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

27

HMC993LP5E

v00.0911

RF AUTOMATIC GAIN CONTROLLER

(RF-AGC), 700 - 3000 MHz

Figure 8: DETOUT vs. input power over frequency.

0

0.3

0.6

0.9

1.2

1.5

-70

-60

-50

-40

-30

-20

-10

0

10

900 MHz

1900 MHz

2400 MHz

2800 MHz

INPUT POWER (dBm)

range of the log detector should be chosen. The gain adjustment range of the HMC993L5E is maximized in this con-

figuration.

If the linear operation range of the HMC993LP5E is maximized by selecting the appropriate coupler ratio, the

HMC993LP5E can handle larger changes in input level. For example, an input voltage of 0.5 V is applied to the Vset

pin to set the constant output power level to -18.7 dBm. A coupler ratio of ~7 dB can be chosen to provide a maximum

dynamic range of 33.6 dB.

1

1.5

2

2.5

3

3.5

4

0

100

200

300

400

500

600

700

800

900 1000

TIME (ms)

Pin = -10 dBm

Figure 9: HMC993LP5E’s gain control voltage when

VSET is toggled between 0.3V - 0.7V and input level

is kept constant in closed loop.

Loop Bandwidth and Response Time

The AGC system has a response time to undesired input level fluctuations. Response time and the stability of the

HMC993LP5E’s AGC loop is determined by C4 and C7 in the application schematic. The HMC993LP5E’s response to

voltage changes in VSET with C4=C7=1μF when the input level is kept constant is shown in Figure 9.