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PDF ( 数据手册 , 数据表 ) U3848C

零件编号 U3848C
描述 HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS
制造商 Unisonic Technologies
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U3848C 数据手册, 描述, 功能
UNISONIC TECHNOLOGIES CO., LTD
U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
HIGH PERFORMANCE
CURRENT MODE PWM
CONTROLLERS
DESCRIPTION
The UTC U3848/A/B/C is designed to provide several special
enhancements to satisfy the needs: Power-Saving mode for low
standby power, Over Current Protection (OCP), Over Voltage
Protection (OVP), Over Load Protection (OLP), Over Temperature
Protection (OTP) etc protection features. IC will be shutdown when
either protection arise and can auto-restart. Its frequency may be
defined by user through resistor RT to external ground. UVLO
featuring typical start-up current 20µA, and VCC(ON) 12.6V, VCC(OFF)
8.1 . Lower typical operation current Icc 3.7mA at inactive output.
The output stage, suitable for driving N-Channel MOSFETs, can
operate to duty cycles approach 70%. The U3848/A/B/C are fully
pin-to-pin compatible with UC3842. But pin RT only connected a
resistor to ground to decide switch frequency, and pin FB with an
4kpull up resistor to internal reference voltage. The U3848/A/B/C
also have soft-start function avoiding overshoot, and controlled
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driver output rise edge time tR for low EMI.
FEATURES
* Low startup and operation current
* User defined switching frequency(Norm is 70kHz)
* Max duty cycle 70%
* Power-saving mode for low power
* Under voltage lockout with hysteresis
* Over temperature protection
* Overload protection
* Over voltage protection
* Leading edge blanking
* Soft start
ORDERING INFORMATION
Order Number
Normal
Lead Free Plating
U3848-D08-T
U3848L-D08-T
U3848-S08-R
U3848L-S08-R
U3848-S08-T
U3848L-S08-T
U3848A-D08-T
U3848AL-D08-T
U3848A-S08-R
U3848AL-S08-R
U3848A-S08-T
U3848AL-S08-T
U3848B-D08-T
U3848BL-D08-T
U3848B-S08-R
U3848BL-S08-R
U3848B-S08-T
U3848BL-S08-T
U3848C-D08-T
U3848CL-D08-T
U3848C-S08-R
U3848CL-S08-R
U3848C-S08-T
U3848CL-S08-T
Package
DIP-8
SOP-8
SOP-8
DIP-8
SOP-8
SOP-8
DIP-8
SOP-8
SOP-8
DIP-8
SOP-8
SOP-8
www.unisonic.com.tw
Copyright © 2005 Unisonic Technologies Co., Ltd
DIP-8
SOP -8
*Pb-free plating product number:
U3848L/U3848AL/U3848BL/U3848CL
Packing
Tube
Tape Reel
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Tape Reel
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Tape Reel
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U3848C pdf, 数据表
U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
FUNCTIONAL DESCRIPTION(Cont.)
(2) Switch Frequency Set
The maximum switch frequency decided by an external resistor RT connected between pin RT and ground. Then
the maximum switch frequency will depend on user requirement. The relation curve between fSW and RT as followed
FIG.5 under the condition of POUT=8W. The equation between fSW and RT as followed (1-2) for U3848A/C, (1-3) for
U3848/B:
fSW = -0.61*RT+115.7--------------------------(1-2)
fSW = -1.1*RT+167.5--------------------------(1-3)
After RT connected, switch frequency is also modulated by output power POUT during IC operating. So lower switch
frequency at lower load, which more and more improve IC’s efficiency at light load. Switch frequency is decreased
minimum at no load, then the U3848/B will operate at Power-Saving mode for Lower standby power. The relation
curve between fSW and POUT as followed FIG.4 under the condition of RT=75k. The frequency wave of U3848A/C is
similar with U3848/B’s, and for them, maximum frequency point is 70kHz.
90
80
70
60
110V
50
40 220V
30
20
10
0 0.6 1.2 1.8 2.4 3 3.6 4.8 6 7.2 12
POUT(W)
(RT=75K)
FIG.4 The relation curve between fSW and output power POUT
100
90
80
70
60
50
40
30
20
10
55 60 65 70 75 80 85 90
RT (k )
( POUT=8W)
FIG.5 The relation curve between fSW and RT
95
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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