UC3846

UNISONIC TECHNOLOGIES CO., LTD
UC3846
LINEAR INTEGRATED CIRCUIT
CURRENT MODE PWM
CONTROLLER

DIP-16
DESCRIPTION
The UTC UC3846 control IC offers all necessary features for
accomplishment of fixed frequency, current mode control functions,
however it contains the least external parts. The performance of this
technique is superior to the others in better line regulation,
enhanced load response characteristics while designing a simpler
and easier control loop for design. It owns topological advantages of
inherent pulse-by-pulse current limiting, automatic symmetry
correction for push-pull converters, and the ability to parallel “power
modules" for equal current sharing.
Protection loop includes soft start, built-in under-voltage lockout
and programmable current limit. The shutdown circuitry can
provide either a complete shutdown with automatic restart or the
supply off-latch.
In addition, many other features can also be available, including
fully latched operation, double pulse suppression, deadline adjust,
and a ±1% trimmed bandgap reference.
The UTC UC3846 features low outputs in the OFF state.

SOP-16W
FEATURES
* Built-in under-voltage lockout
* Soft start
* Shutdown function
* 500kHZ operation
* Feed forward compensation
* ±1% bandgap reference
* Programmable pulse-by-pulse current limiting

SOP-16
* Improved load response characteristics
* Parallel operation capability for modular power systems
* Differential current sense amplifier with wide common mode
range
* Double pulse suppression
* 500mA (Peak) totem-pole outputs
* Automatic symmetry correction in push-pull configuration
ORDERING INFORMATION
Ordering Number
Lead Free
Halogen Free
UC3846L-D16-T
UC3846G-D16-T
UC3846L-S16-T
UC3846G-S16-T
UC3846L-S16-R
UC3846G-S16-R
UC3846L-S16W-T
UC3846G-S16W-T
UC3846L-S16W-R
UC3846G-S16W-R
Package
Packing
DIP-16
SOP-16
SOP-16
SOP-16W
SOP-16W
Tube
Tube
Tape Reel
Tube
Tape Reel
UC3846G-D16-T
(1)Packing Type
(1) T: Tube, R: Tape Reel
(2)Package Type
(2) D16: DIP-16, S16: SOP-16, S16W: SOP-16W
(3)Green Package
(3) G: Halogen Free and Lead Free, L: Lead Free
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Copyright © 2020 Unisonic Technologies Co., Ltd
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QW-R103-061.E
UC3846

LINEAR INTEGRATED CIRCUIT
MARKING
DIP-16
13
12
11
10
9
□
□
UTC
UC3846
1

2
3
4
5
6
7
8
16 15 14
Date Code
12
11
10
9
Date Code
L: Lead Free
G: Halogen Free
Lot Code
UTC
UC3846
L: Lead Free
G: Halogen Free
Lot Code
1
2
3
4
5
6
7
8
PIN CONFIGURATION
C/S SS 1

13
□
□
16 15 14
SOP-16 / SOP-16W
16
Shutdow
n
VREF
2
15 VIN
C/S-
3
14 B Out
C/S+
4
13 VC
E/A+
5
12 GND
E/A-
6
11 A Out
COMP
7
10 Sync
CT
8
9 RT
PIN DESCRIPTION
PIN NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PIN NAME
C/S SS
VREF
C/SC/S+
E/A+
E/ACOMP
CT
RT
SYNC
A OUT
GND
VC
B OUT
VIN
SHUTDOWN
DESCRIPTION
Adjustment of Current Limiting
Internal Reference Voltage
Forward Input of Current Limiting
Backward Input of Current Limiting
Forward Input of Error Amplifier
Backward Input of Error Amplifier
Output of Error Amplifier
External Capacity for Frequency
External Resistor for Frequency
Synchronization for Frequency of Oscillator
Dual Output A
Ground
Power Supply of the Collector
Dual Output B
DC Power Supply Input
Shutdown Controller
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QW-R103-061.E
UC3846

