U3848 [UTC]
HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS; 高性能电流模式PWM控制器
| 型号： | U3848 |
| 厂家： | 
Unisonic Technologies |
| 描述： | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| 文件： | 总13页 (文件大小：239K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
UNISONIC TECHNOLOGIES CO., LTD
U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
HIGH PERFORMANCE
CURRENT MODE PWM
CONTROLLERS
ꢀ
DESCRIPTION
DIP-8
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)
8.1V. Lower typical operation current Icc 3.7mA at inactive output.
SOP-8
*Pb-free plating product number:
U3848L/U3848AL/U3848BL/U3848CL
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
4kΩ pull up resistor to internal reference voltage. The U3848/A/B/C
also have soft-start function avoiding overshoot, and controlled
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
Package
Packing
Normal
Lead Free Plating
U3848L-D08-T
U3848L-S08-R
U3848L-S08-T
U3848AL-D08-T
U3848AL-S08-R
U3848AL-S08-T
U3848BL-D08-T
U3848BL-S08-R
U3848BL-S08-T
U3848CL-D08-T
U3848CL-S08-R
U3848CL-S08-T
U3848-D08-T
U3848-S08-R
U3848-S08-T
U3848A-D08-T
U3848A-S08-R
U3848A-S08-T
U3848B-D08-T
U3848B-S08-R
U3848B-S08-T
U3848C-D08-T
U3848C-S08-R
U3848C-S08-T
DIP-8
SOP-8
SOP-8
DIP-8
Tube
Tape Reel
Tube
Tube
SOP-8
SOP-8
DIP-8
Tape Reel
Tube
Tube
SOP-8
SOP-8
DIP-8
Tape Reel
Tube
Tube
SOP-8
SOP-8
Tape Reel
Tube
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Copyright © 2005 Unisonic Technologies Co., Ltd
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QW-R103-033.B
U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
ORDERING INFORMATION(Cont.)
U3848L-D08-T
(1)Packing Type
(2)Package Type
(3)Lead Plating
(1) R: Tape Reel, T: Tube
(2) D08: DIP-8, S08: SOP-8
(3) L: Lead Free Plating, Blank: Pb/Sn
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
PIN CONFIGURATION
SS
FB
CS
RT
1
2
3
8 VREF
V
CC
7
6
OUT
GND
4
5
ꢀ
PIN DESCRIPTION
PIN
1
SYMBOL
SS
FUNCTION
Soft-start
Feedback
2
FB
3
CS
Controller current sense input
4
RT
The resistor controlling switch frequency
Ground
5
GND
OUT
VCC
6
Output to the gate of external power MOS
Supply voltage
7
8
VREF
Inter 6.3V reference voltage, connected with the filter capacitor
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
BLOCK DIAGRAM
VREF
8
VCC
RT
4
7
UVLO
Reference voltage
Oscillator
OVP
OLP
OTP
SS
1
Soft Start
Latch
Driver
Q
OUT
S
6
3
Power-Saving
Unit
R
Q
FB
Current
Limiting
2
CS
LEB
PWM
COMP
5
GND
Explain:OLP(Over Load Protection)
OVP(Over Voltage Protection)
OTP(Over Temperature Protection)
UVLO(Under Voltage Latch-Out
LEB(Led Edge Blanking)
SS(Soft Start)
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
ABSOLUTE MAXIMUM RATINGS (Ta＝25°C, VCC=15V, RT=75kΩ, unless otherwise specified)
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage
VCC
26
V
Input Voltage to FB Pin
Input Voltage to CS Pin
Input Voltage to RT Pin
Junction Temperature
Operating Temperature
Storage Temperature
VFB
-0.3 ~ 6.2
-0.3 ~ 2.8
-0.3 ~ 6.2
+150
V
VCS
V
VRT
V
TJ
°C
°C
°C
TOPR
