For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, 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

14

HMC987LP5E

v03.1112

LOW NOISE 1:9 FANOUT BUFFER

DC - 8 GHz

Theory of Operation

Parallel Port Control

the various outputs of the can be enabled/disabled by using parallel pin control, or via the sPi. in parallel-mode

(PMoDE-sEl = 1), the sPi input pins (sClk, ski, sEn) are re-interpreted as a 3-bit control bus, and enable the

lVPECl drivers according to the following truth table.

sClk, sDi, sEn

000: out2

001: out2 + out7

010: out2 + out7 + out4

011: out2 + out7 + out4 + out6

100: out2 + out7 + out4 + out6 + out5

101: out2 + out7 + out4 + out6 + out5 + out3

110: out2 + out7 + out4 + out6 + out5 + out3 + out8

111: out2 + out7 + out4 + out6 + out5 + out3 + out8 + out1

is slightly more lexibility in that any combination of buffers can be enabled or disabled via the individual buffer enable

the part features switches on both the input and output signals, so that when the part is disabled (via either the

scheme.

Input Stage

signals. if driven single-ended, a large AC coupling cap to ground should be used on the undriven input. the input

or generated via an lVPECl termination network inside the part.

Chip Enable

the HMC987 has a chip enable feature, CEn, which can be used to power down or deactivate the lVPECl and rF

outputs. this can be done by either hardware, pin 31, or a sPi command, reg01.

For a hardware selection, a logic 0 applied to CEn will power down the HMC987, however, sPi commands can

still be written which will be recognized upon when a logic 1 is applied to CEn. note, there is no internal pull-up or

pull-down and this pin must be terminated. to control CEn by sPi command, reg 01h[0] is set to 1, which is the default

mode, and enables the outputs. When reg01[0]=0 then the outputs are disabled. Either a hardware, pin 31, or a sPi

command will disable the outputs.

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