MAX497CSE [ROCHESTER]
QUAD BUFFER AMPLIFIER, PDSO16, 0.150 INCH, SOIC-16;
| 型号： | MAX497CSE |
| 厂家： | 
Rochester Electronics |
| 描述： | QUAD BUFFER AMPLIFIER, PDSO16, 0.150 INCH, SOIC-16 放大器 光电二极管 |
| 文件： | 总13页 (文件大小：900K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0373; Rev 1; 12/98
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
6/MAX497
________________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ MAX496 Fixed Gain: +1V/V
The MAX496 and MAX497 are quad, closed-loop, ±5V
video buffers that feature extremely high bandwidth and
slew rate for both component video (RGB or YUV) and
composite video (NTSC, PAL, SECAM). The MAX496 is
a unity-gain (0dB) buffer with a 375MHz -3dB bandwidth
and a 1600V/µs slew rate. The MAX497 gain of +2 (6dB)
buffer, optimized for driving back-terminated coaxial
c a b le , fe a ture s a 275MHz -3d B b a nd wid th a nd a
1500V/µs slew rate. The MAX496/MAX497 are not slew-
rate limited, thus providing a high full-power bandwidth
of 230MHz and 215MHz, respectively.
MAX497 Fixed Gain: +2V/V
♦ High Speed:
Small-Signal -3dB Bandwidth: 375MHz (MAX496)
275MHz (MAX497)
Full-Power -3dB Bandwidth: 230MHz (MAX496)
215MHz (MAX497)
♦ 0.1dB Gain Flatness: 65MHz (MAX496)
120MHz (MAX497)
♦ 1600V/µs Slew Rate (MAX496)
1500V/µs Slew Rate (MAX497)
The MAX496/MAX497 incorporate a unique two-stage
architecture that combines the low offset and noise
benefits of voltage feedback with the high bandwidth
and slew-rate advantages of current-mode-feedback.
♦ Fast Settling Time: 12ns to 0.1%
♦ Lowest Differential Phase/Gain Error: 0.01°/0.01%
♦ 2pF Input Capacitance
♦ 5.6nV/√Hz Input-Referred Voltage Noise
♦ Low Distortion: 64dBc (f = 10MHz)
♦ Directly Drives 50Ω or 75Ω Back-Terminated Cables
♦ High ESD Protection: 5000V
________________________Ap p lic a t io n s
Computer Workstations
Surveillance Video
♦ Output Short-Circuit Protected
Broadcast and High-Definition TV Systems
Multimedia Products
_______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
16 Plastic DIP
16 Narrow SO
Dice*
Medical Imaging
MAX496CPE
MAX496CSE
MAX496C/D
MAX497CPE
MAX497CSE
MAX497C/D
High-Speed Signal Processing
Video Switching and Routing
16 Plastic DIP
16 Narrow SO
Dice*
_______________Fre q u e n c y Re s p o n s e
* Dice are specified at T = +25°C, DC parameters only.
A
___________________P in Co n fig u ra t io n
MAX497
SMALL-SIGNAL GAIN vs. FREQUENCY
9
TOP VIEW
8
7
6
GND
IN0
OUT0
V
1
2
3
4
5
6
7
8
16
15 CC
5
4
3
2
1
GND
IN1
OUT1
14
13
12
11
10
9
V
EE
MAX496
MAX497
GND
IN2
OUT2
V
EE
GND
IN3
OUT3
0
V
CC
-1
1M
10M
100M
1G
FREQUENCY (Hz)
DIP/SO
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V to V )................................................. 12V
Operating Temperature Range ...............................0°C to +70°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
CC
EE
Voltage on Any Input Pin to GND ....(V + 0.3V) to (V - 0.3V)
CC
EE
Output Short-Circuit Current Duration ...............................60sec
Continuous Power Dissipation (T = +70°C)
A
Plastic DIP (derate 10.53mW/°C above +70°C) ..........842mW
Narrow SO (derate 8.70mW/°C above +70°C) ............696mW
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
(V = +5V, V = -5V, V = 0V, R = 150Ω, T = T
to T , unless otherwise noted. Typical values are at T = +25°C.)
