低压差线性稳压器 (LDO)
简介
ESP32-P4 芯片内部集成了 4 路低压差线性稳压器 (LDO)，每路的电压都是可编程调节的。在硬件的参考设计中，我们通常会将其中一些的 LDO 输出作为内部 Flash 和 PSRAM 的电源，剩余的一些 LDO 可以用于给外部设备供电。
备注
使用前请阅读手册，确保你需要的电流不会超过芯片的规格。
功能概述
下文将分节介绍 LDO 驱动的功能：
LDO 通道申请 - 介绍LDO通道的种类以及如何申请 LDO 通道资源
LDO 通道电压调节 - 介绍如何调节 LDO 通道的输出电压
LDO 通道申请
LDO 通道可以分为两种，一种是电压固定的，另一种是电压可调的。对于同一个输出通道，如果电压固定，那么可以允许有多个用户同时使用（软件允许一个变量拥有多个不可变引用）。如果电压可调，那么只能允许一个用户使用（软件上不允许一个变量有多个可变引用或者可变和不可变引用同时存在）。
LDO 通道在驱动软件中由 esp_ldo_channel_handle_t 句柄表示。申请 LDO 通道资源的函数是 esp_ldo_acquire_channel()。申请成功后，会返回一个 LDO 通道的句柄，这个句柄可以用于后续的电压调节操作。在申请通道的时候，我们需要通过 esp_ldo_channel_config_t 结构体来指定 LDO 通道的基本信息，包括通道 ID，期望的输出电压，以及电压是否可以动态调节。
esp_ldo_channel_config_t::chan_id- LDO 通道的唯一标记，用于区分不同的 LDO 通道。注意，这需要你根据电路原理图和芯片数据手册来确定。比如，一个标记着 "LDO_VO3" 的 LDO 通道，对应的 ID 是 3。esp_ldo_channel_config_t::voltage_mv- 期望的输出电压，单位是毫伏。esp_ldo_channel_config_t::ldo_extra_flags::adjustable- 是否允许调节输出电压。只有设置为 true，才允许使用esp_ldo_channel_adjust_voltage()函数来动态地调节输出电压。
由于允许多个用户同时使用固定电压的 LDO 通道，所以驱动内部会维持一个引用计数器。当最后一个用户释放 LDO 通道资源时，LDO 通道会被自动关闭。释放 LDO 通道资源的函数是 esp_ldo_release_channel()。另外还需要注意，申请和释放 LDO 通道在使用的时候需要成对出现。
LDO 通道电压调节
esp_ldo_channel_adjust_voltage() 函数用来在运行时调整 LDO 通道的输出电压。但是，这个函数只能用于可调节电压的 LDO 通道，否则会返回错误。
注意，由于硬件限制，LDO 通道电压的精度可能会 50~100mV 左右的偏差，请勿依赖于 LDO 通道的输出电压来进行精确的模拟量控制。
应用示例
Use the internal LDO channel to power up the MIPI DPHY: peripherals/lcd/mipi_dsi
API 参考
Header File
This header file can be included with:
#include "esp_ldo_regulator.h"
Functions
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esp_err_t esp_ldo_acquire_channel(const esp_ldo_channel_config_t *config, esp_ldo_channel_handle_t *out_handle)
Acquire an LDO channel with the specified configuration.
备注
This function can't automatically search a LDO channel for you, you must specify a LDO channel ID manually, based on your schematic.
备注
The same channel can be acquired multiple times in different places of the application code, however, if the LDO channel is adjustable, you can't acquire it multiple times, in case user A changes the voltage and breaks the voltage setting of user B.
备注
You should release the channel by
esp_ldo_release_channelwhen it's no longer needed.- 参数
config -- [in] The configuration of the LDO channel
out_handle -- [out] The returned LDO channel handle
- 返回
ESP_OK: Acquire the LDO channel successfully
ESP_ERR_INVALID_ARG: Acquire the LDO channel failed due to invalid arguments
ESP_FAIL: Acquire the LDO channel failed due to other reasons
-
esp_err_t esp_ldo_release_channel(esp_ldo_channel_handle_t chan)
Release the LDO channel.
- 参数
chan -- [in] The LDO channel handle returned from
esp_ldo_acquire_channel- 返回
ESP_OK: Release the LDO channel successfully
ESP_ERR_INVALID_ARG: Release the LDO channel failed due to invalid arguments
ESP_ERR_INVALID_STATE: Release the LDO channel failed due to invalid state, e.g., the channel handle is double released
ESP_FAIL: Release the LDO channel failed due to other reasons
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esp_err_t esp_ldo_channel_adjust_voltage(esp_ldo_channel_handle_t chan, int voltage_mv)
Adjust the voltage of the LDO channel.
- 参数
chan -- [in] The LDO channel handle returned from
esp_ldo_acquire_channelvoltage_mv -- [in] The voltage value to be set to the LDO channel, in millivolts
- 返回
ESP_OK: Adjust the voltage of the LDO channel successfully
ESP_ERR_INVALID_ARG: Adjust the voltage of the LDO channel failed due to invalid arguments
ESP_ERR_NOT_SUPPORTED: Adjust the voltage of the LDO channel failed due to the channel is not adjustable
ESP_FAIL: Adjust the voltage of the LDO channel failed due to other reasons
Structures
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struct esp_ldo_channel_config_t
LDO channel configurations.
Public Members
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int chan_id
You must set the LDO channel ID according to the datasheet, e.g., set it to 1 for LDO_VO1
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int voltage_mv
The voltage value to be set to the LDO channel
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struct esp_ldo_channel_config_t::ldo_extra_flags flags
Flags for the LDO channel
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int chan_id
Type Definitions
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typedef struct ldo_regulator_channel_t *esp_ldo_channel_handle_t
Type of LDO regulator channel handle.