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# Linear Ramp Voltage Reference Generator

IP.com Disclosure Number: IPCOM000109925D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 56K

IBM

## Related People

Kiciak, PA: AUTHOR [+2]

## Abstract

A voltage reference generator is provided with a band-gap voltage reference arranged in parallel with a capacitor C1 and in series with a resistor R1 to enable a signal voltage at node A, the common point between the capacitor C1 and the resistor R1, to rise from zero volts to its final value as a linear ramp function of time, rather than as an exponential function of time.

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Linear Ramp Voltage Reference Generator

A voltage reference generator is provided with a band-gap
voltage reference arranged in parallel with a capacitor C1 and in
series with a resistor R1 to enable a signal voltage at node A, the
common point between the capacitor C1 and the resistor R1, to rise
from zero volts to its final value as a linear ramp function of time,
rather than as an exponential function of time.

In this voltage reference generator or voltage regulator the
capacitor C1 and the resistor R1 are connected in series between
ground and a voltage source V, with the band-gap voltage reference
being connected in parallel with the capacitor C1, as illustrated in
the figure.  A switch SW1 is connected across the capacitor C1 to
selectively discharge the capacitor C1, as desired.

The linear ramp response is achieved due to the unique
operation of the band-gap voltage reference.  At initial turn-on, the
band-gap voltage reference draws current from the resistor R1 as an
inverse exponential function of time, which directly compensates for
the normal exponential flow of current that is demanded by the
capacitor C1.  Therefore, the rise in voltage as a function of time
at node A is a linear function of time, i.e., a true ramp.

The rate of rise, as well as the shape of the ramp from this
voltage reference generator, directly affects the performance of
control circuits that employ the generator, such as, high or low
power voltag...