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Current Distributor for Digital Noise Reduction

IP.com Disclosure Number: IPCOM000118939D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Ohmori, T: AUTHOR

Abstract

Disclosed is a current distributor of Analog Digital Converter for Digital noise reduction. A flash-type Analog Digital Converter is used for high speed application. A six-bit flash Analog Digital Converter consists of 63 comparaters, two reference voltages (Top, Bottom) and 63 to 6 decoder. Creating two reference voltages without digital nose is a key for the precision of Analog Digital Converter. The current distributor from a voltage source block to two reference voltage (Top, Bottom) circuits is the best way for the reduction of noise from the digital blocks.

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Current Distributor for Digital Noise Reduction

      Disclosed is a current distributor of Analog Digital Converter
for Digital noise reduction.  A flash-type Analog Digital Converter
is used for high speed application.  A six-bit flash Analog Digital
Converter consists of 63 comparaters, two reference voltages (Top,
Bottom) and 63 to 6 decoder.  Creating two reference voltages without
digital nose is a key for the precision of Analog Digital Converter.
The current distributor from a voltage source block to two reference
voltage (Top, Bottom) circuits is the best way for the reduction of
noise from  the digital blocks.

      The Figure shows a current source and a Top/Bottom
circuit.  The current source block consists of a Bandgap Reference
(1.2V), a buffer amplifier, a resistor Ra, current mirror PFETs (P1,
P2) and clamp PFETs (P3, P4, P5).  The right side is a Top/Bottom
circuit and a resistor ladder.  The buffer amplifier gives the same
voltage as  Bandgap reference (1.2V).  And the resistor Ra creates
the current as follows:
  I = 1.2 / Ra

      The current mirror PFETs (P1, P2) create a proportional current
to PFET size.  The clamp PFETs (P3, P4, P5) fix the P2's source-drain
voltage against the various loading conditions and create the stable
current against the Early effect.  The Top/Bottom circuit locates in
the Analog Digital Converter block and creates the voltages as
follows:
  V1 = (Rb1 + Rb2) x I
  V2 = Rb2 x I

      Thus, one ...