AD8307

–20–

REV. A

Table II. Evaluation Board Link Options

Link No.

Default Position

Function

LK1

A

Power Up/Power Down. When this link is in position B, the ENB pin is connected to ground,

putting the AD8307 in power-down mode. Placing this link in position A connects the ENB

pin to the positive supply, thereby putting the AD8307 in normal operating mode.

LK2

Open

Intercept Adjust. When Pin LK2 is left open, the AD8307 has a nominal logarithmic

intercept of –84 dBm. Putting LK2 in place connects the wiper of potentiometer R2 to Pin 5

(INT). By varying the voltage on INT, the position of the intercept can be adjusted. The inter-

cept varies by about 8 dB/V.

LK3

Open

Slope Adjust. When this link is open, the nominal slope of the output is 25 mV/dB. Putting this

link in place connects a ground referenced 12.5 k

Ω load resistor (R3) to the logarithmic out-

put. The parallel combination of this resistor and an internal 12.5 k

Ω resistor reduces the

logarithmic slope to 12.5 mV/dB. R3 may be adjusted for other scaling factors.

LK4

Open

Corner Frequency of Low-Pass Demodulating Filter. When this link is open, the corner fre-

quency of the low pass post demodulation filter has a nominal value of 4 MHz. This is set by

an on-chip load impedance of 12.5 k

Ω and an on-chip load capacitance of 3.5 pF. The load

capacitance (e.g., of an oscilloscope probe) must be added to this capacitance, and will lower

the internal video bandwidth, to a nominal 1 MHz for a total of 13.5 pF. Putting LK4 in place

connects an external load capacitance (C5) of 0.1

µF to the output, reducing the corner fre-

quency of the low-pass filter to about 125 Hz. For large values of C5, the corner frequency can

be calculated using the equation, f

≈ 12.7 Hz/C5 (

µF).

LK5

Open

Offset Control Loop. When this link is open, the internal offset control loop gives the circuit an

overall high pass corner frequency of about 1 MHz. With LK5 link in place, a 1 nF capacitor

(C6) is connected to the OFS pin, reducing the high pass corner frequency to allow accurate

operation down to 10 kHz. To reduce the minimum operational frequency even further, a

larger capacitor can replace C6 (e.g., a 1

µF capacitor allows operation down to 10 Hz). Note

that that external capacitor C6 has no effect on the minimum signal frequency for input levels

that exceed the offset voltage (typically 400

µV). The range for such signals extends down to dc

(for signals applied directly to the input pins).

8-Lead Plastic DIP

(N-8)

8

14

5

0.430 (10.92)

0.348 (8.84)

0.280 (7.11)

0.240 (6.10)

PIN 1

SEATING

PLANE

0.022 (0.558)

0.014 (0.356)

0.060 (1.52)

0.015 (0.38)

0.210 (5.33)

MAX

0.130

(3.30)

MIN

0.070 (1.77)

0.045 (1.15)

0.100

(2.54)

BSC

0.160 (4.06)

0.115 (2.93)

0.325 (8.25)

0.300 (7.62)

0.015 (0.381)

0.008 (0.204)

0.195 (4.95)

0.115 (2.93)

8-Lead SOIC

(SO-8)

0.1968 (5.00)

0.1890 (4.80)

8

5

4

1

0.2440 (6.20)

0.2284 (5.80)

PIN 1

0.1574 (4.00)

0.1497 (3.80)

0.0688 (1.75)

0.0532 (1.35)

SEATING

PLANE

0.0098 (0.25)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)

0.0500

(1.27)

BSC

0.0098 (0.25)

0.0075 (0.19)

0.0500 (1.27)

0.0160 (0.41)

8

0

0.0196 (0.50)

0.0099 (0.25)

45

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).