Voltage sensor senses the voltage of all the supply pins: vdda, vddio and vdd1p0. Each pins active voltage can be sensed by reading the corresponding voltage sensor output register.

All sensors are always active and monitor state machine polls the value of each sensor periodically. Monitor state machine can be further programmed to give higher priority/sampling time to one sensor over another by using MONITOR_CTRL_3 register.

Following software sequence can be used to read out any sensor's output:

• Step1 : Program register[0x0467] = 0x6004 ; Initial configuration of monitors
• Step 2 : Program register [0x046A] = 0x00A6 and then register [0x046A]=0x00A3; Refresh the monitors
• Step 3 : Program register[0x0468] to select the corresponding sensor to be polled and read register [0x047B] [14:7] for selected sensor's output code.
• Step 4 : Feed the values of read sensor's output code (in decimal) in following equations to get the sensor's output value in decimals. Refer to Table 8-3 for required value of constants to be used in equations :
  • vdda_value = 3.3 + (vdda_output_code - vdda_output_mean_code)*slope_vdda_sensor
  • vdd1p0_value = 1.0 + (vdd1p0_output_code - vdd1p0_ouput_mean_code)*slope_vdd1p0_sensor
  • vddio_calculated = 3.3 + (vddio_ouput_code - vddio_output_mean_code)*slope_vddio_sensor
  • temperature_calculated = 25 + (temperature_output_code - temperature_output_mean_code)*slope_temperature_sensor
    Table 8-3 Sensor Select Table

    Register[0x0468]	Sensor Selected To Read-out
    0x1920	VDDA Voltage Sensor
    0x2920	VDD1P0 Voltage Sensor
    0x3920	VDDIO Voltage Sensor
    0x4920	Temperature Sensor

    Table 8-4 Sensor's Constant Values

    Constant	Value (in decimal)
    vdda_output_mean_code	128
    slope_vdda3p3_sensor	8.63014e-3
    vdd1p0_output_mean_code	93
    slope_vdd1p0_sensor	2.85714e-3
    vddio_output_mean_code	224
    slope_vddio_sensor	15.686e-3
    temperature_output_mean_code	161
    slope_temperature_sensor	1.5

    Note: Accuracy of temperature sensor can be maximized (7.5degreeC), if customer can sample "temperature_output_code" at 25C and use it as "temperature_output_mean_code".