NCP1338DR2G ON Semiconductor, NCP1338DR2G Datasheet - Page 12

• Manufacturer Part Number: NCP1338DR2G
• Description: IC CTRLR PWM CM OVP 8SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1338DR2G

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 130kHz
• Voltage - Supply: 11 V ~ 20 V
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 8-SOIC (3.9mm Width, 7 Lead)
• Frequency-max: 130kHz
• Output Voltage: - 0.3 V to + 20 V
• Output Current: 500 mA
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Fall Time: 20 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 50 ns
• Synchronous Pin: No
• Topology: Flyback
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Duty Cycle: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

the feedback loop. The range of current is from 40 mA for
overload detection to 220 mA corresponding to V
In transients, currents from 0 to more than 400 mA may also
appear: the circuitry is able to sustain them.
needs to have a high gain and a wide bandwidth. But the
feedback information used internally needs to be filtered,
because we don’t want the controller to be sensitive to the
switching noise. For this purpose, a 20 kHz filter is added
after the shunt regulator, and any reading of the feedback
signal (for ripple mode, fault detection, or setpoint
elaboration) is done after.
Soft Burst Mode (Protection Mode)
completely independently of the V
the feedback loop asks for the maximum power, a fault is
detected, and an internal timer is started. When the fault
disappears the timer is reset, but if the timer reaches 80 ms,
the protection mode is activated.
and DSS is deactivated (HV current source turn−on
threshold changes from VCC
slowly decreases (the current consumption is ICC3), and
the HV current source is switched ON when V
VCC
controller does not start as the output is still forced low.
V
start−up cycle occurs. On the second attempt, the output is
released, and NCP1338 effectively starts, with the
soft−start activated. Figure 4 illustrates this behavior.
Safety Features
power supply designer to build a rugged design:
•
•
•
•
controller: the DRV pulses are stopped, and the fault timer
is reset. When the condition disappears, the controller
restarts with the soft−start activated.
•
stopped, and the DSS is deactivated (only the start−up
current source is turned on each time V
CC
The input information is the current injected in FB pin by
To regulate the FB pin voltage, the operational amplifier
The NCP1338 features a fault timer to detect an overload
Once this protection is toggled, output pulses are stopped
The NCP1338 includes several safety features to help the
All these events have the same consequence for the
When this comparator is activated, the DRV pulses are
OVP (Overvoltage on V
on pin V
Brown−Out (Undervoltage lockout on bulk voltage):
Activated when voltage on pin BO is below 500 mV
Disable (Comparator activated by an external signal):
Activated when the voltage on BO pin is higher than
3.0 V but below 5.0 V
TSD (Temperature shutdown): Typically activated
when the die temperature is above 150°C, released at
120°C
Permanent Latch (Comparator activated by an external
signal): Activated when the voltage on BO pin is
above 5.0 V
LATCH
decreases again down to VCC
CC
. As a result V
is higher than 18.6 V
CC
CC
increases until VCC
): Activated when voltage
MIN
CC
to VCC
voltage. As soon as
LATCH
LATCH
, and a new
CC
CC
ON
CSrippleIN
, but the
reaches
reaches
). V
http://onsemi.com
CC
.
12
VCC
the controller stays in this position until the V
decreased below 4.0 V, i.e., when the power supply is
unplugged from the mains (in normal operation, as soon as
a voltage is present on the HV pin, V
above 5.0 V).
Soft−Skip Mode
hysteresis on the skip comparator in order to ensure a
noise−free and high−efficiency operation in low−load
conditions (standby). When internal setpoint is reaching
V
maximum setpoint), the output pulses are stopped. Then
FB loop asks for more power and internal setpoint is
increasing: when it reaches V
(corresponding to 25% of the maximum setpoint), the
output starts switching again. Soft−Skip is activated in each
activity following a stop period. See Figure 5 for detailed
timing diagram.
HV Current Source
auxiliary voltage. But to protect the die in case of
short−circuit on V
current source is lowered when V
higher than the DSS capability (high Qg MOSFET or
failure), the HV current source is switched ON when V
reaches VCC
decreasing. If there is no UVLO threshold to stop the DRV
pulses, the gate voltage will become too low and the risk is
high to destroy the MOSFET. NCP1338 features an
additional comparator, which threshold is 9.0 V: when V
reaches this level whereas the HV current source is ON,
DRV pulses are stopped and the protection mode is
activated.
Brown−Out
reference of 500 mV. When the comparator is activated
(i.e., when the input voltage V
a 10 mA internal current source is activated and creates an
offset across the bottom resistor of the external resistor
divider. It gives the minimum hysteresis of the brown−out
protection. By adding a series resistor between the divider
and the BO pin, it is possible to adjust (increase) the
hysteresis.
first one (that toggles at 3.0 V) stops the DRV pulses,
whereas the second one (that toggles at 5.0 V) permanently
latches off the controller (the V
4.0 V to release the latch).
timer is reset, preventing the controller from going into
protection mode if the condition lasts longer than Tfault.
Figure 8 gives the internal implementation of the BO pin.
CSrippleIN
The NCP1338 implements a Soft−Skip mode with a large
NCP1338 features a DSS, to allow operation without any
In the case the current consumed on the DRV pin is
The brown−out protection comparator has a fixed
The BO pin also features two additional comparators: the
When the BO or Enable comparator toggles, the fault
LATCH
, maintaining V
= 100 mV (corresponding to 20% of the
MIN
, but the voltage on V
CC
pin, the current delivered by the HV
CC
IN
between 5.0 V and 12 V):
CC
is above the starting level),
CC
CSrippleOUT
should be forced below
voltage is below 1.5 V.
CC
CC
is always kept
CC
pin keep on
= 130 mV
voltage is
CC
CC