TSTG
-40 ~ +125
-50 ~ +150
Note Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
ꢀ
OPERATING RANGE
PARAMETER
SYMBOL
VCC
RATINGS
8.2 ~ 21
UNIT
V
Supply Voltage
ꢀ
ELECTRICAL CHARACTERISTICS (Ta＝25°C, VCC=15V, RT=75kΩ, unless otherwise specified)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX UNIT
SUPPLY SECTION
Start Up Current
ISTR
IOFF
ION
VCC=12.5V
27
3.7
4.0
45
5.5
6.0
µA
mA
mA
OFF
ON
VSS = 0, IFB = 0
Supply Current with switch
VSS = 5V, IFB = 0
UNDER-VOLTAGE LOCKOUT SECTION
Start Threshold Voltage
Min. Operating Voltage
Hysteresis
VTHD(ON)
VCC(MIN)
VCC(HY)
11.8
7.6
12.6
8.1
13.4
8.6
V
V
V
4.5
INTERNAL VOLTAGE REFERENCE
Reference Voltage
VREF measured at pin VREF
6.1
6.3
6.6
V
CONTROL SECTION
U3848/B(Note1)
85
95
68
20
70
105
75
kHz
kHz
kHz
%
Normal
VFB = 4V
VFB = 1V
Switch Frequency
F(SW)
DMAX
U3848A/C(Note2) 61
Power-Saving
17
65
0
23
MAX
75
Duty Cycle
MIN
DMIN VFB < 0.5V
%
MIN
VFB Operating Level
MAX
VMIN
VMAX
RFB
0.5
V
4.4
5.0
V
Feedback Resistor
2.6
3.8
75
kΩ
External Resistor for controlling Current
Source of OSC
RT
kΩ
CSS=0.05uF
6
ms
ms
ms
Soft-Start Time
TSS
CSS=0.1uF
CSS=1uF
12
120
PROTECTION SECTION
OVP threshold
V(OVP) VSS < 3.5V, VFB > 5V
VFB(OLP) VSS > 5.4V
T(THR)
15.2
4.4
16
4.6
135
3.9
5.1
7.2
16.8
4.9
V
V
OLP threshold
OTP threshold
120
3.7
150
4.2
°C
V
OVP Disable threshold
OLP Enable threshold
Spike Blanking time
CURRENT LIMITING SECTION
LEB
VSS(DEACT) VFB > 5V, VCC > 17V
VSS(ACT) VFB > 5V
TSB
4.9
5.4
V
µs
tLEB
220
ns
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
ELECTRICAL CHARACTERISTICS(Cont.)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
12.2
TYP
MAX UNIT
DRIVER OUTPUT SECTION
Output Voltage Low State
Output Voltage High State
VOL
VOH
ISOURCE = 200 mA
ISINK = 200 mA
CL = 1.0 nF
2.5
V
V
U3848B
U3848C
U3848/A
70
200
300
50
150
300
400
90
ns
ns
ns
ns
Output Voltage Rise Time
Output Voltage Fall Time
tR
tF
CL = 1.0 nF
CL = 1.0 nF
CL = 1.0 nF
Note: 1. RT=65kΩ should be connected for U3848/ U3848B.
2. U3848A/C denote U3848A and U3848C.
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
FUNCTIONAL DESCRIPTION
The internal reference voltages and bias circuit work at VCC>12.6V, and shutdown at VCC< 8.1V.
(1) Soft-Start
When every IC power on, driver output duty cycle will be decided by voltage VSS on soft-start capacitor and VCS on
current sense resistor at beginning. After VSS reach 5.1V, the whole soft-start phase end, and driver duty cycle
depend on VFB and VCS. The relation among VSS, VFB and VOUT as followed FIG.3, here soft-start phase Tsoft-start
should more than VOUT start-up phase Tstart-up, otherwise, IC will enter false OLP protection state. Because after the
soft-start phase end, if VOUT remain in lower voltage, VFB more than 4.6V, then IC enter false OLP state.
Furthermore, soft-start phase should end before VCC reach VCC(MIN) during VCC power on. Otherwise, if soft-start
phase remain not end before VCC reach VCC(MIN) during VCC power on, IC will enter auto-restart phase and not set up
VOUT
.
