480 MHz Single-Supply (5 V) a Triple 2:1 Multiplexers AD8187
FEATURES FUNCTIONAL BLOCK DIAGRAM Fully Buffered Inputs and Outputs Fast Channel-to-Channel Switching: 4 ns IN0A 1 24 V Single-Supply Operation (5 V) CC D 2 LOGIC 23 OE High Speed: GND IN1A 3 22 SEL A/B 480 MHz Bandwidth (–3 dB) 2 V p-p SELECT V 4 21 >1600 V/ s (G = +1) REF ENABLE VCC IN2A 5 0 20 >1500 V/ s (G = +2) OUT 0 V 6 19 V Fast Settling Time of 7 ns to 0.1% CC EE V 7 1 18 OUT 1 Low Current: 19 mA/20 mA EE IN2B 8 17 VCC Excellent Video Specifications (RL = 150 ) V 9 2 16 OUT 2 0.05% Differential Gain Error EE IN1B 10 15 V 0.05 Differential Phase Error EE V 11 14 Low Glitch EE DVCC IN0B 12 13 V All Hostile Crosstalk AD8186/AD8187 CC –84 dB @ 5 MHz –52 dB @ 100 MHz Table I. Truth Table High Off Isolation of –95 dB @ 5 MHz Low Cost SEL A/B OE OUT Fast, High Impedance Disable Feature for Connecting 00High Z Multiple Outputs Logic-Shifted Outputs 10High Z AD8186 is Obsolete 11IN A 01IN B APPLICATIONS Switching RGB in LCD and Plasma Displays RGB Video Switchers and Routers 4.0 6.0 GENERAL DESCRIPTION The AD8186 (G = +1) and AD8187 (G = +2) are high speed, 3.5 5.5 single-supply, triple 2-to-1 multiplexers. They offer –3 dB large signal 3.0 5.0 bandwidth of over 480 MHz along with a slew rate in excess of 2.5 INPUT 4.5
1500 V/µs. With better than –80 dB of all hostile crosstalk and 2.0 4.0 –95 dB OFF isolation, they are suited for many high speed appli- cations. The differential gain and differential phase error of 0.05% 1.5 3.5 and 0.05°, along with 0.1 dB flatness to 85 MHz, make the 1.0 3.0 INPUT VOLTAGE (V) INPUT VOLTAGE
AD8186 and AD8187 ideal for professional and component video 0.5 OUTPUT 2.5 (V) OUTPUT VOLTAGE multiplexing. They offer 4 ns switching time, making them an 0 2.0 excellent choice for switching video signals while consuming less than 20 mA on a single 5 V supply (100 mW). Both devices have a –0.5 1.5 –1.0 1.0 high speed disable feature that sets the outputs into a high 0510 15 20 25 impedance state. This allows the building of larger input arrays TIME (ns) while minimizing OFF channel output loading. The devices are Figure 1. AD8187 Video Amplitude Pulse offered in a 24-lead TSSOP package. Response, VOUT = 1.4 V p-p, RL = 150 Ω The AD8186 is no longer available.
REV. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. under any patent or patent rights of Analog Devices. Trademarks and Tel: 781/329-4700 www.analog.com registered trademarks are the property of their respective companies. Fax: 781/326-8703 © 2003–2017 Analog Devices, Inc. All rights reserved. (TA = 25 C; AD8186: VS = 5 V, RL = 1 k to 2.5 V; AD8187: VS = 5 V, AD8187 –SPECIFICATIONS VREF = 2.5 V, RL = 150 to 2.5 V; unless otherwise noted.)
