基于TPS7A16低压降电压稳压器

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　　1 特性

　　宽输入电压范围：3V 至 60V

　　超低静态电流：5µA

　　关断时的静态电流：1µA

　　输出电流：100mA

　　低压降电压：电流为 20mA 时为 60mV

　　精度：2%

　　可提供：

　　固定输出电压：3.3V，5V

　　可调节输出电压：1.2V 至 18.5V

　　具有可编程延迟的电源正常指示功能

　　限流和热关断保护

　　与陶瓷输出电容搭配使用时可保持稳定：

　　≥ 2.2µF

　　封装：高耐热性能微型小外形尺寸 (MSOP)-8 和小外形尺寸无引线 (SON)-8 封装 PowerPAD™

　　工作温度范围：

　　–40°C 至 125°C

　　2 应用

　　笔记本个人电脑 (PC)、数字电视和私有局域网 (LAN) 系统电源

　　用于电动工具和其它由电池供电的微处理器和微控制器系统的高节数电池组

　　车载音频、导航、信息娱乐、和其它汽车系统

　　烟雾和 CO2 探测器以及电池供电类警报和安全系统

　　3 说明

　　TPS7A16 系列超低功耗、低降压 (LDO) 稳压器提供超低静态电流、高输入电压和小型化、高散热性能封装所具备的优势。

　　TPS7A16 系列器件针对连续或断续(备用电源)电池供电 应用 而设计，超低静态电流在此类应用中对于延长系统电池寿命至关重要。

　　TPS7A16 系列产品提供一个与标准互补金属氧化物半导体 (CMOS) 逻辑电路兼容的使能引脚 (EN) 和一个具有用户可编程延迟的集成开漏高电平有效的电源正常输出 (PG)。这些引脚专用于需要进行电源轨排序、 基于 微控制器的电池供电类应用。

　　此外，TPS7A16 器件非常适用于从多节电池解决方案生成低压电源(从多节电动工具组到汽车 应用);该器件不但能够提供一个稳压良好的电压轨，而且还能够承受瞬态电压并在电压瞬态期间保持稳压状态。这些 功能 意味着电涌保护电路更加简单且更为经济高效。

　　7 Detailed Description

　　7.1 Overview

　　The TPS7A16 family of devices are ultralow power, low-dropout (LDO) voltage regulators that offer the benefits of ultralow quiescent current, high input voltage, and miniaturized, high thermal-performance packaging. The TPS7A16 family also offers an enable pin (EN) and integrated open-drain active-high power-good output (PG) with a user-programmable delay.

　　7.2 Functional Block Diagram

　　7.3 Feature Description

　　7.3.1 Enable (EN)

　　The enable terminal is a high-voltage-tolerant terminal. A high input on EN actives the device and turns on the regulator. For self-bias applications, connect this input to the VIN terminal.

　　7.3.2 Regulated Output (VOUT)

　　The VOUT terminal is the regulated output based on the required voltage. The output has current limitation. During initial power up, the regulator has a soft start incorporated to control the initial current through the pass element. In the event that the regulator drops out of regulation, the output tracks the input minus a drop based on the load current. When the input voltage drops below the UVLO threshold, the regulator shuts down until the input voltage recovers above the minimum start-up level.

　　7.3.3 Power-Good

　　The power-good (PG) pin is an open-drain output and can be connected to any 5-V or lower rail through an external pull-up resistor. When no CDELAY is used, the PG output is high-impedance when VOUT is greater than the PG trip threshold (VIT). If VOUT drops below VIT, the open-drain output turns on and pulls the PG output low. If output voltage monitoring is not needed, the PG pin can be left floating or connected to GND.

　　The power-good feature functionality is only guaranteed when VIN ≥ 3 V (VIN_(MIN))

　　7.3.4 PG Delay Timer (DELAY)

　　The power-good delay time (tDELAY) is defined as the time period from when VOUT exceeds the PG trip threshold voltage (VIT) to when the PG output is high. This power-good delay time is set by an external capacitor (CDELAY) connected from the DELAY pin to GND; this capacitor is charged from 0 V to approximately 1.8 V by the DELAY pin current (IDELAY) once VOUT exceeds the PG trip threshold (VIT).

　　When CDELAY is used, the PG output is high-impedance when VOUT exceeds VIT, and VDELAY exceeds VREF.

　　The power-good delay time can be calculated using: tDELAY = (CDELAY × VREF) / IDELAY. For example, when CDELAY = 10 nF, the PG delay time is approximately 12 ms; that is, (10 nF × 1.193 V) / 1 µA = 11.93 ms.

　　7.3.5 Internal Current Limit

　　The fixed internal current limit of the TPS7A16 family helps protect the regulator during fault conditions. The maximum amount of current the device can source is the current limit (225 mA, typical), and is largely independent of output voltage. For reliable operation, do not operate the device in current limit for extended periods of time.

　　7.3.6 Thermal Protection

　　Thermal protection disables the output when the junction temperature rises to approximately 170°C, allowing the device to cool. When the junction temperature cools to approximately 150°C, the output circuitry is enabled. Depending on power dissipation, thermal resistance, and ambient temperature, the thermal protection circuit may cycle ON and OFF. This cycling limits the dissipation of the regulator, protecting it from damage as a result of overheating.

　　7.4 Device Functional Modes

　　7.4.1 Normal Operation

　　The device regulates to the nominal output voltage under the following conditions:

　　The input voltage is at least as high as VIN(MIN).

　　The input voltage is greater than the nominal output voltage added to the dropout voltage.

　　The enable voltage has previously exceeded the enable rising threshold voltage and has not decreased below the enable falling threshold.

　　The output current is less than the current limit.

The device junction temperature is less than the maximum specified junction temperature.

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　　7.4.2 Dropout Operation

　　If the input voltage is lower than the nominal output voltage plus the specified dropout voltage, but all other conditions are met for normal operation, the device operates in dropout mode. In this mode of operation, the output voltage is the same as the input voltage minus the dropout voltage. The transient performance of the device is significantly degraded because the pass device (such as a bipolar junction transistor, or BJT) is in saturation and no longer controls the current through the LDO. Line or load transients in dropout can result in large output voltage deviations.

　　7.4.3 Disabled

　　The device is disabled under the following conditions:

　　The enable voltage is less than the enable falling threshold voltage or has not yet exceeded the enable rising threshold.

　　The device junction temperature is greater than the thermal shutdown temperature.