ZHCSQT8 October 2023 LM74930-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3
Feature Description
- 7.3.1 Charge Pump
- 7.3.2 Dual Gate Control (DGATE, HGATE)
- 7.3.3 Overcurrent Protection (CS+, CS-, ILIM, IMON, TMR)
- 7.3.4 Overcurrent Protection with Circuit Breaker (ILIM, TMR)
- 7.3.5 Overcurrent Protection With Latch-Off
- 7.3.6 Short-Circuit Protection (ISCP)
- 7.3.7 Analog Current Monitor Output (IMON)
- 7.3.8 Overvoltage and Undervoltage Protection (OV, UVLO, OVCLAMP)
- 7.3.9 Disabling Reverse Current Blocking Functionality (MODE)
- 7.3.10 Device Functional Modes
-
8 Applications and Implementation
- 8.1 Application Information
- 8.2
Typical Application: 200-V Unsuppressed Load Dump Protection Application
- 8.2.1 Design Requirements for 200-V Unsuppressed Load Dump Protection
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 VS Capacitance, Resistor R1 and Zener Clamp (DZ)
- 8.2.2.2 Charge Pump Capacitance VCAP
- 8.2.2.3 Input and Output Capacitance
- 8.2.2.4 Overvoltage and Undervoltage Protection Component Selection
- 8.2.2.5 Selection of Scaling Resistor (RSET) and Short-Circuit Protection Setting Resistor (RSCP)
- 8.2.2.6 Overcurrent Limit (ILIM), Circuit Breaker Timer (TMR), and Current Monitoring Output (IMON) Selection
- 8.2.2.7 Selection of Current Sense Resistor, RSNS
- 8.2.2.8 Hold-Up Capacitance
- 8.2.2.9 MOSFET Q1 Selection
- 8.2.2.10 MOSFET Q2 Selection
- 8.2.2.11 Input TVS Selection
- 8.2.3 Application Curves
- 8.3 Best Design Practices
- 8.4 Power Supply Recommendations
- 8.5 Layout
- 9 Device and Documentation Support
- 10Mechanical, Packaging, and Orderable Information
7.3.6 Short-Circuit Protection (ISCP)
LM74930-Q1 offers fast response to output short circuit events with the short-circuit protection feature. After the voltage across ISCP and CS– exceeds the deafult threshold of 20-mV typical, HGATE is pulled to OUT within 3-µs protecting the load disconnect FET. FLT asserts low at the same time. Subsequent to this event, the charge/discharge cycles of CTMR starts similar to the behavior post FET OFF event in circuit breaker operation.
Short circuit protection threshold can be increased using an external series resistor (RISCP) from ISCP pin to current sense resistor. The shift in the short circuit protection threshold can be calculated using Equation 6.
An additional deglitch filter consisting of RISCP and CISCP can be added from ISCP pin to CS– pin as shown in Figure 7-7 to avoid any false short circuit trigger in case of fast automotive transients such as Input short interruptions (LV124, E-10), AC superimpose (LV124 E-06, ISO16750-2), ISO7637-2 Pulse 2A.
Figure 7-7 Short-Circuit Protection With Deglitch FilterShort-circuit protection with latch off can also be achieved in the similar way as explained in the circuit breaker section.