Gennum GB4550 Monolithic video buffer/clamp Datasheet

GB4550 & GB4550A
Monolithic Video Buffer/Clamp
DATA SHEET
FEATURES
DESCRIPTION
• adjustable clamp level from -5.5 V to +5.5 V at ±10 V
supplies.
• ultra low differential gain (0.02% typ.) and
differential phase (0.03° typ.)
• wideband unity gain: GB4550 ±0.2 dB at 25 MHz
GB4550A ±0.1 dB at 25 MHz
• both drive 150pF loads at full power, flat to 10 MHz.
• GB4550A — tight delay spread of ±0.15°at colorburst.
• convenient 8 pin SIP packaging.
• both can be configured as a gain stage with reduced
bandwidth.
PIN CONNECTIONS
The GB4550 and GB4550A are high performance monolithic video buffer/clamps made on Gennum's LSI process.
They feature a wideband differential amplifier that can be
configured as a gain stage. The output signal voltage is
limited to +2V above the clamp level in order to prevent
damage to crosspoints connected to the output.
The clamping level can be set for normal sync tip clamping
by connecting pin 4 to -0.286 volts. For other applications,
the clamping voltage level can be varied from -5.5 to +5.5
volts.
The GB4550A features a tight delay spread of only ± 0.15
degrees while the GB4550 maintains a ± 1.5 degree delay
spread. Both devices operate from ± 9 to ± 12 V power
supplies and will directly interface with Gennum's video
crosspoint switches.
The 8 pin SIP package is ideally suited for space restricted
board layouts.
GB4550 and GB4550A
APPLICATIONS
• Input buffering and clamping to crosspoint switches
1
2
3
4
5
6
7
• Inter - system video signal clamping
8
CX
Pin No.
GB4550
GB4550A
Function
1
+IN
+IN
non-inverting input
2
VCC
VCC
positive power supply
3
COMP
NC
frequency compensation or NC
4
VCL
VCL
clamp voltage input
5
CX
CX
external capacitor
6
VEE
V EE
negative power supply
7
-IN
-IN
inverting input
8
OUT
OUT
output
(+2 V OUTPUT CLAMP)
100k
30k
(NC on
GB4550A)
+
COMP
VCL
10pF
+IN
+
-IN
-
30k
VCC
OUT
7mA
Nominal
VEE
ORDERING INFORMATION
Part Number
Package Type
All resistors in ohms, all capacitors in microfarads unless otherwise stated
Temperature Range
GB4550 - CSA
8 pin SIP
0 to 70oC
GB4550ACSA
8 pin SIP
0 to 70o C
SIMPLIFIED CIRCUIT DIAGRAM
Revision Date: February 1994
Document No. 520 - 34 - 4
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946
Japan Branch: A-302, Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168, Japan
tel. (03) 3334-7700
fax: (03) 3247-8839
ABSOLUTE MAXIMUM RATINGS
PARAMETER
VALUE
± 13.5 V
Supply Voltage VS
-65°C ≤ TS ≤ 150° C
Storage Temperature Range
Lead Temperature (Soldering, 10 Sec)
260° C
±5 V
Differential Video Input Voltage
VEE + 2.5 V ≤ VCL ≤ Vcc - 2.5 V
ELECTRICAL CHARACTERISTICS
PARAMETER
POWER
SUPPLIES
SIGNAL
PATH
GB4550
SIGNAL
PATH
V S = ± 10 V, TA = 0 - 70°C, R L = 10kΩ, CL = 150 pF, CCOMP = 0 pF unless otherwise shown.
SYMBOL
-
9
13.8
mA
I-
-
9
13.8
mA
VIN MAX
1.8
2.0
2.25
V
-
-
0.03
dB
- Supply Current
I.L.
