WIS2269N8 データシートの表示（PDF） - Shenzhen Winsemi Microelectronics Co., Ltd
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WIS2269N8 Datasheet PDF : 10 Pages
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WIS2269N8
OPERATION DESCRIPTION
The WIS2269 is a highly integrated, high performance
current mode PWM controller chip. Applicable to high power
notebook power adapter switching power supply and
switching power converters. Very low starting current and
operating current, and light load or no load situations
burstmode function, can effectively reduce the switching
power supply system, standby power consumption, improve
power conversion efficiency. Built-in synchronized slope
compensation of the feedback pin of the leading edge
blanking and other functions can not only reduce the number
of switching power supply system components, but also
increase the stability of the system, to avoid the production of
harmonic oscillation. WIS2269 also offers a variety of
comprehensive resume protected mode. Features functions
described as follows:
Startup Current and Start up Control
Startup current of WIS2269 is designed to be very
low(6.5uA) so that VDD could be charged up above UVLO
threshold level and device starts up quickly. A large value
startup resistor can therefore be used to minimize the power
loss yet provides reliable startup in application. For AC/DC
adaptor with universal input range design, a 2 MΩ, 1/8 W
startup resistor could be used together with a VDD capacitor
to provide a fast startup and low power dissipation solution.
Operating Current
The Operating current of WIS2269 is low at 2.3mA. Good
efficiency is achieved with WIS2269 low operating current
together with extended burst mode control features.
Burst Mode
At no load or light load conditions, switching power supply
in most of the power comes from the MOSFET's switching
losses, transformer core losses and the loss of the buffer
circuit. The size and power consumption within a certain
period of time proportional to the number of MOSFET
switches. Reduce the switching frequency also reduces power
consumption, saving energy. WIS2269 built-in Burst Mode
feature that automatically adjusts according to load switch
mode. When the system is in no load or light / medium load,
FB terminal voltage at the pulse input mode (BurstMode)
threshold voltage (1.8V) below. According to the judge based
on the device into the pulse mode control. Gate driver output
voltage only when the VDD level below the pre-set value, and
the FB input is active cases does the output. Other cases, the
gate drive output to maintain the status of long-off to reduce
power consumption, which reduces standby power
consumption. The characteristics of high-frequency switch
also reduced the audio noise at work.
Oscillator Operation
A resistor connected between RI and GND sets the
constant current source to charge/discharge the internal cap
and thus the PWM oscillator frequency is determined. The
relationship between RI and switching frequency follows the
below equation within the specified RI in Kohm range at
nominal loading operational condition.
Fosc= 1560 (KHz)
RI( KΩ )
CurrentSensingand LeadingEdge Blanking
Cycle-by-Cycle current limiting is offered in WIS2269
current mode PWM control. The switch current is detected
by a sense resistor into the sense pin. An internal leading
edge blanking circuit chops off the sense voltage spike at
initial MOSFET on state due to Snubber diode reverse
recovery so that the external RC filtering on sense input is no
longer required. The current limit comparator is disabled and
thus cannot turn off the external MOSFET during the
blanking period. PWM duty cycle is determined by the
current sense input voltage and the FB input voltage.
InternalSynchronized Slope Compensation
Built-in slope compensation circuit adds voltage ramp
onto the current sense input voltage for PWM generation.
This greatly improves the close loop stability at CCM and
prevents the sub-harmonic oscillation and thus reduces the
output ripple voltage.
Gate Drive
WIS2269 Gate is connected to an external MOSFET gate
for power switch control. Too weak the gate drive strength
results in higher conduction and switch loss of MOSFET
while too strong gate drive output compromises the EMI. A
good tradeoff is achieved through the built-in totem pole
gate design with right output strength and dead time control.
The low idle loss and good EMI system design is easier to
achieve with this dedicated control scheme. An internal 18V
clamp is added for MOSFET gate protection at higher than
expected VDD input.
Over-temperature protection
Between RT and GND, and a common thread of a NTC
resistor, can provide temperature sensing and protection.
NTC resistance with the ambient temperature rises. With a
fixed internal current flows through the resistor IRT, RT pin
voltage with temperature
The rises. Within the OTP circuit to detect the voltage is
less than VTH_OP then triggered off when the MOSFET
Protection Controls
WIS2269 provides comprehensive protection features,
the system can obtain the highest reliability. Including by-
week limit protection (OCP), over-load protection (OLP),
over-temperature protection (OTP), on-chip VDD over-
voltage protection (OVP, optional), and low-voltage
shutdown (UVLO).
When the ER into the VIN pin large, OCP threshold value
is automatically reduced. OCP threshold slope adjustment
helps compensate for over-current detection and control of
AC voltage delay caused by the increasing of the power limit.
Recommended by WIS2269 OCP compensation circuit
can obtain constant output power limit. WIS2269 OCP
protection circuitry built-in can detect the duty cycle of PWM
control signals, and through the line voltage compensation
ensure a continuous AC input voltage range was constant
output power limit.
In the case of output overload, FB bias voltage was
higher, when FB input exceeds the power limit threshold.
8 /10
Steady, keep you advance
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