UNISONIC TECHNOLOGIES CO., LTD
U3848/A/B/C
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 R
T
to external ground. UVLO
featuring typical start-up current 20µA, and V
CC(ON)
12.6V, V
CC(OFF)
8.1V. 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 R
T
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 t
R
for low EMI.
LINEAR INTEGRATED CIRCUIT
DIP-8
SOP -8
*Pb-free plating product number:
U3848L/U3848AL/U3848BL/U3848CL
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
www.unisonic.com.tw
Copyright © 2005 Unisonic Technologies Co., Ltd
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
Packing
Tube
Tape Reel
Tube
Tube
Tape Reel
Tube
Tube
Tape Reel
Tube
Tube
Tape Reel
Tube
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QW-R103-033.B
U3848/A/B/C
ORDERING INFORMATION(Cont.)
U3848L-D08-T
(1)Packing Type
(2)Package Type
(3)Lead Plating
LINEAR INTEGRATED CIRCUIT
(1) R: Tape Reel, T: Tube
(2) D08: DIP-8, S08: SOP-8
(3) L: Lead Free Plating, Blank: Pb/Sn
UNISONIC TECHNOLOGIES CO., LTD
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2 of 13
QW-R103-033,B
U3848/A/B/C
PIN CONFIGURATION
LINEAR INTEGRATED CIRCUIT
SS 1
8 V
REF
FB 2
7 V
CC
CS 3
6 OUT
R
T
4
5 GND
PIN DESCRIPTION
PIN
1
2
3
4
5
6
7
8
SYMBOL
SS
FB
CS
R
T
GND
OUT
V
CC
V
REF
FUNCTION
Soft-start
Feedback
Controller current sense input
The resistor controlling switch frequency
Ground
Output to the gate of external power MOS
Supply voltage
Inter 6.3V reference voltage, connected with the filter capacitor
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QW-R103-033,B
U3848/A/B/C
BLOCK DIAGRAM
LINEAR INTEGRATED CIRCUIT
V
CC
7
V
REF
8
R
T
4
OVP
OLP
OTP
UVLO
Reference voltage
Oscillator
SS
1
Soft Start
Latch
S Q
Power-Saving
Unit
Driver
6
OUT
R
Q
FB
2
PWM
COMP
Current
Limiting
LEB
3
CS
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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QW-R103-033,B
U3848/A/B/C
PARAMETER
LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATINGS
(Ta＝25°C, V
CC
=15V, R
T
=75kΩ, unless otherwise specified)
SYMBOL
RATINGS
UNIT
Supply Voltage
V
CC
26
V
Input Voltage to FB Pin
V
FB
-0.3 ~ 6.2
V
Input Voltage to CS Pin
V
CS
-0.3 ~ 2.8
V
Input Voltage to RT Pin
V
RT
-0.3 ~ 6.2
V
Junction Temperature
T
J
+150
°C
Operating Temperature
T
OPR
-40 ~ +125
°C
Storage Temperature
T
STG
-50 ~ +150
°C
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
Supply Voltage
SYMBOL
V
CC
RATINGS
8.2 ~ 21
UNIT
V
ELECTRICAL CHARACTERISTICS
(Ta＝25°C, V
CC
=15V, R
T
=75kΩ, unless otherwise specified)
PARAMETER
SUPPLY SECTION
Start Up Current
Supply Current with switch
SYMBOL
I
STR
I
OFF
I
ON
TEST CONDITIONS
V
CC
=12.5V
V
SS
= 0, I
FB
= 0
V
SS
= 5V, I
FB
= 0
MIN
TYP
27
3.7
4.0
11.8
7.6
12.6
8.1
4.5
6.3
95
68
20
70
MAX
45
5.5
6.0
13.4
8.6
UNIT
µA
mA
mA
V
V
V
V
kHz
kHz
kHz
%
%
V
V
kΩ
kΩ
ms
ms
ms
16.8
4.9
150
4.2
5.4
V
V
°C
V
V
µs
ns
OFF
ON
UNDER-VOLTAGE LOCKOUT SECTION
Start Threshold Voltage
V
THD(ON)
Min. Operating Voltage
V
CC(MIN)
Hysteresis
V
CC(HY)
INTERNAL VOLTAGE REFERENCE
Reference Voltage
V
REF
measured at pin V
REF
CONTROL SECTION
U3848/B(Note1)
Normal
V
FB
= 4V
Switch Frequency
F
(SW)
U3848A/C(Note2)
Power-Saving
V
FB
= 1V
MAX
D
MAX
Duty Cycle
MIN
D
MIN
V
FB
< 0.5V
MIN
V
MIN
V
FB
Operating Level
MAX
V
MAX
Feedback Resistor
R
FB
External Resistor for controlling Current
R
T
Source of OSC
C
SS
=0.05uF
Soft-Start Time
T
SS
C
SS
=0.1uF
C
SS
=1uF
PROTECTION SECTION
OVP threshold
V
(OVP)
V
SS
< 3.5V, V
FB
> 5V
OLP threshold
V
FB(OLP)
V
SS
> 5.4V
OTP threshold
T
(THR)
OVP Disable threshold
V
SS(DEACT)
V
FB
> 5V, V
CC
> 17V
OLP Enable threshold
V
SS(ACT)
V
FB
> 5V
Spike Blanking time
T
SB
CURRENT LIMITING SECTION
LEB
t
LEB
6.1
85
61
17
65
0
0.5
2.6
6.6
105
75
23
75
3.8
75
6
12
120
4.4
5.0
15.2
4.4
120
3.7
4.9
16
4.6
135
3.9
5.1
7.2
220
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R103-033,B
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