ZHCSHW5A September 2017 – December 2017 TPS23521
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Parameter Measurement Information
- 8 Detailed Description
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Application
- 9.2.1 Design Requirements
- 9.2.2
Detailed Design Procedure
- 9.2.2.1 Selecting RSNS
- 9.2.2.2 Selecting Soft Start Setting: CSS and CSS,VEE
- 9.2.2.3 Selecting VDS Switch Over Threshold
- 9.2.2.4 Timer Selection
- 9.2.2.5 MOSFET Selection and SOA Checks
- 9.2.2.6 EMI Filter Consideration
- 9.2.2.7 Under Voltage and Over Voltage Settings
- 9.2.2.8 Choosing RVCC and CVCC
- 9.2.2.9 Power Good Interface to Downstream DC/DC
- 9.2.3 Application Curves
- 10Power Supply Recommendations
- 11Layout
- 12器件和文档支持
- 13机械、封装和可订购信息
9.2.2.7 Under Voltage and Over Voltage Settings
Both the threshold and hysteresis can be programmed for under voltage and over voltage protection. In general the rising UV threshold should be set sufficiently below the minimum input voltage and the falling OV threshold should be set sufficiently above the maximum input voltage to account for tolerances. For this example a rising UV threshold of 35 V and a falling UV threshold of 33 V was chosen as the target. First, choose RUV1 based on the 2 V UV hysteresis as shown below.
Once RUV1 is known RUV2 can be computed based on the target rising UV threshold as shown below.
The OV setting can be programmed in a similar fashion as shown in equations below.
Optional filtering capacitors can be added to the UV and OV to improve immunity to noise and transients on the input bus. These should be tuned based on system requirements and input inductance. In this example place holders were added to the PCB, but the components were not populated.