TIDA-050052 参考设计采用 TPS62903 3V 至 17V 输入电压降压转换器，专门开发用于设计空间十分有限的应用。该参考设计将输入电压降至 1.2V VOUT，不仅可为负载提供高达 3A 的电流，而且具有高效率和低静态电流。该设计使用 DCR 约为 48mΩ 的 1uH 电感器。整体解决方案尺寸（包含所有外部元件）为 25mm²。该设计非常小巧，可实现高效的直流/直流转换和业内超低的工作静态电流 (IQ)。

• 25mm² 的小型总解决方案尺寸
• 120mA/mm² 的功率密度
• 3V 至 17V 的输入电压
• 高达 3A 的持续输出电流
• 低 IQ：4uA（典型值）
• 在 -40°C 至 150°C 温度范围内的总系统电压精度为 ±1.25%
• 工作结温：-40C 至 150C
• 带 100% 模式的 DCS-Control™ 拓扑。

• 楼宇自动化
• 工厂自动化和控制
• 数据中心和企业级计算
• PC 和笔记本电脑
• 电力输送

The TIDA-050052 is designed by using the TPS62903 high efficiency and low IQ DC/DC Buck converter. The design is optimized for small total solution size, low BOM count, high efficiency, best thermal performance, and lowest quiescent current possible. This design is ideal for applications where space is limited such as smart lock, wearable devices, and so on. The high efficiency and low IQ are ideal for battery operated systems. The design allows to efficiently use the battery power and extend its life time.

By connecting 26.1-kΩ resistor on Mode/S-CONF pin, the device is configured to:

• VSET-operation: VOUT is sensed only through the VOS pin by an internal resistor divider. The target Vout is programmed by an external resistor connected between the VSET pin and GND. In this design, FB/VSET is connected to GND and thus the VOUT is programmed to 1.2-V.
• 2.5-MHz Switching Frequency with AEE (Automatic Efficiency Enhancement): The MODE/S-CONF pin is configured for AEE mode, the TPS62903 provides the highest efficiency over the entire input voltage and output voltage range by automatically adjusting the switching frequency of the converter. The efficiency decreases if VOUT decreases, VIN increases, or both. To keep the efficiency high over the entire duty cycle range (VOUT/VIN ratio), the switching frequency is adjusted while maintaining the ripple current. The AEE feature provides an efficiency enhancement for various duty cycles, especially for lower VOUT values where fixed frequency converters suffer from a significant efficiency drop. Furthermore, this feature compensates for the very small duty cycles of high VIN to low VOUT conversion, which limits the control range in other topologies.
• Power Save Mode Operation (Auto PFM/PWM): The MODE/S-CONF pin is configured for power save mode (auto PFM/PWM). The device operates in PWM mode as long the output current is higher than half of the ripple current of the inductor. To maintain high efficiency at light loads, the device enters power save mode at the boundary to discontinuous conduction mode (DCM). This happens if the output current becomes smaller than half of the ripple current of the inductor. The power save mode is entered seamlessly when the load current decreases. This ensures a high efficiency in light load operation. The device remains in power save mode as long as the inductor current is discontinuous. In power save mode, the switching frequency decreases linearly with the load current maintaining high efficiency. The transition in and out of power save mode is seamless in both directions.
• Output Discharge Function Enabled: The discharge function is enabled to ensure a defined down-ramp of the output voltage when the device is being disabled but also to keep the output voltage close to 0-V when the device is off. The output discharge feature is only active once TPS62903 has been enabled at least once since the supply voltage was applied.
• Soft Start: The SS/TR pin left floating for fastest start up time.

The TPS62903 is a highly-efficient, small, and flexible synchronous step-down DC-DC converter that is easy to use. A selectable switching frequency of 2.5-MHz or 1.0-MHz allows the use of small inductors and provides fast transient response. The device supports high VOUT accuracy of ± 1.25% using VSET with the DCS-Control topology. The wide input voltage range of 3-V to 17-V supports a variety of nominal inputs, like 12-V supply rails, single-cell or multi-cell Li-Ion, and 5-V or 3.3-V rails.

The TPS62903 can automatically enter power save mode (if auto PFM/PWM is selected) at light loads to maintain high efficiency. Additionally, to provide high efficiency at very small loads, the device has a low typical quiescent current of 4-µA. AEE, if enabled, provides high efficiency across VIN, VOUT, and load current. The device includes a MODE/Smart-CONF input to set the internal/external divider, switching frequency, output voltage discharge, and automatic power save mode or forced PWM operation. The device is available in small 9-pin VQFN package measuring 1.50-mm × 2.00-mm with 0.5-mm pitch.

The TPS62903 is optimized to work within a range of external components. The LC output filters inductance and capacitance have to be considered together, creating a double pole, responsible for the corner frequency of the converter. See the TPS62903 data sheet for more details.

The TIDA-050052 is designed with a nominal 1-µH inductor to support 1.2-V output voltage. A shielded wire wound Inductor from Murata (DFE201612E-1R0M=P2) is used in this design. It has 4-A current saturation and 48-mΩ maximum DCR. 1-µH inductance is ideal for size and ripple given the VOUT of this design is only 1.2-V. Larger values can be used to achieve a lower inductor current ripple but they can have a negative impact on efficiency and transient response. Smaller values than 1-µH will cause a larger inductor current ripple which causes a larger negative inductor current in forced PWM mode at low or no output current.

A small low equivalent series resistance (ESR) multilayer ceramic capacitor (MLCC) is recommended to obtain the best filtering. For this design, a 10-µF/25V multilayer ceramic chip capacitor from Cal-Chip electronics (GMC21X7R106K25NT) is used as an input capacitor. It is designed to withstand up to 25-V which is enough for the input voltage range that we want to cover in this design.

For the output capacitor, the voltage rating is much smaller than the input, only 6-V to 10-V capacitor rating is needed. A 22-µF/10V multilayer ceramic chip capacitor (C2012X7S1A226M125AC) from TDK is chosen. Both the input and the output capacitors are X7R to cover the full temperature range of this design.

The MODE/S-CONF requires an E96 Resistor Series, 1% Accuracy, Temperature Coefficient better or equal than ±200- ppm/°C. A small size CRCW040226K1FKED from Vishay is used in this design.

For testing purposes, this reference design requires the following equipment:

• A power supply that is capable of supplying at least 2-A of load and up to 20-V.
• Current and Voltage Multimeters to measure the currents and voltages during the related tests.
• The TIDA-050052 board is a printed circuit board (PCB) with all the devices in this design.
• Resistive load or electronic load that is capable at least 3-A.
• Thermal camera used to measure the thermal rise of the board during operation.
• Oscilloscope to capture voltages and a current.

Figure 3-1 shows the set up used to test the TIDA-050052.

Figure 3-2 shows the startup behavior. With no soft start capacitor, it defaults to pre-programmed start up time.