MAX A
CC
EE
L
A
MIN
IN
PARAMETER
SYMBOL
CONDITIONS
MIN
±2.8
±1.4
TYP
±3.2
±1.6
±1
MAX
UNITS
MAX496
MAX497
6/MAX497
Input Voltage Range
V
IN
V
Input Offset Voltage
V
OS
V
OUT
= 0V
±3
±5
mV
µV/°C
µA
Input Offset Voltage Drift
Input Bias Current
TCV
V
= 0V
= 0V
-10
OS
OUT
I
B
V
OUT
±1
MAX496: -2V ≤ V ≤ +2V,
IN
Input Resistance
R
IN
C
IN
0.5
1.2
2
MΩ
MAX497: -1V ≤ V ≤ +1V
IN
Input Capacitance
pF
R
R
R
R
= 150Ω
= 50Ω
= 150Ω
= 50Ω
0.988
0.983
1.975
1.965
1.00
1.00
2.01
2.01
L
L
L
L
MAX496 (Note 1)
MAX497 (Note 2)
Voltage Gain
A
V/V
dB
V
Positive Power-Supply Rejection
Ratio (Change in V
PSRR+
PSRR-
V
CC
= ±4.5V to ±5.5V, V = -5.0V
55
60
74
78
EE
)
OS
Negative Power-Supply
Rejection Ratio (Change in V
V
EE
= ±4.5V to ±5.5V, V = 5.0V
dB
%
CC
)
OS
Gain Linearity
A
VLIN
A
VCL
= +2, V = ±1mV to ±2V
OUT
0.01
31
T
A
= +25°C
36
45
Positive Quiescent Supply
Current (Total)
I
+
mA
SY
T
A
= T to T
MIN MAX
T
= +25°C
32
37
A
Negative Quiescent Supply
Current (Total)
I
-
mA
V
SY
T
A
= T
to T
MAX
45
MIN
Operating Supply Voltage Range
Output Voltage Swing
V
±4.50
±2.8
±2.5
±5.50
S
R
R
= 150Ω
= 50Ω
±3.7
±3.3
0.1
L
L
V
OUT
V
Output Resistance
Output Impedance
R
Z
DC
f = 10MHz
Ω
Ω
OUT
1.5
OUT
Short-Circuit Output Current
I
SC
Short to ground or either supply voltage
170
mA
2
_______________________________________________________________________________________
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
6/MAX497
AC ELECTRICAL CHARACTERISTICS
(V = +5V, V = -5V, V = 0V, R = 100Ω, T = +25°C.)
CC
EE
IN
L
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
375
375
275
275
230
215
1600
1500
12
MAX
UNITS
MAX496CSE
Small-Signal -3dB Bandwidth
MAX496CPE
MAX497CSE
MAX497CPE
BW
MHz
-3dB
MAX496
MAX497
Full-Power Bandwidth
Slew Rate
FPBW
SR
V
OUT
= ±2V
MHz
V/µs
V
OUT
= 4V step, MAX496
= 4V step, MAX497
V
OUT
Settling Time
t
s
0.1% (VOUT = 2V step)
f = 3.58MHz (Note 3)
f = 3.58MHz (Note 3)
f = 10MHz
ns
%
Differential Gain Error
Differential Phase Error
Input Noise Voltage Density
Input Noise Current Density
DG
DP
0.01
0.01
5.6
2
degrees
nV√Hz
pA√Hz
f = 10MHz
MAX496CPE
MAX496CSE
MAX497CPE
MAX497CSE
MAX496
80
80
Gain Flatness
±0.1dB
MHz
100
120
78
Adjacent Channel Crosstalk
All-Hostile Crosstalk
(Note 4)
(Note 4)
dB
dB
MAX497
72
MAX496
72
MAX497
65
MAX496
-64
-58
58
f
V
= 10MHz,
C
Total Harmonic Distortion
Spurious-Free Dynamic Range
THD
dBc
dBc
= 2Vp-p
OUT
MAX497
MAX496
SFDR
f = 5MHz
C
MAX497
60
Note 1: Voltage Gain = (V
- V ) / V , measured at V = ±1V.
