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N3856P PDF даташит

Спецификация N3856P изготовлена ​​​​«NIKO-SEM» и имеет функцию, называемую «Synchronous Rectification Controller».

Детали детали

Номер произв N3856P
Описание Synchronous Rectification Controller
Производители NIKO-SEM
логотип NIKO-SEM логотип 

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N3856P Даташит, Описание, Даташиты
NIKO-SEM Synchronous Rectification Controller N3856V
N3856P
GENERAL DESCRIPTION
The N3856 is a low cost , high efficiency, full
featured ,synchronous re ctification control ler
that specifically des igned for the synchronous
rectification applications of the Flyback AC/DC
PWM mode switching power supply .
The N3856 is included a totem pole output
ideally suited for driving a synchronous rectifi-
cation power MOSFET . 2 way of the current
detect provided for wide applications by any
continuous or disco tinuous mode operating
(patent pending).In cont inuous mode operatin-
g, it included a timi ng control to adjust
maximum turn-on duty to allow the designer to
determine the optimal condition for the best
efficiency by the external resistor and
capacitor. In disconti nuous mode operating, it
included a very sensitive current
detector
(about 20mV) to cont rol the synchronous
rectification MOSFET, avoid happening a large
reverse current via the synchronous
rectification MOSFET to damage the device.
FEATURES
High efficiency operating.
Adjustable Max. duty cycle designed.
Decrease areas of heatsink or PCB.
Solved heat dissipation.
Sensitive current detecter(about 20mV)
Suited for continuous and discontinuous
mode operation.
Auto frequency tracking with PWM
frequency.
Suited for fixed or variable frequency
SOIC-8 and DIP-8 package.
APPLICATION
Flyback AC/DC power supply
DEVICE SELECTION GUIDE
DIP- 8
N3856PG
SOIC- 8
N3856VG
ABSOLUTE MAXIMUM RATING
PARAMETERS SYMBOL
Vcc to GND
Surge Voltage of VCC(below 200nS)
Drain to Other Pin
Power Dissipation at Ta = 25 ,Derate 8mW/ for Ta
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature (Soldering) 10 sec
25
VCC
VCC(surge)
PD
Tj
TSTG
TLEAD
REV : 1.1
1
LIMITS
-0.3 to 30
45
180
725
-40 to +150
-65 to +150
300
UNITS
V
Vp-p
V
mW
DEC-14-2004
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N3856P Даташит, Описание, Даташиты
NIKO-SEM Synchronous Rectification Controller N3856V
N3856P
ELECTRICAL CHARACTERISTICS (TC = 25 °C)
PARAMETER
TEST CONDITIONS
Supply Voltage
Supply Current
GATE Sink Current
GATE Source Current
Rise Time
Fall Time
Delay Time
Max Duty Cycle
Vcc
CL= 1.0nF
CL= 1.0nF
LIMITS
MIN TYP
7 12
- 4.5 -
1
1
40
40
200
90 95
MAX
30
300
UNIT
V
mA
A
A
nS
nS
nS
%
BLOCK DIAGRAM
VCC
PGND
D
10K
RT/CT
DRAIN
OSC
1/3 VCC
COMP.
BUFFER
DRIVER
20mV
ADJ.
SLOPE CURRENT DETECTER
GND
Aout
GATE
BIAS
REV : 1.1
2 DEC-14-2004









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N3856P Даташит, Описание, Даташиты
NIKO-SEM Synchronous Rectification Controller N3856V
N3856P
OPERATION DESCRIPTION
•Discontinuous mode
In discontinuous mode application, the N3856 is detecting the MOSF ET current to control the
MOSFET be ON or OFF by a inte rnal current detecter , in discontinuous mode , the current of
the secondary winding flows thr ough the Source and Drain of t he MOSFET is changing from
maximum level to zero , It cause a voltage drop of the MOSFET from the maximum level
down to zero , the voltage drop is compared with internal refe rence voltage 20mV, if voltage
dropout is over 20mV ,will make the MOSFET tu rn-on, if the voltage drop is under 20mV, will
make the MOSFET become turn-off.
For the various MOSFET applications , different R DS(ON) will cause a different voltage drop
between the MOSFET,s Source and Drain , the BIAS pin provided the “adjustable slope”
function delaying turn-off the MOSFET for bette r efficiency , BAIS pin connected a resistor
with VCC used to adjust the gate output slope , change the resistance will get the different
slope ,a higher resistance will get the smoother slope, and MOSFET turn-off become slower ,
a smaller resistance will get the sharper slope , and MOSFET turn-off become quicker .
Considering of Bias setting, first, adjust output to heavy load but still in discontinuous mode ,
changing the Bias resistor make the Gate wa veform of MOSFET is sloping to connect the
resonant waveform of LC tank of the output circuit, second,adjust output to the minimum load
and check the Gate waveform is OK or not , to decrease the resistance until waveform is
normal .
•Continuous mode
In continuous mode application , the current detecter can not turn-off the MOSFET directly,
the N3856 provided two way to turn off the MO SFET in good time, one is the “maximum duty
control” function by RT/CT ,In low line AC i nput voltage and maximum loading to adjust RTor
CT will determine the maximum duty and timely turn off the MOSFET, another is using
a synchronous signal from the primary side to control the Aout pin , pull Aout pin to low will
turn off the output of Gate driver . Aout pi n can be used to increase Gate drive capability
when two parallel MOSFET application , connected a resistor to VCC if need .
REV : 1.1
3 DEC-14-2004










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Номер в каталогеОписаниеПроизводители
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NIKO-SEM
N3856VSynchronous Rectification ControllerNIKO-SEM
NIKO-SEM

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