A fully integrated solar battery charger

Electronics for Power and Energy Management

“…In addition to a fixed 10 nA beta-multiplier (BM) current reference that has been used to provide the required bias current for a solar energy harvester, a switched-capacitor betamultiplier (SCBM) current source has been designed to generate frequency-proportional bias currents. In this circuit, which can be seen in Figure 6b, SC resistors have been used instead of regular resistors to generate frequency-proportional bias currents [34]. For example, I ADC can be specified as in (3):…”

A miniaturized autonomous microsystem for hydrogen gas sensing applications

“…These ratios can be made precise and nearly insensitive to process variations. Summing this PTAT voltage and V BE , that is a complementary to absolute temperature (CTAT) voltage, with proper weighting factors, leads to a temperature-independent bandgap reference voltage [8]. The ratio between the PTAT and the bandgap reference voltage is measured to calculate temperature.…”

“…The voltage level detector (LD) circuit, shown in Fig. 2, is used for both initial power-on-reset (POR) of the system and detection of the end of charge (EOC) state [8] in the battery. If V bat is not sufficient to power up the circuit, the PV module continuously charges the battery up to V POR threshold voltage by keeping the switch closed.…”

“…Meanwhile bottom plate of C 1 is connected to ground and V BE1 to add V ref as (7) to V o . In order to generate the required PTAT voltage for temperature measurement, only C 2 is used to add V ptat as in (8) to V o .…”

“…(8) By using a 50fF MIM capacitor as C 1 and a 360fF MIM capacitor as C 2 , a temperature-independent reference voltage of approximately 310mV has been generated. Similar to gas sensing, n-bit digital representation of ⁄ is stored in the ADC counter after temperature sensing.…”