OS IN IN
OUT
Note 2: Voltage Gain = (V
- V ) / V , measured at V = ±2V.
OS IN IN
OUT
Note 3: Input test signal is a 3.58MHz sine wave of amplitude 40 IRE superimposed on a linear ramp (0 IRE to 100 IRE).
= 150Ω, see Figure 2.
R
L
Note 4: Input of channel under test grounded through 75Ω. Adjacent channel driven at f = 10MHz (Figure 4a). For All-Hostile
Crosstalk, all inputs are driven except the channel under test (Figure 4b).
_______________________________________________________________________________________
3
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V = +5V, V = -5V, R = 100Ω, T = +25°C, unless otherwise noted.)
EE
L
A
CC
MAX496
MAX496
MAX496
SMALL-SIGNAL GAIN vs. FREQUENCY
GAIN FLATNESS vs. FREQUENCY
LARGE-SIGNAL GAIN vs. FREQUENCY
2
1
0
0.2
0.1
2
1
0
-0.1
-0.2
0
-1
-2
-1
-2
-3
-4
-0.3
-0.4
-3
-4
-5
-6
-7
-8
-0.5
-0.6
-0.7
-0.8
-5
-6
-7
-8
6/MAX497
1M
10M
100M
1G
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
MAX497
SMALL-SIGNAL GAIN vs. FREQUENCY
MAX497
MAX497
GAIN FLATNESS vs. FREQUENCY
LARGE-SIGNAL GAIN vs. FREQUENCY
8
9
8
7
6
5
6.2
6.1
6.0
5.9
DIP
SO
7
6
5
4
5.8
4
3
2
5.7
5.6
3
2
1
0
5.5
5.4
1
0
-1
-2
5.3
5.2
-1
1M
10M
100M
1G
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
MAX496
MAX497
SMALL-SIGNAL GAIN vs. FREQUENCY
SMALL-SIGNAL GAIN vs. FREQUENCY
TOTAL HARMONIC DISTORTION (THD)