AD8186/AD8187 Parameter Conditions Min Typ Max Unit DYNAMIC PERFORMANCE –3 dB Bandwidth (Small Signal) VOUT = 200 mV p-p 1000/1000 MHz –3 dB Bandwidth (Large Signal) VOUT = 2 V p-p 450/480 MHz 0.1 dB Flatness VOUT = 200 mV p-p 90/85 MHz Slew Rate (10% to 90% Rise Time) VOUT = 2 V p-p, RL = 150 Ω 1600/1500 V/s Settling Time to 0.1% VIN = 1 V Step, RL = 150 Ω 6/7.5 ns NOISE/DISTORTION PERFORMANCE Differential Gain 3.58 MHz, RL = 150 Ω 0.05/0.05 % Differential Phase 3.58 MHz, RL = 150 Ω 0.05/0.05 Degrees All Hostile Crosstalk 5 MHz –84/–78 dB 100 MHz –52/–48 dB Channel-to-Channel Crosstalk, RTI 5 MHz –90/–85 dB OFF Isolation 5 MHz –84/–95 dB Voltage Noise, RTI f = 100 kHz to 100 MHz 7/9 nV/√Hz DC PERFORMANCE Voltage Gain Error No Load 0.1/0.1 Ϯ0.3/0.6 % Voltage Gain Error Matching Channel A to Channel B 0.04/0.04 Ϯ0.2/0.2 % VREF Gain Error 1 kΩ Load 0.04 Ϯ0.6 % Input Offset Voltage 0.2/0.5 Ϯ6.5/7.0 mV TMIN to TMAX Ϯ8.0 mV Input Offset Voltage Matching Channel A to Channel B 0.2/0.2 Ϯ5.0/5.5 mV Input Offset Drift 10/5 V/ºC Input Bias Current 1.5/1.5 4/4 A VREF Bias Current (for AD8187 only) 1.0 A INPUT CHARACTERISTICS Input Resistance @100 kHz 1.8/1.3 MΩ Input Capacitance 0.9/1.0 pF Input Voltage Range (About Midsupply) IN0A, IN0B, IN1A, IN1B, IN2A, IN2B Ϯ1.2/Ϯ1.2 V VREF +0.9, –1.2 V OUTPUT CHARACTERISTICS Output Voltage Swing RL = 1 kΩ 3.1/2.8 3.2/3.0 V p-p RL = 150 Ω 2.8/2.5 3.0/2.7 V p-p Short Circuit Current 85 mA Output Resistance Enabled @ 100 kHz 0.2/0.35 Ω Disabled @ 100 kHz 1000/600 kΩ Output Capacitance Disabled 1.5/2.0 pF POWER SUPPLY Operating Range 3.5 5.5 V Power Supply Rejection Ratio +PSRR, VCC = 4.5 V to 5.5 V, VEE = 0 V –72/–61 dB –PSRR, VEE = –0.5 V to +0.5 V, VCC = 5.0 V –76/–72 dB Quiescent Current All Channels ON 18.5/19.5 21.5/22.5 mA All Channels OFF 3.5/4.5 4.5/5.5 mA TMIN to TMAX, All Channels ON 15 23 mA
–2– REV. B AD8187
AD8186/AD8187 Parameter Conditions Min Typ Max Unit SWITCHING CHARACTERISTICS Channel-to-Channel Switching Time 50% Logic to 50% Output Settling, INA = +1 V, INB = –1 V 3.6/4 ns ENABLE to Channel ON Time 50% Logic to 50% Output Settling, INPUT = 1 V 4/3.8 ns DISABLE to Channel OFF Time 50% Logic to 50% Output Settling, INPUT = 1 V 17/5 ns Channel Switching Transient (Glitch) All Channels Grounded 21/45 mV Output Enable Transient (Glitch) All Channels Grounded 64/118 mV DIGITAL INPUTS Logic 1 Voltage SEL A/B, OE Inputs 1.6 V Logic 0 Voltage SEL A/B, OE Inputs 0.6 V Logic 1 Input Current SEL A/B, OE = 2.0 V 45 nA Logic 0 Input Current SEL A/B, OE = 0.5 V 2 A OPERATING TEMPERATURE RANGE Temperature Range Operating (Still Air) –40 +85 ºC JA Operating (Still Air) 85 ºC/W JC Operating 20 ºC/W Specifications subject to change without notice.
