MAX42500 no-OS driver

Supported Devices

Overview

The MAX42500 is a SoC power-system monitor with up to seven voltage monitor inputs that will be SIL 3-Certified. Each input has programmable OV/UV thresholds of between 2.5% and 10% with ±1.3% accuracy over the full temperature range. Two of the inputs have a separate remote ground-sense input and support DVS through the integrated I2C interface.

The MAX42500 contains a programmable flexible power sequence recorder (FPSR). This recorder stores power-up and power-down timestamps separately, and supports on/off and sleep/standby power sequences. The MAX42500 also contains a programmable challenge/response watchdog, which is accessible through the I2C interface, along with a configurable RESET output.

Applications

Industrial Process Control
Robotics
Remote Sensor Modules
Power System Supervision
MCU/SoC Monitoring

MAX42500 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 for the specific application (depends on the way the device is used).

The first API to be called is max42500_init. Make sure that it returns 0, which means that the driver was initialized correctly.

Voltage Monitor

The MAX42500 has up to seven voltage monitor channels. Five of the monitors feature single-ended inputs. For these channels, you first set a nominal voltage, followed by setting the overvoltage (OV) and undervoltage (UV) thresholds as a percentage of that nominal voltage. The other two monitors have differential inputs and share a remote ground-sense pin (INM). Unlike the single-ended monitors, which use a nominal voltage plus percentage-based OV/UV configuration, the differential inputs have independent OV and UV comparators, each of which can be configured with its own reference voltage.

IN1 through IN4 have a nominal voltage set-point range of 0.50V to 3.6875V, while IN5 has an extended range of 0.50V to 5.50V. This can be set using max42500_set_nominal_voltage API.

The OV and UV thresholds can be set using max42500_set_ov_thresh1 API and max42500_set_uv_thresh1 API for IN1 through IN5, from 2.5% to 10% in 0.5% steps. IN6P and IN7P have the differential configuration. Their OV and UV set points can range from 0.50V to 1.775V and can be set using max42500_set_ov_thresh2 API and max42500_set_uv_thresh2 API.

Aside from OV and UV comparators, every monitor channel also has an OFF comparator that asserts when the monitor input voltage falls below 0.25V. The statuses of these comparators can be read using the max42500_get_comp_status API.

Power-Up and Power-Down Timestamps

A power-up timestamp is recorded for an enabled channel when the associated voltage rises above the programmed UV threshold. A power-down timestamp is recorded for an enabled channel when the associated voltage falls below the OFF threshold.

The power-up and power-down timestamps can be read using the max42500_get_power_up_timestamp API and max42500_get_power_down_timestamp API respectively.

Watchdog Configuration

The device contains a windowed watchdog for external SoC monitoring. Aside from configuring the watchdog in the device initialization, you can enable or disable the watchdog using the max42500_set_watchdog_enable API. To refresh the watchdog, you can use the max42500_set_watchdog_key API.

RESET Hold Time Configuration

The device features an open-drain interrupt/reset output that asserts low when any mapped fault conditions occur. RESET remains asserted for a fixed timeout period after all triggering fault conditions are removed. The fixed timeout period can be set to 6μs, 8ms, 16ms, or 32ms using the max42500_set_watchdog_rhld API.

MAX42500 Driver Initialization Example

struct max42500_dev *device;
struct max_i2c_init_param max42500_i2c_ip;
struct max_gpio_init_param max42500_gpio_extra;

struct max42500_init_param max42500_ip = {
        .comm_param = {
                .device_id      = 0,
                .max_speed_hz   = 400000,
                .slave_address  = MAX42500_ADDR(0),
                .platform_ops   = &max_i2c_ops,
                .extra          = (void *)&max42500_i2c_ip,
        },
        .en0_param = {
                .port           = 2,
                .number         = 26,
                .pull           = NO_OS_PULL_DOWN,
                .platform_ops   = &max_gpio_ops,
                .extra          = (void *)&max42500_gpio_extra,
        },
        .en1_param = {
                .port           = 2,
                .number         = 29,
                .pull           = NO_OS_PULL_DOWN,
                .platform_ops   = &max_gpio_ops,
                .extra          = (void *)&max42500_gpio_extra,
        },
        .addr_param = {
                .port           = 2,
                .number         = 9,
                .pull           = NO_OS_PULL_DOWN,
                .platform_ops   = &max_gpio_ops,
                .extra          = (void *)&max42500_gpio_extra,
        },
        .addr_sel   = 0,
        .pece       = NO_OS_BIT(0),
        .vmon_en    = NO_OS_BIT(0),
        .vmon_vmpd  = NO_OS_BIT(7),
        .reset_map  = NO_OS_BIT(0),
        .wd_mode    = MAX42500_WD_MODE_SIMPLE,
        .wd_en      = NO_OS_BIT(3),
        .wd_close   = 0x00,
        .wd_open    = 0x00,
        .wd_cdiv    = 0x00,
        .wd_1ud     = 0x00,
};

ret = max42500_init(&device, &max42500_ip);
if (ret)
        goto error;