LT7170 no-OS driver

Supported Devices

Overview

The LT7170/LT7170-1 are monolithic DC/DC synchronous step-down regulators that deliver up to 20 A of continuous output current. The LT7170-1 option has two switching phases that are connected to two inductors to drive a single-regulated output supply.

Similarly, the LT7171/LT7171-1 are monolithic PolyPhase DC/DC synchronous step-down regulators that also deliver up to 20A of continuous output current. The LT7171-1 option has two switching phases that are connected to two inductors to drive a single-regulated output supply.

Both series offer quick, clean, low-overshoot switching edges deliver high efficiency while minimizing electromagnetic interference (EMI) emissions.

An I2C-based PMBus 1.3-compliant serial interface allows control of device functions while providing telemetry information for system monitoring. The LT7170/LT7170-1 and LT7171/LT7171-1 are supported by the LTpowerPlay graphical user interface (GUI) tool.

Applications

LT7170

  • Communications, Storage, and Industrial Systems

  • Data Center and Solid-State Drives

LT7170 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 lt7170_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 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 can be set using the lt7170_vout_value API.

The output voltage transition rate can be configured using the lt7170_vout_tr API.

Output voltage lower and higher margin can also be configured using the lt7170_vout_margin API.

The OPERATION command via the lt7170_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 lt7170_set_vin API.

Status Configuration

Statuses bytes/words of the device can be read using lt7170_read_status API. Faults asserted by these statuses can be cleared using the lt7170_clear_faults API.

Telemetry

Measurements can be read using the lt7170_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 lt7170_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 lt7170_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 lt7170_set_limit API.

PWM Configuration

The PWM can be set on forced continuous mode or on pulse skip mode. This can be set using the lt7170_pwm_mode API.

The phase offset of the PWM can also be set using the lt7170_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 lt7170_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 lt7170_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 lt7170_software_reset API.

LT7170 Driver Initialization Example

struct lt7170_dev *lt7170_dev;
struct no_os_i2c_init_param lt7170_i2c_ip = {
        .device_id = I2C_DEVICE_ID,
        .max_speed_hz = 100000,
        .platform_ops = I2C_OPS,
        .slave_address = LT7170_PMBUS_ADDRESS,
        .extra = I2C_EXTRA,
};

struct lt7170_init_param lt7170_ip = {
        .i2c_init = &lt7170_i2c_ip,
        .pg_param = NULL,
        .run_param = NULL,
        .alert_param = NULL,
        .fault_param = NULL,
        .fault_cfg = LT7170_FAULT_PIN_OUTPUT,
        .chip_id = ID_LT7170,
        .external_clk_en = false,
        .crc_en = false,
};
ret = lt7170_init(&lt7170_dev, &lt7170_ip);
if (ret)
        goto error;

LT7170 no-OS IIO support

The LT7170 IIO driver comes on top of the LT7170 driver and offers support for interfacing IIO clients through libiio.

LT7170 IIO Device Configuration

Input Channel Attributes

VIN/IIN/TEMP/VCC channels are the input channels of the LT7170 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 using a priv

Output Channel Attributes

IOUT channel is an output channel with the following channel attributes:

  • raw - the raw value of the channel

  • scale - the scale value of the channel calculated accordingly using a priv

Meanwhile, VOUT channel is an output channel 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 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 12 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 - Output overvoltage fault limit

  • vout_ov_warn_limit - Output overvoltage warning limit

  • vout_uv_fault_limit - Output undervoltage fault limit

  • vout_uv_warn_limit - Output undervoltage warning limit

  • iin_oc_warn_limit - Input overcurrent warning limit

  • iout_oc_warn_limit - Output overcurrent warning limit

  • 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 7 debug attributes:

  • status_vout - VOUT status byte value of channel 0

  • status_iout - IOUT status byte value of channel 0

  • status_input - INPUT status byte value of channel 0

  • status_mfr_specific - MFR_SPECIFIC status byte value of channel 0

  • status_word - Status word value of the channel 0

  • status_temperature - TEMPERATURE status byte value of the device

  • status_cml - CML status byte value of the device

LT7170 IIO Driver Initialization Example

int ret;

struct lt7170_iio_desc *lt7170_iio_desc;
struct lt7170_iio_desc_init_param lt7170_iio_ip = {
        .lt7170_init_param = &lt7170_ip,
};

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

ret = lt7170_iio_init(&lt7170_iio_desc, &lt7170_iio_ip);
if (ret)
        return ret;

struct iio_app_device iio_devices[] = {
        {
                .name = "lt7170",
                .dev = lt7170_iio_desc,
                .dev_descriptor = lt7170_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 = lt7170_uart_ip;

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

return iio_app_run(app);