View MAX4028_47232.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-3240; Rev 0; 3/04
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
General Description
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/s 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 -40C to +85C extended temperature range and are offered in 16-pin and 20-pin TSSOP/SO packages.
Features
o Single +5V Operation o Independently Selectable Sync-Tip or Key-Clamp Inputs o Adjustable Key-Clamp Voltage o 130MHz Large-Signal -3dB Bandwidth o 210MHz Small-Signal -3dB Bandwidth o 300V/s Slew Rate o 20ns Switching Time o Ultra-Low 10mVP-P Switching Transient o 0.2% Differential Gain/0.4 Phase Error o Low-Power, High-Impedance Disable Mode
MAX4028/MAX4029
Ordering Information
PART MAX4028EUE MAX4028EWE MAX4029EUP MAX4029EWP TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 16 TSSOP 16 Wide SO 20 TSSOP 20 Wide SO
Applications
In-Car Navigation/Entertainment Blade Servers Security Systems Video Projectors
75 75 CABLE CIN 0.1F
Typical Operating Circuit
A/B VCC IN1A CLAMP CIN 0.1F OUT1 75 IN1B CLAMP 1k CIN 0.1F IN2A CLAMP CIN 0.1F OUT2 75 IN2B CLAMP 1k KEYREF RKEYREF 6k KEY/CLAMP CONTROL CLAMP/KEY_2 DISABLE 1k 75 CABLE 1k 75 CABLE +5V
MAX4028 MAX4029
0.1F
0.01F
Displays and Digital Televisions Broadcast and Graphics Video Set-Top Boxes Notebook Computers Video Crosspoint Switching
75 CABLE 75 CABLE
75
75
Selector Guide
PART MAX4028 MAX4029 NO. OF 2:1 MUX-AMPS 3 4 GAIN 2V/V 2V/V
75 CABLE
75
Pin Configurations appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1
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.
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps MAX4028/MAX4029
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 = +70C) 16-Pin TSSOP (derate 9.4mW/C above +70C) .........755mW 16-Pin Wide SO (derate 9.5mW/C above +70C) ......762mW 20-Pin TSSOP (derate 11mW/C above +70C) ..........879mW 20-Pin Wide SO (derate 10mW/C above +70C) .......800mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = 150 to GND, VDISABLE = +5V, RKEYREF = 6k, CIN = 0.1F to GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER Operating Supply Voltage Range Quiescent Supply Current Disable Supply Current Output Clamp Voltage Input Clamping Current Clamp Voltage Matching Clamp Voltage Drift Input Resistance Output Resistance Disable Output Resistance Power-Supply Rejection Ratio Voltage Gain Channel-to-Channel Gain Matching Output-Voltage High Output-Voltage Low Output Current Logic-Low Threshold Logic-High Threshold Logic-Low Input Current Logic-High Input Current VCLAMP IIN VCLAMP TCVCLAMP RIN ROUT ROUT PSRR AVCL AVCL VOH VOL IOUT VIL VIH IIL IIH VIL = 0V VIH = VCC 2.0 6.6 1.2 25 25 30 0.8 VCLAMP + 2.4 VCLAMP VDISABLE = 0V 4.5V < VCC < 5.5V (Note 5) 48 1.9 SYMBOL VCC ICC CONDITIONS Guaranteed by PSRR MAX4028, RL = MAX4029, RL = VDISABLE = 0V Clamp (Note 3) Key clamp (Note 4) Input voltage = input clamp + 0.5V Measured at output Measured at output MAX4028 MAX4029 0.32 MIN 4.5 29 38 9 11 0.4 1.1 5 10 80 7 0.7 2 58 2.0 1 2.1 2 18 TYP MAX 5.5 40 55 15 20 0.48 UNITS V mA mA V A mV V/C M k dB V/V % V V mA V V A A
LOGIC INPUT CHARACTERISTICS (DISABLE , A/B, CLAMP/KEY_)
2
