LTC5531 データシートの表示（PDF） - Linear Technology

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LTC5531

Precision 300MHz to 7GHz RF Detector with Shutdown and Offset Adjustment

Linear Technology 

LTC5531

APPLICATIO S I FOR ATIO

Operation

The LTC5531 RF detector integrates several functions to

provide RF power detection over frequencies ranging from

300MHz to 7GHz. These functions include an internal fre-

quency compensated buffer amplifier, an RF Schottky di-

ode peak detector and level shift amplifier to convert the RF

input signal to DC and a delay circuit to avoid voltage tran-

sients at VOUT when powering up. The LTC5531 has both

shutdown and voltage offset adjustment capabilities.

Buffer Amplifier

The output buffer amplifier is capable of supplying typi-

cally 4mA into a load. The amplifier has a bandwidth of

2MHz and a fixed internal gain of two.

The VOS input controls the DC input voltage to the buffer

amplifier. VOS must be connected to ground if the DC

output voltage is not to be changed. The buffer is initially

trimmed to approximately 120mV with VOS connected to

ground.

The VOS pin is used to change the initial VOUT starting

voltage. This function enables the LTC5531 output to span

the input range of a variety of analog-to-digital converters.

VOUT will not change until VOS exceeds 120mV. The

voltage at VOUT for VOS ≥120mV and with no RF signal

present is:

VOUT = VOS

VOUT will exactly track VOS above 120mV.

RF Detector

The internal RF Schottky diode peak detector and level

shift amplifier converts the RF input signal to a low

frequency signal. The detector demonstrates excellent

efficiency and linearity over a wide range of input power.

The Schottky diode is biased at about 55µA and drives a

25pF internal peak detector capacitor.

Shutdown

The part is in shutdown mode when SHDN is low. The

supply current is reduced to < 2µA and VOUT is shorted to

ground via a 280Ω resistor. When SHDN is asserted high,

the part is enabled after about 8µs.

Demo Board Schematic

C4 LTC5531ES6

RFIN

39pF

1

6

RFIN VCC

R1

(OPT)

22k

VCC

2

5

GND VOUT

3

4

SHDN VOS

VOS

SHDN

C2

100pF

VCC

2.7V TO 6V

C1

0.1µF

VOUT

C3

(OPT)

5531 DB

5531f

9

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