19-3240; Rev 0; 3/04 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps The MAX4028/MAX4029 are 5V, triple/quad, 2:1 voltagefeedback multiplexer-amplifiers with input clamps and a fixed gain of +2V/V (6dB). Channel 1 (IN1A and IN1B) inputs are clamped to the video sync tip of the input signal, while the remaining inputs can be clamped to either the video sync tip or the video sync of channel 1 (IN1_). The latter is referred to as a key clamp and is pin selectable. Selectable clamp/key-clamp inputs and fixed-gain video output buffers make the MAX4028/MAX4029 ideal for video-source switching applications such as automotive entertainment systems, video projectors, and displays/TVs. Both devices have 20ns channel switching times and low ±10mVP-P switching transients, making them ideal for high-speed video switching applications such as on-screen display (OSD) insertion. The MAX4028/MAX4029 have a -3dB large-signal (2VP-P) bandwidth of 130MHz, a -3dB small-signal bandwidth of 210MHz, and a 300V/µs slew rate. Low differential gain and phase errors of 0.2% and 0.4°, respectively, make these devices ideal for broadcast video applications. The MAX4028/MAX4029 are specified over the -40°C to +85°C extended temperature range and are offered in 16-pin and 20-pin TSSOP/SO packages. Features ♦ Single +5V Operation ♦ Independently Selectable Sync-Tip or Key-Clamp Inputs ♦ Adjustable Key-Clamp Voltage ♦ 130MHz Large-Signal -3dB Bandwidth ♦ 210MHz Small-Signal -3dB Bandwidth ♦ 300V/µs Slew Rate ♦ 20ns Switching Time ♦ Ultra-Low ±10mVP-P Switching Transient ♦ 0.2% Differential Gain/0.4° Phase Error ♦ Low-Power, High-Impedance Disable Mode Ordering Information PART TEMP RANGE PIN-PACKAGE MAX4028EUE -40°C to +85°C 16 TSSOP MAX4028EWE -40°C to +85°C 16 Wide SO MAX4029EUP -40°C to +85°C 20 TSSOP MAX4029EWP -40°C to +85°C 20 Wide SO Typical Operating Circuit Applications In-Car Navigation/Entertainment A/B Blade Servers 75Ω CABLE Security Systems 75Ω CABLE Set-Top Boxes CIN 0.1µF 75Ω CABLE Video Crosspoint Switching PART NO. OF 2:1 MUX-AMPS GAIN MAX4028 3 2V/V MAX4029 4 2V/V 75Ω CABLE 75Ω 0.01µF IN1B OUT1 75Ω 75Ω CABLE OUT2 75Ω 75Ω CABLE 1kΩ 1kΩ CIN 0.1µF IN2A CLAMP 75Ω Selector Guide 0.1µF CLAMP 75Ω Notebook Computers MAX4028 MAX4029 CLAMP 75Ω Broadcast and Graphics Video VCC IN1A Video Projectors Displays and Digital Televisions +5V CIN 0.1µF CIN 0.1µF IN2B 1kΩ CLAMP 1kΩ DISABLE KEYREF RKEYREF 6kΩ KEY/CLAMP CONTROL CLAMP/KEY_2 Pin Configurations appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX4028/MAX4029 General Description MAX4028/MAX4029 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to GND) ..................................-0.3V to +6V IN_A, IN_B, OUT_.......................................-0.3V to (VCC + 0.3V) DISABLE, A/B, KEYREF, CLAMP/KEY_......-0.3V to (VCC + 0.3V) Current Into IN_A, IN_B ...................................................±0.5mA Short-Circuit Duration (VOUT to GND)........................Continuous Short-Circuit Duration (VOUT to VCC) .............................(Note 1) Continuous Power Dissipation (TA = +70°C) 16-Pin TSSOP (derate 9.4mW/°C above +70°C) .........755mW 16-Pin Wide SO (derate 9.5mW/°C above +70°C) ......762mW 20-Pin TSSOP (derate 11mW/°C above +70°C) ..........879mW 20-Pin Wide SO (derate 10mW/°C above +70°C) .......800mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Do not short VOUT to VCC. