Document
Semiconductor
S3842P
Current Mode PWM Controller
Descriptions
The S3842, high performance current mode controller, Provides the necessary features to off-line and DC-DC fixed frequency current control applications offering the designer a cost effective solution with minimal external components. Internally protection circuity includes built-in input and reference under-voltage lockout and current limiting with hysteresis. Also other characteristics of internal circuit provide improved line regulation, enhanced load response, trimmed oscillation for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and totempole output designed to source and sink high peak current from a capacitive load such as the gate of a power MOSFET.
Features
• Optimized for off-line control • Low start up and operating current • Pulse by pulse current limiting • Current mode operation to 500 ㎑ • Under voltage lockout with 6V hysteresis • Internally trimmed bandgap reference about 5V
• Enhanced load response characteristic • Automatic feed forward compensation
Ordering Information
Type NO. S3842P Marking S3842P Package Code DIP-8
Outline Dimensions
unit :
mm
PIN Connections
1. Output / Compensation 2. Voltage feedback. Input 3. Current sense Input 4. Rt/Ct 5. GND 6. Output 7. Vcc 8. Vref
KSI-L006-000
1
S3842P
Absolute Maximum Ratings
Characteristic
Supply voltage Current Sense and Vfb Input Total Power Supply and Zener Current Output Sink of Source Current Error AMP Output Sink Current Operating Ambient Temperature Storage Temperature Range Power Dissipation at Ta≤ 50°C
Ta=25°C
Symbol
Vcc VIN ICC+ IZ Io Ieo Ta Tstg Pd
Ratings
30 -0.3 to Vcc 30 1 10 0 to 70 -65 to 150 1
Unit
V V mA A mA °C °C W
note) All voltages are with respect to PIN5, and current are positive into the specified pin.
PIN Description
PIN NO
1 2 3 4 5 6 7 8
Function
Compensation Voltage feedback Current sense Rt/Ct Ground Output VCC Vref
Description
Error amplifier output and is made available for loop compensation. Inverting input of error amplifier, normally connected to the switching power supply output through a resistor driver. A voltage proportional to inductor current is connected to this input. The PWM uses this information to terminate the output. 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 current up to 1.0A are sourced and sinked by this pin. This pin is the positive supply of the control IC. This is the reference output. it provides charging current for capacitor Ct through resistor Rt.
Block Diagram
KSI-L006-000
2
S3842P
Electrical Characteristics
(Unless otherwise stated, these specifications apply for 0 ≤ Ta ≤ 70°C; VCC =15V(Note.4), RL =10 ㏀, CL =3.3nF)
Characteristic
1. Reference Section
Output Voltage Line Regulation Load Regulation Temperature Stability Output Noise Voltage Long Term Stability Output Short Circuit
Symbol
Vref △Vref △Vref △VT /△VT Vn S ISC fSC △f /△V △f /△T V4
Test Condition
Ta=25°C, IO=1mA
12V ≤ VCC ≤ 25V 1mA ≤ IO ≤ 20mA (Note 1) 10Hz ≤ f ≤10KHz,Ta=25°C(Note
Min.
4.90 -30 47 -
Typ. Max.
5.00 6 6 0.2 50 5 -100 52 0.05 5 1.7 5.10 20 25 0.4 -180 57 1.0 -
Unit
V mV mV mV/°C uV mV mA KHz % % V
1)
-
Ta=125°C, 1000Hrs (Note 1)
2. Oscillator Section
Initial Accuracy Voltage Stability Temperature Stability Amplitude Ta=25°C 12 ≤ Va ≤25V Tmin ≤ Ta ≤ Tmax (Note 1) VPIN4 Peak to Peak
3. Error Amp Section
Input Voltage Input Bias Current Open Loop Voltage Gain Supply Voltage Rejection Output Sink Current Output Source Current VOUT High VOUT Low V2 Ib AVO1 SVR IO IO Vch Vc1 VPIN1=2.5V 2V ≤ VO ≤ 4V 12V ≤ Va ≤ 25V VPIN2=2.7V, VPIN1=1.1V VPIN2=2.3V, VPIN1=5V VPIN2=2.3V, VPIN2=2.7V, RL=15 ㏀ to Ground RL=15 ㏀ Pin8 2.42 65 60 2 -0.5 5 2.50 -0.3 90 70 6 -0.8 6 0.7 2.58 -2.0 1.1 V ㎂ ㏈ ㏈ mA mA V V
4. Current Sense Section
Gain Maximum Input Signal Supply Volt Rejection Input Bias Current GV V3 SVR Ib (Note 2 & 3) VPIN 1=5V (Note 2) 12 ≤ Va ≤ 25V (Note 2) 2.8 0.9 3.0 1.0 70 -2 3.2 1.1 -10 V/V V ㏈ ㎂
5.Output Section
Output Low Level VOl ISINK=20mA ISINK=200mA ISOURCE=20mA ISOURCE=200mA Ta=25°C, Cl=1nF (Note 1) Ta=25°C, Cl=1nF (Note 1) 13.0 12.0 0.1 1.5 13.5 13.5 50 50 0.4 2.2 150 150 V V V V ns ns
Output High Level Rise time Fall time
VOh tr tf
KSI-L006-000
3
S3842P
Electrical Characteristics(continued)
Characteristic
Start Threshold Min. Operation Voltage After Turn-On
Symbol
Vth VCC(min)
Test Condition
VPIN7 where VPIN8 ≥ 4.9V VPIN7 where VPIN8 ≤ 1V
-
Min.
14.5 8.5
Typ. Max.
16.0 10.0 17.5 11.5
Unit
V V
6. Under-Voltage Lockout Section
7. PWM Section
Maximum Duty Cycle DCmax Ist ICC VZ 93 97 100 ns
8. Total Standby Section
Start-Up Current Operating Supply Current Zener Voltage VCC = 15V before turn on 0.4 11 36 0.7 20 mA mA V
VPIN2= .