_______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
AC ELECTRICAL CHARACTERISTICS
(VCC = +5V, GND = 0V, RL = 150 to GND, VDISABLE = +5V, RKEYREF = 6k, CIN = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Small-Signal -3dB Bandwidth Large-Signal -3dB Bandwidth Small-Signal 0.1dB Gain Flatness Bandwidth Large-Signal 0.1dB Gain Flatness Bandwidth Slew Rate Settling Time to 0.1% Power-Supply Rejection Ratio Output Impedance Differential Gain Error Differential Phase Error Group Delay Peak Signal to RMS Noise Channel-to-Channel Crosstalk A/B Crosstalk Off-Isolation Droop SWITCHING CHARACTERISTICS Channel Switching Time Enable Time Disable Time Switching Transient tSW tON tOFF 20 0.1 0.1 10 ns s s mVP-P SYMBOL BWSS BWLS BW0.1dBSS BW0.1dBLS SR tS PSRR ZO DG DP D/dT SNR XTALK XTALKAB AISO DR CONDITIONS VOUT = 100mVP-P VOUT = 2VP-P VOUT = 100mVP-P VOUT = 2VP-P VOUT = 2VP-P VOUT = 2V step f = 100kHz f = 100kHz 5-step modulated staircase 5-step modulated staircase f = 3.58MHz or 4.43MHz 100kHz to 30MHz f = 100kHz f = 100kHz VOUT_ = 2VP-P, f = 100kHz Guaranteed by input clamp current MIN TYP 210 130 30 30 300 20 55 0.7 0.2 0.4 1.0 70 73 91 108 2 MAX UNITS MHz MHz MHz MHz V/s ns dB % degrees ns dB dB dB dB %
MAX4028/MAX4029
Note 2: All devices are 100% production tested at TA = +25C. 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
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps MAX4028/MAX4029
Typical Operating Characteristics
(VCC = +5V, GND = 0V, VDISABLE = +5V, RL = 150 to GND, CIN = 0.1F, RKEYREF = 6.04k 1%, TA = +25C, unless otherwise noted.)
SMALL-SIGNAL BANDWIDTH vs. FREQUENCY
MAX4028 toc01
SMALL-SIGNAL GAIN FLATNESS vs. FREQUENCY
MAX4028 toc02
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
7 LARGE-SIGNAL BANDWIDTH (dB) 6 5 4 3 2 1 0 -1 -2 VOUT = 2VP-P
MAX4028 toc03
8 7 SMALL-SIGNAL BANDWIDTH (dB) 6 5 4 3 2 1 0 -1 -2 100k 1M 10M FREQUENCY (Hz) 100M VOUT = 100mVP-P
6.2 6.1 6.0 GAIN FLATNESS (dB) 5.9 5.8 5.7 5.6 5.5 5.4 5.3 5.2 VOUT = 100mVP-P
8
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
LARGE-SIGNAL GAIN FLATNESS vs. FREQUENCY
DIFFERENTIAL PHASE (deg) DIFFERENTIAL GAIN (%)
MAX4028 toc04
DIFFERENTIAL GAIN AND PHASE
0.3 0.2 0.1 0 -0.1 -0.2 -0.3 0.06 0.04 0.02 0 -0.02 -0.04 -0.06
MAX4028 toc05
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX4028 toc06
6.2 LARGE-SIGNAL GAIN FLATNESS (dB) 6.1 6.0 5.9 5.8 5.7 5.6 5.5 5.4 5.3 5.2 100k 1M 10M FREQUENCY (Hz) 100M VOUT = 2VP-P
0 -10 -20 PSRR (dB) -30 -40 -50 -60
1st
2nd
3rd
4th
5th
6th
1G
1st
2nd
3rd
4th
5th
6th
-70 1k 10k 100k 1M 10M 100M 1G FREQUENCY (Hz)
OFF-ISOLATION vs. FREQUENCY
MAX4028 toc07
ALL-HOSTILE CROSSTALK (CHANNEL TO CHANNEL) vs. FREQUENCY
MAX4028 toc08
ALL-HOSTILE CROSSTALK (A TO B ON ANY CHANNEL) vs. FREQUENCY
-10 -20 CROSSTALK (dB) -30 -40 -50 -60 -70
MAX4028 toc09
0 -20 OFF-ISOLATION (dB) -40 -60 -80 -100 -120 -140 100k 1M 10M FREQUENCY (Hz) 100M
0 -10 -20 CROSSTALK (dB) -30 -40 -50 -60 -70 -80
0
-80 -90 -100 10k 100k 1M 10M 100M 1G 100k 1M 10M FREQUENCY (Hz) 100M 1G FREQUENCY (Hz)
1G
4
_______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
Typical Operating Characteristics (continued)
(VCC = +5V, GND = 0V, VDISABLE = +5V, RL = 150 to GND, CIN = 0.1F, RKEYREF = 6.04k 1%, TA = +25C, unless otherwise noted.)