Finally soft-start also set OVP active phase. OVP active phase between VSS=0 and VSS=3.8V, OVP will not be
sensed after VSS reach 3.8V.The Soft-start phase TSS
：
6 ms
12 ms
120 ms
(CSS=0.05uF)
(CSS=0.1uF)
(CSS=1uF)
TSS
=
VSS
5.1V
TSOFT-START
t
t
VFB
4.6V
VOUT
TSTRAT-UP
t
Driver
t
FIG.3 Soft-start phase
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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=75kΩ. 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
220V
50
40
30
20
10
0
0.6 1.2 1.8 2.4
P
3
3.6 4.8
6
7.2 12
OUT(W)
(RT
=75KΩ)
FIG.4 The relation curve between fSW and output power POUT
100
90
80
70
60
50
40
30
20
10
55
95
60
65
70
75
80
85 90
RT (kΩ)
(POUT=8W)
FIG.5 The relation curve between fSW and RT
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
FUNCTIONAL DESCRIPTION(Cont.)
(3) Protection section
U3848/A/B/C takes on more protection functions such as OLP, OVP and OTP etc. In case of those failure
modes for continual 7.2µs (blanking time), the driver is shut down. At the same time, IC enters auto-restart, VCC
power on and driver is reset after VCC power on again.
OLP
After soft-start phase end (VSS>5.1V), IC will shutdown driver if over load state occurs (corresponding to
VFB>4.6V) for continual 7.2µs. OLP function will not inactive during soft-start phase. OLP case as followed FIG.6.
The test circuit as followed FIG.8 for U3848/A/B/C.
VCC
VCC
16V
12.6V
8.1V
12.6V
8.1V
Trestart
t
t
t
t
Driver
ON/OFF
t
VOUT
t
VFB
VFB
7.2µs Blanking
7.2µs Blanking
7.2µs Blanking
7.2µs Blanking
4.6V
4.6V
t
t
V
SS
V
SS
SS Phase
5.1V
5.1V
3.9V
SS Phase
OVP Phase
FIG.6 OLP case
FIG.7 OVP case
OVP
Power supply VCC’s OVP function are enabled only when VSS<3.9V & VFB>4.6V during soft-start phase. During
above condition, driver will be shutdown if over voltage state occurs (VCC>16V) for continual 7.2µs. OVP function will
not inactive after soft-start phase. OLP case as followed FIG.7. The test circuit as followed FIG.9 for U3848/A/B/C.
OTP
OTP will shut down driver when junction temperature TJ of internal circuits is more than threshold 135°C for
continual 7.2µs.
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
FUNCTIONAL DESCRIPTION(Cont.)
15V
VCC
VCC
C13
C4
C13
C4
IC3
IC3
C3
C3
5.5V
1
2
8
7
1
2
8
7
Driver
Driver
UTC
UTC
U3848/A/B/C
VFB
3.5V
U3848 /A/B/C
3
4
6
5
3
4
6
5
VFB
4.6v
VFB
16v
VCC
7.2us
7.2us
R17
RT
RT
FIG.8 OLP test circuit
(4) Driver Output Section
FIG.9 OVP test circuit
Rise edge time of driver output is about 200ns for avoiding Low EMI. When driver output VOL(MAX) is less than
2.5V with 200mA source current, and VOH(MIN) is more than 12.2V with 200mA sink current.
15v
VCC
C13
15v
VCC
C13
C4
C4
IC3
IC3
C3
C3
1
2
8
7
1
2
8
7
Isource=200mA
UTC
UTC
VFB
U3848 A/B/C
VFB
U3848 /A/B/C
VOH
VOL
(MIN )
(MIN)
3
4
6
5
3
4
6
5
Isink=200mA
R17
R17
RT
RT
FIG.10 driver test circuit with sink current
FIG.11 driver test circuit with source current
(5) External power switch MOS transistor
Because U3848/A/B/C driver output voltage Low level threshold is about 2.5V, User may apply power MOS
transistors with bigger threshold. 4N60 is recommended normally.
