ZHCSKF5C October 2019 – November 2020 LMR33640
PRODUCTION DATA
- 1 特性
- 2 應(yīng)用
- 3 說明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
- DDA|8
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- DDA|8
訂購信息
8.3.2 Enable and Start-up
Start-up and shutdown are controlled by the EN input. This input features precision thresholds, allowing the use of an external voltage divider to provide an adjustable input UVLO (see Section 9.2.2.9). Applying a voltage greater than or equal to VEN-VCC_H causes the device to enter standby mode, which powers the internal VCC, but does not produce an output voltage. Increasing the EN voltage to VEN-H fully enables the device, allowing it to enter start-up mode and begin the soft-start period. When the EN input is brought below VEN-H by VEN-HYS, the regulator stops running and enters standby mode. Further decrease in the EN voltage to below VEN-VCC-L completely shuts down the device. Figure 8-3 shows this behavior. The EN input can be connected directly to VIN if this feature is not needed. This input must not be allowed to float. The values for the various EN thresholds can be found in Section 7.5.
The LMR33640 uses a reference-based soft start that prevents output voltage overshoots and large inrush currents as the regulator is starting up. Figure 8-4 shows a typical start-up waveform, indicating typical timings. The rise time of the output voltage is about 4 ms (see Section 7.5).
Figure 8-3 Precision Enable Behavior
Figure 8-4 Typical Start-up Behavior VIN = 12 V, VOUT = 5 V, IOUT = 4 A