High speed OTP sensing scheme
A high speed sensing scheme for a non-volatile memory array is disclosed. The memory array includes non volatile memory cells arranged in a complementary bitline configuration includes precharge circuits for precharging the bitlines to a first voltage level such as VSS, a reference circuits for applying a reference charge on the reference bitlines of the complementary bitline pairs, and bitline sense amplifiers for sensing a voltage differential between the complementary bitline pairs. A voltage on the data bitline being changed when a programmed non-volatile memory cell connected to an activated wordline couples the wordline voltage to the data bitline.
1. A memory array including one-time-programmable (OTP) memory cells, comprising
a pair of complementary bitlines, each bitline of the pair of complementary bitlines being connected to diffusion terminals of the OTP memory cells;
a precharge circuit for precharging the pair of complementary bitlines to a first voltage level, the precharge circuit including column precharge devices for selectively precharging bitlines adjacent to each bitline of the pair of complementary bitlines to a second voltage level different than the first voltage level;
wordlines connected to gate terminals of the OTP memory cells, at least one wordline for driving one bitline of the pair of complementary bitlines to a third voltage level through a programmable conductive link of a corresponding OTP memory cell;
a bitline sense amplifier for sensing a voltage differential on the pair of complementary bitlines; and,
a reference circuit for selectively providing a reference charge to one bitline of the pair of complementary bitlines.
2. The memory array of claim 1 , wherein each of the OTP memory cells is a single transistor anti-fuse memory cell.
3. The memory array of claim 1 , wherein each of the OTP memory cells is a two transistor anti-fuse memory cell, the two transistor anti-fuse memory cell having an access transistor connected to the wordline and an anti-fuse device connected to the access transistor, said antifuse device having a gate connected to a secondary wordline, where the wordline and the secondary wordline are connected together electrically or logically during a read operation.
4. The memory array of claim 1 , wherein the reference circuit includes a charge storage capacitor circuit and steering circuits for coupling the charge storage capacitor circuit to the one bitline of the pair of complementary bitlines.
5. The memory array of claim 4 , wherein the steering circuits include dummy memory cells for selectively coupling the charge storage capacitor to the one bitline of the pair of complementary bitlines.
6. The memory array of claim 4 , wherein the reference circuit includes a plurality of additional capacitor circuits connected to the charge storage capacitor circuit, each of the additional capacitor circuits being selectively enabled in response to a corresponding control signal.
7. A memory array including one-time-programmable (OTP) memory cells, comprising
a pair of complementary bitlines, each bitline of the pair of complementary bitlines being connected to diffusion terminals of the OTP memory cells;
a precharge circuit for precharging the pair of complementary bitlines to a first voltage level, the precharge circuit including column precharge devices for selectively precharging bitlines adjacent to each bitline of the pair of complementary bitlines to a second voltage level different than the first voltage level;
wordlines connected to gate terminals of the OTP memory cells, at least one wordline for driving one bitline of the pair of complementary bitlines to a third voltage level through a programmable conductive link of a corresponding OTP memory cell;
a bitline sense amplifier for sensing a voltage differential on the pair of complementary bitlines; and,
a reference circuit for selectively coupling a capacitive load means to one bitline of the pair of complementary bitlines during a bitline sensing operation.
8. The memory array of claim 7 , wherein the reference circuit includes a steering circuit for coupling the capacitive load means to the one bitline of the pair of complementary bitlines during a bitline precharge operation.