LINEAR INTEGRATED CIRCUIT
BLOCK DIAGRAM
VIN 15
2
VREF
SYNC 10
T
OSC
CT 8
C/S- 3
-
C/S+ 4
+
Q
Q
11
A OUT
14
B OUT
12
GND
DUAL
+
- COMP
SR
Q
S
0.5V
E/A- 6
VC
OUTPUT
A
E/A+ 5
13
UVLO
LOCKOUT
RT 9
VREF
+
EA
-
0.5mA
1
+
-
COMP 7
UNISONIC TECHNOLOGIES CO., LTD
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350mV
16
C/S SS
SHUTDOWN
6KΩ
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UC3846

LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATING (Note)
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage (Pin 15)
VIN
+40
V
Collector Supply Voltage (Pin 13)
VC
+40
V
Output Current, Source or Sink (Pins 11, 14)
IO
500
mA
Analog Inputs (Pins 3, 4, 5, 6, 16)
VA
-0.3 ~ +VIN
V
Reference Output Current (Pin 2)
IREF
-30
mA
Sync Output Current (Pin 10)
ISYNC-OUT
-5
mA
Error Amplifier Output Current (Pin 7)
IO-EA
-5
mA
Soft Start Sink Current (Pin 1)
ISINK
50
mA
Oscillator Charging Current (Pin 9)
IOSC
5
mA
TA=25°C
1000
mW
Power Dissipation
PD
TC=25°C
2000
mW
Storage Temperature
TSTG
-65 ~ +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.

ELECTRICAL CHARACTERISTICS
(TJ=TA=0°C~+70°C, VIN=15V, RT=10k, CT=4.7nF, Unless otherwise specified)
PARAMETER
REFERENCE SECTION
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Short Circuit Output Current
OSCILLATOR SECTION
Initial Accuracy
Voltage Stability
Temperature Stability
Sync Output High Level
Sync Output Low Level
Sync Input High Level
Sync Input Low Level
Sync Input Current
ERROR AMP SECTION
Input Offset Voltage
Input Bias Current
Input Offset Current
Common Mode Range
Open Loop Voltage Gain
Unity Gain Bandwidth
CMRR
PSRR
Output Sink Current
Output Source Current
High Level Output Voltage
Low Level Output Voltage
SYMBOL
VREF
ΔV1
ΔV2
VS
VREF-O
VN
ΔV3
IS
FOSC
ΔV
ΔTS
VOH(SYNC)
VOL(SYNC)
VIH(SYNC)
VIL(SYNC)
ISYNC
VIO
IBIAS
IIO
VCM
GVO
B
CMRRA
PSRRA
ISINK
ISOURCE
VOH
VOL
TEST CONDITIONS
TJ=25°C, IO=1mA
VIN=8V~40V
IL=1mA~10mA
Over Operating Range, (Note 2)
Line, Load, and Temperature (Note 2)
10Hz≤f≤10kHz, TJ=25°C (Note 2)
TJ=125°C, 1000 Hrs. (Note 2)
VREF=0V
TJ=25°C
VIN=8V~40V
Over Operating Range (Note 2)
TYP
5.0
5.1
5
3
0.4
4.95
-10
39
3.9
Pin 8=0V
Pin 8=0V
Sync Voltage=3.9V, Pin 8=0V
100
5
-45
VIN=8V~40V
∆VO=1.2~3V, VCM=2V
TJ=25°C (Note 2)
VCM=0V~38V, VIN=40V
VIN=8V~40V
VID=-15mV~-5V, VPIN 7=1.2V
VID=15mV~5V, VPIN 7=2.5V
RL=(Pin 7) 15kΩ
MAX UNIT
5.2
20
15
V
mV
mV
mV/°C
5.25
V
µV
mV
mA
43
-1
-1
4.35
2.3
47
2
2.5
1.3
2.5
1.5
kHz
%
%
V
V
V
V
mA
3.9
0.5
-0.6
40
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MIN
0
80
0.7
75
80
2
-0.2
4.3
105
1.0
100
105
6
-0.5
4.6
0.7
10
-2
250
VIN-2V
1
mV
µA
nA
V
dB
MHz
dB
dB
mA
mA
V
V
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UC3846

