ZHCSSO4E September 2010 – September 2024 TPS74801-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Pin Configuration and Functions
- 5 Specifications
- 6 Detailed Description
- 7 Application and Implementation
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
封裝選項
機械數據 (封裝 | 引腳)
散熱焊盤機械數據 (封裝 | 引腳)
訂購信息
6.3.1 Programmable Soft-Start
The TPS74801-Q1 features a programmable, monotonic, voltage-controlled soft-start that is set with an external capacitor (CSS). This feature is important for many applications because soft-start eliminates power-up initialization problems when powering FPGAs, DSPs, or other processors. The controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing start-up transient events to the input power bus.
To achieve a linear and monotonic soft-start, the TPS74801-Q1 error amplifier tracks the voltage ramp of the external soft-start capacitor until the voltage exceeds the internal reference. The soft-start ramp time depends on the soft-start charging current (ISS), soft-start capacitance (CSS), and the internal reference voltage (VREF), and can be calculated using Equation 1:
If large output capacitors are used, the device current limit (ICL) and the output capacitor can set the start-up time. In this case, the start-up time is given by Equation 2:
where:
- VOUT(NOM) is the nominal output voltage
- COUT is the output capacitance
- ICL(MIN) is the minimum current limit for the device
In applications where monotonic start-up is required, the soft-start time given by Equation 1 must be set greater than Equation 2.
The maximum recommended soft-start capacitor is 0.015 μF. Larger soft-start capacitors can be used and do not damage the device; however, the soft-start capacitor discharge circuit can possibly be unable to fully discharge the soft-start capacitor when enabled. Soft-start capacitors larger than 0.015 μF can be a problem in applications where the enable pin must be rapidly pulsed while still requiring the device to soft-start from ground. CSS must be low-leakage; X7R, X5R, or C0G dielectric materials are preferred. See Table 7-3 for suggested soft-start capacitor values.