Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Patent
1994-10-11
1996-08-13
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
327157, 327536, H03L 706
Patent
active
055460313
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a high voltage feed-back circuit for a high voltage generator comprising several voltage multiplying stages connected in series, wherein an oscillator generates at least two clock pulses being 180.degree. out of phase to one another, controlling alternately successive voltage multiplying stages to provide a high voltage pulse at the output of the high voltage generator, the high voltage output being connected to the high voltage feed-back circuit comprising a capacitive input stage and generating a control signal supplied to the oscillator, so that the oscillator output is modified in dependence on the high voltage output voltage, said capacitive input stage comprising at least a first capacitor receiving at one terminal the high voltage output and its other terminal being connected to one terminal of a second capacitor.
Such a high voltage feed-back circuit is known from EP-A-0.323.156. Said known feed-back circuit is applied to a high voltage generator comprising a series connection of voltage multipliers being alternately controlled by clock signals .PHI. and .PHI.. The output voltage of this high voltage generator is capacitively measured and compared with a reference voltage by a comparator. The output signal of the comparator is supplied to a ring oscillator generating the clock signals .PHI. and .PHI.. When the measured high voltage exceeds a certain threshold level the output of the comparator becomes low and as a consequence the ring oscillator stops oscillating and, therefore, the generation of clock pulses is stopped. When the high voltage level decreases below said threshold level the output of the comparator becomes high restarting the ring oscillator and the generation of clock pulses.
The high voltage feed-back circuit as known shows many disadvantages, the most important being discontinuities in the derivative of the high voltage output of the high voltage generator to which the feed-back circuit is applied. This is caused by the application of the comparator in the feed-back circuit, the output of the comparator being only capable of starting or stopping the ring oscillator and, therefore, the multiplying stages in the high voltage generator suffer from sudden stops or starts in the receipt of controlling clock pulses. Such discontinuities in the derivative of the high voltage output reduces the lifetime of EEPROM cells. Moreover, the comparator in the known feed-back circuit must be rather fast. Otherwise the programming voltage will show too large overshoots and undershoots, which will also reduce the lifetime of the EEPROM cells as well as of the high voltage generator itself, because of break-down effects. However, a rather fast comparator consumes substantial power.
Furthermore, in EP-A-0.323.156 the reference voltage being supplied to the comparator is not constant, but is set to a low value before starting the generation of the programming pulse. During the generation of the programming pulse this reference voltage is increased proportional to the desired increase of the programming pulse. A complex network of capacitors and control circuitry is required to realise the slow increase of the reference voltage.
Another high voltage feed-back circuit used in a high voltage generator is known from U.S. Pat. No. 4.527.180. The output voltage of the high voltage generator is capacitively measured to generate a feedback signal. The feed-back signal is supplied to one input of an operational amplifier, the other input of which receives a reference voltage. The output of the operational amplifier, being used as an comparator, supplies a driving signal to a driver stage in the high voltage generator. The reference voltage is not constant, but is set to a low value before the generation of a programing pulse by the high voltage generator. During the generation of the programming pulse the reference voltage is slowly increased proportional to the desired increase of the programming pulse. To realize a slow rise-time of the programming pulse in this way a rather complex c
REFERENCES:
patent: 3333205 (1967-07-01), Featherston
patent: 4316150 (1982-02-01), Crosby
patent: 4527180 (1985-07-01), Oto
patent: 5334953 (1994-08-01), Mijuskovic
Callahan Timothy P.
Kim Jung Ho
Sierra Semiconductor B.V.
LandOfFree
Feed-back circuit for CMOS high voltage generator to program (E) does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Feed-back circuit for CMOS high voltage generator to program (E), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Feed-back circuit for CMOS high voltage generator to program (E) will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1051154