OUTPUT IMPEDANCE vs. FREQUENCY
MAX4028 toc10
MAX4028/MAX4029
INPUT-VOLTAGE NOISE DENSITY vs. FREQUENCY
INPUT-VOLTAGE NOISE DENSITY (nV/Hz)
MAX4028 toc11
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4028 toc12
100
1000
OUTPUT IMPEDANCE ()
10
VIN 500mV/div
1.6VDC
100
1
10
VOUT 1V/div
0.1 10k 100k 1M 10M 100M 1G FREQUENCY (Hz)
1 1 10 100 1k 10k 100k 1M 10ns/div FREQUENCY (Hz)
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4028 toc13
CHANNEL-SWITCHING TRANSIENT
MAX4028 toc14
CHANNEL-SWITCHING TIME (CHA = 1.5VDC, CHB = 1VDC)
MAX4028 toc15
5VDC VIN 25mV/div 1.6VDC A/B 2.5V/div 0VDC A/B 2.5V/div
5VDC
0VDC
SIGNAL 2 50mV/div
VOUT 20mV/div
VOUT 500mV/div
10ns/div
20ns/div
20ns/div
ENABLE RESPONSE TIME (VOUT = 0.5V)
MAX4028 toc16
SMALL-SIGNAL BANDWIDTH vs. FREQUENCY
MAX4028 toc17
OPTIMAL ISOLATION RESISTANCE vs. CAPACITIVE LOAD
OPTIMAL ISOLATION RESISTANCE ()
MAX4028 toc18
11 SMALL-SIGNAL BANDWIDTH (dB) 5VDC 10 9 8 7 6 5 4 3 2 1 100k 1M 10M FREQUENCY (Hz) 100M CLOAD = 5pF CLOAD = 10pF CLOAD = 15pF
30 25 20 15 10 5 0
ENABLE 2.5V/div 0VDC
0.5VDC VOUT 250mV/div 0VDC
50ns/div
1G
0
50
100
150
200
250
CLOAD (pF)
_______________________________________________________________________________________
5
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps MAX4028/MAX4029
Typical Operating Characteristics (continued)
(VCC = +5V, GND = 0V, VDISABLE = +5V, RL = 150 to GND, CIN = 0.1F, RKEYREF = 6.04k 1%, TA = +25C, unless otherwise noted.)
