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Semiconductor data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s
technical experts. ON Semiconductor does not convey any license under its patent rights nor the rights of others. ON Semiconductor products are not designed, intended, or authorized for use as a critical component in life support systems or any FDA
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KA3842B/KA3843B/KA3844B/
KA3845B
SMPS Controller
Features
Description
•
•
•
•
The KA3842B/KA3843B/KA3844B/KA3845B are fixed
frequency current-mode PWM controller. They are
specially designed for Off - Line and DC-to-DC converter
applications with minimum external components. These
integrated circuits feature a trimmed oscillator for precise
duty cycle control, a temperature compensated reference,
high gain error amplifier, current sensing comparator and a
high current totempole output for driving a power MOSFET.
The KA3842B and KA3844B have UVLO thresholds of
16V (on) and 10V (off). The KA3843B and KA3845B are
8.5V (on) and 7.9V (off). The KA3842B and KA3843B can
operate within 100% duty cycle. The KA3844B and
KA3845B can operate with 50% duty cycle.
Low Start up Current
Maximum Duty Clamp
UVLO With Hysteresis
Operating Frequency up to 500KHz
8-DIP
1
14-SOP
1
Internal Block Diagram
Rev. 1.0.2
©2002 Fairchild Semiconductor Corporation
KA3842B/KA3843B/KA3844B/KA3845B
Absolute Maximum Ratings
Parameter
Symbol
Value
Unit
Supply Voltage
VCC
30
V
Output Current
IO
±1
A
V(ANA)
-0.3 to 6.3
V
ISINK (E.A)
10
mA
Power Dissipation at TA≤25°C (8DIP)
PD(Note1,2)
1200
mW
Power Dissipation at TA≤25°C (14SOP)
Analog Inputs (Pin 2.3)
Error Amp Output Sink Current
PD(Note1,2)
680
mW
Storage Temperature Range
TSTG
-65 ~ +150
°C
Lead Temperature (Soldering, 10sec)
TLEAD
+300
°C
Note:
1. Board Thickness 1.6mm, Board Dimension 76.2mm ×114.3mm, (Reference EIA / JSED51-3, 51-7)
2. Do not exceeed PD and SOA (Safe Operation Area)
Power Dissipation Curve
1200
8DIP
POWER DISSIPATION (mW)
1100
1000
900
800
14SOP
700
600
500
400
300
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
AMBIENT TEMPERATURE (℃)
Thermal Data
Characteristic
Thermal Resistance Junction-ambient
Symbol
8-DIP
14-SOP
Unit
Rthj-amb(MAX)
100
180
°C/W
Pin Array
8DIP,8SOP
8-DIP
COMP 1
8
VREF
COMP 1
VFB 2
7
VCC
N/C
3
6
RT/C T 4
5
CURRENT SENSE
2
14SOP
14 VREF
2
13
N/C
OUTPUT
VFB 3
12
VCC
GND
N/C 4
11 PWR VC
CURRENT SENSE
5
10
OUTPUT
N/C
6
9
GND
RT/C T 7
8
PWR GND
KA3842B/KA3843B/KA3844B/KA3845B
Electrical Characteristics
(VCC=15V, RT=10KΩ, CT=3.3nF, TA= 0°C to +70°C, unless otherwise specified)
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
TJ = 25°C, IREF = 1mA
4.90
5.00
5.10
V
REFERENCE SECTION
Reference Output Voltage
VREF
Line Regulation
∆VREF
12V≤VCC≤25V
-
6
20
mV
Load Regulation
∆VREF
1mA≤IREF≤20mA
-
6
25
mV
TA = 25°C
-
-100
-180
mA
TJ = 25°C
47
52
57
KHz
Short Circuit Output Current
ISC
OSCILLATOR SECTION
Oscillation Frequency
Frequency Change with Voltage
Oscillator Amplitude
f
∆f/∆VCC
12V≤VCC≤25V
-
0.05
1
%
VOSC
-
-
1.6
-
VP-P
IBIAS
-
-
-0.1
-2
µA
ERROR AMPLIFIER SECTION
Input Bias Current
Input Voltage
Open Loop Voltage Gain
VI(E>A)
GVO
Vpin1 = 2.5V
2.42
2.50
2.58
V
2V≤ VO ≤4V (Note3)
65
90
-
dB
Power Supply Rejection Ratio
PSRR
12V≤ VCC ≤25V (Note3)
60
70
-
dB
Output Sink Current
ISINK
Vpin2 = 2.7V, Vpin1 = 1.1V
2
7
-
mA
-0.6
-1.0
-
mA
Output Source Current
ISOURCE
Vpin2 = 2.3V, Vpin1 = 5V
High Output Voltage
