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IP.com Disclosure Number: IPCOM000200923D
Publication Date: 2010-Oct-30
Document File: 3 page(s) / 73K

Publishing Venue

The IP.com Prior Art Database

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

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This document will briefly explain how to generate complementary outputs from a single supply Vdd with a charge pump circuit able to operate in two different modes (in which the outputs are +Vdd/2 and -Vdd/2, or +Vdd and -Vdd, respectively).

The circuit must require at most 3 external capacitors. It must also be able to switch back and forth between modes, in response to a digital command.

Description of the invention

The charge pump circuit is powered between a supply voltage source Vdd and ground, and driven by a

clock signal (CLOCK input), See figure 1. It generates two symmetrical output voltages VP (> 0V) &

VM (< 0V).

A digital input MODE SELECT controls the operating mode of the circuit, to drive outputs VP & VM

to the following values:
• VP = +Vdd, VM = -Vdd when MODE SELECT is high (mode 1)
• VP = +Vdd/2, VM = -Vdd/2 when MODE SELECT is low (mode 0)

This charge pump will be used in an audio IC, to power audio amplifiers between symmetrical voltages

VP & VM that must vary dynamically as a function of audio signal level. Mode selection will be done

"on the fly" by a level detector and transitions between modes will be handled by some dedicated

circuitry internal to the charge pump (not the object of this invention).

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Figure 1

ONS01399_DefPub.doc Page 1 of 3

Page 02 of 3

The proposed invention (figure 2) uses 3 external capacitors (2 "flying" c...