Voltage-Divider IC Drops 48-V Input to 6 V for Power POL Regulators (.PDF Download)
Helix Semiconductors’ HS200 DC-DC MuxCapacitor Power IC is a new type of voltage divider that can play an integral role in a distributed power architecture (DPA) system. It provides a high-efficiency approach to reducing the input voltage while delivering a 15-W drive for external point-of-load (POL) converters. To see how the HS200 fits in a DPA system, we first need to look at a typical DPA system.
Current DPA systems use a bus converter to deliver an unregulated, stepped-down voltage of 9.6 to 14 V to power a POL (Fig. 1). This bus converter is ideal for a loosely regulated 12-V dc intermediate bus architecture that powers a variety of downstream non‑isolated, POL regulators. Both the bus converter and POL are well-suited for applications that use a 48-V (±10%) input bus.
1. Shown is one segment of a typical distributed-power-architecture system, which generally incorporates a bus generator.
The HS200 can replace the bus converter by taking the 48-V input and producing a 6-V output to power a POL. Today, POLs produce from 3.3 V to less than 1 V, so 6 V is adequate for most applications.
What is the MuxCapacitor?
Key to the HS200 is the MuxCapacitor, with its topology that consists of three charge pumps (Fig. 2). Each MuxCapacitor stage can be configured in series to obtain greater voltage division or in parallel for higher current capability. The MuxCapacitor controller optimizes power-delivery efficiency from no-load to maximum power.
The MuxCapacitor employs charge pumps that provide dc-dc voltage conversion using a switch network to charge and discharge two capacitors. The switch network toggles between charge and discharge states of the capacitors. As shown in Fig. 2, above each MuxCapacitor, the "flying capacitor" external CEXT shuttles charge, and the external reservoir capacitor at the output of each charge pump holds the charge and filters the output voltage. Charge-pump modulation (which controls the switch resistance) offers more output current for a given die size (or cost), because it does not need a series pass transistor.