NCP1397ADR2G ON Semiconductor, NCP1397ADR2G Datasheet - Page 12

• Manufacturer Part Number: NCP1397ADR2G
• Description: IC CTLR RESONANT HI PERF 16-SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1397ADR2G

• Pwm Type: Controller
• Number Of Outputs: 1
• Frequency - Max: 560kHz
• Duty Cycle: 52%
• Voltage - Supply: 10.3 V ~ 20 V
• Buck: No
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 16-SOIC (3.9mm Width, 15 Leads)
• Frequency-max: 560kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

building a rugged and safe switch−mode power supply
featuring an extremely low standby power. The below
bullets detail the benefits brought by implementing the
NCP1397A/B controller:
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The NCP1397A/B includes all necessary features to help
Wide frequency range: A high−speed Voltage Control
Oscillator allows an output frequency excursion from
50 kHz up to 500 kHz on M
Adjustable dead−time: Due to a single resistor wired
to ground, the user has the ability to include some
dead−time, helping to fight cross−conduction between
the upper and the lower transistor.
Adjustable soft−start: Every time the controller starts
to operate (power on), the switching frequency is
pushed to the programmed starting value by external
components (R
toward the minimum frequency, until the feedback loop
closes. The soft−start discharge input (SS(dis))
discharges the Soft−Start capacitor before any IC restart
excluding the restart after Disable is released AND FB
voltage is higher than 0.3 V. The Soft−Start discharge
switch also activates in case the Fault input detects the
overload conditions.
Adjustable minimum and maximum frequency
excursion: In resonant applications, it is important to
stay away from the resonating peak to keep operating
the converter in the right region. Thanks to a single
external resistor, the designer can program its lowest
frequency point, obtained in lack of feedback voltage
(during the startup sequence or in short−circuit
conditions). Internally trimmed capacitors offer a $3%
precision on the selection of the minimum switching
frequency. The adjustable upper stop being less precise
to $12%.
Low startup current: When directly powered from the
high−voltage DC rail, the device only requires 300 mA
to startup.
Brown−Out detection: To avoid operation from a low
input voltage, it is interesting to prevent the controller
from switching if the high−voltage rail is not within the
right boundaries. Also, when teamed with a PFC
front−end circuitry, the brown−out detection can ensure
a clean startup sequence with soft−start, ensuring that
the PFC is stabilized before energizing the resonant
tank. The BO input features a 28 mA hysteresis current
for the lowest consumption.
Adjustable fault timer duration: When a fault is
detected on the Fault input or when the FB path is
broken, timer pin starts to charge an external capacitor.
If the fault is removed, the timer opens the charging
path and nothing happens. When the timer reaches its
selected duration (via a capacitor on Pin 3), all pulses
Fmin
//R
Fstart
) and slowly moves down
lower
and M
upper
APPLICATION INFORMATION
outputs.
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The second fault comparator thus helps to protect the power
stage in case of hard short circuit (like shorted transformer
winding etc.)
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Voltage−Controlled Oscillator
operation from 100 kHz up to 1 MHz. However, as a division
by two internally creates the two Q and /Q outputs, the final
effective signal on output M
between 50 kHz and 500 kHz. The VCO is configured in
such a way that if the feedback pin voltage goes up, the
switching frequency also goes up. Figure 25 shows the
architecture of the VCO oscillator.
The VCO section features a high−speed circuitry allowing
are stopped. The controller now waits for the discharge
via an external resistor on Pin 3 to issue a new clean
startup sequence via soft−start.
Cumulative fault events: In the NCP1397A/B, the
timer capacitor is not reset when the fault disappears. It
actually integrates the information and cumulates the
occurrences. A resistor placed in parallel with the
capacitor will offer a simple way to adjust the discharge
rate and thus the auto−recovery retry rate.
Overcurrent detection using Fault input: The fault
input is specifically designed to protect LLC
application in case of short circuit or overload. In case
the voltage on this input grows above first threshold the
I
capacitor starts charging. Simultaneously the Soft−Start
discharge switch is activated to increase operating
frequency of the converter. The IC stops operation in
case the Fault timer elapses. The Fault input includes
also second fault comparator that:
Skip cycle possibility: The absence of the soft−start on
the Skip/Disable input (in case the V
an easy way to implement skip cycle when power
saving features are necessary. A simple resistive divider
from the feedback pin to the Skip/Disable input, and
skip can be implemented.
Broken feedback loop detection: Upon startup or any
time during operation, if the FB signal is missing, the
timer starts to charge timer capacitor. If the loop is
really broken, the FB level does not grow−up before the
timer ends charging. The controller then stops all pulses
and waits until the timer pin voltage collapses to 1 V
typically before a new attempt to restart, via the
soft−start. If the optocoupler is permanently broken, a
hiccup takes place.
Common collector or common emitter optocoupler
connection options: This IC allows the designer to
select from two possible optocoupler configurations.
− Speeds up the fault timer capacitor charging by
− Latches off the device – NCP1397B
timer
increasing the I
current source is activated and Fault timer
timer1
current to I
lower
and M
timer2
FB
> 0.3 V) offers
– NCP1397A
upper
switches