REV. B –3– AD8187
ABSOLUTE MAXIMUM RATINGS1, 2, 3, 4 2.5 Supply Voltage ...... 5.5 V DVCC to DGND ...... 5.5 V 2.0 DVCC to VEE ...... 8.0 V VCC to DGND ...... 8.0 V IN0A, IN0B, IN1A, IN1B, IN2A, IN2B, VREF . . . VEE ≤ VIN ≤ VCC 1.5 SEL A/B, OE ...... DGND ≤ VIN ≤ DVCC Output Short Circuit Operation ...... Indefinite Storage Temperature Range ...... –65ºC to +150ºC 1.0 Lead Temperature Range (Soldering 10 sec) ...... 300ºC NOTES 1 0.5 Stresses above those listed under Absolute Maximum Ratings may cause perma- (W) DISSIPATION MAXIMUM POWER nent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the Theory of 0 Operation section of this specification is not implied. Exposure to absolute –50 –40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 maximum rating conditions for extended periods may affect device reliability. AMBIENT TEMPERATURE ( C) 2 Specification is for device in free air (TA = 25ºC). 3 24-lead TSSOP; TJA= 85ºC/W. Maximum internal power dissipation (PD) should be Figure 2. Maximum Power Dissipation vs. Temperature derated for ambient temperature (TA) such that PD < (150ºC TA)/TJA. 4 TJA of 85ЊC/W is on a 4-layer board (2s 2p). PIN CONFIGURATION MAXIMUM POWER DISSIPATION The maximum safe junction temperature for plastic encapsulated devices is determined by the glass transition temperature of the IN0A 1 24 VCC 23 plastic, approximately 150ºC. Temporarily exceeding this limit DGND 2 OE may cause a shift in parametric performance due to a change in IN1A 3 22 SEL A/B 4 21 the stresses exerted on the die by the package. Exceeding a VREF VCC junction temperature of 175ºC for an extended period can result IN2A 5 AD8186/ 20 OUT 0 AD8187 6 19 in device failure. VCC VEE TOP VIEW V 7 18 OUT 1 While the AD8186/AD8187 is internally short circuit protected, EE (Not to Scale) IN2B 8 17 V this may not be sufficient to guarantee that the maximum junction CC V 9 16 OUT 2 temperature (150ºC) is not exceeded under all conditions. To EE IN1B 10 15 V ensure proper operation, it is necessary to observe the maximum EE 11 14 power derating curves shown in Figure 2. VEE DVCC IN0B 12 13 VCC
ORDERING GUIDE
Model1 Temperature Range Package Description Package Option AD8187ARUZ – 40ºC to +85ºC 24-Lead Thin Shrink Small Outline Package (TSSOP) RU-24 AD8187ARUZ-REEL – 40ºC to +85ºC 13" Reel TSSOP RU-24 AD8187ARUZ-REEL 7 – 40ºC to +85ºC 7" Reel TSSOP RU-24 AD8187-EVAL Evaluation Board 1Z = RoHS Compliant Part.
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD8186/AD8187 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
–4– REV. B Typical Performance Characteristics– AD8187
3 0.6 1 0.5 976 2 DUT 0.5 50 52.3 0 0.4 1 0.4 GAIN GAIN –1 0.3 0 0.3
–1 0.2 –2 0.2
–2 0.1
GAIN (dB) –3 0.1
FLATNESS (dB) FLATNESS –3 0 –4 0 NORMALIZED GAIN (dB) –4 –0.1 FLATNESS (dB) NORMALIZED FLATNESS –5 –0.1 –5 –0.2
–6 –0.3 –6 –0.2 0.1 1.0 10.0 100.0 1000.0 10000.0 0.1 1.0 10.0 100.0 1000.0 10000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 1. AD8186 Frequency Response, TPC 4. AD8187 Frequency Response, VOUT = 200 mV p-p, RL = 1 kΩ VOUT = 200 mV p-p, RL = 150 Ω
1 1
0 0 –1 –1 –2
–3 –2
–4
GAIN (dB) –3
–5 –4 NORMALIZED GAIN (dB) –6 150 976 DUT –5 –7 50 52.3
–8 –6 0.1 1.0 10.0 100.0 1000.0 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 2. AD8186 Frequency Response, TPC 5. AD8187 Frequency Response,
VOUT = 2 V p-p, RL = 1 kΩ VOUT = 2 V p-p, RL = 150 Ω
1 1 +85 C –40 C +25 C 0 0 +25 C
–1 –1 –40 C +85 C –2 –2
–3 –3
–4 NORMALIZED GAIN (dB) –4 NORMALIZED GAIN (dB) 150 976 DUT –5 50 52.3 –5
–6 –6 0.1 1.0 10.0 100.0 1000.0 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz)
TPC 3. AD8186 Large Signal Bandwidth vs. TPC 6. AD8187 Large Signal Bandwidth vs.