CLAMP VOLTAGE vs. TEMPERATURE
MAX4028 toc19
KEY-CLAMP REFERENCE VOLTAGE vs. RKEYREF
KEY-CLAMP REFERENCE VOLTAGE (V) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 1 3 5 7 RKEYREF (k) 9 11 13
MAX4028 toc20
0.43 0.42 CLAMP VOLTAGE (V) 0.41 0.40 0.39 0.38 0.37 -50 -25 0 25 50 75
1.8
100
TEMPERATURE (C)
Pin Description
PIN MAX4028 -- 1 2 3 4 5 6 7 8 -- -- 9 10 11 12 13 14 MAX4029 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 NAME IN4A IN3A IN2A IN1A A/B KEYREF IN1B IN2B IN3B IN4B OUT4 CLAMP/KEY_3 GND OUT3 CLAMP/KEY_2 OUT2 VCC Amplifier Input 4A Amplifier Input 3A Amplifier Input 2A 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. Key-Clamp Reference Output. Connect an external resistor from KEYREF to GND to generate the key-clamp voltage. Amplifier Input 1B Amplifier Input 2B Amplifier Input 3B Amplifier Input 4B Amplifier Output 4 Output 3 Clamp or Key-Clamp Input. Drive CLAMP/KEY_3 high to clamp OUT3. Drive CLAMP/KEY_3 low to key clamp OUT3. Ground Amplifier Output 3 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 0.1F and 0.01F capacitors as close to the pin as possible. FUNCTION
6
_______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
Pin Description (continued)
PIN MAX4028 15 16 -- MAX4029 18 19 20 NAME OUT1 DISABLE CLAMP/KEY_4 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. FUNCTION
MAX4028/MAX4029
VCC IN1A CLAMP OUT1 IN1B CLAMP 1k IN2A CLAMP/ KEY CLAMP IN2B CLAMP/ KEY CLAMP CLAMP/KEY_2 IN3A CLAMP/ KEY CLAMP IN3B CLAMP/ KEY CLAMP CLAMP/KEY_3 A/B IN4A CLAMP/ KEY CLAMP IN4B CLAMP/ KEY CLAMP CLAMP/KEY_4 KEYREF CLAMP VOLTAGE 1k 1k 1k 1k
Detailed Description
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/s slew rate. Low differential gain and phase errors of 0.2% and 0.4, respectively, make these devices ideal for broadcast video applications.
OUT2
1k
OUT3
Sync Tip and Key Clamps
1k
OUT4
1k 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
_______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps MAX4028/MAX4029
Therefore, a 6k 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 0.1F capacitor (typ) with low leakage (<1A to 2A, 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
KEY-CLAMP REFERENCE VOLTAGE (V) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 1 3 5 7 RKEYREF (k) 9 11 13
MAX4028 fig02
1.8
tion to the capacitor, a low resistance (75) 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.
Low-Power, High-Impedance Disable Mode
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 2k 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.
Figure 2. Key-Clamp Reference Voltage vs. RKEYREF
Table 1. MAX4028 Clamp Settings for Video Formats
INPUT 1 2 3 INPUT 1 2 3 FORMAT Cvbs1 Cvbs2 Cvbs3 FORMAT G' B' R' CLAMP/KEY Clamp Clamp Clamp CLAMP/KEY Clamp Clamp Clamp INPUT 1 2 3 FORMAT Y C Cvbs CLAMP/KEY Clamp Key Clamp
INPUT 1 2 3
FORMAT Y Pb Pr
CLAMP/KEY Clamp Key Key
R, G, B have sync on all.
INPUT 1 2 3 FORMAT Gs B R CLAMP/KEY Clamp Key Key
Gs, B, R have sync only on Green. 8 _______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
Table 2. MAX4029 Clamp Settings for Video Formats
INPUT 1 2 3 4 FORMAT Cvbs1 Cvbs2 Cvbs3 Cvbs4 CLAMP/KEY Clamp Clamp Clamp Clamp INPUT 1 2 3 4 FORMAT Gs R B Cvbs CLAMP/KEY Clamp Key Key Clamp
MAX4028/MAX4029
Gs, B, R have sync only on Green.
