Design Note
Active Rectifier Controller with Ultrafast Transient Response and
Low Power Dissipation
Bin Wu
Introduction
The LT8672 is an active rectifier controller that (along
with a MOSFET) provides reverse current protection and
rectification for power supplies in automotive environments.
This job is traditionally taken on by a Schottky diode, over
which the LT8672’s active protection has a number of
advantages: Minimal power dissipation Small, predictable, regulated 20mV voltage drop
The LT8672 also includes a number of features to satisfy
supply rail requirements in automotive environments: Reverse input protection to –40V Wide input operation range: 3V to 42V Ultrafast transient response Rectifies 6VP-P up to 50kHz; rectifies 2VP-P up to 100kHz Integrated boost regulator for the FET driver performs
better than charge pump devices
Figure 1 shows a complete protection solution. Fast Response for Input Ripple Rectification
Automotive standards—ISO 16750 or LV124—specify
that automotive electronic control units (ECUs) may face a
supply with a superimposed AC ripple of up to 6VP-P at up to
30kHz. The LT8672's gate driver that controls the external
MOSFET is strong enough to handle ripple frequencies of up VBATT
12V to 100kHz, which minimizes reverse current. An example of
such an AC ripple rectification is shown in Figure 2. Low Power Dissipation Compared with a
Schottky Diode …