- Wed Jun 28, 2006 5:49 am
#15096
Hello,
This is my first time attempting to build anything battery backed-up... Well, aside from an RTC circuit anyway.
Bought a stack of MAX1555's, 3 x 100mAh LiPo batteries and 7x860mAh LiPo batteries. Wired them up the same way as Sparkfun's protoboard - no problem, charging fine and cutting off when full.
Now heres my issue. I need to build some sort of changeover circuit, that will kick the battery in once the main supply is disconnected. My existing circuit mainly contains a dsPIC30F4013, GM862-Python & Lassen IQ GPS module.
GPS & GSM modem both run at ~3v3 via an LT1528, andthe dsPIC runs at 5v via a 7805 (but would be happy down to about 3v6 without losing too much speed)
I've noticed theres a "SYSTEM" connection on the MAX1555 which allows me to draw and charge at the same time, but i'm assuming it'd **** itself if I tried to draw > 100mA
Has anyone built such a changeover circuit, and am I wrong about the >100mA on the System connector?
Thanks!
-Bt
This is my first time attempting to build anything battery backed-up... Well, aside from an RTC circuit anyway.
Bought a stack of MAX1555's, 3 x 100mAh LiPo batteries and 7x860mAh LiPo batteries. Wired them up the same way as Sparkfun's protoboard - no problem, charging fine and cutting off when full.
Now heres my issue. I need to build some sort of changeover circuit, that will kick the battery in once the main supply is disconnected. My existing circuit mainly contains a dsPIC30F4013, GM862-Python & Lassen IQ GPS module.
GPS & GSM modem both run at ~3v3 via an LT1528, andthe dsPIC runs at 5v via a 7805 (but would be happy down to about 3v6 without losing too much speed)
I've noticed theres a "SYSTEM" connection on the MAX1555 which allows me to draw and charge at the same time, but i'm assuming it'd **** itself if I tried to draw > 100mA
Has anyone built such a changeover circuit, and am I wrong about the >100mA on the System connector?
Thanks!
-Bt