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Specification Document
Low Power Original Side Control Circuit MT3612
Overview
The MT3612A/B/D is a series of high-performance AC/DC low-power primary feedback control chips with a built-in 800V (Vcbo) power transistor,
utilizing pulse frequency modulation (PFM) to establish a discontinuous conduction mode (DCM) flyback power supply, with built-in QR mode.
This chip provides precise constant voltage and constant current (CV / CC) without the need for an optocoupler and secondary control circuit adjustments. It eliminates the need
for loop compensation circuits while maintaining good stability. It achieves good regulation and high average efficiency, meeting the requirement of less than 75mW for no-load loss.
There is also a proprietary cable voltage drop compensation feature, which is the output line loss compensation. The amount of line loss compensation can be
adjusted according to the resistance value of the FB voltage divider, with a maximum compensation amount of 12% of the output voltage, effectively compensating
for the voltage drop loss of the output current on the output line. It is mainly used in adapters for mobile phones, cordless phones, PDAs, MP3 players, and other
portable devices; battery chargers; LED driving currents; backup power supplies; and upgrades of linear power supplies and RCC switch power supplies.
Recommended Application Power
Model
Vin: 90-264Vac 50/60Hz
MT3612A 10.5W(5V/2.1A)
MT3612B 12.0W(5V/2.4A)
MT3612D 12.0W(5V/2.4A) Enhanced Version
Features
Suitable for 5V/2A applications, meeting Level 6 energy efficiency;
<75mW standby power;
Bottom conduction technology (QR mode) improves overall efficiency
Built-in high-voltage transistor;
Random frequency jitter modulation reduces system electromagnetic interference;
Open circuit protection；
Overvoltage protection；
Short circuit protection；
Overtemperature protection；
Line loss compensation;
Using SOP-7 packaging, built-in 1300X series transistors.
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Specification Document
Low Power Original Side Control Circuit MT3612
Typical applications
Figure 1: Typical Application Circuit of MT3612A/B/D
Pin Arrangement
Pin Pin Name Description
1 FB The adjustment of CV and CC is based on the implementation of voltage sampling at this pin.
CS is the current sensing pin of the IC. Based on the voltage at the CS pin, the
2 CS
internal circuit will turn off the power transistor.
The VCC pin provides power to the integrated circuit. To ensure the correct operation
3 VCC
of the IC, a low ESR capacitor should be placed as close as possible to the VCC pin.
4 E The emitter electrode E of the built-in power transistor.
5, 6 C The collector C of the built-in power transistor.
The GND pin is the ground of the IC. When the power transistor is off, a fast reverse
7 GND
sinking current will flow from this pin to the BJT gate. Pay attention to the PCB layout.
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Specification Document
Low Power Original Side Control Circuit MT3612
Functional Block Diagram
Extreme parameters
Parameters Symbols Parameters Units
Power supply voltage VCC -0.3 to 30 V
CS Voltage Vcs -0.3 to 7 V
FB Voltage VFB -40 to 8.5 V
Working junction temperature TJ 150 °C
Storage Temperature TST -65 to 150 °C
Pin temperature (during soldering) TLEAD 300 °C
Thermal resistance θJA 250 ºC/W
ESD (Human Body Model) 2000 V
Note: The maximum limit value refers to the range beyond which the chip may be damaged.
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Specification Document
Low Power Original Side Control Circuit MT3612
Electrical parameters
Unless otherwise specified, Vcc=15V, Ta=25℃
Parameters Symbols Test conditions Minimum value Typical Value Maximum Value Units
Power Supply Voltage
Starting Voltage Vst Vcc rising 14 15.5 17 V
Under-voltage protection Vuvlo Vcc drop 4.5 5.0 5.5 V
Starting current Ist Vcc=Vst-1V 0.2 0.2 uA
Working Current Icc 500 uA
Output Driver
Source Current Isource 30 35 40 mA
trapped current Sink 450 500 550 mA
CS Current Sampling
Sampling Threshold 1 Vcs1 500 mV
Sampling Threshold 2 Vcs2 330 mV
Cutting-edge Disappearance Tleb 500 ns
FB Feedback
FB Resistor Rfb VFB=4V 1 1.6 2 MΩ
FB Voltage 3.95 4 4.05 V
FB Protection Voltage Vfb_ovp 6.5 7.0 7.5 V
Line Compensation
Output Compensation Vcomp_line 120 mV
Temperature Protection
Temperature protection point Tsd 150 °C
Temperature hysteresis Thys 30 °C
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Specification Document
Low Power Original Side Control Circuit MT3612
Characteristic Curve
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Specification Document
Low Power Original Side Control Circuit MT3612
Package size
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