Substrate bias generator with power supply control means to sequence application of bias and power to prevent CMOS SCR latch-up
First Claim
1. A bias generator circuit which produces a first higher voltage for biasing a N-well region and a second delayed and lower voltage for biasing a source region of a P-channel field-effect transistor formed within the N-well region so as to increase latch-up immunity, said generator circuit comprising:
- means for generating a power supply voltage;
high voltage means responsive to said power supply voltage for generating a first voltage level for biasing the N-well region;
delay means responsive to said first voltage level for generating a delayed voltage;
level detector means responsive to said delayed voltage and said power supply voltage for generating a control signal when said delay voltage reaches a predetermined level; and
control means responsive to said control signal for generating a second voltage level for biasing the source region of the P-channel field-effect transistor, said second voltage level being delayed and lower than said first voltage level so that the source region and the N-well region defining a PN junction is reverse biased to increase latch-up immunity.
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Abstract
A bias generator circuit includes a first high voltage for biasing a N-well region and a second delayed and lower voltage biasing a source region of a P-channel field-effect transistor so as to increase latch-up immunity. The generator circuit includes a high voltage generator and a multiplier circuit responsive to a power supply voltage for generating a first voltage level for biasing the N-well region. A delay network is responsive to the first voltage for generating a delay voltage. A level detection circuit is responsive to the delay voltage and the power supply voltage for generating a control signal when the delayed voltage reaches a predetermined level. A control device is responsive to the control signal for generating a second voltage for biasing the source region of the P-channel field-effect transistor. The second voltage level is delayed and lower than the first voltage level so that the PN junction is reverse biased to increase latch-up immunity.
45 Citations
17 Claims
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1. A bias generator circuit which produces a first higher voltage for biasing a N-well region and a second delayed and lower voltage for biasing a source region of a P-channel field-effect transistor formed within the N-well region so as to increase latch-up immunity, said generator circuit comprising:
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means for generating a power supply voltage; high voltage means responsive to said power supply voltage for generating a first voltage level for biasing the N-well region; delay means responsive to said first voltage level for generating a delayed voltage; level detector means responsive to said delayed voltage and said power supply voltage for generating a control signal when said delay voltage reaches a predetermined level; and control means responsive to said control signal for generating a second voltage level for biasing the source region of the P-channel field-effect transistor, said second voltage level being delayed and lower than said first voltage level so that the source region and the N-well region defining a PN junction is reverse biased to increase latch-up immunity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 17)
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11. A field-effect integrated circuit which is responsive to a first higher voltage for biasing a well-region and a second delayed and lower voltage for biasing a source region of a field-effect transistor comprising:
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a semiconductor substrate of a first conductivity type having at least one well-region of a second conductivity type embedded in said substrate, two regions of said first conductivity type being embedded within said at least one well-region for forming the source and drain regions of the transistor of said first conductivity type, one region of said second conductivity type also being embedded within said at least one well-region of said second conductivity type; means formed of a high voltage generator and a multiplier circuit for generating and applying a first bias voltage to said at least one well-region of said second conductivity type; and means responsive to said first bias voltage for generating and applying a second bias voltage to said source of said transistor of said first conductivity type, said second bias voltage being delayed and lower in level than said first bias voltage so as to increase latch-up immunity. - View Dependent Claims (12, 13)
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14. An integrated circuit comprising:
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a substrate of a first conductivity type; a well-region of a second conductivity type being embedded within said substrate; two regions of said first conductivity type being embedded within said well-region for forming the source region and drain region of a transistor of said first conductivity type; a region of said second conductivity type being also embedded within said well-region, said well-region being in physical contact with said source region for forming a PN junction; means for applying a first voltage level to said well-region and for applying a second level to said source region, said second voltage being delayed and having a lower voltage level relative to said first voltage level to maintain said PN junction in a reverse biased condition so as to increase latch-up immunity; said means for applying said first and second voltage levels including a high voltage generator, a multiplier circuit, a delay network and a level detection circuit; and control means having a conduction path coupled between a power supply voltage and said source region and a control electrode responsive to said first voltage level for controlling the conductivity across said conduction path, said control means applying said second voltage level to said source region only after the first higher voltage level has already been applied to the well-region. - View Dependent Claims (15, 16)
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Specification