V typical). The device will again enter a double hiccup
mode and try to restart the application.
Operation in Standby Condition
load, the duty cycle on the controller can become very
small. At this point, a significant portion of the power
dissipation is related to the power MOSFET switching on
and off. To reduce this power dissipation, the NCP1271
“skips” pulses when the FB level (i.e. duty cycle) drops too
low. The level that this occurs at is completely adjustable
by setting a resistor on pin 1.
and the FB voltage rises. When the FB voltage rises above
the V
minimize the risk of acoustic noise, when the drive turns
back on the duty cycle of its pulses are also ramped up. This
is similar to the soft start function, except the period of the
Soft−Skip operation is only 300 ms instead of 4.0 ms for the
soft start function. This feature produces a timing diagram
shown in Figure 36.
Table 1. Skip Resistor R
Besides the timer−based fault detection, the NCP1271
During standby operation, or when the output has a light
By discontinuing pulses, the output voltage slowly drops
skip
%Ics
100%
level, the drive is turned back on. However, to
12%
25%
40%
50%
V
0%
skip
FB
skip
Figure 36. Soft−Skip Operation
I D
skip
V
Range for D
skip
0.375 V
0.75 V
1.2 V
1.5 V
3.0 V
0 V
or V
CC
drops below V
pin1
Soft Skip
max
= 80% and I
http://onsemi.com
CC
(off
17.4 kW
34.8 kW
8.7 kW
28 kW
70 kW
R
)
0 W
skip
skip
15
= 43 mA
Skip Duty Cycle
maximum peak current at which the controller enters skip
mode. Ics
by equation 5. However, the higher that %Ics
greater the drain current when skip is entered. This
increases the risk of acoustic noise. Conversely, the lower
that %Ics
expended turning the switch on and off. Therefore it is
important to adjust %Ics
application.
Skip Adjustment
skip level is 1.2 V (V
40% Ics
Therefore, the controller will enter skip mode when the
peak current is less than 40% of the maximum peak current.
However, this level can be externally adjusted by placing
a resistor R
(Pin 4). The level will change according to equation 6.
0 V and 3.0 V. Therefore, R
given in Table 1.
Skip peak current, %Ics
By default, when the Skip/latch Pin (Pin 1) is opened, the
To operate in skip cycle mode, V
skip
skip
skip
Never skips.
−
−
−
−
Always skips.
skip
(%Ics
can be any value from 0 to 100% as defined
is the larger the percentage of energy is
% Ics skip +
between skip/latch pin (Pin 1) and Ground
V skip + R skip
skip
skip
= 1.2 V / 3.0 V
skip
= 1.2 V). This corresponds to a
skip
to the optimal level for a given
V skip
Comment
skip
3 V
, is the percentage of the
must be within the levels
· 100%
I skip
skip
must be between
100% = 40%).
skip
(eq. 5)
(eq. 6)
is, the