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC ELECTRICAL CHARACTERISTICS (VCC = +5V, GND = 0V, RL = 150Ω to GND, VDISABLE = +5V, RKEYREF = 6kΩ, CIN = 0.1µF to GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER SYMBOL Operating Supply Voltage Range VCC Quiescent Supply Current ICC Disable Supply Current Output Clamp Voltage CONDITIONS Guaranteed by PSRR TYP 4.5 MAX UNITS 5.5 V MAX4028, RL = ∞ 29 40 MAX4029, RL = ∞ 38 55 MAX4028 9 15 MAX4029 11 20 0.4 0.48 VDISABLE = 0V VCLAMP MIN Clamp (Note 3) 0.32 Key clamp (Note 4) 1.1 mA V Input Clamping Current IIN Input voltage = input clamp + 0.5V 5 Clamp Voltage Matching ∆VCLAMP Measured at output 10 mV Clamp Voltage Drift TCVCLAMP Measured at output 80 µV/°C MΩ Input Resistance 18 mA µA RIN 7 Output Resistance ROUT 0.7 Ω Disable Output Resistance ROUT VDISABLE = 0V 2 kΩ Power-Supply Rejection Ratio PSRR 4.5V < VCC < 5.5V (Note 5) Voltage Gain AVCL Channel-to-Channel Gain Matching 48 58 1.9 2.0 2.1 V/V ±1 ±2 % ∆AVCL Output-Voltage High VOH Output-Voltage Low VOL Output Current IOUT dB VCLAMP + 2.4 V VCLAMP 30 V mA LOGIC INPUT CHARACTERISTICS (DISABLE , A/B, CLAMP/KEY_) Logic-Low Threshold VIL Logic-High Threshold VIH Logic-Low Input Current IIL VIL = 0V Logic-High Input Current IIH VIH = VCC 2 0.8 V 6.6 25 µA 1.2 25 µA 2.0 V _______________________________________________________________________________________ Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps (VCC = +5V, GND = 0V, RL = 150Ω to GND, VDISABLE = +5V, RKEYREF = 6kΩ, CIN = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Small-Signal -3dB Bandwidth BWSS VOUT = 100mVP-P 210 MHz Large-Signal -3dB Bandwidth BWLS VOUT = 2VP-P 130 MHz Small-Signal 0.1dB Gain Flatness Bandwidth BW0.1dBSS VOUT = 100mVP-P 30 MHz Large-Signal 0.1dB Gain Flatness Bandwidth BW0.1dBLS VOUT = 2VP-P 30 MHz SR VOUT = 2VP-P 300 V/µs Slew Rate Settling Time to 0.1% VOUT = 2V step 20 ns PSRR f = 100kHz 55 dB Output Impedance ZO f = 100kHz 0.7 Ω Differential Gain Error DG 5-step modulated staircase 0.2 % Differential Phase Error DP 5-step modulated staircase 0.4 degrees f = 3.58MHz or 4.43MHz 1.0 ns Power-Supply Rejection Ratio Group Delay tS D/dT Peak Signal to RMS Noise Channel-to-Channel Crosstalk A/B Crosstalk Off-Isolation 100kHz to 30MHz 70 dB XTALK SNR f = 100kHz 73 dB XTALKAB f = 100kHz 91 dB VOUT_ = 2VP-P, f = 100kHz 108 AISO Droop DR Guaranteed by input clamp current dB 2 % SWITCHING CHARACTERISTICS Channel Switching Time tSW 20 ns Enable Time tON 0.1 µs Disable Time tOFF 0.1 µs ±10 mVP-P Switching Transient Note 2: All devices are 100% production tested at TA = +25°C. Specifications over temperature are guaranteed by design. Note 3: The clamp voltage at the input is VCLAMP (measured at the output) divided by gain + VBE. Note 4: The key-clamp voltage is above the sync-tip clamp voltage by approximately 0.7V, and is adjusted by varying RKEYREF. Note 5: Measured at f = 100Hz at thermal equilibrium. _______________________________________________________________________________________ 3 MAX4028/MAX4029 AC ELECTRICAL CHARACTERISTICS Typical Operating Characteristics (VCC = +5V, GND = 0V, VDISABLE = +5V, RL = 150Ω to GND, CIN = 0.1µF, RKEYREF = 6.04kΩ ±1%, TA = +25°C, unless otherwise noted.) 