LTE Module Series
SC20 Charging User Guide
SC20_Charging_User_Guide Confidential / Released 10 / 14
High and Low Temperature Thresholds
High and low temperature thresholds are determined by both software and hardware, and hardware plays
a major role. On hardware side, the thresholds are closely related to thermistor and voltage divider
resistor of battery. On software side, customer only needs to choose the percentage from BTM
comparator of PM8909, which are listed as below, and calculate the thresholds by the following formula.
Table 2: Battery-temperature Monitoring Calculations
PM8909 internal comparator (pointed out by red arrow) is shown as below:
Figure 1: PM8909 Internal Comparator
Battery Charging Window
BTM Comparator Thresholds Minimum Resistor Values
0 to 40 or 45ºC
70% to 35%
R_S1 = 39×(R_cold
– R_hot)/70
R_S2 = (3×R_cold
–13×R_hot)/10
-10 to 60ºC
80% to 25%
R_S1 = 3×(R_cold
– R_hot)/11
R_S2 = (R_cold
– 12×R_hot)/11
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