vs. FREQUENCY
DRIVING A 50Ω LOAD
DRIVING A 50Ω LOAD
2
1
8
7
6
0
V
= 2Vp-p
OUT
-10
-20
-30
-40
0
-1
-2
5
4
3
2
1
MAX497
-3
-4
-50
-60
-70
-80
MAX496
-5
-6
-7
-8
0
-1
-2
-90
1M
10M
100M
1G
1M
10M
100M
1G
10k
100k
1M
10M
100M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
4
_______________________________________________________________________________________
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
6/MAX497
_____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = +5V, V = -5V, R = 100Ω, T = +25°C, unless otherwise noted.)
EE
L
A
CC
MAX497
CROSSTALK vs. FREQUENCY
MAX496
CROSSTALK vs. FREQUENCY
POWER-SUPPLY REJECTION (PSR)
vs. FREQUENCY
-10
-10
-20
-30
-40
0
-10
-20
-30
-40
-50
-60
-70
-80
-20
-30
-40
-50
-60
-70
-80
-90
MAX497
ALL-HOSTILE
ADJACENT CHANNEL
ALL-HOSTILE
-50
-60
-70
-80
ADJACENT CHANNEL
-90
-100
-110
-90
MAX496
-100
-100
1
10
100 200
1M
10M
100M
1G
20k
100k
1M
10M
100M
FREQUENCY (MHz)
FREQUENCY (Hz)
FREQUENCY (Hz)
MAX496
MAX496
MAX497
GAIN MATCH vs. FREQUENCY
GAIN vs. TEMPERATURE
GAIN MATCH vs. FREQUENCY
1.000
0.999
0.998
0.997
0.996
0.995
0.994
0.993
0.3
0.2
0.1
0.0
0.5
0.4
0.3
0.2
CH 2–CH 1
CH 2–CH 0
CH 2–CH 0
CH 1–CH 0
V = -1.0V
IN
CH 3–CH 1
CH 3–CH 1
V
IN
= -1.0V
-0.1
0.1
CH 3–CH 2
-0.2
-0.3
0
CH 1–CH 0
-0.1
CH 3–CH 0
CH 3–CH 0
CH 3–CH 2
CH 2–CH 1
-0.4
-0.5
-0.2
-0.3
0.992
0.991
0.990
-0.6
-0.7
-0.4
-0.5
1M
10M
100M
1G
-40 -20
0
20
40 60
80 100
1M
10M
100M
1G
FREQUENCY (Hz)
TEMPERATURE (°C)
FREQUENCY (Hz)
SUPPLY CURRENT
vs. TEMPERATURE
INPUT OFFSET VOLTAGE
vs. TEMPERATURE
MAX497
GAIN vs. TEMPERATURE
2.05
0.30
40
38
36
34
32
30
28
26
24
R = NO LOAD
L
2.04
2.03
2.02
2.01
2.00
1.99
1.98
1.97
1.96
1.95
0.20
I
EE
0.10
0
V
= +1.0V
IN
I
CC
-0.10
-0.20
-0.30
V
= -1.0V
IN
22
20
-40 -20
0
20
40 60
80 100
-10
0
10 20 30 40 50 60 70 80
TEMPERATURE (°C)
-40 -20
0
20
40 60
80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
_____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = +5V, V = -5V, R = 100Ω, T = +25°C, unless otherwise noted.)
EE
L
A
CC
MAX496
MAX497
SMALL-SIGNAL PULSE RESPONSE
SMALL-SIGNAL PULSE RESPONSE
0.05
IN
to 0.50
IN
-0.05
-0.50
to 0.10
OUT
6/MAX497
0.05
OUT
-0.05
-0.10
TIME (10ns/div)
TIME (10ns/div)
MAX496
MAX497
LARGE-SIGNAL PULSE RESPONSE
LARGE-SIGNAL PULSE RESPONSE
1.0
1.0
IN
IN
-1.0
-1.0
2.0
OUT
-2.0
1.0
OUT
-1.0
TIME (10ns/div)
TIME (10ns/div)
6
_______________________________________________________________________________________
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
6/MAX497
_____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = +5V, V = -5V, R = 100Ω, T = +25°C, unless otherwise noted.)
EE
L
A
CC
MAX496
SMALL-SIGNAL PULSE RESPONSE
MAX497
SMALL-SIGNAL PULSE RESPONSE
(C = 47pF
L
(C = 47pF)
L
0.05
IN
0.50
IN
-0.05
-0.50
0.10
OUT
-0.10
0.05
OUT
-0.05
10ns/div
10ns/div
MAX497
MAX496
LARGE-SIGNAL PULSE RESPONSE
LARGE-SIGNAL PULSE RESPONSE
(C = 47pF)
L
(C = 47pF)
L
1.0
1.0
IN
IN
-1.0
-1.0
2.0
1.0
OUT
-2.0
OUT
-1.0
10ns/div
10ns/div
_______________________________________________________________________________________
7
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
_____________________P in De s c rip t io n
_______________De t a ile d De s c rip t io n
The MAX496/MAX497 are quad, high-speed, closed-loop
voltage-feedback video amplifiers with fixed gain settings
of +1 and +2, respectively (Figure 1). These amplifiers
use a unique two-stage voltage-feedback architecture
that combines the benefits of conventional voltage-feed-
ba c k a nd c urre nt-mod e -fe e db a c k top ologie s. The y
achieve wide bandwidths and high slew rates while main-
taining precision. A resistively loaded first stage provides
low input-referred noise even with low supply currents of
8mA per amplifier. The above features, along with the
ability to drive 50Ω or 75Ω back-terminated cables to
±2.8V and low differential phase and gain errors, make
these amplifiers ideal for the most demanding component
and composite video applications.
