FHT8027C DC/DC Buck Converter Integrated Power Module ( 5V-60V Input, 2.5V-24V Output )

Features

4A Full-Load Output Current

Wide Input Voltage Range: 5V-60V

Output Voltage: 2.5V-24V

Selectable Switching Frequency

Efficiency Up to 95%

15μA Shutdown Current

Programmable Soft-Start

Compact LGA Package with Low Profile (15mm x 15mm x 4.32mm)

Applications

12V and 42V Automotive and Heavy-Duty Equipment

48V Telecommunications Power Supplies

Avionics and Industrial Control Systems

Distributed Power Converters

Description

The FHT8027C is a step-down integrated molded power supply that encapsulates a switching controller, inductor, and related support components within its package. It measures 15.0×15.0×4.32 mm in size.Based on synchronous rectification Buck topology design, it can deliver a maximum output current of 4A. The power conversion efficiency can reach up to 95%.It allows for voltage conversion from 5V to 60V to 2.5V to 24V. Customers can set the switching frequency according to their needs via an external resistor, with a settable frequency range of 100kHz to 1MHz. The soft-start time can be adjusted by a small capacitor. With its integrated small-sized LGA package, only a voltage-regulating resistor, a small number of input and output filter capacitors are required for the peripheral configuration, enabling rapid completion of the power supply system setup.

Typical Applications

Pin Configuration

Electrical Characteristics

Input Current

Note 1: Stress values exceeding those listed in the "Limiting Values" section may cause permanent damage to the device. Prolonged exposure under any absolute maximum rating conditions may affect the reliability and lifespan of the device.

Note 2: The maximum continuous output current may be derated due to the junction temperature of the FHT8027C.

Note 3: The performance specifications of the FHT8027C are guaranteed within the entire internal operating temperature range of -40°C to 125°C. Please note that the maximum internal temperature is determined by specific operating conditions, circuit board layout, the rated thermal resistance of the package, and other environmental factors.

Operation

Output Voltage Setting

The output voltage of this module can be set by an external resistor RADJ connected to the ADJ pin. The reference calculation formula is as follows:

Note: It is recommended to reserve two resistor positions for fine-tuning the output voltage.

Soft Start

The soft start function controls the rise slope of the power supply's output voltage during startup. The controlled output voltage slope minimizes output voltage overshoot and reduces input inrush current. A capacitor connected between the SS pin and GND is used to set the rise slope. The soft start time (tSS) is set by the CSS capacitor, using the following formula:

The soft start capacitor needs to be greater than 2.2nF.

Operating Frequency

The switching frequency can be adjusted by a resistor connected between the RT pin and ground, or synchronized to an external clock signal through the SYNC pin.

The switching frequency range adjustable by the RT resistor is from 100 kHz to 1 MHz. The formula for calculating the RT value is as follows:

Synchronization

In CCM mode, the oscillator can be synchronized to an external clock through the SYNC pin. The requirements for the external clock signal are as follows: the clock range is from 100 kHz to 1 MHz; the clock frequency range is -50% to +50% of the nominal frequency set by RT; the maximum voltage amplitude of the clock is 13V; and the minimum pulse width of the clock is 50 ns.

Operating Modes 

PFM: When the SYNC pin is connected to low level, the module operates in PFM (Pulse Frequency Modulation) mode under light load conditions. In PFM mode, as the load current decreases, the switching frequency also decreases, thereby improving efficiency at light loads by reducing switching losses. Conversely, when the load current increases, the switching frequency increases to minimize output voltage ripple.

FCC: When the SYNC pin is connected to high level, the module maintains Continuous Conduction Mode (CCM) under light load conditions. In FCC mode, the switching frequency remains almost constant across the entire load range, making it suitable for applications that require tight control of switching frequency at the cost of lower efficiency.

Input UVLO

The FHT8027C supports adjustable input UVLO with hysteresis that can be tailored to specific power-up and power-down requirements through the resistor divider connected to the RUN pin. When the RUN pin voltage exceeds 1.2V, an additional 10μA of hysteresis is added. This extra current contributes to the hysteresis of the input voltage. The formulas for calculating the input start-up voltage and the external hysteresis of the input voltage are as follows:

The application circuit is illustrated in the figure of the undervoltage lockout (UVLO) voltage divider.

Undervoltage lockout (UVLO) voltage divider circuit

Layout

It is essential to ensure that the grounding and heat dissipation methods are acceptable. Here are a few key rules to keep in mind:

1. Place the R_ADJ and RT resistors as close as possible to their respective pins.

2. Position the C_IN capacitor as close as possible to the V_IN and GND connections of the FHT8027C.

3. Layout the C_OUT capacitor as close as possible to the V_OUT and GND connections of the FHT8027C.

4. Route C_IN and C_OUT so that their grounding currents flow close to or underneath the FHT8027C.

5 .Connect all GND lines to a large copper pour or plane on the top layer. Avoid disruptions in the grounding connections between external components and the FHT8027C.

Package Description

Soldering and Storage Precautions

Recommended Reflow Soldering Profile

Precautions:

1.Due to the large size of the module, please do not place it on the bottom side of the board during reflow soldering to prevent it from falling off.

2. For bulk and unpacked products, store them in a desiccator (with a relative humidity of less than 10% inside). For products still in their original packaging, it is also recommended to store them in a desiccator if possible.

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