VOH
Vpin2 = 2.3V, RL = 15KΩ to GND
5
6
-
V
Low Output Voltage
VOL
Vpin2 = 2.7V, RL = 15KΩ to Pin 8
-
0.8
1.1
V
GV
(Note 1 & 2)
2.85
3
3.15
V/V
Vpin1 = 5V(Note 1)
0.9
1
1.1
V
-
70
-
dB
-
-3
-10
µA
ISINK = 20mA
-
0.08
0.4
V
ISINK = 200mA
-
1.4
2.2
V
CURRENT SENSE SECTION
Gain
Maximum Input Signal
Power Supply Rejection Ratio
Input Bias Current
VI(MAX)
PSRR
12V≤ VCC ≤25V (Note1,3)
-
IBIAS
OUTPUT SECTION
Low Output Voltage
High Output Voltage
VOL
VOH
ISOURCE = 20mA
13
13.5
-
V
ISOURCE = 200mA
12
13.0
-
V
Rise Time
tR
TJ = 25°C, CL= 1nF (Note 3)
-
45
150
ns
Fall Time
tF
TJ = 25°C, CL= 1nF (Note 3)
-
35
150
ns
KA3842B/KA3844B
14.5
16.0
17.5
V
KA3843B/KA3845B
7.8
8.4
9.0
V
KA3842B/KA3844B
8.5
10.0
11.5
V
KA3843B/KA3845B
7.0
7.6
8.2
V
UNDER-VOLTAGE LOCKOUT SECTION
Start Threshold
Min. Operating Voltage
(After Turn On)
VTH(ST)
VOPR(MIN)
3
KA3842B/KA3843B/KA3844B/KA3845B
Electrical Characteristics (Continued)
(VCC=15V, RT=10KΩ, CT=3.3nF, TA= 0°C to +70°C unless otherwise specified)
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
PWM SECTION
Max. Duty Cycle
Min. Duty Cycle
D(Max)
KA3842B/KA3843B
95
97
100
%
D(MAX)
KA3844B/KA3845B
47
48
50
%
D(MIN)
-
-
-
0
%
IST
-
-
0.45
1
mA
-
14
17
mA
30
38
-
V
TOTAL STANDBY CURRENT
Start-Up Current
Operating Supply Current
ICC(OPR)
Zener Voltage
VZ
Vpin3=Vpin2=ON
ICC = 25mA
Adjust VCC above the start threshould before setting at 15V
Note:
1. Parameter measured at trip point of latch
2. Gain defined as:
∆V pin1
A = ----------------- ,0 ≤ Vpin3 ≤ 0.8V
∆V pin3
3. These parameters, although guaranteed, are not 100 tested in production.
Figure 1. Open Loop Test Circuit
High peak currents associated with capacitive loads necessitate careful grounding techniques Timing and bypass capacitors
should be connected close to pin 5 in a single point ground. The transistor and 5KΩ potentiometer are used to sample the
oscillator waveform and apply an adjustable ramp to pin 3.
4
KA3842B/KA3843B/KA3844B/KA3845B
Figure 2. Under Voltage Lockout
During Under-Voltage Lock-Out, the output driver is biased to a high impedance state. Pin 6 should be shunted to ground with
a bleeder resistor to prevent activating the power switch with output leakage current.
Figure 3. Error Amp Configuration
Figure 4. Current Sense Circuit
Peak current (IS) is determined by the formula:
1.0V
I S ( MAX ) = -----------RS
A small RC filter may be required to suppress switch transients.
5
KA3842B/KA3843B/KA3844B/KA3845B
Figure 5. Oscillator Waveforms and Maximum Duty Cycle
Oscillator timing capacitor, CT, is charged by VREF through RT and discharged by an internal current source. During the discharge time, the internal clock signal blanks the output to the low state. Selection of RT and CT therefore determines both
oscillator frequency and maximum duty cycle. Charge and discharge times are determined by the formulas:
tc = 0.55 RT CT
0.0063R T – 2.7
t D = R T C T I n ----------------------------------------
0.0063R T – 4
Frequency, then, is: f=(tc + td)-1
1.8
ForRT > 5KΩ ,f = --------------RT CT
Figure 6. Oscillator Dead Time & Frequency
Figure 7. Timing Resistance vs Frequency
(Deadtime vs CT RT > 5kΩ)
Figure 8. Shutdown Techniques
6
KA3842B/KA3843B/KA3844B/KA3845B
Shutdown of the KA3842B can be accomplished by two methods; either raise pin 3 above 1V or pull pin 1 below a voltage
two diode drops above ground. Either method causes the output of the PWM comparator to be high (refer to block diagram).
