R
Rusty
A while ago it was suggested in this newsgroup that a Linear
Technology LTC4150 Coulomb counter could be used with a 12V lead-acid
battery by raising the GND pin so as to keep the IC's supply voltage
under its maximum 8.5V. My first thought was simply to use a 7.5V
voltage regulator connected to the GND pin of the LTC4150, however I'm
worried that when the battery is connected that the 7.5V will take a
small but finite time to rise, during which time the LTC4150 would see
the full 12V of the battery. Any comments on this? Am I worrying about
nothing?
Something as simple as a zener diode in place of the 7.5V supply would
solve this, but as the LTC4150 typically uses around 115uA at 8.5V,
I'm not sure if the zener would regulate properly with such a low
current.
A voltage regulator that regulated from the 12V down would be nice, so
that the voltage was equal to the battery voltage when the battery was
connected and then settled to, say, 7.5V below the battery positive
terminal and stayed constant as the battery discharged. But I just
can't get my head round how to do this with simple circuitry. I can't
help feeling theres's an easy adaptation of an existing regulator
possibly. Must be low power due to battery operation. 7.5V power
supply is based on an LP2951. Any ideas?
Technology LTC4150 Coulomb counter could be used with a 12V lead-acid
battery by raising the GND pin so as to keep the IC's supply voltage
under its maximum 8.5V. My first thought was simply to use a 7.5V
voltage regulator connected to the GND pin of the LTC4150, however I'm
worried that when the battery is connected that the 7.5V will take a
small but finite time to rise, during which time the LTC4150 would see
the full 12V of the battery. Any comments on this? Am I worrying about
nothing?
Something as simple as a zener diode in place of the 7.5V supply would
solve this, but as the LTC4150 typically uses around 115uA at 8.5V,
I'm not sure if the zener would regulate properly with such a low
current.
A voltage regulator that regulated from the 12V down would be nice, so
that the voltage was equal to the battery voltage when the battery was
connected and then settled to, say, 7.5V below the battery positive
terminal and stayed constant as the battery discharged. But I just
can't get my head round how to do this with simple circuitry. I can't
help feeling theres's an easy adaptation of an existing regulator
possibly. Must be low power due to battery operation. 7.5V power
supply is based on an LP2951. Any ideas?
