P-Well Charge Pump With Enhanced Reliability for High Voltage Chip Stressing
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
By the addition of two devices to a standard P-well charge pump circuit, excessive voltage stressing of vulnerable devices in the circuit is avoided during high voltage stress tests. Referring to the figure, oscillator 2 connected with charge pump driver 4 feeds the charge pump circuit comprised of transistors T1, T2, T3, T4, and T5. Enhancement mode transistor T5 and low threshold voltage (low Vt) transistor T1 are added to a standard charge pump circuit comprised of transistors T2, T3, and T4. Furthermore, in the standard charge pump design, the gate of low Vt transistor T3 is connected to a phase that is high (at Vdd) when node OUT is at its negative potential. In the enhanced design, transistor T3 becomes gated by ground such that transistor T3 turns on when OUT drops to low Vt (0.7 volt) below ground.