INPUT 1 2 3 FORMAT H-Sync G B CLAMP/KEY Clamp Key Key Key CLAMP/KEY Clamp Key Clamp Clamp INPUT 1 2 3 4 FORMAT Y Pr Pb Cvbs CLAMP/KEY Clamp Key Key Clamp
4 R R, G, B have sync on none. INPUT 1 2 3 4 FORMAT Y C Cvbs Cvbs
INPUT 1 2 3 4
FORMAT Cvbs G' B' R'
CLAMP/KEY Clamp Clamp Clamp Clamp
R, G, B have sync on all.
The MAX4028/MAX4029 have a fixed gain of +2V/V that is internally set with two 1k 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 75 CABLE 0.1F IN_A RT 75
DISABLE RT 75 75 CABLE RT 75
OUT_
Applications Information
75 CABLE 0.1F IN_B RT 75
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.
CLAMP
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-
RKEYREF
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
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps MAX4028/MAX4029
SMALL-SIGNAL BANDWIDTH vs. FREQUENCY
MAX4028 fig04
OPTIMAL ISOLATION RESISTANCE vs. CAPACITIVE LOAD
OPTIMAL ISOLATION RESISTANCE ()
MAX4028 fig06
11 10 SMALL-SIGNAL BANDWIDTH (dB) 9 8 7 6 5 4 3 2 1 100k 1M 10M FREQUENCY (Hz) 100M CLOAD = 5pF CLOAD = 10pF CLOAD = 15pF
30 25 20 15 10 5 0
1G
0
50
100
150
200
250
CLOAD (pF)
Figure 4. Small-Signal Gain vs. Frequency with Capacitive Load and No Isolation Resistor
Figure 6. Optimal Isolation Resistance vs. Capacitive Load
A/B 75 CABLE 0.1F IN_A RT 75
DISABLE
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.
Layout and Power-Supply Bypassing
OUT_ RISO
CL 75 CABLE 0.1F IN_B RT 75
RL
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.
CLAMP
RKEYREF
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
______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
The bypass capacitors should include a 0.1F, ceramic surface-mount capacitor between VCC and the ground plane, located as close to the package as possible. Optionally, place a 10F 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 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.
MAX4028/MAX4029
Pin Configurations
TOP VIEW
IN4A 1 IN3A 1 IN2A 2 IN1A 3 A/B 4 KEYREF 5 IN1B 6 IN2B 7 IN3B 8 16 DISABLE 15 OUT1 14 VCC IN3A 2 IN2A 3 IN1A 4 A/B 5 KEYREF 6 IN1B 7 IN2B 8 IN3B 9 IN4B 10 20 CLAMP/KEY_4 19 DISABLE 18 OUT1 17 VCC
MAX4028
13 OUT2 12 CLAMP/KEY_2 11 OUT3 10 GND 9 CLAMP/KEY_3
MAX4029
16 OUT2 15 CLAMP/KEY_2 14 OUT3 13 GND 12 CLAMP/KEY_3 11 OUT4
TSSOP/SO
TSSOP/SO
Chip Information
TRANSISTOR COUNT: 1032 PROCESS: Bipolar
______________________________________________________________________________________
11
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps MAX4028/MAX4029
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
12
______________________________________________________________________________________
Triple/Quad, 2:1 Video Multiplexer-Amplifiers with Input Clamps
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.)
SOICW.EPS
MAX4028/MAX4029
INCHES
N
MILLIMETERS MIN 2.35 0.10 0.35 0.23 MAX 2.65 0.30 0.49 0.32
E
H
DIM A A1 B C e E H L
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
1.27 7.40 7.60 10.00 10.65 0.40 1.27
VARIATIONS:
1
INCHES
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
TOP VIEW
D
DIM D D D D D
MIN 0.398 0.447 0.496 0.598 0.697
MAX 0.413 0.463 0.512 0.614 0.713
A e B
C 0 -8 L
A1
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, .300" SOIC
APPROVAL DOCUMENT CONTROL NO. REV.
21-0042
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 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX4028

	To Download MAX4028 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .