The function and function of each pin of the chip UC3875

UCC3895 is a phase-shifting resonant full-bridge soft switch controller produced by Texas Instruments, which adopts advanced BCDMOS technology. The UCC3895 is identical to the UC3875 series and UC3879 series controllers in terms of basic functionality, while adding some new features. The following describes its characteristics, pin functions, electrical parameters, and working principles respectively.

2. Features and pin descriptions.

Peculiarity. 1) The output conduction delay time is programmed and controllable;

2) Adaptive delay time setting function;

3) Bidirectional oscillator synchronization function;

4) Voltage mode control or current mode control;

5) Soft start: Soft shutdown and controller chip selection function can be programmed and controlled, and single-pin control;

6) duty cycle control range 0 100;

7) Built-in 7MHz error amplifier;

8) The maximum working frequency reaches 1MHz;

9) The working current is low, the working current under 500kHz is only 5mA;

10) The current in the undervoltage lockout state is only 150 A.

Basic parameters: input voltage: 15V, output voltage:

5V, Current: 200mA, Frequency: Trillion 500kHz, Form Factor:

DIP, Pin Count: 8, Operating Temperature Range: 0°C to +70°C.

Package Type: DIP, Minimum Operating Temperature: 0°C, Maximum Operating Temperature: 70°C, Device Number: 3845, Controller Type: PWM, Temperature Range: Commercial, Maximum Supply Voltage: 25V.

Minimum Supply Voltage: 12V, Chip Number: 3845, Surface Mount Device:

Through-hole mounting, maximum input voltage: 25V, input current: 11mA, maximum output current:

1a, output type: which leakage totem pole, output energy, per cycle: 5 j, logic function number:

3845a。

The functions of each pin of the <>UC3842BN are as follows:

Pin 1 comp is the output of an internal error amplifier, usually there is a feedback network between this pin and pin 2 to determine the gain and frequency response of the error amplifier.

The 2-pin feed back is the feedback voltage input terminal, which is the reference voltage (generally +) at the input terminal in the same direction as the internal error amplifier to generate the control voltage and control the width of the pulse.

The 3-pin iSense is the current sensing end. In the peripheral circuit, a small resistance sampling resistor is connected in series at the source of the power switch (such as VMOS tube) to convert the current of the pulse transformer into a voltage, which is sent to 3 pins to control the pulse width. In addition, when the power supply voltage is abnormal, the current of the power switch increases, and when the voltage on the sampling resistor exceeds 1V, the UC3842 stops output, effectively protecting the power switch.

The 4-pin RT CT is the timing end. The sawtooth wave oscillator is connected to the common terminal of the timing capacitor C and the timing resistor R.

5 pin GND is grounded.

The 6-pin OUT is the output end, this pin is the totem column output, and the driving capacity is LA. This totem-pole structure is beneficial for the shutdown of the driven power tube, because when the triode VTL is cut-off, VT2 is turned on, providing a low-impedance reverse pumping current loop for the power tube to be turned off, accelerating the shutdown of the power tube.

The 7-pin VCC is the power supply. When the supply voltage is lower than 16V, the UC3824 does not work, and the power consumption is less than 1mA. The input voltage can be obtained from a high voltage step-down by means of a large resistance resistor.

After the chip is working, the input voltage can fluctuate between +10 +30V and stop working below +10V. The current consumption is about 15mA during operation, and this current can be supplied by a feedback resistor.

The 8-pin VREF is a reference voltage output that can output an accurate +5V reference voltage up to 50mA.

There are four types of UC3843BN peripheral circuits.

Peripheral circuit diagram:

The first, <>

The second is <>

The third is <>

Fourth, <>

It is a current-controlled pulse width modulation chip with excellent performance. The modulator has a single-ended output and can directly drive bipolar power or MOSFETs. Its main advantages are that it has less pin effect, simple peripheral circuit, voltage regulation, working frequency up to 500kHz, starting current less than 1mA, normal working current of 5mA, and can use high-frequency transformers to achieve isolation from the power grid.

