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 - 15

HMC909LP4E

v02.0511

RMS POWER DETECTOR

SINGLE-ENDED, DC - 5.8 GHz

RF Input Interface

The IN+ and IN- pins are differential RF inputs, which are externally configured for wideband with single ended input.

Power match components are placed at these input terminals, along with Dc blocking capacitors. the coupling

capacitor values also set the lower spectral boundary of the input signal bandwidth. the inputs can be reactively

matched (refer to input return loss graphs), but a resistor network should be sufficient for good wideband performance.

Wideband Single-Ended Input Interface:

Choose the input decoupling capacitor (C3, C4) values by

first determining the lowest spectral component the power

detector is required to sense, ƒL.

Input decoupling capacitor value

1

P x ƒL x 3.2

≈

, Farads, where ƒL is in Hertz

ex. If the power detector needs to sense down to 10MHz, the

decoupling capacitor value should be

1/(π*10E6*3.2) = 10nF

A DC bias (Vcc-1.2V) is present on the IN+ and IN- pins, and

should not be overridden

RMS Output Interface and Transient Response

The HMC909LP4E features digital input pins (SCI1-SCI4) that control the internal integration time constant. Output

transient response is determined by the digital integration controls, and output load conditions.

Shortest integration time is for SCI=0000, allowed longest integration time is for SCI=1100 (1101, 1110 and 1111 SCI

settings are forbidden states).

Using larger values of scI will narrow the operating bandwidth of the integrator, resulting in a longer averaging time

interval and a more filtered output signal; however it will also slow the power detector’s transient response. A larger

scI value favors output accuracy over speed. For the fastest possible transient settling times set scI to 0000. this

configuration will operate the integrator at its widest possible bandwidth, resulting in short averaging time-interval and

an output signal with little filtering. Most applications will choose a SCI setting that maintains balance between speed

and accuracy. Furthermore, error performance over modulation bandwidth is dependent on the scI setting.

For example modulations with relatively low frequency components and high crest factors may require higher scI

(integration) settings.

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