Li-ion battery Charger CMOS 0.7um Process

[Ðavide Melo]

Hello, I need some help with something that I´m working on, a Li-ion battery charger in CMOS 0.7um.

->Battery: Li-ion (4.2V, 1000mAh).

->The charger circuit must implement trickle-charge (Vbat<3V), CC (Vbat>3V), CV(Vbat=4.2V)

At this moment I need 2 voltage references (3V, 4.2V), but I cant figure it out, do you think that with a bandgap reference I can solve this problem?
I'm reading this book: CMOS Circuit design, layout, and simulation.

 

[erikl]

... I need 2 voltage references (3V, 4.2V), but I cant figure it out, do you think that with a bandgap reference I can solve this problem?

Sure you'll need a bandgap reference. You can derive both comparison voltage values (=bandgap voltage) from a resistor chain between output & GND (via analog switches).