ADT7462SM(4) BSD Kernel Interfaces Manual ADT7462SM(4) NNAAMMEE aaddtt77446622ssmm — On Semiconductor (Analog Devices) ADT7462 Flexible Tempera‐ ture, Voltage Monitor, and System Fan Controller SSYYNNOOPPSSIISS aaddtt77446622ssmm** aatt iiiicc?? aaddddrr?? DDEESSCCRRIIPPTTIIOONN The aaddtt77446622ssmm driver provides support for the On Semiconductor ADT7462 system monitor. The chip possesses 8 fan speed sensors, 4 temperature sensors, and 13 voltage sensors. The number of each sensor type config‐ ured by the driver depends on the chip configuration. The values of the sensors are made available through the envstat(8) in‐ terface. SSeennssoorr UUnniittss DDeessccrriippttiioonn fan _N RPM Fan 0–7 local C Local temperature remote _N C Remote temperature 1–3 V2.5 _N mV DC 2.5V voltage 1–3 V1.8 _N mV DC 1.8V voltage 1–3 V1.5 _N mV DC 1.5V voltage 1–4 V3.3 _N mV DC 3.3V voltage 1–2 V1.2 _N mV DC 1.2V voltage 1–2 Vbatt mV DC Battery voltage V12 _N mV DC 12V voltage 1–3 V0.9 mV DC 0.9V voltage V1.25 mV DC 1.25V voltage V5 mV DC 5V voltage fan fault none Fan fault display Configurable limits for the sensors are also available via envstat(8). Initial limit values are read from the chip. Each temperature sensor has therm, high and low limits, which are mapped to _c_r_i_t_m_a_x, _w_a_r_n_m_a_x and _w_a_r_n_m_i_n, respectively. Voltage sensors have high (_w_a_r_n_m_a_x) and low (_w_a_r_n_m_i_n) limits. Fan sensors have a high limit mapped to _w_a_r_n_m_i_n, be‐ cause the fan measurements are revolution intervals, so higher numbers correlate to lower fan speeds. Note, that there are two therm limits per temperature sensor and the one with the lowest value is used as _c_r_i_t_m_a_x. The fan fault sensor has a value of _0 in normal operation. If a fault is detected, the fan fault value will represent the numbers of the failed fans, _1 for fan 0, _1_0 for fan 1, and so on, to _1_0_0_0_0_0_0_0 for fan 8. The chip also supports Pulse-Width Modulated (PWM) fan speed control and the aaddtt77446622ssmm driver makes PWM and temperature settings available via sysctl. For each PWM channel, the controlling temperature channel is shown. For example hw.adt7462sm0.pwm1.channel = remote1_dynamic hw.adt7462sm0.pwm2.channel = remote2_dynamic hw.adt7462sm0.pwm3.channel = remote3 hw.adt7462sm0.pwm4.channel = manual If the channel is shown as _m_a_n_u_a_l, then the PWM duty cycle can be altered through the corresponding _d_u_t_y___c_y_c_l_e variable. For example hw.adt7462sm0.pwm4.duty_cycle The _d_u_t_y _c_y_c_l_e can be set to any value between 0% (off) and 100% (full) although the minimum non-zero value for a fan is usually in the 20% to 33% range. Note, fan speed in % rpm generally relates to the square root of the duty cycle. Therefore, 33% duty cycle will result in a fan speed close to 50%. If the channel is shown as _r_e_m_o_t_e_N, then the. _t_m_i_n and _t_r_a_n_g_e variables for that _r_e_m_o_t_e_N can be used to adjust the PWM value and fan speed. For example: hw.adt7462sm0.remote3.tmin hw.adt7462sm0.remote3.trange The _t_m_i_n value is the temperature in degC at which the fan starts and the _t_r_a_n_g_e value represents the temperature range over which the fan speed increases until it reaches full speed. Both of these values can be al‐ tered, although _t_m_i_n must be lower than the corresponding _c_r_i_t_m_a_x value from envstat and _t_r_a_n_g_e must be between 2 and 80. If the channel is shown as _r_e_m_o_t_e_N___d_y_n_a_m_i_c, then the _t_m_i_n value is read- only, and the _t_r_a_n_g_e and _o_p_p_o_i_n_t variables for that _r_e_m_o_t_e_N are used to adjust the PWM value and fan speed. For example: hw.adt7462sm0.remote1.tmin = 32 hw.adt7462sm0.remote1.trange = 32 hw.adt7462sm0.remote1.oppoint = 60 The _t_m_i_n value is still the temperature in degC at which the fan starts, but is dynamically calculated by the chip based on the _o_p_p_o_i_n_t (operating point) and _t_r_a_n_g_e values. The operating point is a target temperature and the chip will attempt to maintain that temperature or lower. It does this by adjusting the _t_m_i_n value based on the _t_r_a_n_g_e, thus causing the PWM values and fan speed to vary based on the difference between the cur‐ rent and operating point temperatures. Both the _o_p_p_o_i_n_t and _t_r_a_n_g_e val‐ ues can be altered, although _o_p_p_o_i_n_t must be higher than _t_m_i_n. If the channel is shown as _l_o_c_a_l___r_e_m_o_t_e_3, then _t_m_i_n and _t_r_a_n_g_e for both the _l_o_c_a_l and the _r_e_m_o_t_e_3 temperature sensors affect the PWM value and fan speed. If the channel is shown as _o_f_f, then it can not be altered. SSEEEE AALLSSOO iic(4), intro(4), envstat(8) sysctl(8) AAUUTTHHOORRSS The aaddtt77446622ssmm driver was written by Julian Coleman <_j_c_o_l_e_m_a_n_@_N_e_t_B_S_D_._o_r_g>. BBUUGGSS It's not possible to determine if either a sensor is not connected, or the monitored device is producing no output. Therefore, unconnected sen‐ sors will show outputs of 0. The aaddtt77446622ssmm driver does not support interrupt output. BSD February 19, 2026 BSD