Features and Benefits
- Complete fully calibrated measurement/control system
- Accurate rms-to-dc conversion from 50 Hz to 3.8 GHz
- Input dynamic range of >65 dB: −52 dBm to +8 dBm in 50 Ω
- Waveform and modulation independent, such as GSM/CDMA/TDMA
- Linear-in-decibels output, scaled 50 mV/dB
- Law conformance error of 0.5 dB
- All functions temperature and supply stable
- Operates from 4.5 V to 5.5 V at 24 mA
- Power-down capability to 1.3 mW
The AD8362 is a true rms-responding power detector that has a 65 dB measurement range. It is intended for use in a variety of high frequency communication systems and in instrumentation requiring an accurate response to signal power. It is easy to use, requiring only a single supply of 5 V and a few capacitors. It operates from arbitrarily low frequencies to over 3.8 GHz and accepts inputs from −52 dBm to +8 dBm with crest factors that are typical of quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) modulation schemes.
The input signal is applied to a resistive ladder attenuator that comprises the input stage of a variable gain amplifier (VGA). The 12 tap points are smoothly interpolated using a proprietary technique to provide a continuously variable attenuator, which is controlled by a voltage applied to the VSET pin. The resulting signal is applied to a high performance broadband amplifier. Its output is measured by an accurate square-law detector cell. The fluctuating output is then filtered and compared with the output of an identical squarer, whose input is a fixed dc voltage applied to the VTGT pin, usually the accurate reference of 1.25 V pro-vided at the VREF pin.
The difference in the outputs of these squaring cells is integrated in a high gain error amplifier, generating a voltage at the VOUT pin with rail-to-rail capabilities. In a controller mode, this low noise output can be used to vary the gain of a host system’s RF amplifier, thus balancing the setpoint against the input power. Optionally, the voltage at VSET can be a replica of the RF signal’s amplitude modulation, in which case the overall effect is to remove the modulation component prior to detection and low-pass filtering. The corner frequency of the averaging filter can be lowered without limit by adding an external capacitor at the CLPF pin. The AD8362 can be used to determine the true power of a high frequency signal having a complex low frequency modulation envelope, or simply as a low frequency rms volt-meter. The high-pass corner generated by its offset-nulling loop can be lowered by a capacitor added on the CHPF pin.
Used as a power measurement device, VOUT is strapped to VSET. The output is then proportional to the logarithm of the rms value of the input. In other words, the reading is presented directly in decibels and is conveniently scaled 1 V per decade, or 50 mV/dB; other slopes are easily arranged. In controller modes, the voltage applied to VSET determines the power level required at the input to null the deviation from the setpoint. The output buffer can provide high load currents.
The AD8362 has 1.3 mW power consumption when powered down by a logic high applied to the PWDN pin. It powers up within about 20 μs to its nominal operating current of 20 mA at 25°C. The AD8362 is supplied in a 16-lead TSSOP for operation over the temperature range of −40°C to +85°C.
Markets and Technologies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
AD8362-EVALZ is a fully populated, 4-layer, FR4-based evaluation board. For normal operation, it requires a 5 V/50 mA power suppply. The 5 V power supply should be connected to the pins labeled VPOS and AGND. The RF input signal is applied to the SMA connector labeled RFIN and the output voltage is available on the SMA connector labeled VOUT.
Tools & Simulations
ADIsimPLL enables the rapid and reliable evaluation of new high performance PLL products from ADI. It is the most comprehensive PLL Synthesizer design and simulation tool available today. Simulations performed include all key non-linear effects that are significant in affecting PLL performance. ADIsimPLL removes at least one iteration from the design process, thereby speeding the design- to-market.
ADIsimRF is an easy-to-use RF signal chain calculator. Cascaded gain, noise, distortion and power consumption can be calculated, plotted and exported for signal chains with up to 50 stages. ADIsimRF also includes an extensive data base of device models for ADI’s RF and mixed signal components.
AD8362 Companion Parts
Recommended Low-Noise Voltage Regulators
- For a fixed 5V, 300mA low dropout regulator with reverse current protection: ADP7102.
Technical Articles (7)
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
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