I. Introduction
One-time programmable (OTP) metal fuse is an on-chip memory, programmed during both high-volume manufacturing (HVM) and in the field to enable features, such as chip identification, post-Si circuit tuning, security key storage, etc. Metal fuse requires an extra-high voltage (EHV) voltage (~1.6–2.1 V) and 10 s of mA to properly program. In an HVM setting, a high-quality HVM supply provides a specific, yield-optimized programming voltage. On the customer platform, this function is performed by an in-field-programmable (IFP) power solution. Prior IFP solutions use either an on-die power switch with generic EHV platform supply, or an on-die power generation, such as charge pump (CP) or low dropout regulator (LDO) [1], [2]. The power switch with platform supply typically creates a power sequence requirement between nominal and EHV supplies to avoid electrical over (EOS) and prevents the technology from choosing a yield-optimized programming voltage since this supply is shared with nonfuse IP. Prior on-die implementations used either a single-stage open-loop (OL) CP, which provides lower voltage head room for yield optimization for different processes or rely on thick-gate (TG) devices, which are incompatible with performance-optimized logic process [1], [2]. The proposed solution adds another stage to the single-stage CP and places it in a feedback loop for tunability, and to mitigate EOS from the added stage. An internal resistor reference is used, and bandgap reference is also included where greater PSRR might be required. The CP connects to the fuse macro via power-gate power-switch (PGPS), which switches between CP output and nominal voltage for read. Fig. 1 shows the system diagram, including CP with feedback, BGref, and fuse array with PGPS, with fanout to multiple arrays.
CL CP, BGref, and fuse memory with PGPS.