THS4508
www.ti.com .................................................................................................................................... SLAS459E – SEPTEMBER 2005 – REVISED SEPTEMBER 2008
WIDEBAND, LOW NOISE, LOW DISTORTION FULLY DIFFERENTIAL AMPLIFIER
FEATURES
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Fully Differential Architecture
Common-Mode Input Range Includes the
Negative Rail
Minimum Gain of 2 V/V (6 dB)
Bandwidth: 2 GHz
Slew Rate: 6400 V/µs
1% Settling Time: 2 ns
HD2: –72 dBc at 100 MHz
HD3: –79 dBc at 100 MHz
OIP2: 78 dBm at 70 MHz
OIP3: 42 dBm at 70 MHz
Input Voltage Noise: 2.3 nV/√Hz (f > 10 MHz)
Noise Figure: 19.2 dB (G = 10 dB)
Output Common-Mode Control
5-V Power Supply Current: 39.2 mA
Power-Down Capability: 0.65 mA
APPLICATIONS
•
•
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•
5-V Data-Acquisition Systems
High Linearity ADC Amplifier
Wireless Communication
Medical Imaging
Test and Measurement
DESCRIPTION
The THS4508 is a wideband, fully-differential
operational amplifier designed for single-supply 5-V
data acquisition systems. It has very low noise at 2.3
nV/√Hz, and extremely low harmonic distortion of –72
dBc HD2 and –79 dBc HD3 at 100 MHz with 2 VPP,
G = 10 dB, and 1-kΩ load. Slew rate is very high at
6400 Vµs, and with settling time of 2 ns to 1% (2 V
step), it is ideal for pulsed applications. It is designed
for minimum gain of 6 dB, but is optimized for gain of
10 dB.
To allow for dc coupling to analog-to-digital
converters (ADCs), its unique output common-mode
control circuit maintains the output common-mode
voltage within 5-mV offset (typical) from the set
voltage, when set within 0.5 V of mid-supply. The
common-mode set point is set to mid-supply by
internal circuitry, which may be over-driven from an
external source.
The THS4508 is a high-performance amplifier that
has been optimized for use in high performance, 5-V
single-supply data acquisition systems. The output
has been optimized for best performance with its
common-mode voltages set to mid-supply, and the
input has been optimized for best performance with
its common-mode voltage set to 0.7 V. High
performance at a low power-supply voltage is ideal
for
high-performance,
single-supply
5-V
data-acquisition systems with a minimum parts count.
The combined performance of the THS4508 in a gain
of 10-dB driving the ADS5500 ADC, sampling at 125
MSPS, is 82-dBc SFDR, and 68.3-dBc SNR with a
–1-dBFS signal at 70 MHz.
The THS4508 is offered in a quad 16-pin leadless
QFN package (RGT), and is characterized for
operation over the full industrial temperature range
from –40°C to +85°C.
RS = 75 W
VSignal
VIN
175 W
130 W
348 W
VS+ = 5 V
RO
VOUTTHS4508
175 W
75 W
130 W
VS-
RO
VCM
VOUT+
348 W
Figure 1. Video Buffer
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2005–2008, Texas Instruments Incorporated
THS4508
SLAS459E – SEPTEMBER 2005 – REVISED SEPTEMBER 2008 .................................................................................................................................... www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range (unless otherwise noted).
UNIT
VSS
Supply voltage
VI
Input voltage
VS– to VS+
5.5 V
±VS
VID
Differential input voltage
4V
IO
Output current
200 mA
Continuous power dissipation
See Dissipation Rating Table
TJ
Maximum junction temperature (2)
+150°C
TJ
Maximum junction temperature, continuous operation, long term reliability (3)
+125°C
TA
Operating free-air temperature range
–40°C to +85°C
Tstg
Storage temperature range
–65°C to +150°C
ESD ratings
(1)
(2)
(3)
HBM
2000 V
CDM
1500 V
MM
100 V
Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond
those specified is not implied.
