Features and Benefits
- Complete RF detector/controller function
- >50 dB range at 0.9 GHz (-49 dBm to +2 dBm, re 50 Ω)
- Accurate scaling from 0.1 GHz to 2.5 GHz
- Temperature-stable linear-in-dB response
- Log slope of 23 mV/dB, intercept at -60 dBm at 0.9 GHz
- True integration function in control loop
- Low power: 20 mW at 2.7 V, 38 mW at 5 V
- Power-down to 10.8 µW
The AD8315 is a complete low cost subsystem for the precise control of RF power amplifiers operating in the frequency range 0.1 GHz to 2.5 GHz and over a typical dynamic range of 50 dB. It is intended for use in cellular handsets and other batteryoperated wireless devices. The log amp technique provides a much wider measurement range and better accuracy than controllers using diode detectors. In particular, the temperature stability is excellent over a specified range of −30°C to +85°C.
Its high sensitivity allows control at low signal levels, thus reducing the amount of power that must be coupled to the detector.
For convenience, the signal is internally ac-coupled. This high-pass coupling, with a corner at approximately 0.016 GHz, determines the lowest operating frequency. Therefore, the source can be dc grounded.
The AD8315 provides a voltage output, VAPC, that has the voltage range and current drive to directly connect to most handset power amplifiers’ gain control pin. VAPC can swing from 250 mV above ground to within 200 mV below the supply voltage. Load currents of up to 6 mA can be supported.
The setpoint control input is applied to the VSET pin and has an operating range of 0.25 V to 1.4 V. The associated circuit determines the slope and intercept of the linear-in-dB measurement system; these are nominally 23 mV/dB and −60 dBm for a 50 Ω termination (−73 dBV) at 0.9 GHz. Further simplifying the application of the AD8315, the input resistance of the setpoint interface is over 100 MΩ, and the bias current is typically 0.5 μA.
The AD8315 is available in MSOP and LFCSP packages and consumes 8.5 mA from a 2.7 V to 5.5 V supply. When powered down, the sleep current is 4 μA.
- Single, dual, and triple band mobile handset (GSM, DCS, EDGE)
- Transmitter power control
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)
AD8315ACP-EVAL is a fully populated, 4-layer, FR4-based evaluation board. For normal operation, it requires a 2.7V to 5V/15 mA power supply. The power supply should be connected to the vector pins leads labeled VPOS and GND. The RF input signal is applied to the edge-mounted SMA type RF connector (RFIN). The setpoint input signal is applied to the edge-mounted SMA type connector (VSET). The detector output signal is accessible via the edge-mounted SMA connector (VAPC ). The circuit board can accommodate configuration in controller mode and a quasi-measurement mode (via an op-amp feedback loop) depending on the status the jumpers (LK1, LK2).
AD8315-EVAL is a fully populated, 4-layer, FR4-based evaluation board. For normal operation, it requires a 2.7V to 5V/15 mA power supply. The power supply should be connected to the vector pins leads labeled VPOS and GND. The RF input signal is applied to the edge-mounted SMA type RF connector (RFIN). The setpoint input signal is applied to the edge-mounted SMA type connector (VSET). The detector output signal is accessible via the edge-mounted SMA connector (VAPC ). The circuit board can accommodate configuration in controller mode and a quasi-measurement mode (via an op-amp feedback loop) depending on the status the jumpers (LK1, LK2).
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.
Technical Articles (7)
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