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KA3843AM [Wing Shing]

Current���� Mode��PWM��Cont roller; Current􀀃􀀃 Mode􀀃PWM􀀃Cont辊
KA3843AM
型号： KA3843AM
厂家： WING SHING COMPUTER COMPONENTS    WING SHING COMPUTER COMPONENTS
描述：

Current���� Mode��PWM��Cont roller
Current􀀃􀀃 Mode􀀃PWM􀀃Cont辊
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
DESCRIPTION  
PIN  
CONNECTION  
are fixed frequency current mode PWM  
The KA3843AM  
controller. They are specially designed for OFF−Line and DC to DC converter applications  
with a minimal external components. Internally implemented circuits include a trimmed  
(TOP VIEW)  
oscillator for precise duty cycle control, a temperature compensated reference, high gain  
error amplifier, current sensing comparator, and a high current totempole output ideally  
suited for driving a power MOSFET. Protection circuitry includes built undervoltage lockout  
and current limiting.  
The corresponding thresholds for the  
The KA3843AM are 8.4V(on) and 7.6V (off)  
can operate within 100% duty cycle.  
The KA3843AM  
The KA3843AM  
has Start-Up Current 0.17mA (typ).  
FEATURES  
•
•
•
•
Low Start-Up and Operating Current  
High Current Totem Pole Output  
Undervoltage Lockout With Hysteresis  
Operating Frequency Up To  
500KHz  
BLOCK DIAGRAM  
Absolute Maximum Ratings  
Characteristic  
Symbol  
Value  
Unit  
Supply Voltage (low impedance  
source)  
VCC  
30  
V
Output Current  
IO  
VI  
A
V
±1  
−0.3 to 5.5  
10  
Input Voltage (Analog Inputs pins 2,3)  
Error Amp Output Sink Current  
Power Dissipation (TA=250C)  
Storage Temperature Range  
Lead Temperature (soldering 5 sec.)  
ISINK (E.A)  
PO  
mA  
W
oC  
oC  
1
Tstg  
TL  
-65 to150  
260  
1
ꢀ
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
Electrical characteristics (*VCC=15V, RT=10kΩ, CT=3.3nF, TA=00C to +700C, unless otherwise  
specified)  
Characteristics  
Reference Section  
Reference Output Voltage  
Line Regulation  
Symbol  
Test Condition  
Min  
Typ  
Max  
Unit  
VREF  
4.9  
5.0  
6.0  
5.1  
20  
V
TJ = 25°C, IREF = 1 mA  
12V ≤ VCC ≤ 25 V  
1 mA ≤ IREF ≤ 20mA  
TA = 25°C  
mV  
∆VREF  
∆VREF  
ISC  
Load Regulation  
6.0  
25  
Short Circuit Output Current  
Oscillator Section  
-100  
-180  
mA  
f
384XA  
47  
47  
50  
52  
57  
57  
TJ = 25°C  
Oscillation Frequency  
KHz  
384XAM  
Frequency Change with  
Voltage  
0.05  
1.0  
∆f/∆VCC  
12V ≤ VCC ≤ 25 V  
%
V
Oscillator Amplitude  
Error Amplifier Section  
Input Bias Current  
V(OSC)  
(peak to peak)  
1.6  
IBIAS  
VI(E.A)  
AVOL  
VFB=3V  
-0.1  
2.5  
90  
-2  
µA  
Input Voltage  
Vpin1 = 2.5V  
2.42  
65  
2.58  
V
Open Loop Voltage Gain  
Power Supply Rejection Ratio  
Output Sink Current  
Output Source Current  
High Output Voltage  
Low Output Voltage  
Current Sense Section  
Gain  
2V ≤ V0 ≤ 4V  
dB  
PSRR  
ISINK  
60  
70  
12V ≤ VCC ≤ 25 V  
Vpin2 = 2.7V, Vpin1 = 1.1V  
Vpin2 = 2.3V, Vpin1 = 5V  
Vpin2 = 2.3V, RL = 15KΩ to GND  
Vpin2 = 2.7V, RL = 15KΩ to PIN 8  
2
7
mA  
mA  
ISOURCE  
VOH  
-0.5  
5.0  
-1.0  
6.0  
0.8  
V
VOL  
1.1  
GV  
VI(MAX)  
SVR  
(Note 1 & 2)  
2.85  
0.9  
3.0  
1.0  
70  
3.15  
1.1  
V/V  
V
Maximum Input Signal  
Supply Voltage Rejection  
Input Bias Current  
V pin1 = 5V (Note1)  
12V ≤ VCC ≤ 25 V (Note 1)  
Vpin3 = 3V  
dB  
IBIAS  
-3.0  
-10  
µA  
Output Section  
Low Output Voltage  
VOL  
VOH  
ISINK = 20 mA  
0.08  
1.4  
0.4  
2.2  
ISINK = 200 mA  
V
High Output Voltage  
ISINK = 20 mA  
13  
12  
13.5  
13.0  
45  
ISINK = 200 mA  
Rise Time  
tR  
tF  
150  
150  
TJ = 25°C, CL = 1nF (Note 3)  
TJ = 25°C, CL = 1nF (Note 3)  
nS  
Fall Time  