PIN
NAME
FUNCTION
Ground. All ground pins are internally
connected. Connect all ground pins
externally to minimize the ground
impedance.
1, 3,
5, 7
GND
2
4
6
8
IN0
IN1
IN2
IN3
Channel 0 Input
Channel 1 Input
Channel 2 Input
Channel 3 Input
Positive Power Supply. Connect to +5V.
V
CC
pins are internally connected.
Connect both pins to +5V externally to
minimize the supply impedance.
9, 15
10
V
CC
OUT3
Channel 3 Output
6/MAX497
__________Ap p lic a t io n s In fo rm a t io n
Negative power supply. Connect to -5V.
V
pins are internally connected.
The feedback elements of the MAX496/MAX497 are
included internally in the device to set the closed-loop
EE
11, 13
V
EE
Connect both pins to -5V externally to
minimize the supply impedance.
gain to A = +1 and A = +2, respectively. Closing the
V
V
12
14
16
OUT2
OUT1
OUT0
Channel 2 Output
Channel 1 Output
Channel 0 Output
loop internally on the chip minimizes problems associ-
ated with the board and package parasitics influencing
the amplifier’s frequency response.
V
CC
V
EE
0.10µF
0.10µF
-5V
+5V
0.10µF
9
15
11
13
10µF
10µF
0.10µF
75Ω CABLE
75Ω CABLE
75Ω
75Ω
75Ω
2
IN0
IN1
OUT0 16
RED
75Ω
75Ω
75Ω
75Ω
MAX496*
MAX497*
75Ω CABLE
75Ω CABLE
75Ω
4
OUT1 14
GREEN
75Ω CABLE
75Ω CABLE
75Ω CABLE
75Ω CABLE
75Ω
75Ω
75Ω
75Ω
6
8
IN2
IN3
OUT2
12
BLUE
SYNC
75Ω
75Ω
75Ω
75Ω
OUT3 10
GND
*A = +1 (MAX496)
*A = +2 (MAX497)
V
V
3
5
7
Figure 1. Typical Operating Circuit
8
_______________________________________________________________________________________
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
6/MAX497
75Ω CABLE
a)
75Ω
MAX497
75Ω CABLE
75Ω CABLE
75Ω
DUT
75Ω
SOURCE:
TEKTRONIX
75Ω
MEASUREMENT:
TEKTRONIX VM700
VIDEO MEASUREMENT
SET
1910 DIGITAL GENERATOR
b)
75Ω CABLE
75Ω
MAX496
DUT
75Ω
150Ω
Figure 2. Differential Phase and Gain Error Test Circuits: a) MAX497, Gain of +2 Amplifier; b) MAX496 Unity-Gain Amplifier
P o w e r Dis s ip a t io n
The maximum output current of the MAX496/MAX497 is
limited by the packages maximum allowable power dis-
sipation. The maximum junction temperature should not
exceed +150°C. The power dissipation increases with
load, and this increase can be approximated by the fol-
lowing:
MAX496/MAX497
IN0
75Ω
75Ω
OUT1
OUT2
75Ω
For V
> 0V: |V - VOUT| I
OUT
CC
LOAD
75Ω
OR
For V
< 0V: |V - VOUT| I
.
OUT
EE
LOAD
These devices can drive 100Ω loads connected to
each of the outputs over the entire rated output swing
and temperature range. When driving 50Ω loads with
each of the four outputs simultaneously, the output
75Ω
75Ω
75Ω
75Ω
75Ω
OUT3
OUT4
swing must be limited to ±1.25V at T = +70°C. While
A
the output is short-circuit protected to 170mA, this does
not necessarily guarantee that, under all conditions, the
maximum junction temperature will not be exceeded.
