ZHCSIY5A October 2018 – May 2019 LMZM33604
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 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3
Feature Description
- 7.3.1 Adjusting the Output Voltage
- 7.3.2 Input Capacitor Selection
- 7.3.3 Output Capacitor Selection
- 7.3.4 Transient Response
- 7.3.5 Feed-Forward Capacitor
- 7.3.6 Switching Frequency (RT)
- 7.3.7 Synchronization (SYNC/MODE)
- 7.3.8 Output Enable (EN)
- 7.3.9 Programmable System UVLO (EN)
- 7.3.10 Internal LDO and BIAS_SEL
- 7.3.11 Power Good (PGOOD) and Power Good Pullup (PGOOD_PU)
- 7.3.12 Mode Select (Auto or FPWM)
- 7.3.13 Soft Start and Voltage Tracking
- 7.3.14 Voltage Dropout
- 7.3.15 Overcurrent Protection (OCP)
- 7.3.16 Thermal Shutdown
- 7.4 Device Functional Modes
- 8 Application and Implementation
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
7.3.6 Switching Frequency (RT)
The recommended switching frequency range of the LMZM33604 is 350 kHz to 1.2 MHz. Table 6 shows the allowable output voltage range for several switching frequency settings for three common input voltages. Under some operating conditions, the device can operate at higher switching frequencies (up to 2.2 MHz), however, this will reduce efficiency and thermal performance. The switching frequency can easily be set by connecting a resistor (RRT) between the RT pin and AGND. Additionally, the RT pin can be left floating, and the LMZM33604 operates at 500 kHz default switching frequency. Use Equation 3 to calculate the RRT value for a desired frequency or simply select from Table 6.
The switching frequency must be selected based on the output voltage setting of the device. See Table 6 for RRT values and the allowable output voltage range for a given switching frequency at several common input voltages. For the most efficient solution, always select the lowest allowable frequency.
Table 6. Switching Frequency vs Output Voltage
| SWITCHING FREQUENCY (kHz) | RRT RESISTOR (kΩ) | VIN = 5 V (±10%) | VIN = 12 V (±10%) | VIN = 24 V (±10%) | |||
|---|---|---|---|---|---|---|---|
| VOUT RANGE (V) | VOUT RANGE (V) | VOUT RANGE (V) | |||||
| MIN | MAX | MIN | MAX | MIN | MAX | ||
| 350 | 115 | 1 | 4 | 1 | 8.2 | 1 | 8.4 |
| 400 | 100 | 1 | 4 | 1 | 8.8 | 1 | 9.9 |
| 500 | 78.7 or open | 1 | 4 | 1 | 9.9 | 1.1 | 13.9 |
| 600 | 64.9 | 1 | 4 | 1 | 9.9 | 1.3 | 15.6 |
| 700 | 54.9 | 1 | 3.5 | 1 | 9.7 | 1.5 | 16.9 |
| 800 | 47.5 | 1 | 3.4 | 1 | 9.6 | 1.7 | 18 |
| 1000 | 38.3 | 1 | 3.4 | 1.1 | 9.3 | 2.1 | 20 |
| 1200 | 31.6 | 1 | 3.3 | 1.3 | 9.1 | 2.5 | 19.1 |
| 1500 | 25.5 | 1 | 2.9 | 1.8 | 8.1 | 3.2 | 18.1 |
| 1800 | 21.0 | 1.1 | 2.7 | 2.1 | 7.7 | 3.9 | 17.2 |
| 2000 | 19.1 | 1.2 | 2.5 | 2.5 | 7.5 | 4.4 | 16.5 |
| 2200 | 17.4 | 1.3 | 2.4 | 2.7 | 7.2 | 4.8 | 15.9 |