FHT4644 Ultra-Thin Multi-Channel DC/DC Buck Power Module ( 4.0V ~ 15V Input, 0.8V ~ 5.5V Output )

Features

Utilize SMT technology and SIP plastic-encapsulated packaging

General Specificatio： GJB 10164-2021

Detailed Specification: SC-Q/GZX52013-2022

Output Current: Each channel provides a continuous full-load output current of 4A, with a peak of 5.5A

Parallel Connection: Four channels can be paralleled for a total output of 16A

Operating Temperature (Tc) ：-55℃ ~ +125℃

Wide Input Voltage Range: 4.0V to 15V

Output Voltage Range:0.8V to 5.5V

Switching Frequency: Variable frequency, capable of automatic adjustment, typically 1MHz  Operating Mode: Automatic adjustment mode  Efficiency: 92%

No-load Power Consumption: The total for four channels is

0.01W (at 12Vin, 5V output)

Output Ripple Voltage: 15mVp-p (typical)

Voltage Regulation: ±1.0% (typical)）

Load Regulation: ±0.5% (typical)

Soft-start: Internal 1ms soft-start (with an optional external 1ms soft-start)

Protection Features: Protection against output overcurrent, overheating, output overvoltage, and input undervoltage  Regular size: LGA package(9.0*15.0*4.32mm)

BGA package(9.0*15.0*5.01mm)

Ultra-thin size: LGApackage(9.0*15.0*1.82mm)

BGApackage(9.0*15.0*2.42mm)

Applications

Multi-rail Point-of-Load Regulation 

Power Supply for CPUs and GPUs 

Power Supply for ASIC Chips such as CPLDs, DSPs, and FPGAs

Description

The FHT4644 is a non-isolated buck DC/DC power module with a wide input voltage range of 4 to 15V and an adjustable output voltage of 0.8 to 5.5V. It features four output channels, each capable of delivering up to 4A, and offers users the choice of LGA and BGA packaging options. The FHT4644 is an SMT surface-mount module that is welded onto the PCB board using reflow soldering.

It boasts high power density and a compact size, with an ultra-thin thickness of only 1.82mm and a power density reaching 300W/cm³. The power module circuit integrates the power supply chip, inductor, and related components, allowing for the rapid design of a multi-channel power supply system by simply configuring a voltage-adjusting resistor and a few input/output ceramic capacitors for each output channel. This simplified system design maximizes PCB layout space savings. As a point-of-load power supply, the FHT4644 can be directly mounted next to the FPGA, providing high-precision voltages such as 5.0V, 3.3V, 2.5V, and 1.2V for digital circuits, FPGA control circuits, motherboards, CPUs, communication systems, storage, and other components in the system. Each channel can continuously provide a current of 4A, and the four output channels can be combined and used in parallel, as well as paralleled with other FHT4644 power modules.

It is ideally suited for applications requiring low output voltages and multiple channels. The operating mode and frequency of the FHT4644 can be automatically adjusted based on real-time input and output voltages and loads, which not only simplifies the peripheral circuitry but also minimizes no-load power consumption, ensuring that the power module always operates in the optimal state. All components of the FHT4644 are domestically produced, and an autonomous and controllable report can be provided. Additionally, this power module is characterized by high reliability,high efficiency, and long life. Especially when outputting low voltages, its efficiency is significantly higher than similar products, providing a more reliable and stable power supply for the system.

Typical Application

Configurable output array

Non-parallel Application

Parallel Application

PIN CONFIGURATION

Electrical Characteristics

NOTE : 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 life of the device.

Operation

FHT4644 is a four-channel independent output non-isolated DC/DC switching regulator. It has four independent regulator channels, each capable of providing up to 4A of continuous output current, requiring only a small amount of external

input and output capacitance. Within the input voltage range of 4.0V to 15V, each regulated channel can provide an accurately regulated output voltage through an external resistor, with a voltage range of 0.8V to 5.5V.

RUN Start

Pulling the RUN pin of each regulator channel to ground forces the regulator into shutdown mode, turning off the power MOSFET and most of the internal control circuits. Keeping the RUN pin above 0.7V only turns on the internal reference while still keeping the power MOSFET off. Further increasing the RUN pin voltage above 1.2V will turn on the entire regulator channel.

The output voltage setting is internal to the FHT4644, with the FB pin connected to the VOUT terminal of each channel through a 100kΩ precision resistor. The output voltage of this module can be adjusted by the resistor RFB between FB and GND, with the calculation as follows:：

Note 1: It is recommended to reserve two resistor positions with a precision of 0.5% for fine-tuning the output voltage.

Below is List 1, which shows the relationship between the RFB resistor and various output voltages:

Note 2: When used in parallel, such as N parallel circuits, the RFB resistor value at this time is the single-channel RFB resistor value divided by N. For example, when four circuits are paralleled for a 3.3V output, the RFB resistor value would be 32kΩ divided by 4, which equals 8kΩ.

Soft Start

The FHT4644 module incorporates a built-in soft-start feature with a duration of 1 millisecond (mS). Additionally, an external soft-start pin is available for selection, allowing for increased delay time by connecting a ceramic capacitor of approximately 3.3 nanofarads (nF). The following formula can be used to calculate the soft-start capacitor value:Css=4XT SS

Css represents the capacitance value of the soft-start capacitor, measured in nanofarads (nF). Tss stands for the soft-start time, measured in milliseconds (mS). For example, when an additional soft-start time of 1 millisecond is desired, the required soft-start capacitor would be 4 nanofarads.

Input Under-Voltage Protection

The FHT4644 features input under-voltage protection. When the VIN (input voltage) drops below 3.7V, the under-voltage lockout (UVLO) function is activated.

