An　accuracy-improved　and　internal　regulator-free　temperature　on-chip　sensor　is　proposed.　The　proposed　sensor　outputs　an　accuracy-enhanced　pulse　width　modulation　(PWM)　signal　with　a　nonlinear　current　mode　feedback　pseudo-PLL　(Phase-Locked　Loop).　The　pseudo-PLL　is　able　to　greatly　mitigate　the　nonlinearity　caused　by　process　parameters　(eg.　threshold　voltage　and　mobility　of　MOS　transistor)　without　careful　compensation.　Furthermore,　to　optimize　the　area　and　power　supply　rejection　without　an　internal　regulator,　a　current　mode　input　and　feedback　approach　in　the　pseudo-PLL　is　also　presented.　The　proposed　sensor　is　fabricated　with　0.18　mu　m　standard　CMOS　process.　The　measurement　results　show　that　the　power　consumption　of　the　sensor　is　only　2　mu　W　under　1.2V　supply　voltage.　With　the　supply　voltage　varying　within　1　similar　to　1.2V,　the　temperature　detection　error　is　maintained　within　+/-0.2　degrees　C　in　the　range　of　-20　degrees　C　to　100　degrees　C.　And　the　corresponding　power　supply　rejection　(PSR)　ratio　and　resolution　achieve　about　0.15　degrees　C/100mV　and　0.12　degrees　C,　respectively.