ZHCSNR4B May 2021 – April 2022 TPS25946
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Undervoltage Lockout (UVLO and UVP)
- 8.3.2 Overvoltage Lockout (OVLO)
- 8.3.3 Inrush Current, Overcurrent, and Short-Circuit Protection
- 8.3.4 Analog Load Current Monitor
- 8.3.5 Reverse Current Protection
- 8.3.6 Overtemperature Protection (OTP)
- 8.3.7 Fault Response and Indication (FLT)
- 8.3.8 Power Good Indication (PG)
- 8.3.9 Input Supply Good Indication (SPLYGD)
- 8.4 Device Functional Modes
-
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 Device Selection
- 9.2.2.2 Setting Overvoltage Threshold
- 9.2.2.3 Setting Output Voltage Rise Time (tR)
- 9.2.2.4 Setting Power Good Assertion Threshold
- 9.2.2.5 Setting Overcurrent Threshold (ILIM)
- 9.2.2.6 Setting Overcurrent Blanking Interval (tITIMER)
- 9.2.2.7 Selecting External Bias Resistor (R5)
- 9.2.2.8 Selecting External Diode (D1)
- 9.2.3 Application Curve
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
10.1 Transient Protection
In the case of a short-circuit and overload current limit when the device interrupts current flow, the input inductance generates a positive voltage spike on the input, and the output inductance generates a negative voltage spike on the output. The peak amplitude of voltage spikes (transients) is dependent on the value of inductance in series to the input or output of the device. Such transients can exceed the absolute maximum ratings of the device if steps are not taken to address the issue. Typical methods for addressing transients include:
- Minimize lead length and inductance into and out of the device.
- Use a large PCB GND plane.
- Connect a Schottky diode from the OUT pin ground to absorb negative spikes.
- Connect a low ESR capacitor larger than 1 μF at the OUT pin very close to the device.
- Use a low-value ceramic capacitor CIN
= 1 μF to absorb the energy and dampen the transients. The capacitor voltage
rating must be at least twice the input supply voltage to be able to withstand
the positive voltage excursion during inductive ringing.
The approximate value of input capacitance can be estimated with Equation 16:
Equation 16.where
- VIN is the nominal supply voltage.
- ILOAD is the load current.
- LIN equals the effective inductance seen looking into the source.
- CIN is the capacitance present at the input.
- Some applications may require the addition of a Transient Voltage Suppressor (TVS) to prevent transients from exceeding the absolute maximum ratings of the device. In some cases, even if the maximum amplitude of the transients is below the absolute maximum rating of the device, a TVS can help to absorb the excessive energy dump and prevent it from creating very fast transient voltages on the input supply pin of the IC, which can couple to the internal control circuits and cause unexpected behavior.
- For applications such as USB-C ports where a powered cable can be plugged to the output of the device, there can be excess voltage stress from OUT to IN which exceeds the absolute maximum rating of the device. TI recommends to add a TVS diode from OUT to IN to clamp the voltage to a safe level.
The circuit implementation with optional protection components is shown in Figure 10-1.
Figure 10-1 Circuit Implementation with Optional Protection Components