LT7182S no-OS driver¶

Supported Devices¶

Overview¶

The LT7182S is a dual-output monolithic PolyPhase DC/DC synchronous step-down regulator that delivers up to 6A of continuous current from both channels simultaneously and supports loads up to 8A from either channel. The LT7182S features the second generation Silent Switcher architecture with integrated VIN bypass capacitors for fast, clean, low-overshoot switching edges delivering high efficiency at high switching frequencies while minimizing EMI emissions.

The I2C-based PMBus 1.3 compliant serial interface enables control of device functions and provides telemetry information for system monitoring. The LT7182S is supported by the LTpowerPlay graphical user interface tool.

Applications¶

LT7182S¶

Communications, Storage, and Industrial Systems
Data Center and Solid State Drive Power Supplies

LT7182S Device Configuration¶

Driver Initialization¶

In order to be able to use the device, you will have to provide the support for the communication protocol (I2C) alongside other GPIO pins if needed in the specific application (depends on the way the device is used).

The first API to be called is lt7182s_init. Make sure that it return 0, which means that the driver was initialized correctly.

The initialization API uses the device descriptor and an initialization parameter. The initialization parameter contains the chip_id of the device, the selected data format to be used (IEEE754 or LINEAR) and the optional GPIO parameters for controlling POWER GOOD, RUN, FAULT and ALERT pins. Use of packet error checking and the external clock can also be configured in the parameter. These are defined in the header file of the driver.

VOUT Configuration¶

The VOUT_COMMAND sets the output voltage, while the VOUT_MAX sets the upper limit on the commanded voltage. The output voltage and limit for each channel can be set using the lt7182s_vout_value API.

The output voltage transition rate for each channel can be configured using the lt7182s_vout_tr API.

Output voltage lower and higher margin can also be configured using the lt7182s_vout_margin API.

The OPERATION command via the lt7182s_set_operation can be used to command the output voltage to be regulated at the high margin, low margin, or at the nominal VOUT_COMMAND. This can also be used to set a channel off.

VIN Configuration¶

VIN_ON and VIN_OFF command values sets the input voltage window at which power conversion will proceed. Both of which can be configured through the lt7182s_set_vin API.

Status Configuration¶

Statuses bytes/words of the device can be read using lt7182s_read_status API. Faults asserted by these statuses can be cleared using the lt7182s_clear_faults API.

Telemetry¶

Measurements for each output channel can be read using the lt7182s_read_value API. Some telemetry values includes input/output voltage, input/output current, external VCC, die temperature, and output power.

The frequency at which telemetry values are converted, as well as enabling debug telemetries such as external VCC and ITH values, can be configured using the lt7182s_adc_control API.

Timing Configuration¶

The TON_DELAY command sets the time from when a start condition is received until the output voltage starts to rise. The TON_RISE sets the time from the from the time the output starts to rise to the time the output enters the regulation band. The TOFF_DELAY command sets the time from when a stop condition is received until the output voltage starts to fall. The TOFF_FALL command sets the time from the end of the turn-off delay time until the output voltage is commanded to zero. These commands can be set using the lt7182s_set_timing API.

Overvalue and Undervalue Limits Configuration¶

Overvalue and undervalue limits sets the threshold at which the device voltage, current, temperature, and timing must meet. When these measurements cross the limits, a status bit may be asserted. These limits can be configured using the lt7182s_set_limit API.

PWM Configuration¶

The PWM of each output channel can be set on forced continuous mode or on pulse skip mode. This can be set using the lt7182s_pwm_mode API.

The phase offset of the PWM for each channel can also be set using the lt7182s_pwm_phase API.

Clock Configuration¶

When using the device in parallel with others of the same device, the PWM clock of all devices can be synchronized. Using an external clock or enabling the clock input can be configured using the lt7182s_sync_config API.

NVM commands¶

The device has an internal EEPROM that saves the settings configured to the device even when power is removed. The lt7182s_nvm_cmd API allows the user to lock and unlock EEPROM, and store, compare and restore user settings.

Software Reset Configuration¶

Software Reset operation is available through lt7182s_software_reset API.

LT7182S Driver Initialization Example¶

struct lt7182s_dev *lt7182s_dev;
struct no_os_i2c_init_param lt7182s_i2c_ip = {
        .device_id = I2C_DEVICE_ID,
        .max_speed_hz = 100000,
        .platform_ops = I2C_OPS,
        .slave_address = LT7182S_PMBUS_ADDRESS,
        .extra = I2C_EXTRA,
};

struct lt7182s_init_param lt7182s_ip = {
        .i2c_init = &lt7182s_i2c_ip,
        .pg0_param = NULL,
        .pg1_param = NULL,
        .run0_param = NULL,
        .run1_param = NULL,
        .alert_param = NULL,
        .fault0_param = NULL,
        .fault1_param = NULL,
        .fault0_cfg = LT7182S_FAULT_PIN_OUTPUT,
        .fault1_cfg = LT7182S_FAULT_PIN_OUTPUT,
        .format = LT7182S_DATA_FORMAT_IEEE754,
        .external_clk_en = false,
        .crc_en = false,
};
ret = lt7182s_init(&lt7182s_dev, &lt7182s_ip);
if (ret)
        goto error;

LT7182S no-OS IIO support¶

The LT7182S IIO driver comes on top of the LT7182S driver and offers support for interfacing IIO clients through libiio.