Operating Range
ƒ = 100kHz
Full Power Bandwidth
FPBW
-3.0dB, V IN = 1V p-p
15
18
-
MHz
Small Signal Bandwidth
SSBW
± 0.2dB, V IN = 100mV p-p
20
25
-
MHz
at 10MHz, VIN = 1V p-p
-
0.05
-
dB
at 3.58MHz
-
-8
-
deg
at 3.58MHz
-
± 1.5
-
deg
Frequency Response
øD
Full Power Bandwidth
FPBW
-3.0dB, V IN = 1V p-p
17
20
-
MHz
Small Signal Bandwidth
SSBW
± 0,1dB, V IN=100mV p-p, C L=100pF
25
30
-
MHz
at 10MHz, VIN = 1V p-p
-
0.1
-
dB
at 3.58 MHz
-
-7.5
-
deg
at 3.58MHz
-
± 0.15
-
deg
Frequency Response
Signal Path Delay
øD
Differential Gain
dg
at 3.58MHz
-
0.02
0.05
%
Differential Phase
dp
at 3.58MHz
-
0.03
0.05
deg
Input Resistance
RIN
80
100
-
kΩ
Input Capacitance
CIN
-
2.0
-
pF
Output Resistance
R OUT
-
8.6
53
-
Ω
Ω
-5.5
-
+5.5
V
-
7
28
mV
Clamp Voltage Range
520 - 34 - 4
UNITS
I+
Delay Tolerance
CLAMP
MAX
V
Delay Tolerance
SIGNAL
PATH
TYP
± 12
+ Supply Current
Insertion Loss
MIN
± 10
VS
Maximum Input Voltage
Above VCL
CONDITIONS
±9
Supply Voltage
Signal Path Delay
GB4550A
SIGNAL
PATH
DO NOT OPEN PACKAGES OR HANDLE
EXCEPT AT A STATIC-FREE WORKSTATION
0°C ≤ TA ≤ 70° C
Operating Temperature Range
Clamp Input Voltage
CAUTION
ELECTROSTATIC
SENSITIVE DEVICES
Clamp Accuracy
AV = +1, ƒ = 0 to 10MHz
AV = +1, ƒ = 100MHz
V CL
VIN = 1V p-p
2
DETAILED DESCRIPTION
The GB4550(A) is intended for video applications requiring
coarse DC restoration coupled with flat frequency response.
As shown in Figure 1, the signal path features a wide band
operational amplifier designed to be unity gain stable. While
this amplifer is not intended to drive 75 Ω transmission lines,
it is ideal for applications where high capactive loads, up to
several hundred picofarads, must be driven, such as input
buffering and DC restoration of video signals.
Under equilibrium conditions the average current supplied by
the comparator output is just sufficient to balance the current
discharging the input capacitor. This discharge current is
simply the input bias current of the op-amp, typically less than
20 µA . However, an external resistor can be added to increase
the pull down current. Under dynamic conditions, where the
system is adjusting for a change in the signal level, the
charging current may be in the milliamp range. Because the
corrective current is small under equilibrium conditions, the
error voltage at the comparator input is small also, so clamping
accuracy to within ± 7 mV is achievable.
Optimal frequency response for the GB4550(A) occurs with
load capacitances in the range of 80 pF to 100 pF as shown in
Figure 4. For smaller loads, an external capacitor can be
added to extend the bandwidth and improve the flatness of the
device response.
The clamp circuit makes use of a "peak hold" capacitor, CX, at
the output of the comparator . This gives rise to a more
constant voltage at the comparator output which is translated
to a more constant corrective current by an internal 100 kΩ
resistor connected between the comparator output and the
signal input.
The clamping function is achieved through the use of a simple
comparator. The inverting input of the comparator is connected
to the GB4550(A) output, while the non-inverting input is
connected to the clamp voltage reference. For output signal
voltages more positive than the clamp reference the comparator
output is essentially open-circuit, while signal voltages more
negative than the clamp reference result in the charging of CX.
The action of the comparator is to provide a positive current
which is fed back to the op-amp non-inverting input under
conditions where the op-amp output is more negative than the
clamp reference voltage. This negative feedback raises the
DC level of the input signal to the point where all signal
fluctuations occur at voltages above the clamp reference
level. This is the desired clamp action.
To avoid excessive phase shift and consequent instability of
the clamp feedback loop, the peak hold capacitor needs to be
considerably smaller (e.g. 1000 times) than the input coupling
capacitor. If a faster clamp is desirable (e.g. for 60 Hz hum
elimination) the peak hold capacitor can be removed and a
smaller input coupling capacitor employed. In this application
some distortion of the signal "tip" is unavoidable.
The input to the op-amp must be AC coupled using an
appropriate size of capacitor, which then acts as a DC "reservoir"
for the corrective level shift.