Temperature, VOUT = 2 V p-p, RL = 1 kΩ Temperature, VOUT = 2 V p-p, RL = 150 Ω
REV. B –5– AD8187
0 0
–10 –10
–20 –20
–30 –30
–40 –40
–50 –50
–60 –60
–70 –70 CROSSTALK (dB) CROSSTALK CROSSTALK (dB) CROSSTALK –80 –80
–90 –90
–100 –100 –110 –110 0.1 110100 1000 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 7. AD8186 All Hostile Crosstalk* vs. Frequency TPC 10. AD8187 All Hostile Crosstalk* vs. Frequency
0 0
–10 –10
–20 –20 –30 –30 –40 –40 –50 –50 –60 –60 –70 –70 CROSSTALK (dB) CROSSTALK CROSSTALK (dB) CROSSTALK –80 –80 –90
–90 –100 –100 –110 –110 –120 0.1 1.0 10.0 100.0 1000.0 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 8. AD8186 Adjacent Channel Crosstalk* vs. Frequency TPC 11. AD8187 Adjacent Channel Crosstalk* vs. Frequency
0 0
–10 –10 –20 –20 –30 –30 –40 –40 –50
–50 –60
–60 –70 –80 OFF ISOLATION (dB) OFF ISOLATION OFF ISOLATION (dB) OFF ISOLATION –70 –90 –80 –100 –90 –110 –100 –120 0 10 100 1000 110100 1000 FREQUENCY (MHz) FREQUENCY (MHz) TPC 9. AD8186 OFF Isolation* vs. Frequency TPC 12. AD8187 OFF Isolation* vs. Frequency
*All hostile crosstalk—Drive all INA, listen to output with INB selected. Adjacent channel crosstalk—Drive one INA, listen to an adjacent output with INB selected. Off isolation—Drive inputs with OE tied low.
–6– REV. B AD8187
0 0
–10 –10
–20 –20
–30 –30
–40 –40
–50 –50
–60 –60 THIRD THIRD DISTORTION (dBc) DISTORTION DISTORTION (dBc) DISTORTION –70 –70 SECOND –80 –80 SECOND –90 –90
–100 –100 1 10 100 1 10 100 FREQUENCY (MHz) FREQUENCY (MHz) TPC 13. AD8186 Harmonic Distortion vs. Frequency TPC 16. AD8187 Harmonic Distortion vs. Frequency VOUT = 2 V p-p, RL = 150 Ω VOUT = 2 V p-p, RL = 150 Ω
0 0
–10 –10
–20 –20
–30 –30
–40 –PSRR –40 –PSRR –50 PSRR (dB) PSRR (dB) –50 –60 +PSRR –60 –70 +PSRR –70 –80
–90 –80 0.01 0.10 1 10 100 0.01 0.10 1 10 100 FREQUENCY (MHz) FREQUENCY (MHz)
TPC 14. AD8186 PSRR vs. Frequency, RL = 150 Ω TPC 17. AD8187 PSRR vs. Frequency, RL = 150 Ω
20 20
18 18
16 16
14 14 Hz) 12 Hz) 12
10 10
8 8 NOISE (nV/ NOISE (nV/ 6 6
4 4
2 2
0 0 0.01 0.10 1 10 100 1000 10000 0.01 0.1 1 10 100 1000 10000 FREQUENCY (MHz) FREQUENCY (MHz)
TPC 15. AD8186 Input Voltage Noise vs. Frequency TPC 18. AD8187 Input Voltage Noise vs. Frequency
REV. B –7– AD8187
10000 10000
1000 1000 ) ) 100 100
10 10 IMPEDANCE (k IMPEDANCE IMPEDANCE (k IMPEDANCE
1 1
0.1 0.1 0.1 1 10 100 1000 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 19. AD8186 Input Impedance vs. Frequency TPC 22. AD8187 Input Impedance vs. Frequency
1000 1000
100 100
10 10 IMPEDANCE ( ) IMPEDANCE IMPEDANCE ( ) IMPEDANCE
1 1
0.1 0.1 0.1 1 10 100 1000 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 20. AD8186 Enabled Output Impedance vs. Frequency TPC 23. AD8187 Enabled Output Impedance vs. Frequency
10000 10000
1000 1000 ) 100 100
10 10 IMPEDANCE (k IMPEDANCE IMPEDANCE ( ) IMPEDANCE
1 1
