ZHCSI22F October   2017  – December 2021

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. Parameter Measurement Information
9. Detailed Description
1. 9.1 Overview
2. 9.2 Functional Block Diagram
3. 9.3 Feature Description
4. 9.4 Device Functional Modes
10. 10Application and Implementation
1. 10.1 Application Information
2. 10.2 Typical Application
3. 10.3 System Examples
4. 10.4 Do's and Don'ts
11. 11Power Supply Recommendations
12. 12Layout
13. 13Device and Documentation Support
14. 14Mechanical, Packaging, and Orderable Information

• DRC|10
• DRC|10

### 9.3.3 Hot Plug-In and Inrush Current Control

The devices are designed to control the inrush current upon insertion of a card into a live backplane or other hotpower source. This design limits the voltage sag on the backplane’s supply voltage and prevents unintended resets of the system power. The controlled start-up also helps to eliminate conductive and radiative interferences. An external capacitor connected from the dVdT pin to RTN defines the slew rate of the output voltage at power-on as shown in Figure 9-2 and Figure 9-3.

Figure 9-2 Output Ramp Up Time tdVdT is Set by C(dVdT)

The dVdT pin can be left floating to obtain a predetermined slew rate (tdVdT) on the output. When the terminal is left floating, the devices set an internal output voltage ramp rate of 24 V/660 µs. A capacitor can be connected from dVdT pin to RTN to program the output voltage slew rate slower than 24 V/660 µs. Use Equation 1 and Equation 2 to calculate the external C(dVdT) capacitance.

Equation 1 governs slew rate at start-up.

Equation 1.

where

• I(dVdT) = 1.98 µA (typical)
• = Desired output slew rate
• Gain(dVdT) = dVdT to VOUT gain = 24.6

The total ramp time (tdVdT) of V(OUT) for 0 to V(IN) can be calculated using Equation 2.

Equation 2. tdVdT = 20.5 × 103 × V(IN) × C(dVdT)
 CdVdT = 22 nF COUT = 22 µF RILIM = 7.5 kΩ
Figure 9-3 Hot Plug-In and Inrush Current Control at 24-V Input