Linear 747 User manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747
LOG-LINEAR RF/IF DETECTOR
1
LT5537
DESCRIPTION
Demonstration circuit 747 is a log-linear RF/IF detector
featuring the LT
®
5537.
The LT5537 is a wide dynamic range RF/IF log detec-
tor, operational from below 10MHz to 1000MHz. The
lower limit of the operating frequency range can be
extended to near DC by the use of an external capaci-
tor. The input dynamic range at 200MHz with ±3dB
nonlinearity is 90dB (from –76dBm to 14dBm, single-
ended 50Ωinput). The detector output voltage slope
is normally 20mV/dB, and the typical temperature
coefficient is 0.01dB/°C at 200MHz.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Table 1. Typical Performance Summary (VCC = 3V, ENBL = 3V, TA= 25°C, unless otherwise noted. Test circuit shown in Figure 1.)
PARAMETER CONDITION VALUE
Supply Voltage 2.7V to 5.25V
Supply Current 13.5mA
Shutdown Current ENBL = Low 500µA
ENBL Voltage Low, Chip Disabled
High, Chip Enabled
0.3V max
1.0V min
ENBL Input Current V
ENBL
= 0V
V
ENBL
= 3V
0µA
100µA
RF/IF Input DC Common Mode Voltage (V
CC
– 0.4) V
Small-Signal Impedance Measured at 200MHz 1.73kΩ// 1.45pF
Output Start Voltage No Input Signal Present 0.4V
Response Time Input from –30dBm to 0dBm, C
LOAD
= 2.5pF 110ns
Baseband Modulation Bandwidth Output Load Capacitance = 2.5pF 6MHz
Input Frequency Range Operation at lower frequency is possible. See LT5537 datasheet. 10MHz to 1GHz
Maximum Input Power for
Monotonic Output
50ΩTermination
200MHz
600MHz
1GHz
14.0dBm
11.6dBm
9.4dBm
f = 10MHz
Linear Dynamic Range ±3dB Error
±1dB Error
88.8dB
72.5dB
Slope R1 = 33k (The output slope is adjustable using R1.) 19.6mV/dB
Intercept V
OUT
= 0V, extrapolated -97dBm
Sensitivity Sensitivity can be improved by as much as 10dB by using a narrow-
band input matching network. See LT5537 datasheet. -76.7dBm
Temperature Coefficient P
IN
= -20dBm -0.007dB/°C

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747
LOG-LINEAR RF/IF DETECTOR
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f = 100MHz
Linear Dynamic Range ±3dB Error
±1dB Error
90.5dB
82.8dB
Slope R1 = 33k (The output slope is adjustable using R1.) 20.3mV/dB
Intercept V
OUT
= 0V, extrapolated -95dBm
Sensitivity Sensitivity can be improved by as much as 10dB by using a narrow-
band input matching network. See LT5537 datasheet. -77dBm
Temperature Coefficient P
IN
= -20dBm -0.004dB/°C
f = 200MHz
Linear Dynamic Range ±3dB Error
±1dB Error
90.3dB
83.5dB
Slope R1 = 33k (The output slope is adjustable using R1.) 21.2mV/dB
Intercept V
OUT
= 0V, extrapolated -94dBm
Sensitivity Sensitivity can be improved by as much as 10dB by using a narrow-
band input matching network. See LT5537 datasheet. -76.4dBm
Temperature Coefficient P
IN
= -20dBm 0.010dB/°C
f = 400MHz
Linear Dynamic Range ±3dB Error
±1dB Error
88.2dB
70.8dB
Slope R1 = 33k (The output slope is adjustable using R1.) 23.1mV/dB
Intercept V
OUT
= 0V, extrapolated -91dBm
Sensitivity Sensitivity can be improved by as much as 10dB by using a narrow-
band input matching network. See LT5537 datasheet. -75.3dBm
Temperature Coefficient P
IN
= -20dBm 0.019dB/°C
f = 600MHz
Linear Dynamic Range ±3dB Error
±1dB Error
85.8dB
72.5dB
Slope R1 = 33k (The output slope is adjustable using R1.) 25.2mV/dB
Intercept V
OUT
= 0V, extrapolated -89dBm
Sensitivity Sensitivity can be improved by as much as 10dB by using a narrow-
band input matching network. See LT5537 datasheet. -74.1dBm
Temperature Coefficient P
IN
= -20dBm 0.026dB/°C
f = 1GHz
Linear Dynamic Range ±3dB Error
±1dB Error
63.5dB
51.7dB
Slope R1 = 33k (The output slope is adjustable using R1.) 31.4mV/dB
Intercept V
OUT
= 0V, extrapolated -80dBm
Sensitivity Sensitivity can be improved by as much as 10dB by using a narrow-
band input matching network. See LT5537 datasheet. -69.2dBm
Temperature Coefficient P
IN
= -20dBm 0.031dB/°C

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747
LOG-LINEAR RF/IF DETECTOR
3
QUICK START PROCEDURE
Demonstration circuit 747 is easy to set up to evalu-
ate the performance of the LT5537. Refer to Figure 1
for proper measurement equipment setup and follow
the procedure below:
1. Connect voltmeter’s negative (-) lead to demo
board GND test point (E4 or E5).
2. Connect voltmeter’s positive (+) lead to the demo
board OUTPUT test point (E2).
3. Connect DC power supply’s negative (-) output to
demo board GND test point (E4 or E5).
4. Connect DC power supply’s positive (+) output
(2.7V to 5.25V) to demo board V
CC
test point (E3).
NOTE: Do not exceed 5.5V, the absolute maximum
supply voltage.
5. Connect signal generator’s output to demo board
INPUT port (SMA connector J1) via coaxial cable.
A 3dB attenuator may be inserted to improve input
match.
6. Using a jumper cable, connect demo board V
CC
test
point (E3) to ENBL test point (E1). Now the detec-
tor is enabled (on) and is ready for measurement.
NOTE: Make sure that the power is not applied to
ENBL before it is applied to V
CC
. The voltages on
the ENBL test point must never exceed V
CC
+ 0.2V.
7. Apply RF input signal and measure OUTPUT DC
voltages.
NOTE: Do not exceed +22dBm, the absolute maxi-
mum RF input power.
Figure 1. Proper Measurement Equipment Setup

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 747
LOG-LINEAR RF/IF DETECTOR
4

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