The absolute maximum temperature under any condition is limited by the constraints of the silicon process.
The maximum junction temperature for continuous operation is limited by the package constraints. Operation above this temperature
may result in reduced reliability and/or lifetime of the device. The THS4508 incorporates a (QFN) exposed thermal pad on the underside
of the chip. This acts as a heatsink and must be connected to a thermally dissipative plane for proper power dissipation. Failure to do so
may result in exceeding the maximum junction temperature which could permanently damage the device. See TI technical brief
SLMA002 and SLMA004 for more information about utilizing the QFN thermally enhanced package.
DISSIPATION RATINGS TABLE (PER PACKAGE)
PACKAGE
θJC
θJA
RGT (16)
2.4°C/W
39.5°C/W
POWER RATING
TA ≤ 25°C
TA = 85°C
2.3 W
225 mW
ORDERING INFORMATION (1)
(1)
2
PRODUCT
PACKAGELEAD
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
THS4508
QFN-16
RGT
–40°C to +85°C
THS4508
ORDERING
NUMBER
TRANSPORT MEDIA,
QUANTITY
THS4508RGTT
Tape and Reel, 250
THS4508RGTR
Tape and Reel, 3000
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
Web site at www.ti.com.
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DEVICE INFORMATION
THS4508
(RGT PACKAGE)
(TOP VIEW)
VS-
16
15
14
13
NC
1
12
PD
VIN-
2
11
VIN+
VOUT+
3
10
VOUT-
CM
4
9
5
6
7
CM
8
VS+
TERMINAL FUNCTIONS
TERMINAL
(RGT PACKAGE)
NO.
DESCRIPTION
NAME
1
NC
No internal connection
2
VIN–
Inverting amplifier input
3
VOUT+
Noninverting amplifier output
4, 9
CM
Common-mode voltage input
5–8
VS+
Positive amplifier power-supply input
10
VOUT–
Inverting amplifier output
11
VIN+
Noninverting amplifier input
12
PD
Power-down, PD = logic low puts part into low-power mode, PD = logic high or open for normal operation
13–16
VS–
Negative amplifier power-supply input
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THS4508
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ELECTRICAL CHARACTERISTICS; VS+ – VS– = 5 V:
Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, T = +25°C Single-Ended Input, Differential Output, Input Referenced to Ground, and Output Referenced to
Mid-supply.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
TEST
LEVEL (1)
AC PERFORMANCE (see Figure 44)
Small-Signal Bandwidth
G = 6 dB, VO = 100 mVPP
2
G = 10 dB, VO = 100 mVPP
1.7
GHz
G = 14 dB, VO = 100 mVPP
600
MHz
G = 20 dB, VO = 100 mVPP
300
MHz
Gain-Bandwidth Product
G = 20 dB
Bandwidth for 0.1 dB flatness
Large-Signal Bandwidth
3
GHz
G = 10 dB, VO = 2 VPP
400
MHz
G = 10 dB, VO = 2 VPP
1.5
GHz
6400
V/µs
0.5
ns
0.5
ns
Slew Rate (Differential)
Rise Time
Fall Time
GHz
VO = 2-V Step
Settling Time to 1%
2
ns
Settling Time to 0.1%
12
µs
2nd-Order Harmonic Distortion
3rd-Order Harmonic Distortion
f = 10 MHz
–104
f = 50 MHz
–82
f = 100 MHz
–69
f = 10 MHz
–105
f = 50 MHz
–92
f = 100 MHz
2nd-Order Intermodulation Distortion
200-kHz tone spacing,
RL = 499 Ω
3rd-Order Intermodulation Distortion
2nd-Order Output Intercept Point
200-kHz tone spacing,
RL = 100 Ω
3rd-Order Output Intercept Point
dBc
–81
fC = 70 MHz
–78
fC = 140 MHz
–64