Note: If the input cable is relatively long, there may be a voltage drop along the cable due to resistance. To ensure normal output, it is necessary to guarantee that the voltage at the module's input pin is greater than 4.0V.  

Output Over-Current Protection

The FHT4644 also incorporates output over-current protection. When the output current exceeds the preset current limit, the converter enters a protection state to prevent damage to the load or the converter itself. Once the output current returns to within the normal range, the converter automatically resumes normal operation.

Power  Good

The PGOOD pin is an open-drain pin that can be used to monitor each valid output voltage. When the Vout falls below the threshold voltage set for the output voltage, the PGOOD pin goes high. It can also be used to monitor protective functions such as UVLO (Under-Voltage Lockout) and OTP (Over-Temperature Protection). By connecting a resistor to pull the PGOOD pin up to a specific supply voltage, monitoring can be achieved.

Below is a schematic diagram of the PGOOD circuit, and List 2 provides the logic table for the PGOOD pin:

VFB stands for the voltage feedback pin voltage, VTH_PG represents the PGOOD threshold voltage, TJ denotes the junction temperature, and TSD signifies the temperature at which the power supply protection shutdown occurs.

Over-Temperature Protection

When the case temperature of the FHT4644 rises above 135°C, it enters an over-temperature protection state. 

Package Description

Operating Conditions、Testing and Special Application Notes

1、Recommended Operating Conditions for This Module：

★Input Voltage Range：VIN = 4.0V～ 15V（It is recommended that the minimum input voltage be greater than 4.2V）

★ Output Voltage Range：VOUT = 1.0V～5.0V

★ Output Current Range： （Recommendation for 80% Derating Usage)）

Iout= 0～4A Operating independently in a single channel

Iout=N ×（ 0～4A） N represents the number of parallel channels

★ Operating Case Temperature TC： -55℃ ~ 125℃

2、Testing and Application Instructions

It is not recommended to use a linear power supply for functional testing of this power module (as linear power supplies tend to generate transient voltage fluctuations when adjusting the output, posing a risk of exceeding the maximum rated voltage). Instead, it is recommended to use a switching power supply or a DC/DC module power supply.

★ This power module features a high power density circuit, and it is recommended to use a PCB board with 4 layers or more for layout. Considering long-term stable operation under high temperature conditions, it is advisable to implement appropriate load derating (80% of rated load) or thermal management measures (options include: system-level air cooling, attaching a heatsink above the power module, increasing the copper-clad area on the PCB board beneath the power module, etc.).

★ For the PCB board application of this power module, it is recommended to use wider copper foil for the layout of VIN, VOUT, and GND to reduce conduction losses and thermal stress caused by high currents. It is advisable to place the input and output filtering capacitors close to the power module. To avoid interference, it is recommended to layout the input capacitors and output capacitors with a distance greater than 1 cm between them.

★  If you were previously using an LTM4644 peripheral circuit design, you will need to recalculate RFB according to the following formula.，Only the resistance value needs to be changed, and there is no need to modify the PCB layout.

★ This power module is a hermetically sealed product. Before soldering, check the changes on the humidity indicator card to determine if pre-baking treatment is necessary.

★ Attention should be paid to electrostatic protection during product transportation.

Operating Conditions、Testing and Special Application Notes

3、Thermal Derating Curve Reference Diagram (Load Current vs. Ambient Temperature, Tested in Temperature Chamber, Without Additional Cooling Devices, Evaluating Loading Conditions of Power Supply Module at Different Ambient Temperatures)

4、Thermal Derating Curve Reference Diagram (Load Current vs. Case Temperature, Tested at Room Temperature, Without Additional Cooling Devices, Evaluating the Rise in Case Temperature of the Power Supply Module Under Different Load Conditions)

Precautions for Reflow Soldering

1. Products that are well-packaged must undergo baking at 125°C for 24 hours before use. If the packaging bag is found to be torn or if the desiccant or indicator label has changed color, the products must undergo baking at 125°C for 48 hours before use. For more information, please refer to the IPC/JEDEC J-STD-033 standard.

2. For reflow soldering of lead-free BGA solder ball products, the peak temperature should not exceed 245°C; for lead-containing BGA solder ball products, the peak temperature should not exceed 225°C.

3. It is recommended to use a stencil thickness of 125um-160um, with stencil openings slightly smaller than the solder pads. Taking a Φ0.635mm solder pad as an example, the recommended stencil opening size is Φ0.620mm.

4. The solder paste can be either lead-free SAC or SnPb (with lead). Powder types 3 or 4 are recommended. Different brands of solder paste may have different welding recommendations, so please pay attention to the references. The porosity rate is recommended to not exceed 25%.

Recommended Reflow Soldering Parameters Table

Recommended Reflow Soldering Profile (for reference)

Appendix I: Key Differences and Explanation between FHT4644 and LTM4644

1.  Functional Differences

Note: Due to differences in the calculation formula for the external voltage regulation resistor, the resistance

values of the voltage regulation resistors for FHT4644 and LTM4644 are not the same.

FHT4644 voltage regulation resistance calculation formula and voltage regulation resistance value list:

LTM4644 voltage regulation resistance calculation formula and voltage regulation resistance value list：

2. Pin Configuration Comparison

Through the above comparison, due to the automatic frequency conversion technology adopted by FHT4644, the operating mode does not require additional circuit control, and the peripheral circuitry is simpler than that of LTM4644. This allows for more component layout savings. By simply changing the voltage regulation resistor RFB, FHT4644 can be used as a drop-in replacement for LTM4644 without the need to modify the existing PCB layout.