DEMO CIRCUIT 1638A
LTC5587
QUICK START GUIDE
LTC5587
6GHz RMS Power Detector
with 12-bit Digital Output
DESCRIPTION
Demonstration circuit 1638A is a Mean-Squared Power
Detector with integrated 12-bit ADC featuring the
LTC
®
5587 IC.
The LTC5587 is a wide dynamic range Mean Squared
RF Power Detector, operational from 10MHz to 6GHz,
with sample rate up to 500ksps. The input dynamic
range at 2.14GHz, with ±1dB nonlinearity, is 40dB
(from –34dBm to +6dBm, single-ended 50 input).
The detector output, VOUT is also the input to the
internal ADC, the digital output slope is typically
70LSB/dB, and the typical output variation over
temperature is ±1dB at 2.14GHz.
LTC5587 has the internal 12-bit SPI compatible ADC.
DC1638A demonstrates the performance in
conjunction with DC590B Quick-Eval board. The
DC590B board samples the ADC at approximately
200Hz. Faster sampling rate is possible, contact LTC
applications for more information.
The 1638A Demo Circuit input is optimized for wide
frequency range of 1.75GHz to 2.2GHz. However,
input match can be shifted down to 10MHz or up to
6GHz with simple external matching.
Design files for this demo board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Typical Performance Summary (V
CC
= V
DD
= OV
DD
= 3.3V, EN=3.3V, V
REF
=1.8V, V
OUT
=ADC OUTPUT(LSB) *1.8/4096,T
A
= 25°C, unless otherwise
noted. Test circuit shown in Figure 1.)
PARAMETER
CONDITION
TYPICAL VALUE
OV
DD
Supply Voltage
V
DD
Supply Voltage
V
CC
Supply Voltage
V
REF
Reference Voltage
Total Supply Current
Shutdown Current
EN Voltage
No RF input signal, ADC operational at 500ksps
EN = 0.3V, CONV=3.3V, ADC Sleep-Mode
Low, Chip Disabled
HIGH, Chip Enabled
V
EN
= 0V
V
EN
= 3.3V
No Input Signal Present
0.2V to 1.6V, 10% to 90%, F
RF
= 2140 MHz
1.6V to 0.2V, 90% to 10%, F
RF
= 2140 MHz
With external matching components
Should be equal to V
DD
1.0 to V
DD
2.7V to 3.6V
2.7V to 3.6V
1.4 to V
DD
+0.05V
3mA
0.2μA
0.3V max
2V min
0μA
20μA
0.18V
1μs
8μs
10MHz to 6GHz
EN Input Current
Output Detector Voltage, V
OUT
Rise Time(1000pF on V
OUT
)
Fall Time(1000pF on V
OUT
)
Input Frequency Range
f = 880MHz
RF Input Power Range
Linear Dynamic Range, CW
Output Slope
Logarithmic Intercept
CW input: Externally Matched to 50Ω Source
±1 dB linearity error
-34 to 6 dBm
40 dB
73LSB/dB
-42dBm
1
LTC5587
Output Variation vs Temperature
Deviation from CW Response
f = 2140MHz
RF Input Power Range
Linear Dynamic Range, CW
Output Slope
Logarithmic Intercept
Output Variation vs Temperature
Deviation from CW Response
F=3500MHz
Linear Dynamic Range, CW
Slope
Logarithmic Intercept
Output Variation vs Temperature
Deviation from CW Response
ADC Resolution
ADC Resolution
Differential Linearity Error
Measurement Resolution
(no missing code)
EN=0V, Voltage on V
OUT
=0V to 1.8V, V
REF
=1.8V
1LSB= V
REF
/(4096
*29mV/dB),
V
REF
=1.8V
12 bits
±0.25
15mdB
P
IN
= -30 to +6dBm
WiMAX OFDM Burst; P
IN
= -34 to +4dBm
±1 dB linearity error
36dB
73LSB/dB
-40dBm
±1 dB
±0.5dB
P
IN
= -34 to +6dBm
12 dB peak-to-average ratio (4 carrier WCDMA)
CW input: Externally Matched to 50Ω Source
±1 dB linearity error
-34 to 6 dBm
43 dB
73 LSB/dB
-42dBm
±1 dB
±0.5 dB
P
IN
= -34 to +6dBm
EDGE 3π/8 Shifted 8PSK, P
IN
= -34 to +6dBm
±1 dB
±0.1 dB
Table 1.
