FHT4618 Integrated DC/DC Adjustable Buck Power Module ( 4.5V-24V Input, 0.6V-5.5V Output )

Features

6A output current

Wide input voltage range: 4.5V-24V

Output voltage: 0.6V-5.5V

Switching frequency: 800kHz

Efficiency up to 95%

Soft start

Small size, surface mount package: LGA(15mm×9mm×4.32mm

Applications

ATCA boards

Telecommunications, data communications, networking, and industrial equipment

Card-type and rack-mounted data storage devices

Medical systems

Servers

Description

The FHT4618 is an integrat ed 6A DC/DC st ep-down power suppl y wit h an integrat ed chip, induc tors , res i s tors and capac itors . The FHT4618 has an input voltage range of 4.5V to 24V, an output voltage range of 0.6V to 5.5V, and a switching frequency of 800kHz, and can be used with a small number of input and output filter capacitors. The small size of this product allows it to be mounted on compact PCB boards to supply power to high-density mounted load points.The FHT4618 is packaged in a fast-dissipating, compact, low-profile molded package in an LGA package that measures:15mm×9mm×4.32mm , suitable for SMT auto mounting.

Typical Applications

Pin Configuration

TOP VIEW

Electrical Characteristics

Note 1: Stresses above the values listed in the "Limit Values" section may cause permanent damage to the device. Prolonged exposure to any of the absolute maximum ratings may affect the reliability and service life of the device.

Note 2: The maximum continuous output current may be derated due to the junction temperature of the FHT3860.

Note 3: The performance specifications of the FHT3860 are guaranteed over the full -40°C to 125°C internal operating stability range. Note that the maximum internal temperature is determined by specific operating conditions in conjunction with the board layout, rated thermal resistance of the package, and other environmental factors.

Operation

Overview

The FHT4618 is a standalone, non-isolated buck switching DC/DC power module with an input range of 4.5V to 24V, capable of providing an output current up to 6A. This power module offers ultra-high conversion efficiency and precisely adjustable output voltage ranging from 0.6V to 5.5V. Since the FHT4618 is a buck converter, please ensure that the input voltage is sufficiently high to support the required output voltage and load current.

Selection of Input Capacitance

It is recommended to choose a ceramic capacitor with a capacitance of 10μF, a voltage rating of 35V, and an X5R or higher specification. Ceramic capacitors are characterized by their small size, high reliability, and very low Equivalent Series Resistance (ESR). X5R and X7R ceramic capacitors maintain stable performance over a wide range of temperatures and voltages, effectively reducing input voltage ripple.

Selection of Output Capacitance

It is recommended to choose a ceramic capacitor with a capacitance of 100μF, a voltage rating of 6.3V, and an X5R or higher specification for the output capacitor. It is advisable to use multiple capacitors in parallel, with a total capacitance of 100μF or more. Connecting multiple ceramic capacitors in parallel can reduce their equivalent ESR (Equivalent Series Resistance) and ESL (Equivalent Series Inductance), thereby effectively lowering the output voltage ripple.

Output Voltage Setting

The output voltage of the module can be set by the external GND resistor RFB on the FB pin, and the reference formula is as follows:

Note: It is recommended that two resistor positions be reserved for precise adjustment of the output voltage.The resistance value of RFB is adjusted according to the customer's requirement, where RFB is in kΩ.

PFM model

At light load, the FHT4618 operates in PFM mode, and to improve the efficiency at light load, the switching frequency decreases as the load current decreases.

This reduces switching losses. When the load is increased, the switching frequency increases and the ripple decreases.

Over-current protection

When the output current exceeds 9A, the module triggers hiccup over-current protection.

Input Under-Voltage Protection 

The input under-voltage protection is triggered and locked when the input voltage drops below 4.2V. The module will start up when the input voltage rises above 4.5V and the voltage at the RUN pin is above 0.8V.

PCB Layout

Due to the high integration of components required for power conversion in the FHT4618, it eliminates most of the tricky issues related to PCB layout. However, it is still necessary to optimize the PCB routing as much as possible to ensure its proper operation. Even with its high integration, good grounding and heat dissipation are still essential when using the module. The recommended layout diagram is shown below:

1.  Place the R_FB resistor as close as possible to its corresponding pin.

2. Position the Cin capacitor as close as possible to the Vin and GND connections of the FHT4618.

3. Locate the Cout capacitor as close as possible to the Vout and GND connections of the FHT4618.

4. When placing the Cin and Cout capacitors, ensure that their grounding currents flow directly near or underneath the FHT4618.

5. Connect all GNDs to the largest possible copper pour area on the top layer, avoiding any breaks in the grounding connection between external components and the FHT4618.

6. For effective heat dissipation, use vias to connect the GND copper pour area to the internal grounding plane of the circuit board, providing both a good grounding connection and a thermal path to the internal plane of the board. Since they are close to the internal power processing components, the FHT4618 can benefit from these vias connecting to the internal GND plane of the PCB for heat dissipation. The optimal number of thermal vias depends on the PCB design. For example, if the board uses very small vias, more thermal vias may be required to ensure adequate heat dissipation.

Package Description

Soldering and Storage Precautions

Recommended reflow soldering profile

Caution:

1. Due to the large size of the module, please do not place the module under the board for reflow soldering to avoid falling off.

2. For bulk products and those that have been taken out of their original packaging, they should be stored in a desiccator (with a relative humidity of less than 10% inside). For products still in their original packaging, they should also be stored in a desiccator whenever possible.

3. Before mounting on the board, it is necessary to strictly follow the baking conditions to dry the samples: bake at 125°C for more than 48 hours, and control the reflow soldering temperature within 245°C.