Data Sheet

ADL5506

Rev. A | Page 17 of 23

APPLICATIONS INFORMATION

BASIC CONNECTIONS

Figure 42 shows the basic connections for measurement mode.

A supply voltage of 2.5 V to 5.5 V is required. Decouple the

supply to the VPOS pin with a low inductance 0.1 μF surface-

mount ceramic capacitor. A series resistor of about 10 Ω can be

added; this resistor slightly reduces the supply voltage to the

ADL5506 and depends on the load resistance at the output to

ground. Avoid its use in applications where the power supply

voltage is very low. A series inductor provides similar power

supply filtering with minimal drop in supply voltage.

Figure 42. Basic Connections

The ADL5506 has an internal input coupling capacitor. This

eliminates the need for external ac coupling. In this example, a

broadband input match is achieved by connecting a 52.3 Ω

resistor between RFIN and ground. This resistance combines

with the internal input impedance to give an overall broadband

input resistance of 50 Ω. Several other coupling methods are

possible; these are described in the Input Coupling Options

section.

so that the full-scale output can be generated with the limited

available sourcing current of 4 mA. Figure 43 shows the

logarithmic conformance under the same conditions.

TRANSFER FUNCTION IN TERMS OF SLOPE AND

INTERCEPT

The transfer function of the ADL5506 is characterized in terms

of its slope and intercept. The logarithmic slope is defined as the

change in the RSSI output voltage for a 1 dB change at the input.

For the ADL5506, the slope is nominally 18 mV/dB. Therefore,

a 10 dB change at the input results in a change at the output of

approximately 180 mV. Figure 43 shows the range over which

the device maintains its constant slope. The dynamic range can

be defined as the range over which the error remains within a

certain band, usually ±1 dB or ±3 dB. In Figure 43 for example,

the ±1 dB dynamic range is approximately 46 dB (from

−44 dBm to +2 dBm).

The intercept is the point at which the extrapolated linear

response intersects the horizontal axis (see Figure 43). Using the

slope and intercept, calculate the output voltage for any input

level within the specified input range, or calculate the input

level from the output voltage by the following complementary

equations:

where:

reference level (dBm in this case).

the same reference level.

voltage is

ADL5506

ENBL

1

VLOG

2

COMM

3

CFTL

6

VPOS

5

RFIN

4

INPUT

52.3Ω

0.1µF

100pF

NC

5

0

–5

–10

–15

–20

–25

–30

–35

–40

–45

–50

–55

–60

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

6

5

4

3

2

1

0

–1

–2

–3

–4

–5

–6

ERROR

INTERCEPT

±3dB DYNAMIC RANGE

±1dB DYNAMIC RANGE