Using a Window Comparator...
hi guys , gals,
i considering use of dual comparator ts9002 (which similar max923 costs hobbyists 5x less) me lipo backup battery backpack i'm thinking of developing. have no experience either of these chips , wonder if else has used them in similar capacity. tsm9002 has 2 schmitt-trigger comparators , voltage reference 1 can set hysteresis.
the overarching idea behind keeping simple. know there cool solutions out there (i ltc4081 in particular) better job of extracting , power, optimize efficiency, etc. @ expense of simplicity, $$$, and potential emi. moreover, rig supposed keep mcu running short bits @ time, no more minute @ 200ma or so.
anyhow, proposed power circuit consists of wall-wart puts out 5v nominal fed through polyfuse , schottky diode feed main bus. trio of 3.3v ldo voltage regulators dropout voltages ranging 220mv 150mv turn main bus power well-regulated 3.3v power sensors , main mcu. thus, main bus voltage should 4.7v-5v, long wall-wart running usual. backup battery (a single cell 100mah lipo, 3.7v nominal) charged wall-wart using separate power connection mcp7381t trickle charger.
i'd using window comparator detect whether external power supply has been disconnected (i.e. vpowersupply drops below 3.9v) , if lipo battery still has enough potential (i.e. vbattery>3.6v). next, considering using nand gate combined p-channel mosfet since i'm switching on 'high' side of circuit connect , disconnect battery main bus. once external power supply jumps on 3.9v, battery disconnected bus , mcp7381t charger can refill it. similarly, if battery voltage drops below 3.6v, it's lights-out protect battery pack.
the window comparator circuit similar example given in ts9002 , max923 datasheets except instead of using series of 3 resistors detect on , under-voltage on single supply i'd querying status of 2 separate power supplies using 4 resistors altogether. conceptually, seem on right track?
i considering use of dual comparator ts9002 (which similar max923 costs hobbyists 5x less) me lipo backup battery backpack i'm thinking of developing. have no experience either of these chips , wonder if else has used them in similar capacity. tsm9002 has 2 schmitt-trigger comparators , voltage reference 1 can set hysteresis.
the overarching idea behind keeping simple. know there cool solutions out there (i ltc4081 in particular) better job of extracting , power, optimize efficiency, etc. @ expense of simplicity, $$$, and potential emi. moreover, rig supposed keep mcu running short bits @ time, no more minute @ 200ma or so.
anyhow, proposed power circuit consists of wall-wart puts out 5v nominal fed through polyfuse , schottky diode feed main bus. trio of 3.3v ldo voltage regulators dropout voltages ranging 220mv 150mv turn main bus power well-regulated 3.3v power sensors , main mcu. thus, main bus voltage should 4.7v-5v, long wall-wart running usual. backup battery (a single cell 100mah lipo, 3.7v nominal) charged wall-wart using separate power connection mcp7381t trickle charger.
i'd using window comparator detect whether external power supply has been disconnected (i.e. vpowersupply drops below 3.9v) , if lipo battery still has enough potential (i.e. vbattery>3.6v). next, considering using nand gate combined p-channel mosfet since i'm switching on 'high' side of circuit connect , disconnect battery main bus. once external power supply jumps on 3.9v, battery disconnected bus , mcp7381t charger can refill it. similarly, if battery voltage drops below 3.6v, it's lights-out protect battery pack.
the window comparator circuit similar example given in ts9002 , max923 datasheets except instead of using series of 3 resistors detect on , under-voltage on single supply i'd querying status of 2 separate power supplies using 4 resistors altogether. conceptually, seem on right track?
a window comparator determining whether voltage, test voltage, both greater 1 threshold , less threshold - fits within range (or in window.)
you have described application monitoring 2 different voltages, 1 presence (> level) of external supply , battery's level.
that points more toward 2 comparators, each satisfying threshold setting.
you need reference compare against.
any thoughts?
you have described application monitoring 2 different voltages, 1 presence (> level) of external supply , battery's level.
that points more toward 2 comparators, each satisfying threshold setting.
you need reference compare against.
any thoughts?
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