LTC2992 no-OS driver

Supported Devices

Overview

The LTC2992 is a rail-to-rail system monitor that measures current, voltage, and power of two supplies. It features an operating range of 2.7V to 100V and includes a shunt regulator for supplies above 100V. The voltage measurement range of 0V to 100V is independent of the input supply. Two ADCs simultaneously measure each supply current. A third ADC monitors the input voltages and four auxiliary external voltages. Each supply current and power is added for total system consumption. Minimum and maximum values are stored and an overrange alert with programmable thresholds minimizes the need for software polling.

Applications

LTC2992

Telecom infrastructure
Industrial equipment
Automotive
Computer systems and servers

LTC2992 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 function to be called is ltc2992_addr_gen to generate the corresponding device’s slave address. Once a proper address is generated, use the function ltc2992_init to initialize the device and make sure that it returns 0. This indicates a successful driver initialization.

The LTC2992 must be configured such that ADC resolution and shunt resistor values are indicated in the ltc2992_init_params structure. Optionally, other parameters such as calibration mode, measurement mode, and voltage selection can also be set at initialization.

Voltage, Current and Power readings

The LTC2992 voltage, current and power monitoring features are exposed via the ltc2992_get_voltage, ltc2992_get_vshunt, ltc2992_get_current, and ltc2992_get_power functions. LTC2992 also saves the maximum and minimum voltage, current and power data. These can be accessed via the ltc2992_get_max_data and the ltc2992_get_min_data APIs.

Alert and Thresholds

The LTC2992 can be configured to assert alert when a voltage, current or power readings reaches a maximum or minimum threshold limit. To enable alert, the ltc2992_set_alert can be used. This requires an enum ltc2992_alert_value parameter.

Threshold limits can then be set using the ltc2992_set_max_thresh and ltc2992_set_min_thresh functions. Fault statuses can be polled by calling ltc2992_get_fault and can also be cleared by ltc2992_clear_fault.

General Purpose Input Output

The LTC2992 also features GPIOs that can be configured as a general purpose output, logic input or data converter input. GPIO3 can be used as a data ready signal which pulses low when ADC data becomes available. GPIO4 can be used as an alert pin which allows interrupt-based fault monitoring. An alert pin can be configured as an interrupt input using the alert_gpio_init parameter at initialization.

LTC2992 Driver Initialization Example

struct ltc2992_init_param ltc2992_ip = {
        .i2c_init = {
                .device_id = 1,
                .max_speed_hz = MXC_I2C_STD_MODE,
                .extra = &max32655_i2c_extras,
                .platform_ops = &max_i2c_ops,
        },
        .shunt_resistor = 10,
        .alert_clear = true,
        .alert_gpio_init = {
                .number = -1,
        },
        .resolution = LTC2992_RESOLUTION_12_BIT,
};

ret = ltc2992_addr_gen(&ltc2992_ip, LTC2992_ADR_NC, LTC2992_ADR_NC);
if (ret)
        goto error;

ret = ltc2992_init(&dev, &ltc2992_ip);
if (ret)
        goto error;