The HDC3120 can be disabled by setting the RESET_EN pin low (below V_IL). In this state, the RH and Temp DAC outputs move to a near-zero condition (V_{OUT_DISABLE}), and the device current consumption is significantly reduced to I_{DD_DISABLE}. The reduced current consumption helps conserve the system power if no sensor measurement is needed. The device disable sequence and the DAC output voltages are illustrated in Figure 7-5.

Figure 7-5 HDC3120 Disable Behavior

To enable the HDC3120, the RESET_EN pin needs to be set to high (above V_IH). The enabling sequence and the sensor output voltages behave similarly to the device power-up, as described in Section 7.3.1. After the RESET_EN pin is raised above V_IH, the device loads the default settings from the memory and subsequently performs temperature and humidity measurements. During the first temperature and humidity measurement, the DAC outputs are driven to a default level of 0.1× V_DD. Each DAC channel remains at the default voltage level until the measurement is completed, which takes approximately RH_PUR for the humidity measurement and T_PUR for the temperature measurement. After the measurement is completed, the DAC outputs are driven to the voltage level corresponding to the measured humidity and temperature values. Figure 7-6 illustrates the HDC3120 enable sequence.

Figure 7-6 HDC3120 Enable Behavior

Note the HDC3120 RESET_EN pin has a weak 51kΩ internal pull-up to V_DD, thus the pin can be left floating is the RESET or the Disable functions are not utilized.