Datasheet LTC5507 (Analog Devices) - 5
| Manufacturer | Analog Devices |
| Description | 100kHz to 1GHz RF Power Detector |
| Pages / Page | 8 / 5 — APPLICATIO S I FOR ATIO. Operation. Applications. Buffer Amplifier. C1, … |
| File Format / Size | PDF / 134 Kb |
| Document Language | English |
APPLICATIO S I FOR ATIO. Operation. Applications. Buffer Amplifier. C1, C2 Capacitor Selection (Refer to Figure 3). RF Detector
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LTC5507
U U W U APPLICATIO S I FOR ATIO Operation Applications
The LTC5507 integrates several functions to provide RF The LTC5507 can be used as a self-standing signal strength power detection over frequencies up to 1000MHz. These measuring receiver for a wide range of input signals from functions include an internally compensated buffer ampli- –34dBm to 14dBm for frequencies up to 1000MHz. fier, an RF Schottky diode peak detector and level shift The LTC5507 can be used as a demodulator for AM and amplifier to convert the RF signal to DC, a delay circuit to ASK modulated signals with data rates up to 1.5MHz. avoid voltage transients at VOUT when coming out of shut- Depending on specific application needs, the RSSI output down, and a gain compression circuit to extend the can be split into two branches, providing AC-coupled data detector dynamic range. (or audio) output and DC-coupled, RSSI output for signal strength measurements and AGC.
Buffer Amplifier
The buffer amplifier has a gain of two and is capable of
C1, C2 Capacitor Selection (Refer to Figure 3)
driving a 2mA load. The buffer amplifier typically has an C1 couples the RF input signal to the detector input RF output voltage range of 0.25V to V IN CC – 0.1V. which is referenced to VCC. C2 is the peak detector capacitor connected between PCAP and V
RF Detector
CC. The value of C2 will affect the slew rate and bandwidth. Typically C1 can The internal RF Schottky diode peak detector and level equal C2. Ceramic capacitors are recommended for C1 shift amplifier converts the RF input signal to a low and C2. The values for C1 and C2 are dependent on the frequency signal. The frequency range of the RF pin is operating RF frequency. The capacitive reactance should typically up to 1000MHz. The detector demonstrates ex- be less than 5Ω to minimize ripple on C2. cellent operation over a wide range of input power. The C2(µF) ≥ 1/(30 • f) where f is the lowest RF input Schottky detector is biased at about 70µA. The hold frequency (MHz) capacitor is external. C1 = C2
Gain Compression
In general, select C1 and C2 large enough to pass the The gain compression circuit changes the feedback ratio lowest expected RF signal frequency, as described by the as the RF peak-detected input voltage increases above above formulas. But optimize C1 and C2, subject to this 60mV. Below 60mV, the DC voltage gain from the peak constraint, to improve output slew rate and bandwidth, detector to the buffer output is 4. Above 140mV, the DC and to enable good AC performance for the highest voltage gain is reduced to 0.75. The compression expands expected RF signal frequency. the low power detector range due to higher gain.
Modes of Operation MODE SHDN OPERATION
Shutdown Low Disabled Enable High Power Detect 5507f 5
U U W U APPLICATIO S I FOR ATIO Operation Applications
The LTC5507 integrates several functions to provide RF The LTC5507 can be used as a self-standing signal strength power detection over frequencies up to 1000MHz. These measuring receiver for a wide range of input signals from functions include an internally compensated buffer ampli- –34dBm to 14dBm for frequencies up to 1000MHz. fier, an RF Schottky diode peak detector and level shift The LTC5507 can be used as a demodulator for AM and amplifier to convert the RF signal to DC, a delay circuit to ASK modulated signals with data rates up to 1.5MHz. avoid voltage transients at VOUT when coming out of shut- Depending on specific application needs, the RSSI output down, and a gain compression circuit to extend the can be split into two branches, providing AC-coupled data detector dynamic range. (or audio) output and DC-coupled, RSSI output for signal strength measurements and AGC.
Buffer Amplifier
The buffer amplifier has a gain of two and is capable of
C1, C2 Capacitor Selection (Refer to Figure 3)
driving a 2mA load. The buffer amplifier typically has an C1 couples the RF input signal to the detector input RF output voltage range of 0.25V to V IN CC – 0.1V. which is referenced to VCC. C2 is the peak detector capacitor connected between PCAP and V
RF Detector
CC. The value of C2 will affect the slew rate and bandwidth. Typically C1 can The internal RF Schottky diode peak detector and level equal C2. Ceramic capacitors are recommended for C1 shift amplifier converts the RF input signal to a low and C2. The values for C1 and C2 are dependent on the frequency signal. The frequency range of the RF pin is operating RF frequency. The capacitive reactance should typically up to 1000MHz. The detector demonstrates ex- be less than 5Ω to minimize ripple on C2. cellent operation over a wide range of input power. The C2(µF) ≥ 1/(30 • f) where f is the lowest RF input Schottky detector is biased at about 70µA. The hold frequency (MHz) capacitor is external. C1 = C2
Gain Compression
In general, select C1 and C2 large enough to pass the The gain compression circuit changes the feedback ratio lowest expected RF signal frequency, as described by the as the RF peak-detected input voltage increases above above formulas. But optimize C1 and C2, subject to this 60mV. Below 60mV, the DC voltage gain from the peak constraint, to improve output slew rate and bandwidth, detector to the buffer output is 4. Above 140mV, the DC and to enable good AC performance for the highest voltage gain is reduced to 0.75. The compression expands expected RF signal frequency. the low power detector range due to higher gain.
Modes of Operation MODE SHDN OPERATION
Shutdown Low Disabled Enable High Power Detect 5507f 5
