AD8368 Analog Devices, AD8368 Datasheet
AD8368
Available stocks
Related parts for AD8368
AD8368 Summary of contents
Page 1
... Furthermore, the setpoint level can be raised by dividing down the output signal before applying it to the detector. The AD8368 operates from a supply voltage of 4 5.5 V and consumes current. It can be fully powered down to < grounding the ENBL pin. The AD8368 is fabricated using Analog Devices’ ...
Page 2
... AD8368 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 5 ESD Caution.................................................................................. 5 Pin Configuration and Function Descriptions............................. 6 Typical Performance Characteristics ............................................. 7 Circuit Description......................................................................... 12 Input Attenuator and Interpolator ........................................... 12 REVISION HISTORY 4/06—Revision 0: Initial Version Fixed-Gain Stage and Output Buffer ....................................... 12 Output Offset Correction ...
Page 3
... V, 0 dBm per output tone 2 GAIN = 0 V MODE = 141 MHz dBm per output tone 2 GAIN = 0 V MODE = 241 MHz dBm per output tone 2 GAIN = 0 V MODE = 381 MHz dBm per output tone 2 GAIN = 0 V MODE AD8368 ...
Page 4
... AD8368 25°C, system impedance Z S Table 2. Parameter SQUARE LAW DETECTOR (DETI, DETO) Output Setpoint DETI DC Bias Level to ICOM DETI Impedance 1 DETO Output Range AGC Step Response MODE CONTROL INTERFACE (MODE) Mode Threshold MODE Input Bias Current POWER INTERFACE (VPSI, VPSO) ...
Page 5
... Exposure to absolute 440 mW maximum rating conditions for extended periods may affect 52°C/W device reliability. 125°C −40°C to +85°C −65°C to +150°C 300°C Rev Page AD8368 ...
Page 6
... DECL 4 15 (Not to Scale) DETI 5 14 OCOM Figure 2. AD8368 24-Lead LFCSP Pin Out /2. Decoupling capacitance may need to be adjusted for AGC operation (see S ≤ VPSI ) to activate device. ENBL Rev Page ICOM ICOM ICOM DECL DECL VPSI ...
Page 7
... V GAIN 0.4 0.3 0.2 V OUTP 0.1 0 –0.1 –0.2 –0.3 –0.4 –0.5 –0.4 –0.3 –0.2 –0.1 0 0.1 0.2 TIME (µs) Figure 8. Gain Step Time Domain Response (6 dB Gain Step) AD8368 4 240MHz –1 –40°C –2 –3 –4 0.8 1 240 MHz) 4 380MHz –1 –40°C –2 – ...
Page 8
... AD8368 110 150 190 230 RF INPUT (MHz) Figure 9. OIP3 vs. Frequency at Maximum Gain (V 40 70MHz 240MHz 380MHz 0.2 0.4 0.6 V (V) GAIN Figure 10. OIP3 vs GAIN MODE 0 –10 –20 –30 –40 380MHz 240MHz –50 –60 –70 140MHz – ...
Page 9
... Rev Page 0.75V GAIN GAIN GAIN V = 0.25V GAIN V = 0.5V GAIN Figure 18. Input Reflection Coefficient vs. Frequency 0 10 100 FREQUENCY (MHz) Figure 19. Output Reflection Coefficient vs. Frequency GAIN GAIN Figure 20. Output Reflection Coefficient vs. Frequency AD8368 = GAIN GAIN 1000 ...
Page 10
... AD8368 1.0 0.9 0.8 0.7 0.6 0.5 +85°C 0.4 0.3 +25°C 0.2 0.1 –40°C +85°C 0 –40 –35 –30 –25 –20 –15 RF INPUT (dBm) Figure 21. RSSI (V ) and Conformance Error vs. Input Power ( MHz) DETO 1.0 0.9 0.8 0.7 0.6 0.5 +85°C 0.4 0.3 –40°C 0.2 0.1 +25°C +85°C 0 –40 –35 –30 –25 –20 –15 RF INPUT (dBm) Figure 22. RSSI (V ) and Conformance Error vs. Input Power (f = 140 MHz) DETO 1 ...
Page 11
... CH3 5V Ω M2.0µs 250MS/s A CH3 4.0ns/PT Figure 27. ENBL Response Time 36.8 37.0 37.2 37.4 37.6 37.8 SLOPE (dB/V) Figure 28. Gain Scaling Distribution (140 MHz 0.0V –15.0 Figure 29. Gain Intercept Distribution (140 MHz) 38.0 38.2 Rev Page AD8368 –14.7 –14.4 –14.1 –13.8 –13.5 INTERCEPT (dB) ...
Page 12
... AD8368 CIRCUIT DESCRIPTION The AD8368 is a single-ended VGA with a bandwidth of 800 MHz and a gain control span ranging from − +22 dB. It incorporates an uncommitted square law detector that can be used to form a tight AGC loop around the VGA. Using Analog Devices’ patented X-AMP architecture, the AD8368 achieves accurate linear-in-dB gain control with excellent linearity (OIP3) and noise figure (NF) ...
Page 13
... GAIN CONTROL INTERFACE The AD8368 has a linear-in-dB gain control interface that can be operated in either a gain-up mode or gain-down mode. In the gain-up mode with the MODE pin pulled high, the gain increases with increasing gain voltages. In the gain-down mode, with the MODE pin pulled low, the gain decreases with increasing gain voltages. In both modes of operation, the gain control slope is maintained at +37.5 dB/V or − ...
Page 14
... AD8368 APPLICATIONS VGA OPERATION The AD8368 is a general-purpose VGA suitable for use in a wide variety of applications where accurate, continuous, linear-in-dB gain control over a broad range of frequencies is important. Its stability over temperature and supply in comparison to other variable-gain techniques can be traced back to the X-AMP architecture ...
Page 15
... Figure 36. Monitoring the GAIN/DETO RSSI Voltage vs. Input Power In some cases, it may be found that, if driven into AGC overload, the AD8368 requires unusually long times to recover; that is, the voltage at DETO remains at an abnormally high value, and the gain is at its lowest value. To avoid this situation, ...
Page 16
... AD8368 The choice compromise of averaging time constant, DETO response time, and carrier leakage DETO small to speed up the response time, the AGC loop could start tracking and leveling any amplitude envelope and corrupt the Figure 38 illustrates a 16 QAM, 100 ksymbols/s constellation ...
Page 17
... R10 = R11 = R12 = 0 Ω C10 = C11 = C12 = 1 nF C13 = C14 = C15 = 0.1 μ OUT R31 = R32 = open (VGA mode) R35 = open C23 = not populated R30 = not populated C20 = JP4 = not populated (VGA mode) SW1 = JP2 SW2 = JP3 AD8368 ...
Page 18
... AD8368 OUTLINE DIMENSIONS PIN 1 INDICATOR 1.00 0.85 0.80 SEATING PLANE ORDERING GUIDE Temperature Model Range 1 AD8368ACPZ-REEL7 −40°C to +85° AD8368ACPZ-WP −40°C to +85°C 1 AD8368-EVALZ Pb-free part Waffle pack. 4.00 BSC SQ 0.60 MAX 0.50 BSC TOP 3.75 VIEW BSC SQ 0.50 0.40 0.30 0.80 MAX 12° MAX 0.65 TYP 0.05 MAX ...
Page 19
... NOTES Rev Page AD8368 ...
Page 20
... AD8368 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05907-0-4/06(0) Rev Page ...