Jumper Description for DC1638A
JUMPER FUNCTION
JP1
VDD, ADC power supply voltage
JP2
VREF, ADC reference input voltage
JP3
OVDD, ADC output driver supply voltage
RANGE/SETTING (DEFAULT)
3.3V
VREG=1.8V
3.3V
DC590B QUICK START PROCEDURE
The DC590B is a USB controller board that allows PC to
communicate through serial data interface. The Quick
start guide for DC590B can be found here:
http://cds.linear.com/docs/Reference%20Design/dc590B.
pdf.
Download and install the QuickEval software
supplied
for
DC590B
here:
http://www.linear.com/designtools/software/quick_eval.js
p.
Connect DC590B to the host PC with the USB A/B
cable.
1. Connect the DC1638A to the DC590B USB serial
controller board using the supplied 14-
conductor ribbon cable.
2. Set
VCCIO on DC590B to 3.3V
on the USB
controller board.
3. Set the JP4, the “EN”, which will enable the
EEPROM for DC590B to automatically recognize
the DC1638A board with LTC5587 when
connected.
4. Set JP5 to ON, for both ISO and SW, they
provide the VCCIO voltage to DC1638.
5. JP1, and JP2 are not used. Leave open.
2
LTC5587
DC1638A QUICK START PROCEDURE
Demonstration circuit 1638A is easy to set up to
evaluate the performance of the LTC5587. Refer to
Figure 2
for measurement equipment setup and follow
the procedure below:
1. Connect DC power negative (-) supply to GND
test point.
2. Connect DC power positive(+) supply to VCC
and EN.
3. Set JP1(VDD) to 3.3V. This will power the
LTC5587 Digital supply using the on board 3.3V
regulator. The on board 3.3V regulator receives
power from the DC590B board.
4. Set JP2(VREF) to VREG. This will supply the
VREF using the on board 1.8V regulator. The on
board 1.8V regulator receives power from the
VCC supply.
5. Set JP3(OVDD) to 3.3V. This will power up the
ADC output digital driver using the on board
3.3V regulator, which gets the power from
DC590B.
6. Connect the signal generator’s output to
J1(RFIN), using the SMA connector. A 3dB
attenuator pad may be used to improve
broadband match, which will shift the detected
power range up by 3dB.
7. The LTC5587 software control panel
automatically opens when the DC1638A demo
board is connected to the DC590B board. Using
the Quick Eval software, set the VREF voltage to
1.8V.
8. Click on Collect to start reading the ADC.
NOTES:
1.
The voltage on the EN test point must never
exceed VCC + 0.3V.
Figure 1. Standard Demo Board Return Loss
2.
For digitally modulated signals, an oscilloscope
can be used to observe the AC components of
the output.
3.
If no DC power supply is available. DC1638A can
also be power up using the on board 3.3V
regulator. Connect the 3.3V test point to VCC
and EN.
4.
Pin 6, C
SQ
is the Optional Low Frequency Range
Extension Capacitor.
Use this pin for
frequencies below 250MHz. Connect 0.01uF
from Pin 8 to ground for 10MHz operation.
5.
The software can display either ADC count, or
the calculated voltage based on the ADC VREF
input. Go to tools=>options to select.
6.
The vertical axis can be toggled between Auto
and Full by clicking on it at the upper left corner
of the control panel.
7.
Do not exceed +15dBm, the absolute maximum
average RF input power.
8.
Vout is the analog input voltage to the ADC.
VREF defines the full-scale output range of ADC,
0V to VREF.
3
LTC5587
9.
The Software allows datalog of output data, and
saves the file as .adc format, which Microsoft
Excel
®
can be used to open. Equivalent output
voltage can be calculated from the ADC code
based on the V
REF
as follows.
=
Where VREF=1.8V for the standard demo board.
10. Linearity Error at any input power level can be
calculated from the Vout, given the best fit
slope and Log intercept, as follows:
Best fit slope is taken for Pin from -20dBm to 0dBm.
11. Averaging Function can be turned on by clicking
on the upper left hand corner on the front control
panel, Figure 3.
4
LTC5587
Figure 2. Proper test setup to connect DC1638A demo board to DC590A
5
Embedded System
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