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Analog Devices LTM4657 Micro-Module Regulator with External Frequency Synchronisation

June 17, 2020 by Abdulwaliy Oyekunle

The LTM4657 product manufactured by Analog Devices is a step-down DC/DC micro-module regulator.

It is packaged in a 6.25 mm × 6.25 mm × 3.87 mm ball grid array package. It can be used in instrumentation and telecommunication applications.


The Main Features

The micro-module regulator features a high switching frequency as high as 500KHz and is controlled by a switching controller. To perform switching and noise-sensitive operations, the product allows users to make an external frequency clock synchronisation within ±30% of the set frequency. Stability is achieved thanks to the product’s current mode control that allows a speedy transient response to line and load changes.

In addition, the LTM4657 has 2 modes of operations: discontinuous current mode (DCM) and continuous current mode (CCM). DCM is used in applications that require low output ripple and high efficiency at intermediate current, while CCM is used in applications where low current efficiency is not important.

The component supports multiphase operation, which is made possible by connecting multiple versions of the product in a parallel configuration to achieve a high output current.


LTM4657, LTM4626, and LTM4638 Analog Devices regulator.

Product images of the LTM4657, LTM4626, and LTM4638 Analog Devices regulators. Image Credit: Analog Devices


Pin Configuration

The product is made up of 16 pins comprising both output and input pins. It has power input and output pins, ground pin, output clock signal pin, and a pin for internal compensation operation. Also, the component supports a differential remote sensing amplifier with its positive input and negative input differential remote sense amplifier pins.

The LTM4657 also features internal temperature monitor pins. It also features a switching frequency pin that sets the default switching frequency to 500KHz. A run control input pin serves to enable regulator operation when the voltage across the pin is above 1.2V.

While using the component, it is advisable to place a decoupling capacitor between the output voltage pin and ground.


Electrical Characteristics

The LTM4657 can be operated by an input supply voltage ranging from 3.1V to 20V. The voltage across the output voltage pin ranges from 0.5V to 5.5V. An output current of 8A flows through the pin when the input voltage is 12V and the output voltage is 1.5V.

At an output current of 8A and input voltage of 3.3V, the component proves power efficient, as it has an efficiency of about 95% under those conditions.

In addition, the run pin can operate comfortably over a wide range of input voltage from −0.3V to 22V. The pin deactivates the regulator operation mode when a voltage below 1.1V is fed to it. The product has a switching mode regulator channel that operates by feeding 3.3V to the internal regulator output pin.


An annotated diagram showing a top-view of the LTM4657 regulator.

An annotated diagram that refers to the top-view of the LTM4657 regulator. Image Credit: Analog Devices.


Points of Comparison with Other Micro-module Regulators

Unlike the LTM4657 that features an external frequency synchronisation, the LTM4664 (which is also a micro-module regulator) features a digital power system management. The LTM4664 operates from an input voltage ranging from 30V to 58V. It has applications in storage systems and electronic test equipment.

Another micro-module regulator manufactured by Analog Devices is the LTM4668, which has an external frequency synchronisation like the LTM4657. It has a wide range of applications in telecom and embedded systems.

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