ZHCSP51B december 2020 – may 2023 LMR43610 , LMR43620
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 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 Enable, Start-Up, and Shutdown
- 8.3.2 External CLK SYNC (with MODE/SYNC)
- 8.3.3 Adjustable Switching Frequency (with RT)
- 8.3.4 Power-Good Output Operation
- 8.3.5 Internal LDO, VCC, and VOUT/FB Input
- 8.3.6 Bootstrap Voltage and VBOOT-UVLO (BOOT Terminal)
- 8.3.7 Output Voltage Selection
- 8.3.8 Soft Start and Recovery from Dropout
- 8.3.9 Current Limit and Short Circuit
- 8.3.10 Thermal Shutdown
- 8.3.11 Input Supply Current
- 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
- 9.2.3 Application Curves
- 9.3 Best Design Practices
- 9.4 Power Supply Recommendations
- 9.5 Layout
- 10Device and Documentation Support
- 11Mechanical, Packaging, and Orderable Information
8.3.3 Adjustable Switching Frequency (with RT)
The select variants in the LMR436x0 family with the RT pin allow the power designers to set any desired operating frequency between 200 kHz and 2.2 MHz in their applications. See Figure 8-7 to determine the resistor value needed for the desired switching frequency. The RT pin and the MODE/SYNC pin variants share the same pin location. The power supply designer can either use the RT pin variant and adjust the switching frequency of operation as warranted by the application or use the MODE/SYNC variant and synchronize to an external clock signal. See Table 8-2 for selection on programming the RT pin.
| RT INPUT | SWITCHING FREQUENCY |
|---|---|
| VCC | 1 MHz |
| GND | 2.2 MHz |
| RT resistor to GND | Adjustable according to Figure 8-7 |
| Float (Not Recommended) | No switching |
Equation 1 can be used to calculate the value of RT for a desired frequency.
where
- RT is the frequency setting resistor value (kΩ).
- FSW is the switching frequency.
Figure 8-7 RT Values
vs Frequency