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
TYPICAL APPLICATION CIRCUIT
BD1
L3
D3
R12
+
D1
5V 3A
TR1
AC IN
F1
TH1
C8
RD1
+
CX1
CD1
+
C5
C9
D2
IC3
R6
GND
R7
Q1
4
3
2
5
6
UTC
U3848 /
A/B/C
7
8
R5
R
R4
R3
C15
R2
RF
C2
1
IC1
R11
C3
+ C4
R17
C14
IC2
CY1
FIG.12 U3848/A/B/C Typical Application Circuit
Table1 Components Reference description for U3848/A/B/C application circuit
D3
C12
C14
C2
CC
CC
CC
10nF/1000V
100nF/50V
33nF/50V
104/275V
1000uF/15V
22uF/50V
68uF/400V
1000uF/16V
1nF/1KV
Diode
IC
IC
IC
L
UF1007
PC817
TL431CLP
U3848/A/B/C
1.2uH
R
R
470KΩ
1/8W
IC1
IC2
IC3
L3
TH1
BD1
RD1
R12
TR1
RF
SCK-103
KBP-208
10Ω
R
R
R
CX1
C5
1/8W
1/8W
EC
CC
3.3kΩ
C4
Q1
R7
MOS
R
4N60
optional
4.7kΩ
C8
EC
68KΩ
1/8W
1/8W
1/8W
1/8W
1/8W
1/8W
R
1/8W
C9
EC
R17
R2
R
1.2Ω/1W
680Ω
C15 CC
0.1µF/50V
CD1
CY1
D1
CC
R
CC
4.7nF/250V
C63-004
R3
R
ADJ
Diode
Diode
R4
R
5.6KΩ
D2
1N4148
R5
R
5.6KΩ
Note: C5 and C9 are lower ESR capacitors.
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
TYPICAL CHARACTERISTICS(Cont.)
Feedback Voltage During Loadjump From10%
Up To 100% Load (VDCIN=120V)
Feedback Voltage During Loadjump From10%
Up To 100% Load (VDCIN=350V)
60.0mV
3.30V
120mV
3.86V
3.29kHz
1.70kHz
1.64kHz
850Hz
Ch1 max
5.90V
Ch1 max
6.00V
Ch1 min
40.0mV
Ch1 min
460mV
Ch1 frequency
1.906kHz
Ch1 frequency
785.5Hz
Ch1 1.00V
A
M 200μs
Ch1 ∫
2.68V
Ch1 1.00V
3.18V
M
400μs A Ch1 ∫
Startup With Full Load Condition At VDCIN=350V,
Vc4 and Vout
Startup With Full Load Condition At VDCIN=120V,
Vc4 and Vout
12.3V
12.3V
12.3V
12.3V
VC4
VC4
Ch1 max
5.04V
Ch1 max
5.04V
Ch1 min
-120mV
Ch1 min
1.32V
Ch1 frequency
-----Hz
Ch1 frequency
-----Hz
VOUT
VOUT
Ch1 2.00V
Ch2 5.00V
A
M 10.0ms
Ch1 ∫ 3.16V
Ch1 2.00V
Ch2 5.00V
A
Ch1 ∫ 3.16V
M 10.0ms
Startup Behavior At Nominal Load Condition VDCIN =120V
Startup Behavior At Nominal Load Condition VDCIN=350V
120mV
12.3V
240mV
12.0V
357Hz
21.2Hz
1.79kHz
147Hz
VC4
VC4
VFB
VFB
VSS
VSS
Ch1 2.00V
Ch3 2.00V
Ch2 2.00V
M 4.00ms A Ch3 ∫ 4.96V
Ch1 2.00V
Ch3 2.00V
Ch2 2.00V
M 4.00ms A Ch3 ∫ 4.96V
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U3848/A/B/C
LINEAR INTEGRATED CIRCUIT
ꢀ
TYPICAL CHARACTERISTICS(Cont.)
NO Load Input Power vs. Line Voltage
(Normal Mode)
Frequency vs. Output Power
120
1
0.9
0.8
0.7
0.6
0.5
0.4
100
80
60
Vdcin=120V
40
20
0
0.3
0.2
0.1
0
Input Power NO Load (PoUT=0W)
0
2
4
6
8
10 12 14 16 18 20
100
150
200
250
300
Output Power (W)
DC Input Voltage(V)
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
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