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SD4851
PRIMARY SIDE POWER CONTROLLER WITH BUILT-IN HIGH VOLTAGE
MOSFET
DESCRIPTION
SD4851 is primary side power controller with built-in high voltage
MOSFET. It senses the output voltage indirectly by using the
auxiliary wind of the power transformer. It adopts Pulse Frequency
Modulation (PFM) technology for flyback power supply controller.
SD4851 provides accurate constant voltage, constant current
(CV/CC) regulation for higher efficiency and higher reliability.
By using SD4851 for flyback power controller, Few peripheral
components are needed, the Opto-coupler and secondary control
circuitry is not needed and the loop compensation circuitry for
maintaining stability is also unnecessary.
DIP-8A-300-2.54
FEATURES
* Lower start-up current
* Primary side control for Constant Voltage (CV) and Constant
Current (CC)
* Leading edge blanking
* Pulse-Frequency Modulation
* Overvoltage protection
* Undervoltage lockout
* Over temperature protection
* Built-in high voltage MOSFET
* Cycle by cycle current limiting
* Open Loop Protection
* Cable drop compensation
* Peak current compensation
APPLICATIONS
* Chargers for Cell Phones
* Adapters
* MP3 and Other Portable Apparatus
* Standby Power Supply
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http: //www.silan.com.cn
REV:1.0 2009.04.27
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ORDERING INFORMATION
SD4851
Part No.
SD4851DD3
SD4851DD3G
SD4851DD35
SD4851DD35G
SD4851DD4
SD4851DD4G
Package
DIP-8A-300-2.54
DIP-8A-300-2.54
DIP-8A-300-2.54
DIP-8A-300-2.54
DIP-8A-300-2.54
DIP-8A-300-2.54
BLOCK DIAGRAM
Marking
SD4851DD3
SD4851DD3G
SD4851DD35
SD4851DD35G
SD4851DD4
SD4851DD4G
Output power
3W
3W
3.5W
3.5W
4W
4W
Material
Pb free
Halogen free
Pb free
Halogen free
Pb free
Halogen free
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http: //www.silan.com.cn
REV:1.0 2009.04.27
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SD4851
ABSOLUTE MAXIMUM RATING
Characteristics
Power Supply Voltage
Internal Voltage Reference
FB Pin Input Voltage
Other Pin Input Voltage
Input Current
Operating Junction Temperature
Operating Temperature
Storage Temperature
Symbol
VCC
VREF5V
VFB
VIN
IIN
TJ
Tamb
TSTG
Rating
-0.3~25
-0.3~5.5
-20~22
-0.3~ 5.3
-10~10
+160
-25~ +85
-55~+150
Unit
V
V
V
V
mA
°C
°C
°C
ELECTRICAL CHARACTERISTICS (for sense MOSFET part, unless otherwise specified, Tamb=25°C)
Characteristics
Drain-Source Breakdown Voltage
Zero VGATE Voltage Drain Current
Static Drain-Source On Resistance
Forward Trans-Conductance
Input Capacitance
Output Capacitance
Reverse Transfer Capacitance
Turn On Delay Time
Rise Time
Turn Off Delay Time
Fall Time
Symbol
Test conditions
BVDSS
IDSS
VGS=0V, ID=50μA
VDS=Max. VGS=0V
VDS=0.8Max. VGS=0V
Tamb=125°C
SD4851DD3,SD4851DD4,
VGS=10V, ID=0.5A
RDS(ON)
SD4851DD3, SD4851DD4,
VGS=10V, ID=0.5A
Gfs VDS=50V, ID=0.5A
Ciss
VGS=0V, VDS=25V,
f=1MHz
Coss
Crss
td(ON)
tr
td(OFF)
tf
VGS=0V, VDS=25V,
f=1MHz
Vds=0.5BVDSS, ID=25mA
Min.
700
--
--
--
--
1.5
--
--
--
--
--
--
--
Typ.
--
--
Max.
