Charge pump breakthrough
1 min read
In a move aimed at improving led driver capabilities, Catalyst Semiconductor has unveiled the CAT3643, which it claims is the smallest fractional charge pump yet developed. It adds the device also offers the highest efficiency.
Scott Brown, vp of marketing, said: “This device addresses the sweet spot of the portables market, where three leds are becoming the norm.”
The CAT3643 offers four modes: 1x, 1.33x, 1.5x and 2x, with the fourth mode being 1.33x. According to Catalyst, the 1.33x mode is traditionally achieved using three flying capacitors and two phases – charge and pump. In its new architecture, Catalyst says it has eliminated the need for the third flying capacitor by incorporating a third switching phase.
Phase 1 charges flying capacitors C1 and C2 by connecting them in series across the input. The second phase then pumps the output by connecting C1 from the input to the output. C2 is left unconnected. In the third phase, the output is pumped again by connecting the capacitors in series from the input to the output with C1 inverted. As a result, C1 charges to 1/3 of the input voltage and C2 charges to 2/3 of the input voltage. Between them, they produce 1.33 time Vin.
Apart from removing the need for the third capacitor, the architecture also reduces pin count.