6.2 5 4 3 2 1 6.0 5.8 5.7 5.6 5.5 5.4 -1 5.3 -2 8 1M 10M 100M 1G 6 5 4 3 2 1 0 -1 -2 100k 1M 10M 1G 100M 100k 1M 100M FREQUENCY (Hz) LARGE-SIGNAL GAIN FLATNESS vs. FREQUENCY DIFFERENTIAL GAIN AND PHASE POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 5.9 5.8 5.7 5.6 5.5 5.4 5.2 1M 10M 100M 1G 1G MAX4028 toc06 0 -10 -20 1st 0.06 0.04 0.02 0 -0.02 -0.04 -0.06 2nd 3rd 4th 5th PSRR (dB) 6.0 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 MAX4028 toc05 MAX4028 toc04 VOUT = 2VP-P DIFFERENTIAL PHASE (deg) DIFFERENTIAL GAIN (%) FREQUENCY (Hz) 5.3 6th -30 -40 -50 -60 1st 2nd 3rd 4th 5th -70 6th 1k 10k 100k FREQUENCY (Hz) 1M 10M 100M 1G FREQUENCY (Hz) -20 0 MAX4028 toc08 0 MAX4028 toc07 0 ALL-HOSTILE CROSSTALK (A TO B ON ANY CHANNEL) vs. FREQUENCY ALL-HOSTILE CROSSTALK (CHANNEL TO CHANNEL) vs. FREQUENCY -10 -10 -20 CROSSTALK (dB) -60 -80 CROSSTALK (dB) -20 -40 -30 -40 -50 MAX4028 toc09 OFF-ISOLATION vs. FREQUENCY -30 -40 -50 -60 -70 -100 -60 -80 -120 -70 -90 -140 -80 -100 100k 1M 10M FREQUENCY (Hz) 4 10M FREQUENCY (Hz) 6.2 100k VOUT = 2VP-P 7 5.2 100k LARGE-SIGNAL GAIN FLATNESS (dB) 5.9 0 6.1 VOUT = 100mVP-P 6.1 MAX4028 toc03 6 LARGE-SIGNAL BANDWIDTH vs. FREQUENCY MAX4028 toc02 VOUT = 100mVP-P GAIN FLATNESS (dB) SMALL-SIGNAL BANDWIDTH (dB) 7 MAX4028 toc01 8 SMALL-SIGNAL GAIN FLATNESS vs. FREQUENCY LARGE-SIGNAL BANDWIDTH (dB) SMALL-SIGNAL BANDWIDTH vs. FREQUENCY OFF-ISOLATION (dB) MAX4028/MAX4029 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps 100M 1G 10k 100k 1M 10M FREQUENCY (Hz) 100M 1G 100k 1M 10M FREQUENCY (Hz) _______________________________________________________________________________________ 100M 1G Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps OUTPUT IMPEDANCE vs. FREQUENCY INPUT-VOLTAGE NOISE DENSITY vs. FREQUENCY 1 MAX4028 toc12 0.1 MAX4028 toc11 MAX4028 toc10 10 LARGE-SIGNAL TRANSIENT RESPONSE 1000 INPUT-VOLTAGE NOISE DENSITY (nV/√Hz) OUTPUT IMPEDANCE (Ω) 100 VIN 500mV/div 1.6VDC 100 10 VOUT 1V/div 1 10k 100k 1M 10M 100M 1G 1 10 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) SMALL-SIGNAL TRANSIENT RESPONSE CHANNEL-SWITCHING TRANSIENT MAX4028 toc13 1M 10ns/div CHANNEL-SWITCHING TIME (CHA = 1.5VDC, CHB = 1VDC) MAX4028 toc15 MAX4028 toc14 5VDC 5VDC VIN 25mV/div 1.6VDC A/B 2.5V/div A/B 2.5V/div 0VDC 0VDC VOUT 500mV/div VOUT 20mV/div 20ns/div 20ns/div ENABLE RESPONSE TIME (VOUT = 0.5V) SMALL-SIGNAL BANDWIDTH vs. FREQUENCY 0VDC 0.5VDC VOUT 250mV/div 0VDC CLOAD = 15pF 10 SMALL-SIGNAL BANDWIDTH (dB) 5VDC ENABLE 2.5V/div MAX4028 toc17 11 MAX4028 toc16 OPTIMAL ISOLATION RESISTANCE vs. CAPACITIVE LOAD 9 CLOAD = 10pF 8 7 6 5 4 CLOAD = 5pF 3 2 1 50ns/div 30 MAX4028 toc18 10ns/div OPTIMAL ISOLATION RESISTANCE (Ω) SIGNAL 2 50mV/div 25 20 15 10 5 0 100k 1M 10M FREQUENCY (Hz) 100M 1G 0 50 100 150 200 250 CLOAD (pF) _______________________________________________________________________________________ 5 MAX4028/MAX4029 Typical Operating Characteristics (continued) (VCC = +5V, GND = 0V, VDISABLE = +5V, RL = 150Ω to GND, CIN = 0.1µF, RKEYREF = 6.04kΩ ±1%, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +5V, GND = 0V, VDISABLE = +5V, RL = 150Ω to GND, CIN = 0.1µF, RKEYREF = 6.04kΩ ±1%, TA = +25°C, unless otherwise noted.) KEY-CLAMP REFERENCE VOLTAGE vs. RKEYREF CLAMP VOLTAGE vs. TEMPERATURE 0.41 0.40 0.39 0.38 MAX4028 toc20 0.42 1.8 KEY-CLAMP REFERENCE VOLTAGE (V) MAX4028 toc19 0.43 CLAMP VOLTAGE (V) MAX4028/MAX4029 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0.37 -50 -25 0 25 50 75 100 1 3 5 7 9 11 13 RKEYREF (kΩ) TEMPERATURE (°C) Pin Description PIN MAX4028 6 MAX4029 NAME FUNCTION — 1 IN4A Amplifier Input 4A 1 2 IN3A Amplifier Input 3A 2 3 IN2A Amplifier Input 2A 3 4 IN1A Amplifier Input 1A Channel-Select Input. Drive A/B high or leave floating to select channel A. Drive A/B low to select channel B. 4 5 A/B 5 6 KEYREF 6 7 IN1B Amplifier Input 1B 7 8 IN2B Amplifier Input 2B 8 9 IN3B Amplifier Input 3B — 10 IN4B Amplifier Input 4B — 11 OUT4 Amplifier Output 4 9 12 CLAMP/KEY_3 10 13 GND Ground 11 14 OUT3 Amplifier Output 3 12 15 CLAMP/KEY_2 13 16 OUT2 14 17 VCC Key-Clamp Reference Output. Connect an external resistor from KEYREF to GND to generate the key-clamp voltage. Output 3 Clamp or Key-Clamp Input. Drive CLAMP/KEY_3 high to clamp OUT3. Drive CLAMP/KEY_3 low to key clamp OUT3. Output 2 Clamp or Key-Clamp Input. Drive CLAMP/KEY_2 high to clamp OUT2. Drive CLAMP/KEY_2 low to key clamp OUT2. Amplifier Output 2 Power-Supply Voltage. Bypass VCC to GND with 0.1µF and 0.01µF capacitors as close to the pin as possible. _______________________________________________________________________________________ Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps PIN NAME MAX4028 MAX4029 15 18 OUT1 16 19 DISABLE — 20 CLAMP/KEY_4 FUNCTION Amplifier Output 1 Disable Input. Pull DISABLE high for normal operation. Drive DISABLE low to disable all outputs. Output 4 Clamp or Key-Clamp Input. Drive CLAMP/KEY_4 high to clamp OUT4. Drive CLAMP/KEY_4 low to key clamp OUT4. Detailed Description VCC IN1A CLAMP OUT1 IN1B 1kΩ CLAMP 1kΩ IN2A CLAMP/ KEY CLAMP OUT2 IN2B 1kΩ CLAMP/ KEY CLAMP 1kΩ CLAMP/KEY_2 IN3A CLAMP/ KEY CLAMP OUT3 IN3B 1kΩ CLAMP/ KEY CLAMP Sync Tip and Key Clamps 1kΩ CLAMP/KEY_3 A/B IN4A CLAMP/ KEY CLAMP OUT4 IN4B 1kΩ CLAMP/ KEY CLAMP 1kΩ CLAMP/KEY_4 KEYREF The MAX4028/MAX4029 are 5V, triple/quad, 2:1 voltagefeedback multiplexer-amplifiers with input clamps and a fixed gain of +2V/V (6dB). Channel 1 (IN1A and IN1B) inputs are clamped to the video sync tip of the input IN1_ channel, while the remaining inputs can be clamped to either the video sync tip of the respective input channel (IN_A and IN_B) or the video sync of channel 1 (IN1_). The latter is referred to as a key clamp and is pin selectable. Selectable clamp/keyclamp inputs and fixed-gain video output buffers make the MAX4028/MAX4029 ideal for video-source switching applications such as automotive entertainment systems, video projectors, and displays/TVs. Both devices have 20ns channel switching times and low ±10mVP-P switching transients, making them ideal for both high-speed video switching applications such as OSD insertion. The MAX4028/MAX4029 have a -3dB large-signal (2VP-P) bandwidth of 130MHz, a -3dB small-signal bandwidth of 210MHz, and a 300V/µs slew rate. Low differential gain and phase errors of 0.2% and 0.4°, respectively, make these devices ideal for broadcast video applications. CLAMP VOLTAGE DISABLE MAX4029 GND Figure 1. MAX4029 Functional Diagram The MAX4028/MAX4029 have AC-coupled inputs, with either a sync tip or key clamp to provide bias for the video signal. Channel 1 of the MAX4028/MAX4029 always has a sync tip clamp at the input, while the remaining channels are selectable as either sync tip or key clamps to accommodate the various video waveforms (see the Clamp/Key-Clamp