Datasheet LTC5531 (Analog Devices) - 9

LTC5531
U U W U APPLICATIO S I FOR ATIO Operation
the input range of a variety of analog-to-digital converters. V The LTC5531 RF detector integrates several functions to OUT will not change until VOS exceeds 120mV. The voltage at V provide RF power detection over frequencies ranging from OUT for VOS ≥120mV and with no RF signal present is: 300MHz to 7GHz. These functions include an internal fre- quency compensated buffer amplifier, an RF Schottky di- VOUT = VOS ode peak detector and level shift amplifier to convert the RF V input signal to DC and a delay circuit to avoid voltage tran- OUT will exactly track VOS above 120mV. sients at VOUT when powering up. The LTC5531 has both
RF Detector
shutdown and voltage offset adjustment capabilities. The internal RF Schottky diode peak detector and level
Buffer Amplifier
shift amplifier converts the RF input signal to a low frequency signal. The detector demonstrates excellent The output buffer amplifier is capable of supplying typi- efficiency and linearity over a wide range of input power. cally 4mA into a load. The amplifier has a bandwidth of The Schottky diode is biased at about 55µA and drives a 2MHz and a fixed internal gain of two. 25pF internal peak detector capacitor. The VOS input controls the DC input voltage to the buffer amplifier. V
Shutdown
OS must be connected to ground if the DC output voltage is not to be changed. The buffer is initially The part is in shutdown mode when SHDN is low. The trimmed to approximately 120mV with VOS connected to supply current is reduced to < 2µA and VOUT is shorted to ground. ground via a 280Ω resistor. When SHDN is asserted high, The V the part is enabled after about 8µs. OS pin is used to change the initial VOUT starting voltage. This function enables the LTC5531 output to span
Demo Board Schematic
VCC 2.7V TO 6V C1 C4 LTC5531ES6 0.1µF RF 39pF IN C2 1 6 RF 100pF IN VCC R1 2 5 GND VOUT (OPT) VOUT C3 3 4 SHDN V (OPT) OS VOS 22k VCC SHDN 5531 DB 5531f 9