The chip integrates an oscillator, a high-gain error amplifier with high-temperature compensation, a current-sense comparator, totem-pole output current, input and reference undervoltage lockout circuitry, and PWM latch circuitry.

Input voltage: 15V

Output voltage: 5V

Output current: 200mA

Frequency: 500kHz

Form factor: DIP

Number of pins: 8Operating temperature range: 0°C to +70°C

Package Type: DIP

Minimum operating temperature: 0°C

Maximum operating temperature: 70°C

Device designation: 3845

Controller type: PWM

Temperature Range: Commercial.

Power supply voltage max: 25V

Power supply voltage Minimum: 12V

Chip designation: 3845

Surface Mount Devices: Through-hole mounting.

Input voltage Max: 25V

Input current: 11mA

Output current Max: 1A

Output Type: Totem Pole

Output energy, 5 J per cycle

Logical function number: 3845a

Power chip type: PWM controller.

Input voltage: 15V

Output voltage: 5V

Output current: 200mA

Frequency: 500kHz

Form factor: DIP

Number of pins: 8Operating temperature range: 0°C to +70°C

Package Type: DIP

Minimum operating temperature: 0°C

Maximum operating temperature: 70°C

Device designation: 3845

Controller type: PWM

Temperature Range: Commercial.

Power supply voltage max: 25V

Power supply voltage Minimum: 12V

Chip designation: 3845

Surface Mount Devices: Through-hole mounting.

Input voltage Max: 25V

Input current: 11mA

Output current Max: 1A

Output Type: Totem Pole

Output energy, 5 J per cycle

Logical function number: 3845a

Power chip type: PWM controller.

The chip UC3638, the complete model number is UC3638DW, is a motor driver IC in SOP-20 package.

Voltage - Power supply: 10V 36V

Operating temperature: 0°C 70°C (ta).

Dual 500mA totem pole output drivers.

Dual 60V, 50mA open collector drivers.

1. The 5th foot of UC3842 is the ground.

2. First test the 5th pin and the 8th pin, the 8th pin outputs a reference voltage of 5V, and the test of this pin can quickly judge the quality of UC3842.

3. If the voltage of the 8th pin is normal, there is no problem with UC3842 under normal circumstances, and there is no need to test the others.

4. If the voltage of the 8th pin is not there, measure the 7th pin to see if the power supply voltage is correct. However, the voltage value of the 7 pins depends on the specific circuit design.

One pin of UC3843 can be used for feedback and compensation. When doing feedback, connect the 2 pins to the ground to make negative feedback for receiving the feedback voltage. For compensation, pin 2 is used as the feedback terminal, and a capacitor resistor is applied between pin 1 and pin 2 to absorb the interference of the feedback terminal.

UC3843 Fixed Frequency Current Mode Controller.

Model: UC3843A

Package: dip8

Main application: switching power supply.

The UC3842 and UC3843 are high-performance fixed-frequency current-mode controllers designed for off-line and DC-to-DC converter applications, providing designers with a cost-effective solution with minimal external components. These ICs feature a fine-tunable oscillator, precise duty cycle control, temperature-compensated references, and high-gain error amplifiers. The current sampling comparator and high-current totem pole output are ideal devices for driving power MOSFETs.

Other protection features include input and reference undervoltage lockout, each with hysteresis, cycle-by-cycle current limit, programmable output quiet time, and individual pulse measurement latch.

The UC3842A has 16V (on) and 10V (off) low-voltage lockout thresholds, making it ideal for off-line converters. The UC3843A is designed for low-voltage applications with low-voltage lockout thresholds of volts (on) and off). Peculiarity.

Fine-tuned oscillator discharge current for precise duty cycle control. Current mode operation up to 500kHz automatic feedforward compensation.

Latched pulse-width modulation with cycle-by-cycle current limit Internally trimmed reference voltage with under-voltage lockout High-current totem pole output Undervoltage lockout with hysteresis Low start-up and operating current.

Interfaces directly with ON Semiconductor's senseFET products.