Step 2.
Plug the battery cable in the related BATT connector slot.
Step 3.
Place the cover back, paying attention to the SWD connector position, and screw it in place.
Figure 12.
STEVAL-GPT001V1 watch-shape silicon strap (external back view) and battery
connection (internal view)
1.4.3.2
Protection
The high precision voltage monitoring on the
SPV1050TTR
STORE pin allows a reliable recharge or discharge of
the battery avoiding over-voltage or under-voltage events that may shorten the battery lifetime or damage the
battery itself. In fact,in both cases, the SPV1050TTR stops supplying or draining current when the concerned set
threshold is triggered.
When the battery is connected, the pass transistor Q1 remains OFF until the system is supplied.
Q1 activation occurs when the STORE pin voltage triggers EOC threshold = 4.1 V.
When Q1 is not active the voltage on its body diode (V
FW
) links the STORE pin voltage to the battery voltage
(V
STORE
= V
FW
+ V
BATT
).
Thus, the V
FW
defines the minimum battery voltage level for the system to connect the battery: Q1 is ON and the
battery can start supplying the load only when V
BATT
= 4.1 V-V
FW
.
The V
FW
can vary according to the current flowing through Q1 body diode (V
FW
= 150 mV
@IFW=500nA
; V
FW
= 500
mV
@IFW=50mA
).
Vice versa, when the STORE pin voltage is below the UVP threshold (2.4 V according to R15, R16, R17 settings),
the SPV1050TTR turns Q1 off to disconnect the battery from the load.
1.4.3.3
Recharge through PV modules
The
SPV1050
controls the PV panel harvesting and conditioning of the extracted power to recharge the battery.
It integrates a high efficiency boost architecture which, combined with the high accuracy MPPT algorithm, ensures
long SensorTile module autonomy and battery recharging in indoor and outdoor conditions(For further details,
refer to the SPV1050 datasheet at www.st.com.).
The
STEVAL-GPT001V1
cradle board embeds a sensing circuit automatically able to track the environmental
irradiance and to optimize the system MPP working point. It is based on an operational amplifier (TSU111) in
differential configuration that discriminates the PV panel current values above 1 mA or below 0.8 mA as per
firmware value set-up.
By default, its companion Q2 MOSFET is OFF and the whole harvesting system is optimized for indoor irradiation
conditions(i.e. The input current is below 0.8 mA (~6 k Lux or 50 mW/m2)).
On the contrary, if the input sensed current is higher than 1 mA (Corresponding to ~10 k Lux or 70 mW/m2.), then
Q2 switches ON consequently modifying the resistor partitioning ratio on the SPV1050 MPP-SET pin. The MPP
has to be changed due to the PV panels different specs below 0.8 and above 1 mA (Vmpp/Voc).
On the battery return path, the
STC3115
implements a high performance gas gauge for current and voltage
battery monitoring; related data are used by the firmware running on the SensorTile STM32L4 to check the
battery charging status, calculate and show either the system autonomy increases in running mode or the battery
charge gain after a micro sleep mode period.
UM2260
UM2260
-
Rev 2
page 11/25