0.1 0.1 0.1 1.0 10.0 100.0 1000.0 0.1 1.0 10.0 100.0 1000.0 FREQUENCY (MHz) FREQUENCY (MHz) TPC 21. AD8186 Disabled Output Impedance vs. Frequency TPC 24. AD8187 Disabled Output Impedance vs. Frequency
–8– REV. B AD8187
2.80 3.30 2.8 3.2
2.70 2.7 3.1 INPUT 2.60 2.6 3.0
2.50 2.5 INPUT 2.9
2.40 2.4 2.8
2.30 2.80 2.3 2.7
2.20 2.2 2.6 OUTPUT INPUT VOLTAGE (V) VOLTAGE INPUT INPUT VOLTAGE (V) VOLTAGE INPUT OUTPUT VOLTAGE (V) VOLTAGE OUTPUT 2.10 (V) VOLTAGE OUTPUT 2.1 OUTPUT 2.5
2.00 2.0 2.4
1.90 1.9 2.3
1.80 2.30 1.8 2.2 051015 20 25 0510 15 20 25 TIME (ns) TIME (ns) TPC 25. AD8186 Small Signal Pulse Response, TPC 28. AD8187 Small Signal Pulse Response, VOUT = 200 mV p-p, RL = 1 kΩ VOUT = 200 mV p-p, RL = 150 kΩ
3.0 5.0 4.0 6.0
3.5 5.5 2.5 INPUT 4.5 3.0 5.0 2.0 4.0 2.5 INPUT 4.5 1.5 3.5 2.0 4.0
1.0 3.0 1.5 3.5
1.0 3.0 0.5 OUTPUT 2.5 INPUT VOLTAGE (V) VOLTAGE INPUT INPUT VOLTAGE (V) VOLTAGE INPUT OUTPUT VOLTAGE (V) VOLTAGE OUTPUT OUTPUT VOLTAGE (V) VOLTAGE OUTPUT 0.5 OUTPUT 2.5 0 2.0 0 2.0 1.5 –0.5 –0.5 1.5
–1.0 1.0 –1.0 1.0 051015 20 25 0510 15 20 25 TIME (ns) TIME (ns) TPC 26. AD8186 Video Signal Pulse Response, TPC 29. AD8187 Video Amplitude Pulse
VOUT = 700 mV p-p, RL = 1 kΩ Response, VOUT = 1.4 V p-p, RL = 150 kΩ
4.0 7.0 4.0 6.0 3.5 6.5 3.5 5.5 INPUT 3.0 6.0 3.0 5.0 INPUT 2.5 5.5 2.5 4.5 2.0 5.0 2.0 4.0 1.5 4.5 1.5 3.5 1.0 4.0 1.0 3.0 0.5 3.5 0.5 OUTPUT 2.5 OUTPUT INPUT VOLTAGE (V) VOLTAGE INPUT INPUT VOLTAGE (V) VOLTAGE INPUT 0 3.0 0 2.0 OUTPUT VOLTAGE (V) VOLTAGE OUTPUT OUTPUT VOLTAGE (V) VOLTAGE OUTPUT –0.5 2.5 –0.5 1.5
–1.0 2.0 –1.0 1.0 –1.5 1.5 –1.5 0.5 –2.0 1.0 –2.0 0 051015 20 25 0 510152025 TIME (ns) TIME (ns) TPC 27. AD8186 Large Signal Pulse Response, TPC 30. AD8187 Large Signal Pulse Response,
VOUT = 2 V p-p, RL = 1 kΩ VOUT = 2 V p-p, RL = 150 kΩ
REV. B –9– AD8187
tSETTLED tSETTLED OUTPUT (1mV/DIV) OUTPUT (1mV/DIV)
t0 TIME (2ns/DIV) t0 TIME (2ns/DIV) TPC 31. AD8186 Settling Time (0.1%), TPC 34. AD8187 Settling Time (0.1%), VOUT = 2 V Step, RL = 1 kΩ VOUT = 2 V Step, RL = 150 Ω
2.3 6.0 2.0 5.5 SEL A/B 1.8 5.5 1.5 5.0 SEL A/B 1.3 5.0 1.0 4.5 0.8 4.5 0.5 4.0 0.3 4.0 0 3.5 –0.3 OUTPUT 3.5 OUTPUT –0.5 3.0 –0.8 3.0 B PULSE AMPLITUDE (V) B PULSE AMPLITUDE (V) –1.0 2.5 –1.3 2.5 OUTPUT AMPLITUDE (V) OUTPUT AMPLITUDE (V) –1.5 2.0 –1.8 2.0 SELECT A/ SELECT A/ –2.3 1.5 –2.0 1.5
–2.8 1.0 –2.5 1.0 051015 20 25 051015 20 25 TIME (ns) TIME (ns) TPC 32. AD8186 Channel-to-Channel Switching TPC 35. AD8187 Channel-to-Channel Switching Time, VOUT = 2 V p-p, INA = 3.5 V, INB = 1.5 V Time, VOUT = 2 V p-p, INA = 3.0 V, INB = 2.0 V
2.0 3.0 2.00 3.00 B SEL A/ SEL A/B 1.5 2.9 1.50 2.90
1.0 2.8 1.00 2.80
0.5 2.7 0.50 2.70 OUTPUT B PULSE AMPLITUDE (V) B PULSE AMPLITUDE (V) 0 OUTPUT 2.6 0 2.60 OUTPUT AMPLITUDE (V) OUTPUT AMPLITUDE (V)
2.5 –0.50 2.50 SELECT A/ –0.5 SELECT A/
–1.0 2.4 –1.00 2.40 051015 20 25 30 35 40 45 50 051015 20 25 30 35 40 45 50 TIME (ns) TIME (ns) TPC 33. AD8186 Channel Switching Transient (Glitch), TPC 36. AD8187 Channel Switching Transient INA = INB = 0 V (Glitch), INA = INB = VREF = 0 V