Settings for Video Formats section). The value of the sync-tip clamp voltage is set internally for the lowest value, consistent with linear operation, and cannot be adjusted. The key-clamp voltage is adjustable, to compensate for variations in the voltage between component video inputs such as Linear RGB, YPbPr, and Y-C, by varying RKEYREF. The keyclamp voltage can be computed from: VKey-Clamp = 0.40 + 2000/[(5000 x RKEYREF) / (5000 + RKEYREF)] _______________________________________________________________________________________ 7 MAX4028/MAX4029 Pin Description (continued) Therefore, a 6kΩ resistor will produce a 1.13V keyclamp voltage as shown in Figure 2. The clamp voltage (VCLAMP) is measured at the output; the voltage at the input is VCLAMP (sync tip or key clamp) divided by the gain (+2V/V) + VBE. In order for these clamps (sync tip or key) to work properly, the input must be coupled with a 0.1µF capacitor (typ) with low leakage (<1µA to 2µA, max). Without proper coupling, the clamp voltage will change during the horizontal line time causing the “black level” to vary, changing the image brightness from left to right on the display. In addiKEY-CLAMP REFERENCE VOLTAGE vs. RKEYREF MAX4028 fig02 1.8 KEY-CLAMP REFERENCE VOLTAGE (V) MAX4028/MAX4029 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps 1.6 1.4 1.2 tion to the capacitor, a low resistance (≤75Ω) is required on the source side to return the capacitor to ground. The clamps used here are active devices with the coupling capacitor serving two functions; first, as a charge reservoir to maintain the clamp voltage, and second, as the compensation capacitor for the clamp itself. If an input is not used, it must be terminated to avoid causing oscillations that could couple with another input. In general, a sync-tip clamp is used for composite video (Cvbs), gamma corrected primaries (R’G’B’), and the luma signal (Y) in S-video. A key clamp is preferred for component color difference signals (Pb and Pr), linear primaries (RGB in PCs), and chroma (C) in S-video. The rule is to sync tip clamp a signal if sync is present and key clamp all others. Several examples are given in the Clamp/Key-Clamp Settings for Video Formats section. Clamp/Key-Clamp Settings for Video Formats Tables 1 and 2 provide the clamp settings on the MAX4028/MAX4029 to interface with various video formats. 1.0 Low-Power, High-Impedance Disable Mode 0.8 All parts feature a low-power, high-impedance disable mode that is activated by driving the DISABLE input low. Placing the amplifier in disable mode reduces the quiescent supply current and places the output impedance at 2kΩ typically. Multiple devices can be paralleled to construct larger switch matrices by connecting the outputs of several devices together and disabling all but one of the paralleled amplifiers’ outputs. 0.6 0.4 0.2 0 1 3 5 7 9 11 13 RKEYREF (kΩ) Figure 2. Key-Clamp Reference Voltage vs. RKEYREF Table 1. MAX4028 Clamp Settings for Video Formats INPUT FORMAT CLAMP/KEY INPUT FORMAT CLAMP/KEY 1 Cvbs1 Clamp 1 Y Clamp 2 Cvbs2 Clamp 2 C Key 3 Cvbs3 Clamp 3 Cvbs Clamp INPUT FORMAT CLAMP/KEY INPUT FORMAT CLAMP/KEY 1 G’ Clamp 1 Y Clamp 2 B’ Clamp 2 Pb Key 3 R’ Clamp 3 Pr Key INPUT FORMAT CLAMP/KEY 1 Gs Clamp 2 B Key 3 R Key R, G, B have sync on all. Gs, B, R have sync only on Green. 