Hello,
Regarding the power system we are designing for our on-going project now, we have some questions with selecting the right solutions for 3.3V (Power for Microcontroller), and 5V (Power for sensor). The whole project is powered up by a 3.7V single cell Lithium battery.
We simply sorted out two possible solutions by using TI devices, but would you give some comments on them please?
1st solution:
We are going to use two DC/DC converter for two sub- power system, TPS63031 for 3.3V power to the microcontroller, some LEDs, buttons, and one Buzzer(90mA max), which will be constant on. This is chosen because when the microcontroller is in sleep mode, the current consumption is pretty low, and since the device could be configured as Power Save mode, I guess it is ok to leave the regulator constant on. For 5V supply, it requires only 200mA current, I in the beginning planned to use TPS61222, however I found out the shutdown mode of this device does not switch off the output, instead the input is connected to the output through the back-gate diode. This is definitely not what we would like to have. May I then ask if the shutdown mode is just to save power, and it does not mean the output will be switched off? Soon I found another device for 5V power supply, which is TPS61240, and I guess load disconnection is the key feature to differentiate from just shutdown mode, right?
2nd solution:
The other solution could be using a 5V like TPS61253, and set it up like constant on. And I could then use a LDO like LP5907 to lower the level down to 3.3V, to have both voltages. This solution we only have one switching regulator, which is easy for the design. However, both the DC/DC booster and the LDO will be constantly on, which consumes energy.
We are developing a handheld medical device, which of these two solutions is better? Or both are fine? Could you give us some comments please?
Thank you very much!