–10– REV. B AD8187
2.0 5.5 2.0 6.0 OE 1.5 1.5 5.0 5.5 OE 1.0 5.0 1.0 4.5
0.5 4.5 0.5 4.0 0 4.0 0 3.5 OUTPUT OUTPUT –0.5 3.5 3.0
–0.5 OUTPUT AMPLITUDE (V) OUTPUT AMPLITUDE (V) OE PULSE AMPLITUDE (V)
OE PULSE AMPLITUDE (V) –1.0 3.0
2.5 –1.0 –1.5 2.5
–1.5 2.0 –2.0 2.0 04080120 160 200 04080120 160 200 TIME (ns) TIME – ns TPC 37. AD8186 Enable ON/OFF Time, TPC 39. AD8187 Enable ON/OFF Time, VOUT = 0 V to 1 V VOUT = 0 V to 1 V
1.5 3.0 2.00 3.00
2.9 1.50 2.90 )
OE OE V ( 1.0 2.8 1.00 2.80
2.7 0.50 2.70
0.5 2.6 0 2.60
OUTPUT AMPLITUDE (V) OUTPUT OUTPUT AMPLITUDE OE PULSE AMPLITUDE (V) OUTPUT OE PULSE AMPLITUDE (V) 2.5 –0.50 2.50
0 2.4 –1.00 2.40 051015 20 25 30 35 40 45 50 01020304051525354550 TIME (ns) TIME (ns) TPC 38. AD8186 Channel Enable/Disable TPC 40. AD8187 Channel Enable/Disable Transient (Glitch) Transient (Glitch)
REV. B –11– AD8187
THEORY OF OPERATION The peak slew rate is not the same as the average slew rate. The The AD8186 (G = +1) and AD8187 (G = +2) are single-supply, average slew rate is typically specified as the ratio triple 2:1 multiplexers with TTL compatible global input switch- V ing and output-enable control. Optimized for selecting between ∆ OUT two RGB (red, green, blue) video sources, the devices have high ∆ t peak slew rates, maintaining their bandwidth for large signals. measured between the 20% to 80% output levels of a suffi- Additionally, the multiplexers are compensated for high phase ciently large output pulse. For a natural response, the peak slew margin, minimizing overshoot for good pixel resolution. The rate may be 2.7 times larger than the average slew rate. There- multiplexers also have respectable video specifications and are fore, calculating a full power bandwidth with a specified average superior for switching NTSC or PAL composite signals. slew rate will give a pessimistic result. In specifying the large The multiplexers are organized as three independent channels, signal performance of these multiplexers, we’ve published the each with two input transconductance stages and one output large-signal bandwidth, the average slew rate, and the measure- transimpedance stage. The appropriate input transconductance ments of the total harmonic distortion. (Large signal bandwidth stages are selected via one logic pin (SEL A/B) such that all is defined as the –3 dB point measured on a 2 V p-p output three outputs switch input connections simultaneously. The sine wave.) Specifying these three aspects of the signal path’s unused input stages are disabled with a proprietary clamp cir- large signal dynamics allows the user to predict system behavior cuit to provide excellent crosstalk isolation between “on” and for either pulse or sinusoid waveforms. “off” inputs while protecting the disabled devices from damag- Single-Supply Considerations ing reverse base-emitter voltage stress. No additional