--
50
-- 200
10 12
8 10
-- --
210 --
18 --
8 --
10 --
3 --
27 --
8 --
Unit
V
μA
μA
Ω
Ω
S
pF
pF
pF
nS
ELECTRICAL CHARACTERISTICS (unless otherwise specified, VCC=16V, Tamb=25°C)
Characteristics
Supply Section
Start-up Current
Supply Current (Control Part)
Undervoltage Section
Start Threshold Voltage
Stop Threshold Voltage
Symbol
Test conditions
Istart
Iop
VCC=14V
Vstart
Vstop
Min. Typ. Max.
-- 6 20
400 600
14 16 18
789
Unit
μA
μA
V
V
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http: //www.silan.com.cn
REV:1.0 2009.04.27
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SD4851
Characteristics
Feedback Section
Enable Turn on Voltage
Over Voltage Protection
Loop Open Voltage
S&H Reference
S&H Range
Dynamitic parameter
Leading-edge Blanking Time
CV Loop Off-time
Over voltage recover time
Current Limit
Peak Current Limit
Peak Current Compensation
Cable Compensation
Cable Compensation Voltage
OTP Section
Over Temperature Detection
Over Temperature Hysteresis
PIN CONFIGURATION
Symbol
Test conditions
VFREIG
VOVP
VAUSB
VS&HREF
VS&Hub
TLEB
TCVmin
TCVmax
TOVP
FB > VS&HREF+0.2V
ISENSE
ISENSE
IPCC=0
IPCC=-1uA
VCDC RCDC=100K,DS=50%
Tsd
Tsdhys
Min. Typ. Max. Unit
50 100 140
7.8 8.8 9.8
-1.2 -1 -0.8
3.9 4.2 4.6
±0.1
mV
V
V
V
V
0.4 0.7 1.1
μs
1.0 2.8 μs
3.5 4.2 7.3 ms
11 19 30 ms
170 185 200
1.94 2.16 2.38
mA
mA
310 344 378
mV
125 140
20 35
--
50
°C
°C
PIN DESCRIPTION
Pin No.
1
2
3
4
5
6
7
8
Pin Name
PGND
SGND
VCC
FB
CDC
PCC
--
Drain
I/O Function description
- Ground for power MOSFET.
- Ground control part.
- Power Supply Pin.
I Feedback input pin.
I Cable drop compensation pin.
I Input AC line voltage compensation for peak current limiting.
-- No pin
O Drain pin.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http: //www.silan.com.cn
REV:1.0 2009.04.27
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SD4851
FUNCTION DESCRIPTION
SD4851 is designed for off-line SMPS, consisting of high voltage MOSFET, cable compensation and peak
current compensation without opto-coupler. SD4851 provides constant voltage/constant current (CV/CC) output
through primary current and auxiliary voltage. It adopts PFM technology and accurate constant voltage/constant
current (CV/CC) control loop for higher stability and efficiency.
A whole work period of SD4851 can be divided into two period sections:
When MOSFET is on, primary current is detected by sample resistor and voltage at pin FB is negative, load is
powered by output capacitor and output voltage VO decreases.
When primary current exceeds the limit, MOSFET is off and voltage at pin FB is detected. Output capacitor is
powered by secondary current and VO increases. MOSFET is on again after stop for TCV and hold for TCC.
And then, it comes to peak current detect again.
1. Under Voltage Lockout and Self-Start
At the beginning, the capacitor connected to pin VCC is charged via start resistor by high voltage DC bus and the
circuit start to work if voltage at Vcc is 16V. The output is shutdown if there is any protection during normal
operation and Vcc is decreased because of no powering of auxiliary winding. The whole control circuit is
shutdown if voltage at Vcc is 8V below to lower current dissipation and the capacitor is recharged for restarting.
2. Driver Circuit
The driver circuit is powered by VCC.
When VGATE1, the power MOSFET is on. When VGATE0, the power MOSFET is off. It is recommended to
set TLEB0.7μs to avoid error trigger caused by burr.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http: //www.silan.com.cn
REV:1.0 2009.04.27
Page 5 of 11