fC = 70 MHz
–95
fC = 140 MHz
–78
fC = 70 MHz
78
fC = 140 MHz
58
fC = 70 MHz
42
fC = 140 MHz
dBc
dBm
35
fC = 70 MHz
12.2
fC = 140 MHz
10.8
Noise Figure
50-Ω system, 10 MHz
19.2
dB
Input Voltage Noise
f > 10 MHz
2.3
nV/√Hz
Input Current Noise
f > 10 MHz
2.9
pA/√Hz
1-dB Compression Point (2)
C
dBm
DC PERFORMANCE
Open-Loop Voltage Gain (AOL)
Input Offset Voltage
68
TA = +25°C
1
4
TA = –40°C to +85°C
1
5
Average Offset Voltage Drift
Input Bias Current
2.3
TA = +25°C
TA = –40°C to +85°C
Average Bias Current Drift
Input Offset Current
(2)
4
8
15.5
8
18.5
20
TA = +25°C
0.5
3.6
TA = –40°C to +85°C
0.5
7
Average Offset Current Drift
(1)
1.75
7
dB
C
mV
A
µV/°C
B
µA
A
nA/°C
B
µA
A
nA/°C
B
Test levels: (A) 100% tested at 25°C. Overtemperature limits by characterization and simulation. (B) Limits set by characterization and
simulation. (C) Typical value only for information.
The 1-dB compression point is measured at the load with 50-Ω double termination. Add 3 dB to refer to amplifier output.
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ELECTRICAL CHARACTERISTICS; VS+ – VS– = 5 V: (continued)
Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, T = +25°C Single-Ended Input, Differential Output, Input Referenced to Ground, and Output Referenced to
Mid-supply.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
TEST
LEVEL (1)
V
B
INPUT
Common-Mode Input Range High
2.3
Common-Mode Input Range Low
–0.3
Common-Mode Rejection Ratio
Differential Input Impedance
Common-Mode Input Impedance
90
dB
B
18.2 ||
2.2
MΩ || pF
C
3.8 || 2.5
MΩ || pF
C
OUTPUT
Maximum Output Voltage High
Each output with 100 Ω
to mid-supply
Minimum Output Voltage Low
Differential Output Voltage Swing
TA = +25°C
3.7
3.8
TA = –40°C to
+85°C
3.6
3.8
V
TA = +25°C
1.2
1.3
TA = –40°C to
+85°C
1.2
1.4
TA = +25°C
4.8
5.2
TA = –40°C to +85°C
4.4
5.2
A
V
A
Differential Output Current Drive
RL = 10 Ω
96
mA
C
Output Balance Error
VO = 100 mV, f = 1 MHz
–43
dB
C
Closed-Loop Output Impedance
f = 1 MHz
0.3
Ω
C
Small-Signal Bandwidth
700
MHz
Slew Rate
110
V/µs
1
V/V
OUTPUT COMMON-MODE VOLTAGE CONTROL
Gain
Output Common-Mode Offset from CM input
1.25 V < CM < 3.5 V
5
mV
CM Input Bias Current
1.25 V < CM < 3.5 V
±40
µA
CM Input Voltage Range
1.25 to
3.75
V
CM Input Impedance
32 || 1.5
kΩ || pF
2.5
V
CM Default Voltage
C
POWER SUPPLY
3.75 (3)
Specified Operating Voltage
Maximum Quiescent Current
TA = +25°C
TA = –40°C to +85°C
Minimum Quiescent Current
TA = +25°C
TA = –40°C to +85°C
5
5.25
39.2
42.5
39.2
43.5
35.9
39.2
35
39.2
Power-Supply Rejection (±PSRR)
To differential output
POWER-DOWN
Referenced to VS–
Enable Voltage Threshold
Device assured on above 2.1 V
> 2.1
Disable Voltage Threshold
Device assured off below 0.7 V
< 0.7
TA = +25°C
0.65
0.9
TA = –40°C to +85°C
0.65
1
Power-Down Quiescent Current
Input Bias Current
PD = VS–
Input Impedance
90
V
C
mA
A
dB
C
V
C
mA
A
100
µA
50 || 2
kΩ || pF
Turn-on Time Delay
Measured to output on
55
ns
Turn-off Time Delay
Measured to output off
10
µs
(3)
C
See the Application Information section of this data sheet for device operation with full supply voltages less than 5 V.