input buffering is necessary, resulting in low input capacitance and DC-Coupled Inputs, Integrated Reference Buffers, and high input impedance without additional signal degradation. Selecting the VREF Level on the AD8187, (G = +2) The AD8186 and AD8187 offer superior large signal dynamics. The transconductance stage, a high slew rate, class AB circuit, The trade-off is that the input and output compliance is limited sources signal current into a high impedance node. Each output to ~1.3 V from either rail when driving a 150 ⍀ load. These stage contains a compensation network and is buffered to the sections address some challenges of designing video systems output by a complementary emitter-follower stage. Voltage within a single 5 V supply. feedback sets the gain, with the AD8186 configured as a unity gain follower and the AD8187 as a gain-of-two amplifier with a The AD8186 feedback network. This architecture provides drive for a reverse- The AD8186 is internally wired as a unity-gain follower. Its terminated video load (150 ⍀) with low differential gain and inputs and outputs can both swing to within ~1.3 V of either phase errors while consuming relatively little power. Careful rail. This affords the user 2.4 V of dynamic range at input and chip layout and biasing result in excellent crosstalk isolation output, which should be enough for most video signals, whether between channels. the inputs are ac- or dc-coupled. In both cases, the choice of output termination voltage will determine the quiescent load High Impedance, Output Disable Feature, and Off Isolation current. The output-enable logic pin (OE) controls whether the three outputs are enabled or disabled to a high impedance state. For improved supply rejection, the VREF pin should be tied to The high impedance disable allows larger matrices to be built an ac ground (the more quiet supply is a good bet). Internally, by busing the outputs together. In the case of the AD8187 the VREF pin connects to one terminal of an on-chip capacitor. (G = +2), a feedback isolation scheme is used so that the The capacitor’s other terminal connects to an internal node. impedance of the gain-of-two feedback network does not load The consequence of building this bypass capacitor on-chip is the output. When not in use, the outputs can be disabled to twofold. First, the VREF pin on the AD8186 draws no input bias reduce power consumption. current. (Contrast this to the case of the AD8187, where the VREF pin typically draws 2 µA of input bias current). Second, The reader may have noticed that the off isolation performance of on the AD8186, the VREF pin may be tied to any voltage within the signal path is dependent upon the value of the load resistor, the supply range. RL. For calculating off isolation, the signal path may be modeled as a simple high-pass network with an effective capacitance of AD8186 3 fF. Off isolation will improve