The PWM latch is reset dominant so that the output will remain low until the next clock cycle after the shutdown condition at
pins 1 and/or 3 is removed. In one example, an externally latched shutdown may be accomplished by adding an SOR which
will be reset by cycling VCC below the lower UVLO threshold. At this point the reference turns off, allowing the SCR to reset.
Figure 9. Slope Compensation
A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope compensation for
converters requiring duty cycles over 50%. Note that capacitor, CT, forms a filter with R2 to suppress the leading edge switch
spikes.
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 10. Temperature Drift (Vref)
Figure 11. Temperature Drift (Ist)
TEMPERATURE (°C)
Figure 12. Temperature Drift (Icc)
7
KA3842B/KA3843B/KA3844B/KA3845B
Mechanical Dimensions
Package
Dimensions in millimeters
1.524 ±0.10
#5
2.54
0.100
5.08
MAX
0.200
7.62
0.300
3.40 ±0.20
0.134 ±0.008
+0.10
0.25 –0.05
+0.004
0~15°
8
0.010 –0.002
3.30 ±0.30
0.130 ±0.012
0.33
0.013 MIN
0.060 ±0.004
#4
0.018 ±0.004
#8
9.60
MAX
0.378
#1
9.20 ±0.20
0.362 ±0.008
(
6.40 ±0.20
0.252 ±0.008
0.46 ±0.10
0.79
)
0.031
8-DIP
KA3842B/KA3843B/KA3844B/KA3845B
Mechanical Dimensions (Continued)
Package
Dimensions in millimeters
14-SOP
MIN
#8
0.60 ±0.20
0.024 ±0.008
MAX0.10
MAX0.004
1.80
MAX
0.071
3.95 ±0.20
0.156 ±0.008
5.72
0.225
0~
8°
+0.10
0.20 -0.05
+0.004
0.008 -0.002
6.00 ±0.30
0.236 ±0.012
1.27
0.050
#7
+0.10
0.406 -0.05
+0.004
0.016 -0.002
#14
8.70
MAX
0.343
#1
8.56 ±0.20
0.337 ±0.008
(
0.47
)
0.019
1.55 ±0.10
0.061 ±0.004
0.05
0.002
9
KA3842B/KA3843B/KA3844B/KA3845B
Ordering Information
Product Number
Package
Operating Temperature
KA3842B
KA3843B
KA3844B
8-DIP
KA3845B
0 ~ + 70°C
KA3842BD
KA3843BD
KA3844BD
14-SOP
KA3845BD
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY
PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body,
or (b) support or sustain life, and (c) whose failure to
perform when properly used in accordance with
instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
www.fairchildsemi.com
2/18/02 0.0m 001
Stock#DSxxxxxxxx
2002 Fairchild Semiconductor Corporation
ON Semiconductor and
are trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries.
ON Semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor’s product/patent
coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. ON Semiconductor reserves the right to make changes without further notice to any products herein.
ON Semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does ON Semiconductor assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
Buyer is responsible for its products and applications using ON Semiconductor products, including compliance with all laws, regulations and safety requirements or standards,
regardless of any support or applications information provided by ON Semiconductor. “Typical” parameters which may be provided in ON Semiconductor data sheets and/or
specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer
application by customer’s technical experts. ON Semiconductor does not convey any license under its patent rights nor the rights of others. ON Semiconductor products are not
designed, intended, or authorized for use as a critical component in life support systems or any FDA Class 3 medical devices or medical devices with a same or similar classification
in a foreign jurisdiction or any devices intended for implantation in the human body. Should Buyer purchase or use ON Semiconductor products for any such unintended or unauthorized
application, Buyer shall indemnify and hold ON Semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and
expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such
claim alleges that ON Semiconductor was negligent regarding the design or manufacture of the part. ON Semiconductor is an Equal Opportunity/Affirmative Action Employer. This
literature is subject to all applicable copyright laws and is not for resale in any manner.
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