LINEAR INTEGRATED CIRCUIT
ELECTRICAL CHARACTERISTICS (Cont.)
PARAMETER
SYMBOL
CURRENT SENSE AMPLIFIER SECTION
Amplifier Gain
GA
Maximum Differential Input
VIN(MAX)
Signal (VPIN 4-VPIN 3)
Input Offset Voltage
VIO
CMRR
CMRRA
PSRR
PSRRA
Input Bias Current
IBIAS
Input Offset Current
IIO
Input Common Mode Range
ΔVR
Delay to Outputs
tD
CURRENT LIMIT ADJUST SECTION
Current Limit Offset
VL
TEST CONDITIONS
MIN
TYP
VPIN 3=0V, Pin 1 Open (Note 3, 4)
2.5
2.75
Pin 1 Open (Note 3), RL (Pin 7)=15kW
1.1
1.2
VPIN 1=0.5V, Pin 7 Open (Note 3)
VCM=1V~12V
VIN=8V~40V
VPIN 1=0.5V, Pin 7 Open (Note 3)
VPIN 1=0.5V, Pin 7 Open (Note 3)
60
60
5
83
84
-2.5
0.08
VPIN 3=0V, VPIN 4=0V, Pin 7 Open
(Note 3)
VPIN 5=VREF,VPIN 6=0V
0.45
3.0
V
V
200
-10
1
VIN-3
500
mV
dB
dB
µA
µA
V
ns
0.5
0.55
V
0
TJ=25°C, (Note 2)
MAX UNIT
25
Input Bias Current
IB
-10
-30
µA
SHUTDOWN TERMINAL SECTION
Threshold Voltage
VTH
250
350
550
mV
Input Voltage Range
ΔVSHUT
0
VIN
V
Minimum Latching Current
ILATCH
(Note 6)
3.0
1.5
mA
(IPIN 1)
Maximum Non-Latching
INONLATCH (Note 7)
1.5
0.8
mA
Current (IPIN 1)
Delay to Outputs
tD-SHUT
TJ=25°C (Note 2)
300
600
ns
OUTPUT SECTION
Collector-Emitter Voltage
VT
40
V
Collector Leakage Current
IL
VC=40V (Note 5)
200
µA
VOL1
ISINK=20mA
0.1
0.4
V
Output Low Level
VOL2
ISINK=100mA
0.4
2.1
V
VOH1
ISOURCE=20mA
13
13.5
V
Output High Level
VOH2
ISOURCE=100mA
12
13.2
V
Rise Time
tR
CL=1nF, TJ=25°C (Note 2)
50
300
ns
Fall Time
tF
CL=1nF, TJ=25°C (Note 2)
50
300
ns
UNDER-VOLTAGE LOCKOUT SECTION
Start-Up Threshold
VSTART
7.7
8.0
V
Threshold Hysteresis
VH
0.75
V
TOTAL STANDBY CURRENT
Supply Current
IT
17
21
mA
Notes: 1. All voltages are with respect to Ground, Pin 13. Currents are positive into, negative out of the speficied
terminal.
2. These parameters are not 100% tested in production, although guaranteed over the recommended
operating conditions
3. Parameter measured at trip point of latch with VPIN 5=VREF, VPIN 6=0V.
ΔVPIN7
4.
Amplifier gain defined as: G=
, VPIN4=0~1.0V
ΔVPIN4
5. Applies to UTC UC3846 only due to polarity of outputs.
6. Current into Pin 1 guaranteed to latch circuit in shutdown state.
7. Current into Pin 1 guaranteed not to latch circuit in shutdown state.
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QW-R103-061.E
UC3846
TEST CIRCUIT
VREF
9
Sawtooth
8
Comp
(Pin 8)
RT
7.5mA
Osc
CT
(Pin 10)
10
Output Deadtime (τd)
Sync
ID
Output deadtime is determined by the external capacitor, CT, according to the formula: τd (µs)=145CT (µf)〔 ID - 3.6
RT(kΩ)
ID = Oscillator discharge current at 25°C is typically 7.5.
〔

