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Texas Instruments’ TPS543620 Step-Down Converter Featuring Variable Switching Frequencies

November 16, 2020 by Abdulwaliy Oyekunle

Texas Instruments’ TPS543620 is a highly efficient synchronous buck converter. It has a small body size of 2.5 millimetres by 3 millimetres and suits both test and measurement applications and healthcare. It is designed to tolerate environments that have a high ambient temperature.

Introduction of the TPS543620

The TPS543620 by Texas Instruments (aka TI) comes in a very thin quad flat no-lead (VQFN) package. The product is characterised by the wide range of its variable frequency switch: 500 kilohertz to 2.2 megahertz.

TI’s step-down converter has a fixed-frequency ACM (advanced current mode) control. ACM allows stable static and transient operation in the component without the use of complex external compensation design.

A photograph of Texas Instruments’ TPS543620 step-down converter, alongside its simplified schematic. Image Credit: Texas Instruments.

The TPS543620’s Functionalities

In the advanced current mode, an internal ramp signal is generated by a resistor connected to a ground return pin for internal analogue circuits and ramp generation capacitors with values of one picofarad, two picofarads, and four picofarads. These capacitors determine the amplitude of the generated ramp signal.

The advanced current control architecture is designed to give the component a good noise immunity by creating a high signal-to-noise ratio.  In addition, the component features two N-channel metallic-oxide semiconductor field-effect transistors (or MOSFETs).

At start-up, the device exhibits a ‘soft start’. Soft start occurs when the reference voltage ramps up to about 0.5V to reduce inrush current. The soft start time varies from one millisecond to four milliseconds (the time is selected using a resistor connected to a ground return pin for internal analogue circuits).

Furthermore, the product has different protection mechanisms against damages that can be caused by over-voltage, under-voltage, over-temperature, and over-current. When the temperature is over 165 ⁰C, the over-temperature protection is triggered and the device switches off; and when the temperature falls below 12 ⁰C, it simply restarts. The over-current protection incorporates both the positive inductor current protection and negative inductor current protection.


Texas Instruments’ functional block diagram of the TPS543620, which shows the various parts of the Texas Instruments product, including its ACM (advanced current mode) controller. Image Credit: Texas Instruments.


The TPS543620’s Electrical Characteristics

Engineers can comfortably operate the TPS543620 by feeding it a wide range of input voltages from 4V to 18V. It also gives an output voltage that ranges from 0.5V to 5.5V. The variable switching frequencies can be synchronised to an external clock of frequencies from 400 hertz to 2,200 hertz.

When operating the TPS543620, it is recommended that the engineer or other user utilises a bypass capacitor, such as a 4µF (four-microfarad) ceramic capacitor, between the input voltage pin and the power ground pin. This ensures good electrical performance.

The operating junction temperature of the component varies from −40 ⁰C to 150 ⁰C.


Pin Description and Configuration

The TPS543620 has 14 pins that are packaged in its said VQFN package. The product has two input voltages and two power ground pins. The frequency select pin enables users to connect an external clock to synchronise the switching frequencies.

The enable pin is employed to turn the device on and off. For input voltages that vary from 4V to 18V, the device turns on when the voltage across the enable pin passes a threshold voltage of 1.25V. The device turns off when the voltage across the enable pin drops to 1.05V.

Texas Instruments’ top-down view diagram of the TPS543620. Image Credit: Texas Instruments.


The TPS543620 has four feedback pins, which are each used to achieve output voltage regulation when they are connected to the midpoint of a resistor divider.


Examples of the TPS543620’s Applications

The TPS543620 synchronous buck converter suits applications in a wide range of disciplines: these include healthcare, as it is used in the manufacturing of medical equipment; plus, instrumentation engineers also use the product in test and measurement applications.

In telecommunications, moreover, the product is useful in infrastructure equipment for both wireless and wired communication.

Altogether, the TPS543620 is ideal for engineers working with small hardware solutions: as Texas Instruments explains, the product is “optical for designs requiring a small solution size”.

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