Low Dropout Voltage Regulator (LDO)
Introduction
The ESP32-P4 chip internally integrates 4 channels of low-dropout voltage regulators (LDOs). Each channel's voltage is programmable. In our hardware reference designs, some of these LDO outputs are typically used to power the internal Flash and PSRAM, while the remaining LDOs can be used to supply external devices.
Note
It's essential to read the manual first and ensure that the required current does not exceed the chip's specifications.
Functional Overview
The description of the LDO driver is divided into the following sections:
LDO Channel Acquisition - Introduces the types of LDO channels and how to apply for LDO channel resources.
LDO Voltage Adjustment - Describes how to adjust the voltage of the LDO channel.
LDO Channel Acquisition
LDO channels can be classified into two types: fixed voltage and adjustable voltage. For a fixed voltage channel, it allows multiple users to simultaneously use it (in software, we allow a variable to have multiple immutable references ). However, for an adjustable voltage channel, only one user is allowed to use it at a time (in software, we don't allow a variable to have multiple mutable references or coexistence of mutable and immutable references).
In the driver, the LDO channel is represented by the esp_ldo_channel_handle_t
. You can use the esp_ldo_acquire_channel()
function to request LDO channel resources. Upon successful acquisition, a handle for the LDO channel will be returned, which can be used for subsequent voltage adjustment operations. When applying for a channel, the esp_ldo_channel_config_t
structure is used to specify the basic information of the LDO channel, including the channel ID, the desired output voltage, and whether the voltage can be dynamically adjusted.
esp_ldo_channel_config_t::chan_id
- LDO channels are uniquely identified by a label, which is used to distinguish different LDO channels. Please note that this information needs to be determined based on the circuit schematic and chip datasheet. For example, an LDO channel labeled asLDO_VO3
corresponds to an ID of3
.esp_ldo_channel_config_t::voltage_mv
- The desired output voltage of the LDO channel, in millivolts.esp_ldo_channel_config_t::ldo_extra_flags::adjustable
- Whether the LDO channel's output voltage can be dynamically adjusted. Only when it is set to true, can theesp_ldo_channel_adjust_voltage()
function be used to dynamically adjust the output voltage.
Since multiple users are allowed to use a fixed voltage LDO channel simultaneously, the driver internally maintains a reference counter. The LDO channel will be automatically closed when the last user releases the LDO channel resources. The function to release LDO channel resources is esp_ldo_release_channel()
. Additionally, it is important to note that the acquisition and release of LDO channels should appear in pairs during usage.
LDO Voltage Adjustment
esp_ldo_channel_adjust_voltage()
function is used to adjust the output voltage of an LDO channel at runtime. However, please note that this function can only be used for LDO channels with adjustable voltage. Attempting to use this function on a fixed voltage LDO channel will result in an error.
Also, it is important to keep in mind that due to hardware limitations, the LDO channel voltage may have a deviation of approximately 50-100mV. Therefore, it is not advisable to rely on the LDO channel's output voltage for precise analog control.
Application Examples
Use the internal LDO channel to power up the MIPI DPHY: peripherals/lcd/mipi_dsi
API Reference
Header File
This header file can be included with:
#include "esp_ldo_regulator.h"
Functions
-
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.
Note
This function can't automatically search a LDO channel for you, you must specify a LDO channel ID manually, based on your schematic.
Note
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.
Note
You should release the channel by
esp_ldo_release_channel
when it's no longer needed.- Parameters
config -- [in] The configuration of the LDO channel
out_handle -- [out] The returned LDO channel handle
- Returns
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.
- Parameters
chan -- [in] The LDO channel handle returned from
esp_ldo_acquire_channel
- Returns
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
-
esp_err_t esp_ldo_channel_adjust_voltage(esp_ldo_channel_handle_t chan, int voltage_mv)
Adjust the voltage of the LDO channel.
- Parameters
chan -- [in] The LDO channel handle returned from
esp_ldo_acquire_channel
voltage_mv -- [in] The voltage value to be set to the LDO channel, in millivolts
- Returns
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
-
struct esp_ldo_channel_config_t
LDO channel configurations.
Public Members
-
int chan_id
You must set the LDO channel ID according to the datasheet, e.g., set it to 1 for LDO_VO1
-
int voltage_mv
The voltage value to be set to the LDO channel
-
struct esp_ldo_channel_config_t::ldo_extra_flags flags
Flags for the LDO channel
-
struct ldo_extra_flags
Extra flags of a LDO channel.
-
int chan_id
Type Definitions
-
typedef struct ldo_regulator_channel_t *esp_ldo_channel_handle_t
Type of LDO regulator channel handle.