L5987TR Integrated Circuits (ICs)

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The L5987TR is a highly integrated DC/DC switching regulator with a synchronous rectifier. It is a System on chips (SOC) device belonging to the PMIC-Voltage Regulators-DC/DC Switching Regulators category. The aim of this integerated circuit is to provide a regulated steady continuous power supply in various difficult and harsh environments, and is suitable for both mobile and stationary applications.

L5987TR has a wide input voltage range of 4.5V to 34V, and provides an adjustable output voltage up to 18V with a maximum current of 3A. Thanks to its high precision and low ripple current ensures outstanding efficiency, low operating temperature and high reliability. Additionally, its built-in soft-start function prevents the abrupt current surging at start-up, and its internal OVP protection prevents it from catastrophically destructive events. A unique feature of the L5987TR DC/DC switching regulator is its "power good" signal for reporting the status of the output voltage. This feature simplifies the power supply design by serving as an indicator of the output voltage/current status.

The working principle of the L5987TR is based on a common switching topology, with a power switch connected in series with a catch or a catch diode. It hosts an outer PWM signal which control the series switch over time; when the power switch is turned off the catch diode allows the current to flow through and maintain the voltage in the secondary side until the switch is closed again. The PWM frequency can reach up to 1MHz, allowing faster transistors to be used. The switching voltage is generated by the integrated high-speed drive technology. The precise PWM voltage and pulse width is adjusted to make the energy efficient conversion.

The DC/DC converter uses an error amplifier which supervises the output voltage and provides feedback to the PWM circuit. The error amplifier compares the output voltage with an adjustable reference voltage and sends a signal to on/off controllers. In the PWM circuit, internal circuits combine the error amplifier output with the internal clock signal which extracts PWM pulse width; and when a pulse is generated the internal MOSFET or external switching transistor is turned ON/OFF accordingly.

The power good signal is generated by comparing the output voltage with the inner reference voltage. When the output voltage exceeds the regulated level (+3%), the power good signal is released and indicates to the system whether the Voltages are within range or not. The accuracy of the Power-Good signal is within +-5%. If a voltage lower than the regulated level is detected, then the power process is reported and a shut-down procedure is carried out.

In conclusion, the L5987TR is a highly integrated Switching Regulator capable of precisely regulating a wide range of input voltages. It can be integrated in various kinds of power supply designs, and its Power-Good signal feature enables status monitoring in place. Moreover, other features that this integrated circuit carries such as in-line soft-start, over-voltage protection, contributes to improve the system reliability and safety.

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