Linear Technology Corporation introduces the LTC4365, an overvoltage (OV), undervoltage (UV) and reverse protection controller, with a -40V to 60V protection range, for applications that require windowed supply protection.
The LTC4365 provides two comparator inputs to configure the OV and UV set points within the normal operating range of 2.5V to 34V using an external resistive divider. A gate pin controls a dual N-channel MOSFET to ensure only voltages within the OV and UV window are passed to the output. Reverse supply protection circuits automatically isolate the load from negative input voltages. In addition to providing transient protection to 60V, the LTC4365 also blocks 50Hz and 60Hz AC power. No TVS or input capacitor is required for most applications, providing a low component count solution for compact designs. The LTC4365 is targeted for portable instrumentation, industrial automation and automotive applications where accurate overvoltage, undervoltage and reverse protection is required to protect loads from faulty supply connections. The LTC4365 consumes only 125uA in normal operation, and has a shutdown pin for enabling and disabling the external MOSFETs, and for providing a low current shutdown state of 10uA. A fault output indicates gate status. Using the shutdown pin, two LTC4365's can be configured in a novel application to select between two power supplies. If reverse protection is not needed, only a single external MOSFET is required.
The device comprises a pair of 60dB dynamic range RMS detectors that are matched to 1.25dB. This provides accurate RF power measurement of high crest-factor signals such as those used in LTE, WiMAX, W-CDMA, TD-SCDMA and CDMA2000 3G or 4G basestations and other high-performance radios employing complex modulation waveforms. Each channel can detect signals accurately from as small as -58dBm to 2dBm, in a log-linear response with a typical linearity of better than +/-0.5dB covering all cellular frequency bands. At higher frequencies, the device is capable of providing 47dB of useful dynamic range up to 6GHz. Unique to the LTC5583; each detector simultaneously tracks the envelope of the modulated input waveform, providing on-chip capability to measure both peak and average signal power.
The LTC5583 has best-in-class channel-to-channel isolation of over 55dB at 2.14GHz, when driven differentially. Unlike other detectors, the LTC5583 can operate single-ended for RF input frequencies up to 2.14GHz, requiring no external balun transformers. This configuration greatly reduces costs without trading off dynamic range and provides isolation better than 40dB. An integrated amplifier measures the difference between the two detector outputs. For applications where one RF input is measuring the forward power and the other the reflected power, the difference output provides real time VSWR results. The two matched detectors are also useful in applications such as monitoring and controlling RF amplifier stage gain. The LTC5583's matching and isolation performance minimize calibration requirements, thus simplifying designs and reducing costs. The detectors exhibit outstanding temperature performance. Each detector maintains accuracy of +/-1dB error over a 53dB dynamic range over its specified operating temperature range of -40°C to 85°C. This enables the LTC5583 to be used in rugged environments such as Remote Radio Units (RRUs) or Outdoor Units (ODUs) deployed on cellular towers. Moreover, the device has on-chip provisions for first- and second-order temperature compensation which enable easy calibration for improved temperature performance.