# Low Power Supercapacitor LTE modem supply

I am interested in your comments about the following LTE modem power supply from a single 3.6V ER34165 battery with minimal Iq (quiescent current).

The battery can only handle 200mA continuous current at 3.6V, so I plan to use two 1F supercapacitors (e.g. HV0810-2R7105-R) in series, to support the battery during LTE transmission bursts. During LTE activity, the supply voltage must not be under 3.3V.

Since battery life time is a critical parameter and the system should stay with a total quiescent current << 10uA in sleep mode, I designed the following schematic:

"-PRECHARGE_EN" and "-HIGH_POWER_EN" are controlled by the central MCU seconds / just before the next LTE transmission. The upper transistor will be on if the ideal diodes are off and vice versa. The Schottky diode assures that the voltage will not drop below brown-out level during the switch to high power supply.

I am wondering if there is a easier solution to my problem and appreciate any comments on this.

• As an alterntive to the ideal diodes iam thinking of using TPS2115A switcher... – wildcard May 29 '19 at 15:07
• It depends on specs for duration , cost, size and Tx burst current. A single Lithium Ion perhaps? – Tony Stewart Sunnyskyguy EE75 May 29 '19 at 15:14
• I would probably switch the battery for a higher current before adding expensive caps, that also add volume – Voltage Spike May 29 '19 at 15:42
• How much more current does the LTE modem require during fast bursts? – Voltage Spike May 29 '19 at 16:25
• $5 cap with low mWh battery or$5 battery with 10Wh ?? – Tony Stewart Sunnyskyguy EE75 May 29 '19 at 16:32