Le blog de l'entreprise TI TPS548B28 Synchronous Step-Down Converter With Remote Sense And Hiccup Current Limit

Shenzhen Mingjiada Electronics Co., Ltd. supplies the TI TPS548B28 synchronous step-down converter with remote sensing and intermittent current limiting capabilities.

I. TPS548B28 Product Overview
The TPS548B28 is a high-performance, high-current synchronous step-down DC-DC converter designed specifically for high-density, high-precision and high-reliability industrial and data centre power supply applications. The chip supports an input voltage range of 2.7V to 16V and can deliver a stable continuous output current of up to 20A. It utilises a single-chip solution with integrated high-side and low-side MOSFETs, eliminating the need for additional power devices, thereby significantly simplifying power supply hardware design and reducing PCB footprint.

The TPS548B28 incorporates TI’s proprietary D-CAP3 adaptive on-time control architecture, which requires no external compensation circuitry and offers ultra-fast transient response and wide load line adaptability. It comes standard with two key features: differential remote output sensing and intermittent hiccup current limit. It also integrates a 3V internal LDO, programmable soft-start, pre-biased start-up, power-on indication and multiple fault protection functions, balancing output accuracy, operational stability and load protection capabilities, making it the preferred choice for high-current precision step-down power supplies. The chip utilises a compact 4mm × 3mm package, making it suitable for high-power power supply applications with limited space.

II. Key Product Features of the TPS548B28
Based on a comprehensive hardware architecture and functional design, the TPS548B28 offers several distinctive performance advantages. Its key features are as follows:

- Wide-range electrical performance: Input voltage range of 2.7 V to 16 V, maximum output current of 20 A, and a fixed, high-precision 0.6 V reference voltage. Output voltage accuracy reaches ±1 per cent, meeting the demands of precision power supply applications; supports pin-selectable switching frequencies, configurable to three levels—600 kHz, 800 kHz and 1 MHz—to accommodate varying efficiency and ripple design requirements.
- High-precision remote sensing: Equipped with a differential remote sensing architecture, it directly measures the actual voltage at the load terminal, mitigating voltage losses caused by PCB trace voltage drops and contact resistance, thereby completely resolving output voltage deviation issues in high-current power supply scenarios.
- Intelligent intermittent current-limiting protection: Features a unique valley current detection-based overcurrent protection mechanism; in the event of a fault, the device enters an intermittent ‘hiccup’ mode. Unlike traditional constant-current limiting, this effectively reduces overload losses, prevents component damage due to overheating, and significantly enhances the long-term operational reliability of the power supply.
- Highly Integrated, Minimalist Design: Internally integrates high-side and low-side synchronous MOSFETs, gate driver circuits and a 3V LDO; requires no external compensation network and uses a minimal number of external components, reducing PCB layout complexity and hardware costs.
- Comprehensive Start-up and Control Functions: Supports programmable soft start and pre-bias start-up functions to eliminate inrush current and voltage spikes during start-up; supports external reference input to enable sequential tracking and adaptation in multi-power-supply configurations.
- Comprehensive fault protection mechanisms: Integrated over-current (OC), under-voltage (UV), over-voltage (OV) and over-temperature protection. OC and UV faults trigger intermittent protection, whilst OV faults trigger lockout protection. Combined with an open-drain output indicating normal power supply status, this enables real-time fault monitoring and precise protection.

III. Detailed Explanation of the Key Core Functional Principles of the TPS548B28
1. Remote Sense Function
Under 20A high-current output conditions, the parasitic resistance of PCB output traces, pads and connectors causes significant voltage drops, resulting in a deviation between the power supply output voltage and the actual voltage supplied to the load. The greater the load current, the more pronounced the voltage drop error becomes; in severe cases, this can lead to insufficient power supply to precision loads and system malfunctions. The differential remote sensing function incorporated into the TPS548B28 perfectly resolves this industry-wide challenge.
This function utilises independent SENSE+ and SENSE- differential sensing pins to directly measure the voltage across the load terminals, rather than monitoring the voltage at the chip’s local output pins. An internal error amplifier continuously samples the differential voltage at the load end, dynamically adjusting the PWM duty cycle to precisely compensate for line voltage drop losses, thereby ensuring that the voltage at the load end remains stable within ±1%. Compared to traditional local voltage sampling solutions, remote sensing completely eliminates voltage drop interference caused by high-current traces, making it particularly suitable for high-current precision power supply applications in servers, industrial equipment, and FPGAs/chips.
Furthermore, the remote sensing circuit features a high-impedance input; the sensing branch consumes no additional power and does not interfere with the main power supply circuit, thereby balancing sensing accuracy with power conversion efficiency.