as the load resistance is decreased. In MUX SYSTEM the case of the AD8186, off isolation is specified with a 1 k IN0A Ω OUT0 load. However, a practical application would likely gang the IN0B outputs of multiple muxes. In this case, the proper load resistance IN1A OUT1 for the off isolation calculation is the output impedance of an IN1B enabled AD8186, typically less than a 10th of an ohm. IN2A OUT2 Full Power Bandwidth vs. –3 dB Large Signal Bandwidth IN2B Note that full power bandwidth for an undistorted sinusoidal signal “C_BYPASS” VREF is often calculated using the peak slew rate from the equation INTERNAL CAP Peak Slew Rate Full Power Bandwidth = BIAS REFERENCE 2π×Sinusoid Amplitude DIRECT CONNECTION TO ANY “QUIET” AC GROUND (FOR EXAMPLE, GND, VCC, VEE)
Figure 3. VREF Pin Connection for AD8186 (Differs from AD8187)
–12– REV. B AD8187
The AD8187 3) To maximize the output dynamic range, the reference voltage The AD8187 uses on-chip feedback resistors to realize the gain- should be chosen with some care. of-two function. To provide low crosstalk and a high output For example, consider amplifying a 700 mV video signal with a impedance when disabled, each set of 500 Ω feedback resistors is sync pulse 300 mV below black level. The user might decide to set terminated by a dedicated reference buffer. A reference buffer is VREF at black level to preferentially run video signals on the faster a high speed op amp configured as a unity-gain follower. The NPN transistor path. The AD8186 would, in this case, allow a three reference buffers, one for each channel, share a single, high reference voltage as low as 1.3 V + 300 mV = 1.6 V. If the AD8187 impedance input, the VREF pin (see Figure 4). VREF input bias is used, the sync pulse would be amplified to 600 mV. Therefore, current is typically less than 2 µA. the lower limit on VREF becomes 1.3 V + 600 mV = 1.9 V. For routing RGB video, an advantageous configuration would be to 5V A0 employ +3 V and –2 V supplies, in which case VREF could be OUT 0 tied to ground. 1 If system considerations prevent running the multiplexer on split 5V B0 supplies, a false ground reference should be employed. A low
500 impedance reference may be synthesized with a second opera- VFO tional amplifier. Alternately, a well bypassed resistor divider 5V may serve. Refer to the Application section for further explana- V GBUF 0 500 REF tion and more examples.
VF-1 5V 5V GBUF 1 OUT1 10k 500 500 100k VF-2 5V 0.022 F GBUF 2 V OUT2 REF 100 500 500 OP21 1 F
1 F Figure 4. Conceptual Diagram of a Single Multiplexer Channel, G = +2 FROM 1992 ADI AMPLIFIER This configuration has a few implications for single-supply APPLICATIONS GUIDE operation: GND Figure 6a. Synthesis of a False Ground Reference 1) On the AD8187, VREF may not be tied to the most negative analog supply, VEE. 5V Limits on Reference Voltage (AD8187, see Figure 5):
10k VVVVVEE +<<13.–.REF CC 16