LM2596S-3.3

1. Description

LM2596S-3.3 regulator is monolithic Integrated circuit that provides all active functions Used in step-down switching regulators, capable of Drive 3A load with excellent line and load regulation. These devices have fixed outputs

Voltage is 3.3 V, 5 V, 12 V and adjustable output Version.

Minimum number of external Components, these regulators are easy to use and Including internal frequency compensation and fixed frequency oscillator.

LM2596S-3.3 works at switching frequency 150 kHz, which allows the use of smaller filters Fewer components than required Frequency switching regulator. can be use on Standard 5-pin TO-220 package with several different

Lead bending option and 5-pin TO-263 surface mount package.

These inductors are aimed at LM2596S-3.3. This function greatly simplifies the design of the switching power supply.

Other features include ±4% tolerance of output voltage under specified input voltage and output load Condition, the oscillator frequency is ±15%. Including external shutdown function, typical value is 80μA stand-by current. Self-protection function includes two-level frequency reduction output current limit The switch and thermal shutdown function provide comprehensive protection in the event of a fault.

2. Pin Configuration and Functions

3. Feature

   1. 3.3V, 5V, 12V and adjustable output versions

   2. Adjustable version output voltage range: 1.2V to The maximum value under line and load conditions is 37V±4%

   3. Available in TO-220 and TO-263 packages

   4. 3A output load current

   5. Input voltage range up to 40 V

   6. Only four external components required

   7. Excellent line and load regulation specifications

   8. 150kHz fixed frequency internal oscillator

   9. TTL shutdown function

 10. Low power consumption standby mode, IQ, usually 80μA

 11. high efficiency

 12. Use ready-made standard inductors

 13. Thermal shutdown and current limit protection

 14. Use the following options to create a custom design

4. Typical Application

5. Feature Description

5.1. Overview

The LM2596 SIMPLE SWITCHER® regulator is an easy-to-use, nonsynchronous, step-down DC-DC converter with a wide input voltage range up to 40 V. The regulator is capable of delivering up to 3-A DC load current with

excellent line and load regulation. These devices are available in fixed output voltages of 3.3-V, 5-V, 12-V, and an adjustable output version. The family requires few external components, and the pin arrangement was designed for simple, optimum PCB layout.

5.2. Delayed Start-Up

The circuit in Figure 1 uses the ON/OFF pin to provide a time delay between the time the input voltage is applied and the time the output voltage comes up (only the circuitry pertaining to the delayed start-up is shown).

As the input voltage rises, the charging of capacitor C1 pulls the ON/OFF pin high, keeping the regulator OFF.

Once the input voltage reaches its final value and the capacitor stops charging, resistor R2 pulls the ON/OFF pin low, thus allowing the circuit to start switching. Resistor R1 is included to limit the maximum voltage applied to the ON/OFF pin (maximum of 25 V), reduces power supply noise sensitivity, and also limits the capacitor C1 discharge current. When high input ripple voltage exists, avoid long delay time, because this ripple can be coupled into the ON/OFF pin and cause problems.

This delayed start-up feature is useful in situations where the input power source is limited in the amount of current it can deliver. It allows the input voltage to rise to a higher voltage before the regulator starts operating.

Buck regulators require less input current at higher input voltages.

Figure 1. Delayed Start-Up