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PDF NCP4302 Data sheet ( Hoja de datos )
| Número de pieza | NCP4302 | |
| Descripción | Synchronous Rectification Controller | |
| Fabricantes | ON Semiconductor | |
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NCP4302
Secondary Side
Synchronous Flyback
Controller
The NCP4302 is a full featured controller and driver that provide all
the control and protection functions necessary for implementing a
synchronous rectifier operation in a flyback converter. With the use of
the NCP4302, the space conscious flyback applications such as
Adaptors, chargers, set top boxes can achieve significant efficiency
improvements at minimal extra cost. In addition to the synchronous
rectifier control, the IC incorporates an accurate TL431 type shunt
regulator, current monitoring circuit and optocoupler driver to provide
a single IC secondary solution. The NCP4302 works with any type of
flyback topology (continuous mode, Quasi−resonant mode or
discontinuous mode) – providing a high level of versatility.
8
1
http://onsemi.com
SO−8
D SUFFIX
CASE 751
MARKING
DIAGRAM
8
4302x
ALYW
G
1
Features
• Self−contained Control of Synchronous Rectifier in CCM, DCM, and
QR Flyback Applications
• Interface to External Signal for CCM Mode
• True Secondary Zero Current Detection
• High Gate Drive Currents (2.5 A Source/Sink)
• High Voltage Operation
• Current Sense Flexibility (MOSFET RDS(on) OR CS Resistor)
• Accurate Low Voltage Reference
− NCP4302A 2.55 V, 1%
− NCP4302B 1.275 V, 1%
• Programmable Independent Secondary Side ton and toff Delays
• Maximum Frequency of Operation up to 250 kHz
Typical Applications
• Notebook Adapters
• LCD TV Adapters
• Consumer Appliances such as DVD, VCR
• Power Over Ethernet Applications (IP phones, Wireless Access
Points)
• Battery Chargers
• This is a Pb−Free Device
x = Reference Voltage (A or B)
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
PIN CONFIGURATION
SYNC/CS 1
TRIG 2
CATH 3
VREF 4
8 VCC
7 DRV
6 GND
5 DLYADJ
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
NCP4302ADR2G SO−8 2500/Tape & Reel
(Pb−Free)
NCP4302BDR2G SO−8 2500/Tape & Reel
(Pb−Free)
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2007
April, 2007 − Rev. 0
1
Publication Order Number:
NCP4302/D
1 page  
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NCP4302
ELECTRICAL CHARACTERISTICS
(VCC = 19 V, Sync frequency = 100 kHz, VREF = VKA (IKA = 1 mA), RS = 75 ohms, VTRIG = GND, CDRV = 1 nF, RDLYADJ = 30.1 k,
VDLYADJ = 2.0 V, for typical values TJ = 25°C, for min/max values TJ = −5°C to +85°C, Max TJ = 150°C, unless otherwise noted)
Rating
Test Conditions
Symbol Min Typ Max Unit
VCC
Start−up Threshold
VCC ↑, SYNC/CS = 0 to −0.5 V
100 kHz, 5 ms pulse, Trig = 0 V
VCC(on)
9.6 10.4 11.2 V
Stop Threshold
VCC ↓, SYNC/CS = 0 to −0.5 V
100 kHz, 5 ms pulse, Trig = 0 V
VCC(off) 8.5 9.2 − V
VCC shutdown Hysteresis
Supply current after turn−on
VCC(on) – VCC(off)
VCC(HYS)
0.9
1.2
1.4
V
no−load on DRV pin, SYNC/CS = 0 to
−0.5 V 100 kHz, 5 ms pulse, Trig = 0 V
ICC1
− 2.7 5.6 mA
Supply current after turn−on
SYNC/CS = 0 to −0.5 V 100 kHz, 5 ms
pulse, Trig = 0 V
ICC2
− 3.6 7.5 mA
DRIVE OUTPUT
Output voltage rise−time
10−90% of the output signal SYNC/
CS = 0 to −0.5 V 100 kHz, 5 ms pulse,
Trig = 0 V
tr
− − 40 ns
Output voltage fall−time
10−90% of the output signal SYNC/
CS = 0 to −0.5 V, 100 kHz, 5 ms pulse,
Trig = 0 V
tf
− − 40 ns
Output source current (Note 3)
IDRV(source)
−
2.5
− Apk
Driver high level output voltage
ISOURCE = 200 mA, SYNC/CS = 0 to VDRV(H) 6.5 9.5 − V
−0.5 V 100 kHz, 5 ms pulse, Trig = 0 V,
VCC = 12 V
Output sink current (Note 3)
IDRV(sink)
−
2.5
− Apk
Driver Output low level output volt-
age
ISINK = 200 mA, SYNC/CS = 0 to
−0.5 V 100 kHz, 5 ms pulse, Trig = 0 V,
VCC = 12 V
VDRV(L)
− 160 500 mV
Drive voltage internal clamp
VCC = 28 V, SYNC/CS = 0 to −0.5 V
100 kHz, 5 ms pulse, Trig = 0 V,
DRVpin = 10 kW
VDRV(CLMP)
−
− 17 V
Minimum drive output voltage
VCC = VCC(off) + 200 mV, DRV pin =
VDRV(MIN)
5.5
6.5
−
V
10 kW + 1 nF, SYNC/CS = 0 to −0.5 V
100 kHz, 5 ms pulse, Trig = 0 V
SYNC/CS
The total propagation delay from
SYNC/CS to the DRV output
SYNC/CS = +0.5 V to −0.5 V 100 kHz,
5 ms pulse, (Trig = 0 V)(Refer to the
Drive Output specifications for Tr 50%
of the output signal
tp1
− 70 135 ns
Zero Current Detection
Current Sense Pin Offset Voltage at
Zero Current Level (Note 3)