LINEAR INTEGRATED CIRCUIT
Figure 1. Oscillator Circuit
VREF
VREF
5
0.5mA
+
EA
6
ZS
7
Comp
ZF
IF<0.5mA
Error Amplifier can source up to 0.5mA
Figure 2. Error Amp Output Configuration
IS
RS
(+)4
ISENSE
(-)3
A
+
VREF
0.5mA
0.5V
R1
1
EA
Current
Limit
R2
Comp
-
Comp
7
Peak Current (Is) is determined by the formula: IS=
R2 VREF
-0.5
R1+R2
3RS
Figure 3. Pulse by Pulse Current Limiting
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QW-R103-061.E
UC3846

LINEAR INTEGRATED CIRCUIT
TEST CIRCUIT (Cont.)
VREF
ISENSE
Comp
R1
C
1 Current
Limit
*
0.5
S
S
EA
R2
VREF
16
Shutdown
-
+
+
350mV
Shutdown With Auto-Restart
Current Limit
(Pin 1)
0.5V
Shutdown Without Auto-Restart
(Latched)
0
Shutdown
(Pin 16)
ON
OFF
PWM
VREF
< 0.8mA
R1
If
VREF
< 0.8mA, the shutdown latch will commutate when
R1
ISS=0.8mA and a restart cycle will be initiated.
VREF
(Latched Off)
R1 > 3mA
VREF
If R1 > 3mA, the device will
latch off until power is recycled.
Figure 4. Soft Start and Shutdown /Restart Functions
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QW-R103-061.E
UC3846

LINEAR INTEGRATED CIRCUIT
TYPICAL APPLICATION CIRCUIT
+5V
R1
9
150K
2C
B
Q8
2N222 1
3E
VR1
R2 10K
+C1
0.1µF
4 C/S+
6 E/AC2
R5 103P
47K
R6
2.2K
7 COMP
R4
2.2K +5V
R3
400R
VIN
+12V
15
+
C5
0.1µF
Sync
Sync 10
Shut 16
R7
+
C6
0.1µF
VR2
1K 5 E/A+
+5V
VREF
+ C4
CT
0.1µF
510R
VREF
8
UTC UC3846
2
RT
VREF
VC
13
VR4
1K
2K
+5V
+12V
+C7
1µF
VR3
1K
+
1 C/S
C3
0.1µF
B Out 14
A Out 11
GND 12
C/S- 3
Out A
R8
Out B
VR5
2K
2.1K
+5V
R9
390R
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UC3846

LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS
Rising Time
Falling Time
VIN&VDD=15V,AOUT=1nF,
CT=4.7nF, RT=10KΩ, output fall
time from 90%~ 10%.
5V/div
5V/div
VIN&VDD=15V, AOUT=1nF,
CT=4.7nF, RT=10KΩ, output rise
time from 10%~ 90%.
0
0
500
Time (100ns/div)
0
1000
0
VIN=8V, CT=4.7nF,
RT=10KΩ
0
0
50
Time (10µs/div)
1000
Voltage Stability
1V/div
1V/div
Voltage Stability
500
Time (100ns/div)
100
VIN=40V, CT=4.7nF,
RT=10KΩ, no effect on
the frequency
0
0
50
Time (10µs/div)
100
RT-Timing Resistor Versus
Oscillator Frequency
1000
Oscillator Frequency (KHz)
1nF
100
10nF
10
100nF
1
1μF
0.1
0.01
1
10
100
1000
RT-Timing Resistor (KΩ)
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QW-R103-061.E
UC3846
LINEAR INTEGRATED CIRCUIT
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. UTC reserves the right to
make changes to information published in this document, including without limitation specifications and
product descriptions, at any time and without notice. This document supersedes and replaces all
information supplied prior to the publication hereof.
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QW-R103-061.E