3 Low Power Modes with Multiple Sensors

Consider the left and right linear triggers in a gaming controller that use two different position sensors to measure the respective trigger positions. Instead of using multiple ADCs to digitize each of the sensors, it is possible to reduce the system power by reducing the number of ADC’s by multiplexing the sensor outputs using the EN pin, as shown in Figure 3-1. During shutdown, TMAG5253 places the outputs in a high impedance state that enables multiple devices to be connected together to the same ADC, eliminating the need for additional multiplexers in the system.

Figure 3-1 Multiple Sensors Connected Together in Same Bus

Figure 3-2 shows the timing diagram on the GPIO's of the microcontroller o multiplex the outputs from the two sensors. B₁ and B₂ correspond to the magnetic fields seen by Device 1 and Device 2 respectively. When the GPIO1 goes high, the Device 1 is enabled and drives the output line to the voltage corresponding to the field B₁. During this time, GPIO2 is driven low and the Device 2 is placed in shutdown mode. To avoid both the devices to be turned on simultaneously, a dead time, t_mux has to be programmed when switching between the devices. It is also important to note that these devices have to have a fast power on time, t_on , so that they can be sampled quickly before they are turned off to save power.

Figure 3-2 Timing Diagram Showing the Signals When Multiple TMAG5253 Devices are Connected Together