- Thu Apr 10, 2014 10:10 pm
#170157
I am designing the power system for a board that will run on a 3.7V lipo battery, all of the IC's are 3.3v; naturally I want to squeeze as much battery life as possible. The power system includes a charger for the lipo battery and which also allows the board to be used while plugged to a usb port (for debugging or using while charging).
I expect most of the IC's will be on power down mode for 70% of the time, and active for 30% of the time. When the system is active/inactive is controlled by external interrupts and not by a user controllable switch. The maximum current draw when active is 250mA, but for the most part while active it should be around 120mA while active; when in power down mode the current draw is of 30uA (last sentence edited for clarity).
I've been debating with a few choices.
1. Should I use an LDO regulator or a buck-boost regulator?
2. Should I disconnect the battery from the load when operating with USB power?
The MPC1700 is an LDO regulator with a very low quiescent current of 1.6uA and a voltage dropout of ~200mV. Problem is, when battery drops below a certain point the whole system will shut off even if the lipo still had some life left in it. An alternative would be the TPS61200 which is a buck-boost type regulator, it has a higher quiescent current of 55uA but will let me use the whole battery range. Unfortunately, in that case I would have to worry about under-voltage protection and the added components will also consume power.
Here is the circuit I came up with (open in new tab since it gets chopped by the forum)
Thoughts are welcome.
I expect most of the IC's will be on power down mode for 70% of the time, and active for 30% of the time. When the system is active/inactive is controlled by external interrupts and not by a user controllable switch. The maximum current draw when active is 250mA, but for the most part while active it should be around 120mA while active; when in power down mode the current draw is of 30uA (last sentence edited for clarity).
I've been debating with a few choices.
1. Should I use an LDO regulator or a buck-boost regulator?
2. Should I disconnect the battery from the load when operating with USB power?
The MPC1700 is an LDO regulator with a very low quiescent current of 1.6uA and a voltage dropout of ~200mV. Problem is, when battery drops below a certain point the whole system will shut off even if the lipo still had some life left in it. An alternative would be the TPS61200 which is a buck-boost type regulator, it has a higher quiescent current of 55uA but will let me use the whole battery range. Unfortunately, in that case I would have to worry about under-voltage protection and the added components will also consume power.
Here is the circuit I came up with (open in new tab since it gets chopped by the forum)
Thoughts are welcome.
Last edited by alexc on Fri Apr 11, 2014 7:30 am, edited 1 time in total.