For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824

Phone: 978-250-3343

Fax: 978-250-3373

Order On-line at www.hittite.com

Application Support: Phone: 978-250-3343 or apps@hittite.com

11

11 - 18

HMC909LP4E

v02.0511

RMS POWER DETECTOR

SINGLE-ENDED, DC - 5.8 GHz

LOG-Slope and Intercept

The HMC909LP4E provides for an adjustment of output scale with the use of an integrated operational amplifier. Log-

slope and intercept can be adjusted to “magnify” a specific portion of the input sensing range, and to fully utilize the

dynamic range of the rMs output.

A log-slope of 36.9mV/dB (@1900 MHz) is set by connecting RMS Output to VSET through resistor network for ß = 1

(see application schematic).

the log-slope is adjusted by applying the appropriate resistors on the rMs and Vset pins. Log-intercept is adjusted

by applying a Dc voltage to the Vset pin.

optimized slope =

ß * log-slope

Optimized intercept = log-intercept – (R

FBK /rset) * VBLINE

rFBK

rFBK // rsHUNt // rset

ß =

when r

FBK=0 to set rMsoUt=Vset, then ß=1/2

If rset is not populated, then

ß = ½ * (RFBK/ (RFBK // RSHUNT)) and intercept is at nominal value.

example: the logarithmic slope can be simply increased by choosing appropriate rFBK and rsHUNt values while

not populating the rset resistor on the evaluation board to keep the intercept at nominal value.

setting rFBK =4.7KΩ and rsHUNt = 2.2KΩ results in an optimized slope of:

Optimized Slope = ß * log_slope = 1.57* 36.9mV / dB

optimized slope = 58 mV / dB

Slope Adjustment

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

-70

-60

-50

-40

-30

-20

-10

0

High Slope

Nominal

INPUT POWER (dBm)

Slope = 58 mV/dB

Rset = open

Rfbk = 4.7 Kohm

Rshunt = 2.2 Kohm

Slope = 36.9 mV/dB

Rset = open

Rfbk = 4.7 Kohm

Rshunt = 4.7 Kohm

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners.

For price, delivery, and to place orders: Analog Devices, Inc.,

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106

Phone: 781-329-4700 • Order online at www.analog.com

Application Support: Phone: 1-800-ANALOG-D