FHT3860 DC/DC Step-Down Buck Power Module ( 2.3V-5.5V Input, 0.5V-3.3V Output )

Features

6A continuous output current

Input voltage range: 2.3V-5.5V

Output voltage: 0.5V-3.3V

Switching frequency: 3MHz

Light duty PFM mode

Power Good Indicator (PG)

Internal fixed soft start time

Small size LGA package： (4mm x 6mm x 1.6mm)

Applications

Optical Modules

Telecommunications and Network Systems

Industrial equipment

Embedded power supplies

Description

The FHT3860 is a high-frequency, high-efficiency DC/DC step-down converter that provides a complete power supply solution, simplifies the design, and requires few external resistors to achieve a 2.3~5.5V input voltage, 6A rated output current, adjustable output voltage, and excellent load and linearity regulation. The FHT3860 has a full range of protection features, including overcurrent protection (OCP), input undervoltage lockout protection (UVLO), and thermal protection.

Typical Applications

Pin Configuration

Top View

Electrical Characteristics

Input current

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.

 Test conditions are  VIN = 3.3V ，VOUT  = 1.8V，external CIN=2x10μF ，COUT  = 3x22μF ，TA = 25。C , unless otherwise noted. 

Test conditions are VIN = 3.3V ，VOUT  = 1.8V，external CIN=2x10μF ，COUT  = 3x22μF ，TA = 25。C, unless otherwise noted. CH1: Vo, CH2: SW, CH4: Io

IN OUT  INOUT  Test conditions are V = 3.3V, V = 1.8V, external C = 2x10μF, C = 3x22μF, TA = 25.C, unless otherwise noted. 

Test conditions are VIN = 3.3V ，VOUT  = 1.8V，external CIN=2x10μF ，COUT  = 3x22μF ，TA = 25。C , unless otherwise noted.

Operation

The FHT3860 is a synchronous step-down DC-DC voltage converter with a switching frequency of 3MHz. The FHT3860 achieves a continuous output current of 3A over the 2.3V to 5.5V input voltage range.

Enable Control (EN)

The FHT3860 can be enabled or disabled by setting the EN pin; when EN is high, the module is enabled. When EN is low, the module is disabled. In this mode, the output current is less than 3μA and the output is connected to ground through a resistive load. When the EN pin is left open, the output is connected to ground through an internal 2 MΩ resistor.

Soft Start (SS)

The soft-start function controls the ramp of the output voltage within 3ms during startup, which suppresses inrush current.

Input Under Voltage Lockout (UVLO) Protection

The FHT3860 maintains UVLO in shutdown mode when the input voltage falls below 2.0V. If enabled during a UVLO condition, the module remains in shutdown mode until the input voltage is above a set threshold. When the input falls below 1.8V, the module shuts down with a 200mV hysteresis.

Operating Modes

The FHT3860 uses a constant on-time control, and at heavy load currents, the switching frequency is almost constant at 3MHz.

At light load currents, the FHT3860 automatically enters PFM mode to maintain high efficiency at light loads.

As the load current changes, the FHT3860 switches between PFM and PWM modes to optimize performance. If the input voltage is too close to the output voltage, the FHT3860 enters 100% duty cycle mode, where the high-side switch is always on, providing a low input-to-output voltage differential.

Over Temperature Protection (OTP)

When the junction temperature of the FHT3860 exceeds the threshold of 150 °C, thermal shutdown protection is activated. This protection is non-latching. Once the junction temperature drops to approximately 130 °C, the module resumes operation through a soft start.

Overcurrent protection (OCP)

The FHT3860 is overcurrent protected to avoid damage under overcurrent conditions. The overcurrent protection is triggered when the valley current reaches 9A. After 16 consecutive cycles of reaching the valley current limit, the output will be disabled. After 1.5ms of disabling, the module will reboot and start a new soft start cycle.

Power GOOD Output Indication (PGOOD)

The PGOOD pin is an open drain output. When the FB voltage is less than 92% of the nominal internal reference voltage, the PG pin will be driven low; when the FB voltage is greater than 96% of the nominal internal reference voltage, the PG pin will be restored.

Output Voltage Setting

The output voltage of the FHT3860 is set by an external feedback resistor divider as shown in equation (1), and the voltage regulator circuit is shown in Figure 1.

Figure 1 Voltage Divider Resistor for Output Voltage Setting

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.