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ENYCAP and LoRa™ RF Transmission
The equivalent series resistance (ESR) of ENYCAP devices
was intensively tested for use in radio applications.
The voltage drop across the capacitor is proportional
to the ESR and the current. For example, it would be
proportional with a 2.5W ESR per 1.4V cell for the 15F
ENYCAP or 7.5W per 1.4V cell for the 4F version.
Even the 4F/4.2V three-cell version, specified at a
conservative 22.5W internal resistance in the datasheet,
exhibits a voltage drop of only 0.7V at room temperature
and pulse loading. Thus, an ESR of 5W can be calculated
in the first 50ms.
The measured currents on the 4.1V side were 80mA to
125mA; the IoT sensor contained a buck converter that
converted to the best transceiver voltage. OOK, FSK,
and LoRa™ burst were transmitted; after these the circuit
waited to receive a response.
The readily available V-Harvester reference board
combines the TEMD5080X01 photovoltaic (PV) cell
with the ENYCAP HVC196 4F/4.2V capacitor to build
a platform for attaching Vishay's low-power optical
proximity or ambient light sensors at the configurable
interface, such as the VCNL36826/21, VEML6030/35, or a
comparable device. These sensors consume around 2μA
to 8μA by sampling every 300ms to 4.1s. Many of these
sensors start running at 1.7V already.
Figure 3: Testing of internal resistance (ESR). (Source: Vishay)
