LTC5535ES6 Ver la hoja de datos (PDF) - Linear Technology

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LTC5535ES6

Precision 600MHz to 7GHz, RF Detector with Adjustable Gain and 12MHz Baseband Bandwidth

Linear Technology 

LTC5535

APPLICATIO S I FOR ATIO

Operation

The LTC5535 RF detector integrates several functions to

provide RF power detection over frequencies ranging

from 600MHz to 7GHz. These functions include an internal

frequency compensated output amplifier, an RF Schottky

diode peak detector and a level shift amplifier to convert the

RF input signal to DC. The LTC5535 has both gain setting

and voltage offset adjustment capabilities.

Output Amplifier

The output amplifier is capable of supplying typically

20mA into a load. The negative terminal VM is brought out

to a pin for gain selection. External resistors connected

between VOUT and VM (RA) and VM to ground (RB) will set

the gain of this amplifier.

Gain = 1 + RA/RB

The amplifier is not unity gain stable; a minimum gain of

two is required. The output amplifier has a bandwidth of

20MHz with a gain of 2. For increased gain applications,

the bandwidth is reduced according to the formula:

Bandwidth = 40MHz/(Gain) = 40MHz • RB/(RA + RB)

For stable operation the gain setting resistors should be

low values and the board capacitance on VM should be

minimized. RB is recommended to be no greater than

500Ω for all gain settings.

The VOS input controls the DC input voltage to the output

amplifier. VOS must be connected to ground if the DC

output voltage is not to be changed. The output amplifier

is initially trimmed to 200mV (Gain = 2) with VOS con-

nected to ground.

The VOS pin is used to change the initial VOUT starting

voltage. This function, in combination with gain adjust-

ment enables the LTC5535 output to span the input range

of a variety of analog-to-digital converters. VOUT will not

change until VOS exceeds 200mV. The starting voltage at

VOUT for VOS >200mV is:

VOUT = 0.5 • VOS • Gain

where gain is the output amplifier gain. For a gain of 2,

VOUT will exactly track VOS above 200mV.

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 50µA and drives a

5pF internal peak detector capacitor.

Demo Board Schematic

C4 LTC5535ES6

RFIN

39pF

1

6

RFIN VCC

R1

2

5

(OPT)

GND VOUT

3

4

VOS VM

OFFSET

ADJUSTMENT

C2

100pF

VCC

2.7V TO 5.5V

C1

0.1µF

R2

500Ω

1%

RLOAD

(OPT)

VOUT

R3

500Ω

1%

GND

5535 DB

5535f

9

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