CX
(+2 V OUTPUT CLAMP)
100k
30k
(NC on
GB4550A)
+
COMP
VCL
10pF
+IN
+
-IN
-
30k
VCC
7mA
Nominal
OUT
VEE
All resistors in ohms, all capacitors in microfarads unless otherwise stated.
Fig. 1 Simplfied Circuit Diagram
3
520 - 34 - 4
+10V
-10V
0.1
+5V
0.1
0.1
2
4
6
1
0.1
*22
SIGNAL IN
FROM
NETWORK
ANALYSER
1
8
D.U.T.
4
CLC110
NON-POLAR
OUTPUT TO
NETWORK
ANALYSER
8
5
7
5
3
10k
75
**RCOMP
-5V
10n
All resistors in ohms,
all capacitors in microfarads
unless otherwise stated.
**CCOMP
CLOAD
0.1
NOTES: This circuit can be used for Frequency Response, Delay and Differential Gain and Phase measurements.
* This input capacitor must be shorted out when performing Differential Gain and Phase tests.
** RCOMP and CCOMP are only used on GB4550.
Fig. 2 Test Circuit
+10V
0.1
VIDEO OUT 1
0.1
4 2
VIDEO
IN
GX4314
XPOINT
-10V
GB4550
GB4550A
0.1 to 22
1
GX4314
XPOINT
6
NON-POLAR
8
7
5
VIDEO OUT 2
3
GX4314
XPOINT
VIDEO OUT 3
GX4314
XPOINT
VIDEO OUT 4
*RCOMP
All resistors in ohms,
all capacitors in microfarads
unless otherwise stated.
**10n
*CCOMP
CLOAD
NOTES: In most applications RCOMP and CCOMP will not be needed since the bandwidth depends on the bus capacitance.
In general, the maximum occurs when CLOAD is between 82 pF and 100 pF.
They are used to control the roll-off for higher load conditions.
* Not used on GB4550A.
**
The value of this capacitor should be proportional to the input capacitor used.
The value shown is for a 22 µF input capacitor.
Fig. 3 Typical Application Circuit
520 - 34 - 4
4
TYPICAL PERFORMANCE CURVES
Unless otherwise shown SV = ±10V
0.5
-3
0.4
CL = 180 pF
0.3
0.1
150 pF
DEGREES
GAIN (dB )
0.2
0
-0.1
120 pF
-0.2
-0.3
82 pF
-0.4
-0.5 1
1
40
10
40
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dpCL = 100 pF
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dg
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-10 2
2
3
4
5
FREQUENCY (MHz)
Fig. 4 GB4550 Frequency Response
0.5
Fig. 5 GB4550 Phase Delay Spread
-3
CL = 180 pF
CL = 100 pF
0.1
DEGREES
GAIN ( dB )
0.3
0
-0.1
CL = 82 pF
-0.3
-0.5 1
1
6
6
FREQUENCY (MHz)
40
10
40
-4 1234
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CL = 100pF
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-5
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1
234
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-6
1234
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1
2345
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1
234
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-7
1
23
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1
234
123
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1
23
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-8
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-9
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-10 2
2
3
4
5
FREQUENCY (MHz)
6
6
FREQUENCY (MHz)
Fig. 6 GB4550A Frequency Response
Fig. 7 GB4550A Phase Delay Spread
0.05
REVISION NOTE: Detailed Description added
dg (%) / dp (°)
0.03
dg
0.01
DOCUMENT
IDENTIFICATION
dp
0
PRODUCT PROPOSAL
This data has been compiled for market investigation purposes
only, and does not constitute an offer for sale.
-0.01
V IN = 40 IRE
ADVANCE INFORMATION NOTE
This product is in development phase and specifications are
subject to change without notice. Gennum reserves the right to
remove the product at any time. Listing the product does not
constitute an offer for sale.
-0.03
-0.05
1
1
3
5
10
10
PRELIMINARY DATA SHEET
The product is in a preproduction phase and specifications are
subject to change without notice.
FREQUENCY (MHz)
DATA SHEET
The product is in production. Gennum reserves the right to make
changes at any time to improve reliability, function or design, in
order to provide the best product possible.
Fig. 8 Differential Gain and Phase
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.
© Copyright April 1991 Gennum Corporation. All rights reserved. Printed in Canada.
5
520 - 34 - 4
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