2. Intermittent Hiccup Current Limit Function
Traditional buck converters typically employ cycle-by-cycle constant-current limiting protection; however, when a fault persists, the power devices remain in a high-current conduction state for extended periods, which can easily lead to chip overheating, component ageing, or even the destruction of the power circuit. The TPS548B28 employs a valley current detection combined with an intermittent ‘hiccup’ overcurrent protection mechanism, providing a highly reliable protection solution suited to high-current operating conditions.
By monitoring the drain-source current during the low-side MOSFET’s conduction phase, the chip captures the inductor’s valley current in real time, enabling precise detection of output overloads and short-circuit faults. When the output current is detected to exceed the current-limiting threshold, the device immediately triggers the protection logic: it suspends the PWM switching output and enters a sleep mode to reduce the current, allowing the inductor current to decay rapidly; after a fixed sleep cycle, the chip automatically restarts to attempt to resume output. If the fault has been resolved, the power supply resumes normal operation; if the overload or short-circuit fault persists, the chip will repeat the intermittent cycle of ‘shutdown and sleep – restart and detection’.
This intermittent operating mode significantly reduces average power consumption during fault conditions, preventing continuous overheating of power devices such as MOSFETs and inductors. Compared to traditional current-limiting solutions, it markedly enhances device safety and system stability under short-circuit and overload conditions. Additionally, the chip supports programmable adjustment of the current-limiting threshold via an external resistor R_TRIP, allowing flexible configuration of protection parameters to suit varying load power requirements and accommodate differentiated designs across multiple scenarios. Furthermore, the device integrates a fixed reverse overcurrent protection function, which suppresses high reverse current surges, thereby further enhancing the current protection system.

IV. TPS548B28 Key Electrical Parameters
To clearly illustrate the device’s performance limits, the key electrical parameters of the TPS548B28 are summarised as follows:
- Input voltage range: 2.7 V to 16 V
- Maximum continuous output current: 20 A
- Reference voltage accuracy: ±1% (at room temperature)
- Switching frequency options: 600 kHz, 800 kHz, 1 MHz (selected via pin configuration)
- Internal LDO output: 3 V (fixed)
- Reverse overcurrent threshold: typically –10 A
- Protection modes: OC/UV intermittent hiccup protection, OV lockout protection, over-temperature shutdown protection
- Package Specifications: 4 mm × 3 mm compact QFN package

V. Typical Applications of the TPS548B28
Leveraging its core strengths of high precision, high current capability and high reliability, the TPS548B28 is widely used in various high-power precision power supply applications:
- High-power on-board power supplies for data centre servers and switches;
- High-current regulated power supplies for industrial control equipment and industrial control motherboards;
- Precision power supply for FPGA, DSP and high-end processor cores;
- High-power embedded power systems for telecommunications equipment and automotive applications;
- High-density, high-power power module designs in space-constrained environments.

VI. TPS548B28 Design Advantages and Summary
The TPS548B28 is a high-performance synchronous buck converter specifically designed to address the pain points associated with high-current buck power supplies, such as poor accuracy, weak protection and complex design. The remote differential sensing function resolves, at the hardware level, the issue of insufficient supply accuracy caused by voltage drops in high-current traces, ensuring long-term, precise voltage regulation at the load end; the innovative intermittent ‘hiccup’ current-limiting protection mechanism significantly enhances the power supply’s fault tolerance and operational safety, preventing component damage caused by overloads or short circuits.
Furthermore, the device’s highly integrated architecture eliminates the need for numerous external components and compensation circuits, simplifying PCB layout. Combined with flexible frequency configuration, soft-start control and multi-dimensional fault protection functions, it strikes a balance between design convenience, conversion efficiency and system stability. Compared with step-down chips in the same class, the TPS548B28 offers significant advantages in terms of accuracy, reliability and adaptability under high-current conditions of 20A, making it an excellent solution for high-end, high-power power supply designs in industrial, telecommunications and data centre applications.