LT7182S IIO Device Configuration¶

Input Channel Attributes¶

VIN0/VIN1/IIN0/IIN1/TEMP/VCC channels are the input channels of the LT7182S IIO device and each of them has a total of 2 channel attributes:

raw - the raw value of the channel
scale - the scale value of the channel calculated accordingly to each specific channel using a priv

Output Channel Attributes¶

IOUT0/IOUT1 channels are two output channels with the following channel attributes:

raw - the raw value of the channel
scale - the scale value of the channel calculated accordingly to each specific channel using a priv

Meanwhile, VOUT0/VOUT1 channels are two output channels with a separate channel attributes. Each channel has 11 attributes:

raw - the raw value of the channel
scale - the scale value of the channel calculated accordingly to each specific channel using a priv
enable - state of the channel
enable_available - list of available states for the channel
vout_command - VOUT_COMMAND value of the channel output
vout_max - VOUT_COMMAND value of the channel output
vout_margin_low - VOUT_MARGIN_LOW value of the channel output
vout_margin_high - VOUT_MARGIN_HIGH value of the channel output
phase - Phase offset value of the channel output
pulse_skipping - PWM pulse skip mode of the channel output
pulse_skipping_available - pulse skipping available states of the each channel

Global Attributes¶

The device has a total of 18 global attributes:

freq_sync - Clock frequency sync enable of the device
freq_sync_available - Available state of the clock sync enable
frequency - Device switching frequency
vout_ov_fault_limit_0 - Output overvoltage fault limit for channel 0
vout_ov_fault_limit_1 - Output overvoltage fault limit for channel 1
vout_ov_warn_limit_0 - Output overvoltage warning limit for channel 0
vout_ov_warn_limit_1 - Output overvoltage warning limit for channel 1
vout_uv_fault_limit_0 - Output undervoltage fault limit for channel 0
vout_uv_fault_limit_1 - Output undervoltage fault limit for channel 1
vout_uv_warn_limit_0 - Output undervoltage warning limit for channel 0
vout_uv_warn_limit_1 - Output undervoltage warning limit for channel 1
iin_oc_warn_limit_0 - Input overcurrent warning limit for channel 0
iin_oc_warn_limit_1 - Input overcurrent warning limit for channel 1
iout_oc_warn_limit_0 - Output overcurrent warning limit for channel 0
iout_oc_warn_limit_1 - Output overcurrent warning limit for channel 1
ot_fault_limit - Overtemperature fault limit for both channels
ot_warn_limit - Overtemperature warning limit for both channels
vin_uv_warn_limit - Output undervoltage warning limit for both channels

Debug Attributes¶

The device has a total of 12 debug attributes:

status_vout_0 - VOUT status byte value of channel 0
status_vout_1 - VOUT status byte value of channel 1
status_iout_0 - IOUT status byte value of channel 0
status_iout_1 - IOUT status byte value of channel 1
status_input_0 - INPUT status byte value of channel 0
status_input_1 - INPUT status byte value of channel 1
status_mfr_specific_0 - MFR_SPECIFIC status byte value of channel 0
status_mfr_specific_1 - MFR_SPECIFIC status byte value of channel 1
status_word_0 - Status word value of the channel 0
status_word_1 - Status word value of the channel 1
status_temperature - TEMPERATURE status byte value of the device
status_cml - CML status byte value of the device

LT7182S IIO Driver Initialization Example¶

int ret;

struct lt7182s_iio_desc *lt7182s_iio_desc;
struct lt7182s_iio_desc_init_param lt7182s_iio_ip = {
        .lt7182s_init_param = &lt7182s_ip,
};

struct iio_app_desc *app;
struct iio_app_init_param app_init_param = { 0 };

ret = lt7182s_iio_init(&lt7182s_iio_desc, &lt7182s_iio_ip);
if (ret)
        return ret;

struct iio_app_device iio_devices[] = {
        {
                .name = "lt7182s",
                .dev = lt7182s_iio_desc,
                .dev_descriptor = lt7182s_iio_desc->iio_dev,
        }
};

app_init_param.devices = iio_devices;
app_init_param.nb_devices = NO_OS_ARRAY_SIZE(iio_devices);
app_init_param.uart_init_params = lt7182s_uart_ip;

ret = iio_app_init(&app, app_init_param);
if (ret)
        return ret;

return iio_app_run(app);