ZLDO270T8TA

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Linear regulators have been ubiquitous in the power supply industry for many years, serving as an effective and straightforward way of deriving a stable regulated voltage from an unregulated voltage supply. Such linear regulators control either a greater or lesser output voltage by controlling their output current. The ZLDO270T8TA is a three-terminal adjustable linear regulator which combines the elimination of external components, high-efficiency voltage regulation, and adjustable output voltage in a single package. The obvious benefit is that the external components and their cost can be reduced.

Application field and features

The ZLDO270T8TA is a low cost, efficient voltage regulator which is suitable for a broad range of applications in both industrial and consumer electronics. These range from laptop adapters, digital photo frames and CD/DVD players, to electric bikes and industrial lighting. Due to its high efficiency of up to 98%, the ZLDO270T8TA operates with lower quiescent currents and input to output ratios of up to 3:1, and thus enables the design of more power-efficient systems. As a result of the use of two external components and its 0.8mm ultra-thin profile, it makes it suitable for portable consumer electronic and electronic machine applications. Additionally, it offers wealth of features such as wide input voltage range of 3V~30V, output current of up to 800mA, on-chip power-on reset and over-current limiting, soft start and thermal shutdown, making it an ideal choice for designers.

Working principle and operations

The ZLDO270T8TA is a low power consumption three-terminal adjustable linear voltage regulator. It is composed of a band-gap reference, error amplifier and output driver circuit. This regulator operates with a voltage applied to the input pin (IN) which is greater than the voltage applied to the reference pin (REF). The output voltage is usually preset inputting the appropriate feedback resistor resistance at (FB) pin, providing an accurate and stable output voltage. From the designer’s point of view, this provides extra freedom for the output voltage selection range.

The internal schematic of the ZLDO270T8TA can be seen in Figure 1. As can be seen, the ZLDO270T8TA includes an error amplifier (U1A) and output driver (U1B). A feedback loop is established between the output voltage and the error amplifier’s non-inverting input terminal. The reference voltage generated from the band-gap reference of the error amplifier is set to the inverting input terminal of the amplifier. Thus, the difference between the two input voltages of the error amplifier is used to control the operation of the output driver, which in turn controls the output current.

When the ZLDO270T8TA is in normal operation (not in current limiting or regulation) the voltage across the output pin is equal to the voltage of the reference pin. This means that the output current is equal to the current through the load and the current through the feedback resistors. When the load current is increased, the voltage at the output pin will be momentarily decreased causing the output current to also be momentarily decreased. This will in turn decrease the voltage at the non-inverting input terminal of the error amplifier and ramp up the voltage reference pin of the ZLDO270T8TA. This causes the regulator to increase the output current and thus maintain a constant output voltage.

The ZLDO270T8TA also has the protection features such as voltage, current and temperature protection. The current limiting and internal thermal protection are integrated on-chip, eliminating external components and their costs. The device includes a power-on reset circuit that is triggered when the input voltage is higher than the voltage reference. Additionally, it offers thermal protection which shuts off the device when the die temperature rises to a preset level, providing a thermal margin.

In summary, the ZLDO270T8TA is a 3-terminal adjustable linear regulator which combines the elimination of external components, efficient voltage regulation, adjustable output voltage in a single package. The device is suitable for a broad range of applications in both industrial and consumer electronics. It offers a wide input voltage range of 3V~30V, output current of up to 800mA, and on-chip protection functions such as power-on reset, current limit and thermal shutdown, making it an ideal choice for designers.

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