35  
Undervoltage Lockout Section  
Start Theshold  
VTH(ST)  
V
V
3843A(AM)  
7.8  
7.0  
95  
8.4  
7.6  
97  
9.0  
8.2  
100  
0
Min. Operating Voltage  
(After Turn On)  
VOPR(min)  
3843A(AM)/45A(AM)  
3842A(AM)/43A(AM)  
PWM Section  
Max. Duty Cycle  
D(MAX)  
D(MAX)  
%
Min. Duty Cycle  
Total Standby Current  
Start−Up Current  
IST  
ICC (OPR)  
VZ  
384XA(AM)  
Vpin3 = Vpin2 = 0V  
ICC=25 mA  
0.17  
13  
0.3  
17  
mA  
V
Operating Supply Current  
Zener Voltage  
30  
38  
* Adjust VCC above the start threshold before setting it to 15V.  
Note 1: Parameter measured at trip point of latch with Vpin2=0.  
Note 2: Gain defined as A=∆Vpin1/∆Vpin3 ; 0 ≤ Vpin3 ≤ 0.8V.  
Note 3: These parameters, although guaranteed, are not 100% tested in production.  
2
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
PIN FUNCTION  
N FUNCTION  
DESCRIPTION  
1
2
COMP  
VFB  
This pin is the Error Amplifier output and is made for loop compensation.  
This is the inverting input of the Error Amplifier. It is normally connected to the  
switching power supply output through a resistor divider.  
A voltage proportional to inductor current is connected to this input. The PWM  
uses this information to terminate the output switch conduction.  
The oscillator frequency and maximum Output duty cycle are programmed by  
connecting resistor RT to Vref and capacitor CT to ground.  
This pin is the combined control circuitry and power ground.  
This output directly drives the gate of a power MOSFET. Peak currents up to 1A  
are sourced and sink by this pin.  
3
4
ISENSE  
RT/CT  
5
6
GROUND  
OUTPUT  
7
8
VCC  
Vref  
This pin is the positive supply of the integrated circuit.  
This is the reference output. It provides charging current for capacitor CT through  
resistor RT .  
APPLICATION INFORMATION  
Figure 1. Error Amp Configuration  
WS  
WS  
Figure 2. Undervoltage Lockout  
3
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
Figure 3. Current Sense Circuit  
Figure 4. Slope Compensation Techniques  
4
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
SCR must be selected for a holding current of less than 0.5mA.  
The simple two transistor circuit can be used in place of the SCR as shown.  
Figure 5. Latched Shutdown  
Figure 6. Error Amplifier Compensation  
5
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
Figure 7. External Clock Synchronization  
Figure 8. Soft-Start Circuit  
6
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
TYPICAL PERFORMANCE CHARACTERISTICS  
Figure 1. Timing Resistor vs. Oscillator Frequency  
Figure 2. Output Dead-Time vs. Oscillator Frequency  
Figure 3. Maximum Output Duty Cycle vs.  
Timing Resistor (3842/43)  
Figure 4. Error Amp Open-Loop Gain vs.  
Frequency  
Figure 5. Current Sense Input Threshold vs.  
Error Amp Output Voltage  
Figure 6. Reference Short Circuit Current vs.  
Temperature  
7
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
Figure 7. Output Saturation Voltage vs. Load Current  
Figure 8. Supply Current vs. Supply Voltage  
TA = 25°C  
Figure 9. Oscillator and Output Waveforms  
8
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ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀCurrentꢀꢀModeꢀPWMꢀControllerꢀ  
KA3843A(AM)  
PAD LOCATION  
Chip size: 2.38 x 1.63 mm  
Coordinates µm  
Pad N  
Pad Name  
X
Y
1
2
3
4
5
6
7
8
9
COMP  
VFB  
ISENSE  
90  
110  
110  
110  
150  
1280  
1450  
1410  
1410  
1410  
1390  
1050  
1310  
2000  
1700  
1680  
1310  
990  
RT/CT  
POWER GND  
GND  
OUT  
POWER VCC  
VCC  
815  
460  
10  
VREF  
9

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