3V这边：VL5通过一个二极管给BST3一个5V电压，3V电感出的电压一路经过耦合电容在BST3和前面的5V电压叠加，为芯片本身提供自举电压作者: 红尘一笑哈哈 时间: 2010-8-29 21:52
14楼的朋友说的应该是正确的作者: aliangli 时间: 2010-9-4 23:12
升压，那3V这边为什么才3V呢，我问有人说是滤波作者: 维派科技 时间: 2010-9-4 23:44
Boost High-Side Gate-Drive Supply (BST3 and BST5) Gate-drive voltage for the high-side N-channel switchesis generated by a flying-capacitor boost circuit (Figure 2). The capacitor between BST_ and LX_ isalternately charged from the VL supply and placed par-allel to the high-side MOSFET’s gate-source terminals.On start-up, the synchronous rectifier (low-side MOSFET) forces LX_ to 0V and charges the boostcapacitors to 5V. On the second half-cycle, the SMPSturns on the high-side MOSFET by closing an internalswitch between BST_ and DH_. This provides the nec-essary enhancement voltage to turn on the high-sideswitch, an action that “boosts” the 5V gate-drive signalabove the battery voltage.Ringing at the high-side MOSFET gate (DH3 and DH5)in discontinuous-conduction mode (light loads) is a nat-ural operating condition. It is caused by residual ener-gy in the tank circuit, formed by the inductor and straycapacitance at the switching node, LX. The gate-drivenegative rail is referred to LX, so any ringing there isdirectly coupled to the gate-drive output.