8 _______________________________________________________________________________________ Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps INPUT FORMAT CLAMP/KEY INPUT FORMAT CLAMP/KEY 1 Cvbs1 Clamp 1 Gs Clamp 2 Cvbs2 Clamp 2 R Key 3 Cvbs3 Clamp 3 B Key 4 Cvbs4 Clamp 4 Cvbs Clamp MAX4028/MAX4029 Table 2. MAX4029 Clamp Settings for Video Formats Gs, B, R have sync only on Green. INPUT FORMAT CLAMP/KEY INPUT FORMAT CLAMP/KEY 1 H-Sync Clamp 2 G Key 1 Y Clamp 2 Pr 3 B Key Key 3 Pb Key 4 R R, G, B have sync on none. Key 4 Cvbs Clamp INPUT FORMAT CLAMP/KEY INPUT FORMAT CLAMP/KEY 1 Y Clamp 1 Cvbs Clamp 2 C Key 2 G’ Clamp 3 Cvbs Clamp 3 B’ Clamp 4 Cvbs Clamp 4 R’ Clamp R, G, B have sync on all. The MAX4028/MAX4029 have a fixed gain of +2V/V that is internally set with two 1kΩ thin-film resistors. The impedance of the internal feedback resistors must be taken into account when operating multiple MAX4028/ MAX4029s in large multiplexer applications. A/B 75Ω CABLE DISABLE 0.1µF IN_A OUT_ RT 75Ω RT 75Ω 75Ω CABLE Applications Information 75Ω CABLE Video Line Driver The MAX4028/MAX4029 are well suited to drive coaxial transmission lines when the cable is terminated at both ends, as shown in Figure 3, where the fixed gain of +2V/V compensates for the loss in the resistors, RT. Driving Capacitive Loads A correctly terminated transmission line is purely resistive and presents no capacitive load to the amplifier. Reactive loads decrease phase margin and may produce excessive ringing and oscillation. Another concern when driving capacitive loads is the amplifier’s output impedance, which appears inductive at high frequencies. This inductance forms an L-C reso- RT 75Ω 0.1µF IN_B RT 75Ω RKEYREF CLAMP MAX4028 MAX4029 Figure 3. Video Line Driver nant circuit with the capacitive load, which causes peaking in the frequency response and degrades the amplifier’s phase margin. _______________________________________________________________________________________ 9 SMALL-SIGNAL BANDWIDTH vs. FREQUENCY OPTIMAL ISOLATION RESISTANCE vs. CAPACITIVE LOAD CLOAD = 10pF 8 7 6 5 4 CLOAD = 5pF 3 2 1 1M 10M 100M 1G A/B DISABLE 5 50 100 150 200 250 Figure 6. Optimal Isolation Resistance vs. Capacitive Load Layout and Power-Supply Bypassing IN_A OUT_ RISO CL RL 0.1µF IN_B CLAMP MAX4028 MAX4029 Figure 5. Using an Isolation Resistor (R ISO ) for a HighCapacitive Load Although the MAX4028/MAX4029 are optimized for AC performance and are not designed to drive highly capacitive loads, they are capable of driving up to 15pF without oscillations. However, some peaking may occur in the frequency domain (Figure 4). To drive larger capacitive loads or to reduce ringing, add an isolation resistor between the amplifier’s output and the load (Figure 5). The value of RISO depends on the circuit’s 10 10 gain (+2V/V) and the capacitive load (Figure 6). Also note that the isolation resistor forms a divider that decreases the voltage delivered to the load. 0.1µF RT 75Ω RKEYREF 15 CLOAD (pF) Figure 4. Small-Signal Gain vs. Frequency with Capacitive Load and No Isolation Resistor RT 75Ω 20 0 FREQUENCY (Hz) 75Ω CABLE 25 0 100k 75Ω CABLE MAX4028 fig06 9 OPTIMAL ISOLATION RESISTANCE (Ω) CLOAD = 15pF 10 30 MAX4028 fig04 11 SMALL-SIGNAL BANDWIDTH (dB) MAX4028/MAX4029 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps The MAX4028/MAX4029 have high bandwidths and consequently require careful board