The new generation positron emission tomography (PET) detectors for combined PET/magnetic resonance imaging (MRI) must achieve extremely good timing resolution while also being capable of simultaneous data acquisition in a high power, dynamic electromagnetic environment. SiPM-based detectors are a natural choice for this application, given the high gain and fast response of the SiPMs and their insensitivity to magnetic fields. We present the highly-integrated readout circuit “PETA”, specifically designed for SiPM readout and optimal timing resolution required for high performance TOF-PET. PETA is a bump-bonded chip, with pitch between bumps of 272 µm, suitable for compact detector design. It includes 36 readout channels, available with both single-ended and differential-ended front-ends. The event arrival time and energy are measured and digitized on chip with TDC/ADC circuits. The readout architecture is optimized for coping with high hit rate per channel. Two very compact MR-compatible TOF-PET detector modules based on PETA readout have been constructed and tested. Each is built on a single layer (ceramic and PCB substrate respectively), hosting the SiPM array and the readout electronics on opposite surfaces, and thermally decoupled with efficient integrated cooling. Coincidence measurements have shown coincidence time resolution of 230 ps FWHM using arrays of 2.25x2.25x10 mm3 LYSO crystals coupled to matching SiPMs.