MB3759 is a 16 pins control IC that has three different packages containing most of the features required for switching regulator control circuits. MB3759 is a complete pulse-width modulation control system on single monolithic chip. The three different packages are in different materials i.e. Plastic DIP package, Ceramic DIP package and Plastic FPT package. MB3759 is switchable between its single-ended or push-pull mode of operation. 

MB3759 Pins Assignment:

Block Diagram of MB3759:

The block diagram of MB3759 IC is given in below Figure 

Features of MB3759:

• Adjustable dead time.
• Push-pull or single-ended mode of operation.
• Dual error amplifiers.
• PWM with power control circuit.
• Power supply voltage: 41 V (Max)
• Collector output voltage: 41 V (Max)
• Collector output current: 250 mA (Max)
• Amplifier Input Voltage: V_CC + 0.3 (Max)
• Built-in internal 5v reference voltage.
• Can drive 200 mA loads.

MB3759 Equivalent: TL494, TL495.

Use of MB3759:

The MB3759 as discussed is a control IC for a fixed frequency pulse width modulation switching regulator. It has specialty that this single IC comprised maximum functions required for switching due to this property it not only reduce the cost but also minimize the component counts and the required efforts for assembly work.

It’s recommended to use IC under its operating ranges for safe operations. MB3759 can be selected for either single-ended or push-pull operation by utilizing output control selection pin i.e. Pin 13.

MB3759 due to its features can be used in various applications like power supply controls, error amplifiers gain adjustment, limiting output current, protecting transistor from parasitic effects, inverters etc.

Working of MB3759:

The block diagram of 16 pins MB3759 switching regulator controller is shown in Figure 3. We can learn from figure 3 that MB3759 IC consists of dead time control comparator, PWM comparator, oscillator, two error amplifiers, reference regulator and few logic gates with total of 16 pins. This entire circuitry of MB3759 helps in various applications.

The oscillator provides waveform to both comparators for comparison of control signal, where RT and CT play key role in selecting the frequency of this oscillator. The oscillator frequency will be equal to output frequency for single ended operation while, for push-pull the output frequency will be the half of oscillator frequency.

MB3759 also creates it internal reference of 5V. Internal reference voltage is fed to reference pin which ensure stable supply and power different internal stages of IC.

The OFF time between two outputs are regulated by Dead-time pin. The dead-time feature can be utilized when control of the output of duty cycle is must otherwise for normal operation this pin should not be left floating.

The pin 13 Output-Control (OC) input is asynchronous and has direct control over output. OC also determines that the output transistor would function in parallel or in push-pull. For push-pull this Output-control pin should be connected with Vref or shall be connected to ground...