layout, including the possible use of constant-impedance microstrip or stripline techniques. To realize the full AC performance of these high-speed amplifiers, pay careful attention to power-supply bypassing and board layout. The PC board should have at least two layers: a signal and power layer on one side, and a large, low-impedance ground plane on the other side. The ground plane should be as free of voids as possible. Whether or not a constant-impedance board is used, it is best to observe the following guidelines when designing the board: 1) Do not use wire-wrapped boards or breadboards. 2) Do not use IC sockets; they increase parasitic capacitance and inductance. 3) Keep signal lines as short and straight as possible. Do not make 90° turns; round all corners. 4) Observe high-frequency bypassing techniques to maintain the amplifier’s accuracy and stability. 5) Use surface-mount components. They generally have shorter bodies and lower parasitic reactance, yielding better high-frequency performance than through-hole components. ______________________________________________________________________________________ Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps directly from the capacitor to the VCC pin. To minimize parasitic inductance, keep PC traces short and use surface-mount components. If input termination resistors and output back-termination resistors are used, they should be surface-mount types, and should be placed as close to the IC pins as possible. Pin Configurations TOP VIEW IN4A 1 20 CLAMP/KEY_4 IN3A 1 16 DISABLE IN3A 2 19 DISABLE IN2A 2 15 OUT1 IN2A 3 18 OUT1 14 VCC IN1A 4 17 VCC 13 OUT2 A/B 5 IN1A 3 A/B 4 MAX4028 12 CLAMP/KEY_2 KEYREF 5 MAX4029 16 OUT2 15 CLAMP/KEY_2 KEYREF 6 14 OUT3 IN1B 6 11 OUT3 IN1B 7 IN2B 7 10 GND IN2B 8 13 GND IN3B 8 9 IN3B 9 12 CLAMP/KEY_3 IN4B 10 11 OUT4 CLAMP/KEY_3 TSSOP/SO TSSOP/SO Chip Information TRANSISTOR COUNT: 1032 PROCESS: Bipolar ______________________________________________________________________________________ 11 MAX4028/MAX4029 The bypass capacitors should include a 0.1µF, ceramic surface-mount capacitor between VCC and the ground plane, located as close to the package as possible. Optionally, place a 10µF capacitor at the power supply’s point-of-entry to the PC board to ensure the integrity of incoming supplies. The power-supply traces should lead Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) TSSOP4.40mm.EPS MAX4028/MAX4029 Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps 12 ______________________________________________________________________________________ Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps E DIM A A1 B C e E H L H MAX MIN 0.104 0.093 0.012 0.004 0.019 0.014 0.013 0.009 0.050 0.299 0.291 0.394 0.419 0.050 0.016 SOICW.EPS INCHES N MILLIMETERS MIN 2.35 0.10 0.35 0.23 MAX 2.65 0.30 0.49 0.32 1.27 7.40 7.60 10.00 10.65 0.40 1.27 VARIATIONS: 1 INCHES TOP VIEW DIM D D D D D D A B e MIN 0.398 0.447 0.496 0.598 0.697 MAX 0.413 0.463 0.512 0.614 0.713 MILLIMETERS MIN 10.10 11.35 12.60 15.20 17.70 MAX 10.50 11.75 13.00 15.60 18.10 N MS013 16 AA 18 AB 20 AC 24 AD 28 AE C 0 -8 A1 L FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, .300" SOIC APPROVAL DOCUMENT CONTROL NO. 21-0042 REV. B 1 1 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX4028/MAX4029 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)