SYNC/CS Leakage current
VSYNC/CS < −30 mV
VSYNC/CS = 95 V
Is(zcd)
50 230 450 mA
VS(ZCD)
−30
−
− mV
SCSLeakage
−
− 10 mA
TRIGGER SECTION
Minimum Trigger pulse duration
3. Guaranteed by Design
SYNC/CS = 0 to −0.5 V 100 kHz,
5Ăms pulse, Trig ↑
trig−pw
75
−
− ns
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5
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NCP4302
Detailed Operating Description
The NCP4302 is designed to operate either as a standalone
IC or as a companion IC to a primary side controller to help
achieve efficient synchronous rectification for flyback
converter systems. It has high current gate driver along with
fast logic circuitry to provide appropriately timed drive
signals to a synchronous MOSFET used for output
rectification in a flyback converter. With its novel
architecture, the NCP4302 has enough versatility to increase
the synchronous rectification efficiency under any operating
mode without requiring too much complexity.
Supply Section
The NCP4302 works from an available bias supply that
can range from 10.4 V to 28 V (typical). This allows direct
connection to the output voltage of many adapters such as
notebook and LCD TV adapters. As a result, the NCP4302
simplifies circuit operation compared to other devices
which require specific bias power supplies (e.g. 5 V). The
high voltage capability of the VCC is also a unique feature
designed to allow operation across a broader range of
applications. To prevent gate signal from operating under
inadequate bias conditions, the NCP4302 features a UVLO
circuit that turns on at 10.4 V (VCC rising) typical and turns
off at 9.2 V typical (VCC falling).
Gate Drive Section
The NCP4302 features high current gate drivers
delivering up to (>2.5 A peak) to achieve fast turn−on and
turn−off requirements in a synchronous rectifier. Having a
high gate drive current enables fast turn−on when SYNC/CS
signal is received (to minimize body diode conduction at the
peak of the current waveform) and fast turn−off when zero
current or a TRIG signals are received (to prevent current
reversal or cross conduction). The higher sink current also
allows the MOSFET to be kept off during the instances when
there is high dv/dt on the drain.
The gate voltage is clamped at 13.5 V typical to prevent
larger excursion of gate voltage than needed when VCC is
operating from a 28 Vdc output.
The propagation delays through the logic circuits and the
gate drivers are kept at a minimum as shown in the
specification table.
45.0 V
SYNC/CS Input
In a synchronous rectification application after the
primary side MOSFET is turned−off, the current in the
secondary of the flyback transformer initially flows through
the synchronous rectification MOSFET’s internal body
diode. When this occurs, the drain of the MOSFET will be
−0.5 to −1.0 V negative with respect to ground (the VF of the
internal body diode) and the NCP4302 current sense
differential amplifier will output a 230 mA current (typical).
This current detection method is used by the NCP4302 to
determine when current is flowing in the secondary of the
transformer and the Synchronous Rectification MOSFET
needs to be turned−on.
The zero current detection senses the current with a slight
negative offset so that the switch turn−off occurs without
reversal of the current.
R2 75
Cout Vout
Current Sense Amplifier
Mirror
To Reset
Dominant
Flip−Flop
Figure 25. Input Current Sense
Adjustable ton Delay
The SYNC/CS input to the NCP4302 is used as a Reset
(through logic) input to the drive enable Flip Flop; refer to
the internal block diagram of the NCP4302. When current
flows in the secondary of the Flyback transformer any
parasitic inductance due to printed wiring board traces, or
component lead can cause the voltage at the SYNC/CS input
to ring above ground (refer to Figure 26). This ringing may
cause the controller dive output to turn−off. To eliminate this
problem the NCP4302 has a programmable ton time which
blanks the secondary voltage ringing by adding a minimum
controller drive on time.
37.5 V
25.0 V
12.5 V
0V
V(U1:4) 60 ms
70 ms
80 ms
90 ms
100 ms
110 ms
Figure 26. Discontinuous Conduction Mode Drain Waveform
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11
120 ms Time
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| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet NCP4302.PDF ] | |
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