Hello,
I’m working in a circuit in which I need an item with the following functionality:
- When the external power is connected (BATEXT in the range 4.5~40V), my output must be <0.4V;
- When the external power is off or turning off (BATEXT <4.5V), my output must be >=1.4V;
- The range of the transition area (around the 4.5V point) should be short, so that this voltage point is controlled (the activation point is always close to 4.5V, independent of component variations)
I was thinking of the possibility of using a shunt regulator (like the TL431) as in the image below, but I couldn’t find a cheap shunt regulator that satisfies the condition of an output lower than 0.4V, when external power is on. (caused by the shunt regulator zener voltage, which usually is around 1V)
Do you guys have any other suggestions of solutions/circuits with that behavior?
PS.: in the circuit above, the Li-Ion battery is a regular 3.7V cell (3.0~4.4V)
PS2.: the circuit must work over the temperature range of -40~85ºC
PS3.: the output is going to be used to control the enable of a SN74LVC1G175 and a TPS61085 (which shall both be disabled when the power is over 4.5V)
PS4.: sorry for the big post and the great number of PSs.. =|