Do not e xc e e d the d e ra ting va lue s g ive n in the
absolute maximum ratings.
Figure 3. One-to-Four Distribution Amplifier
_______________________________________________________________________________________
9
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
MAX496/MAX497
MAX496/MAX497
50Ω
50Ω
100Ω
100Ω
V = 4Vp-p,
IN
f = 10MHz,
R = 75Ω
S
50Ω
50Ω
50Ω
100Ω
100Ω
50Ω
100Ω
100Ω
100Ω
50Ω
50Ω
6/MAX497
V = 4Vp-p,
IN
f = 10MHz,
100Ω
R = 75Ω
S
a) ADJACENT CHANNEL
b) ALL-HOSTILE
Figure 4. Crosstalk: a) Adjacent Channel; b) All-Hostile
To t a l No is e
The MAX496/MAX497’s low inp ut c urre nt nois e of
2pA/√Hz and voltage noise of 5.6nV/√Hz provide for
lower total noise compared to typical current-mode-
feedback amplifiers, which usually have significantly
higher input current noise. The input current noise mul-
tiplied by the feedback resistor is the dominant noise
source of current-mode-feedback amplifiers.
Co a x ia l Ca b le Drive rs
Hig h-s p e e d p e rforma nc e , e xc e lle nt outp ut c urre nt
capability, and an internally fixed gain of +2 make the
MAX497 ideal for driving back-terminated 50Ω or 75Ω
coaxial cables to ±2.8V.
In a typical application, the MAX497 drives a back-ter-
minated 75Ω video cable (Figure 1). The back-termina-
tion re s is tor (a t the MAX497’s outp ut) ma tc he s the
impedance of the cable’s driven end to the cable’s
impedance, to eliminate signal reflections. This, along
with the loa d -te rmina tion re s is tor, forms a volta g e
divider with the load impedance, which attenuates the
signal at the cable output by one-half. The MAX497
operates with an internal +2V/V closed-loop gain to pro-
vide unity gain at the cable’s output.
Diffe re n t ia l Ga in a n d P h a s e Erro rs
Differential gain and phase errors are critical specifica-
tions for a buffer in composite (NTSC, PAL, SECAM) video
applications, because these errors correspond directly to
color changes in the displayed picture of composite video
systems. The MAX496/MAX497’s ultra-low differential gain
and phase errors (0.01%/ 0.01°) make them ideal in
broadcast-quality composite video applications.
Ca p a c it ive Lo a d Drivin g
In most amplifier circuits, driving large capacitive loads
increases the likelihood of oscillation. This is especially
true for circuits with high loop gains, such as voltage
followers. The amplifier’s output resistance and the
capacitive load form an RC filter that adds a pole to the
loop response. If the pole frequency is low enough (as
when driving a large capacitive load), the circuit phase
margin is degraded and oscillation may occur.
Dis t rib u t io n Am p lifie r
The circuit in Figure 3 is a one-to-four distribution amplifier
using a single MAX496 or MAX497 IC. A one-to-eight dis-
tribution amplifier can be implemented with a MAX496 or
MAX497 by driving an additional cable from each of the
four outputs. When driving more than four outputs from a
single device, see the Continuous Power Dissipation
specifications in the Absolute Maximum Ratings.
