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CYALKIT-E02 Solar-Powered BLE Sensor Beacon Reference Design Kit Guide, Doc. No. 002-11317 Rev. *C
83
Solar Cell
(U1)
power
Solar BLE Sensor
KitProg
Programmer/Serial
Communication
(U3)
PRoC BLE
(U1)
Debug Board
USB
Type-A Plug
(J1)
EZ-BLE
Module
(U3)
MB39C022G
LDO
5V
3.3V
10pin Connector (CN1)
10pin Connector (CN1)
EH
PMIC
(U2)
Super
Capacitor
(SC1)
A.3
Equivalent Series Resistance of the Supercapacitor
The VOUT setting of S6AE103A is set as 3.24 V (VOUTH) to 1.62 V (VOUTL). There is a 0.28-V VOUTL margin to supply
voltage to the VOUT load (operation voltage is 3.6 V to 1.9 V). This margin is for taking measures to mitigate the voltage drop
because of equivalent series resistance (ESR). The ESR of the supercapacitor (C1) on the Solar BLE Sensor is 200
Ω. When
the VOUT load current is 5 mA, the voltage drop will be 1000 mV (V = IR). To resolve such a problem, the S6AE103A has two
storage pins: VSTORE1 and VSTORE2. VSTORE1 connects the low-ESR capacitor, such as a ceramic capacitor. VSTORE2
connects the large capacitance such as the supercapacitor. The energy of the supercapacitor (VSTORE2) passes to the
low-ESR capacitor (VSTORE1), and then the low-ESR capacitor supplies the energy to the VOUT load. This operation
reduces the voltage drop.
S6AE103A
EH PMIC
(U2)
Solar Cell
(U1)
EZ-BLE
Module
(U3)
Super Capacitor
(SC1)
200 mF
ESR = 200
Ω
+
Ceramic Capacitor
(C1 to C4)
400 uF
ESR < 1
Ω
VSTORE2
VSTORE1
SW1
VOUT1
VDD
A few voltage drops will still occur, however, because VOUT is supplied using only a ceramic capacitor
when there is no solar
energy. The kit connects the 400-µF capacitor to VSTORE1, and the energy of the BLE sensor transmission is about 200 µJ.
If the VSTORE1 voltage is 1.9 V and it uses 200 µJ of energy, the voltage drop is about 0.28 V. Refer to the following equation.