10 ______________________________________________________________________________________
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
6/MAX497
5
8
6
4
C
= 60pF
= 22pF
L
C
= 47pF
L
4
3
2
R
L
= 50Ω
R
= 50Ω
= 0Ω
L
R
ISO
= 20Ω
R
ISO
C
L
C
= 10pF
L
2
C
L
= 22pF
1
0
0
-2
-4
-6
-8
C
L
= 10pF
C
L
= 0pF
-1
-2
-3
C
= 47pF
= 60pF
L
C
L
-4
-5
-10
-12
* -3dB ATTENUATION DUE
TO R NOT SHOWN
ISO
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 5a. MAX496 Small-Signal Gain vs. Frequency and Load
Figure 5b. MAX496 Small-Signal Gain vs. Frequency and
Capacitor (R = 50Ω, R
= 0Ω)
Load Capacitor (R = 50Ω, R
= 20Ω)
L
ISO
L
ISO
20
20
C
= 68pF
C
L
= 47pF
L
15
10
5
15
10
5
R
=
R =
L
L
C
= 20pF
L
R
ISO
= 0Ω
R
ISO
= 20Ω
C
L
= 47pF
0
-5
0
-5
C = 68pF
L
C
= 10pF
L
C
L
= 22pF
-10
-15
-20
-10
-15
-20
C
L
= 0pF
C
= 10pF
L
-25
-30
-25
-30
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 5d. MAX496 Small-Signal Gain vs. Frequency and
Load Capacitor (R = ∞, R = 20Ω)
Figure 5c. MAX496 Small-Signal Gain vs. Frequency and Load
Capacitor (R = ∞, R = 0Ω)
L
ISO
L
ISO
The MAX496/MAX497 drive capacitive loads up to 75pF
without sustained oscillation, although some peaking
may occur. When driving larger capacitive loads, or to
Connect both positive power-supply pins together and
bypass with a 0.10µF ceramic capacitor at each power
supply pin, as close to the device as possible. Repeat
the s a me for the ne g a tive p owe r-s up p ly p ins . The
capacitor lead lengths should be as short as possible
to minimize le a d ind uc ta nc e ; s urfa c e -mount c hip
capacitors are ideal. A large-value (4.7µF or greater)
tantalum or electrolytic bypass capacitor on each sup-
ply may be required for high-current loads. The location
of this capacitor is not critical.
reduce peaking, add an isolation resistor (R ) between
ISO
the output and the capacitive load (Figures 5a–5d).
Gro u n d in g a n d La yo u t
The MAX496/MAX497 bandwidths are in the RF fre-
quency range. Depending on the size of the PC board
used and the frequency of operation, it may be neces-
sary to use Micro-strip or Stripline techniques.
The MAX496/MAX497’s analog input pins are isolated
with ground pins to minimize parasitic coupling, which can
degrade crosstalk and/or amplifier stability. Keep signal
paths as short as possible to minimize inductance. Ensure
that all input channel traces are the same length to main-
tain the phase relationship between the four channels. To
further reduce crosstalk, connect the coaxial-cable shield
to the ground side of the 75Ω terminating resistor at the
ground plane, and terminate all unused inputs ground and
outputs with a 100Ω or 150Ω resistor to ground.
To realize the full AC performance of these high-speed
buffers, pay careful attention to power-supply bypassing
and board layout. The PC board should have at least two
layers (wire-wrap boards are too inductive, bread boards
are too capacitive), with one side a signal layer and the
other a large, low-impedance ground plane. With multilay-
er boards, locate the ground plane on the layer that is not
dedicated to a specific signal trace. The ground plane
should be as free from voids as possible. Connect all
ground pins to the ground plane.
______________________________________________________________________________________ 11
3 7 5 MHz Qu a d Clo s e d -Lo o p
Vid e o Bu ffe rs , A = +1 a n d +2
V
___________________Ch ip To p o g ra p h y
GND
IN0
OUT0 V
CC
GND
IN1
OUT1
V
EE
0. 101"
(2. 56mm)
OUT2
GND
IN2
V
EE
6/MAX497
IN3
OUT3
GND
V
CC
0. 076"
(1. 930mm)
TRANSISTOR COUNT: 544
SUBSTRATE CONNECTED TO V
EE
________________________________________________________P a c k a g e In fo rm a t io n
12 ______________________________________________________________________________________
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