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TYPICAL CHARACTERISTICS
TYPICAL AC PERFORMANCE: VS+ – VS– = 5 V
Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
Small-Signal Frequency Response
Figure 2
Large Signal Frequency Response
Figure 3
HD2, G = 6 dB, VOD = 2 VPP
vs Frequency
Figure 4
HD3, G = 6 dB, VOD = 2 VPP
vs Frequency
Figure 5
HD2, G = 10 dB, VOD = 2 VPP
vs Frequency
Figure 6
HD3, G = 10 dB, VOD = 2 VPP
vs Frequency
Figure 7
HD2, G = 14 dB, VOD = 2 VPP
vs Frequency
Figure 8
HD3, G = 14 dB, VOD = 2 VPP
vs Frequency
Figure 9
HD2, G = 10 dB
vs Output voltage
Figure 10
HD3, G = 10 dB
vs Output voltage
Figure 11
HD2, G = 10 dB
vs CM input voltage
Figure 12
HD3, G = 10 dB
vs CM input voltage
Figure 13
IMD2, G = 6 dB, VOD = 2 VPP
vs Frequency
Figure 14
IMD3, G = 6 dB, VOD = 2 VPP
vs Frequency
Figure 15
IMD2, G = 10 dB, VOD = 2 VPP
vs Frequency
Figure 16
IMD3, G = 10 dB, VOD = 2 VPP
vs Frequency
Figure 17
IMD2, G = 14 dB, VOD = 2 VPP
vs Frequency
Figure 18
IMD3, G = 14 dB, VOD = 2 VPP
vs Frequency
Figure 19
OIP2
vs Frequency
Figure 20
OIP3
vs Frequency
Figure 21
S-Parameters
vs Frequency
Figure 22
Transition Rate
vs Output Voltage
Figure 23
Harmonic
Distortion
Intermodulation
Distortion
Output Intercept Point
Transient Response
Figure 24
Settling Time
Figure 25
0.1 dB Flatness
Figure 26
Rejection Ratio
vs Frequency
Figure 27
Output Impedance
vs Frequency
Figure 28
Overdrive Recovery
Output Voltage Swing
Figure 29
vs Load Resistance
Figure 30
Turn-Off Time
Figure 31
Turn-On Time
Figure 32
Input Offset Voltage
vs Input Common-Mode Voltage
Figure 33
Open Loop Gain
vs Frequency
Figure 34
Input Referred Noise
vs Frequency
Figure 35
Noise Figure
vs Frequency
Figure 36
Quiescent Current
vs Supply Voltage
Figure 37
Output Balance Error
vs Frequency
Figure 38
CM Input Impedance
vs Frequency
Figure 39
CM Small-Signal Frequency Response
Figure 40
CM Input Bias Current
vs CM Input Voltage
Figure 41
Differential Output Offset Voltage
vs CM Input Voltage
Figure 42
Output Common-Mode Offset
vs CM Input Voltage
Figure 43
6
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TYPICAL AC PERFORMANCE: VS+ – VS– = 5 V
Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
SMALL-SIGNAL FREQUENCY RESPONSE
LARGE-SIGNAL FREQUENCY RESPONSE
22
G = 20 dB
20
20
18
18
16
Small Signal Gain - dB
Small Signal Gain - dB
22
G = 14 dB
14
12
G = 10 dB
10
8
G = 6 dB
6
G = 20 dB
16
G = 14 dB
14
12
G = 10 dB
10
8
G = 6 dB
6
4
4
VO = 100 mVPP
2
VOD = 2 VPP
2
0
0
100 k
10 M
100 M
f - Frequency - Hz
1M
1G
100 k
10 G
10 M
100 M
f - Frequency - Hz
1M
Figure 2.
HD2 vs FREQUENCY
HD3 vs FREQUENCY
-60
G = 6 dB,
VOD = 2 VPP
-70
-70
G = 6 dB,
VOD = 2 VPP
-80
-80
HD3 - dBc
HD2 - dBc
10 G
Figure 3.
-50
-60
1G
RL = 100 W
-90
RL = 1 kW
RL = 200 W
-90
-100
RL = 499 W
RL = 100 W
-100
-110
-110
R L = 1 kW
RL = 499 W
-120
1M
10 M
100 M
1G
-120
1M
RL = 200 W
10 M
100 M
1G
f - Frequency - Hz
f - Frequency - Hz
Figure 4.
Figure 5.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
HD2 vs FREQUENCY
HD3 vs FREQUENCY
-60
-60
G = 10 dB,
VOD = 2 VPP
-70
-70
-80
HD3 - dBc
-80
HD2 - dBc
G = 10 dB,
VOD = 2 VPP
RL = 100 W
-90
RL = 200 W
RL = 1 kW
-90
RL = 100 W
-100
-100
RL = 200 W
-110
RL = 499 W
-110
RL = 499 W
RL = 1 kW
-120
1M
10 M
100 M
-120
1M
1G
10 M
Figure 6.
1G
Figure 7.
HD2 vs FREQUENCY
HD3 vs FREQUENCY
-60
-50
-60
100 M
f - Frequency - Hz
f - Frequency - Hz
G = 14 dB,
VOD = 2 VPP
G = 14 dB,
VOD = 2 VPP
-70
-70
RL = 100 W
-80
-90
HD3 - dBc
HD2 - dBc
RL = 200 W
-90
-100
RL = 499 W
-80
RL = 1 kW
RL = 499 W
RL = 100 W
-100
-110
RL = 200 W
R L = 1 kW
-120
1M
10 M
100 M
1G
-110
1M
f - Frequency - Hz
Figure 8.
8
10 M
f - Frequency - Hz
100 M
1G
Figure 9.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
HD2 vs OUTPUT VOLTAGE
HD3 vs OUTPUT VOLTAGE
-40
-40
-50
f = 100 MHz
f = 100 MHz
-60
-60
f = 64 MHz
HD3 - dBc
f = 64 MHz
-70
HD2 - dBc
f = 150 MHz
G = 10 dB,
VOD = 2 VPP
f = 150 MHz
G = 10 dB,
VOD = 2 VPP
-50
f = 32 MHz
-80
-90
-70
f = 32 MHz
-80
-90
f = 8 MHz
-100
-100
f = 16 MHz
-110
-110
-120
-120
0
1
3
2
4
f = 16 MHz
f = 8 MHz
0
5
1
VO - Output Voltage -VPP
Figure 10.
HD2 vs CM OUTPUT VOLTAGE
HD3 vs CM OUTPUT VOLTAGE
0
VCM = 1.2 V to 3.8 V
VOD = 2 VPP
150 MHz
-40
HD3 - dBc
HD2 - dBc
VCM = 1.2 V to 3.8 V
VOD = 2 VPP
-20
150 MHz
100 MHz
-30
-50
-70
64 MHz
100 MHz
-60
-80
64 MHz
-90
16 MHz
-100
-110
1 MHz
1.2
1.6
1 MHz
16 MHz
4 MHz
-130
2
2.4
5
4
Figure 11.
10
-10
3
2
VO - Output Voltage -VPP
2.8
4 MHz
-120
3.6 3.8
3.2
1.2
CM - Common Mode Output Voltage - V
Figure 12.
1.6
2
2.4
2.8
3.2
3.6 3.8
CM - Common Mode Output Voltage - V
Figure 13.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
IMD2 vs FREQUENCY
IMD3 vs FREQUENCY
−30
-50
G = 6 dB,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
−40
G = 6 dB,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
-60
RL = 200 W
RL = 100 W
RL = 100 W
-70
IMD3- dBc
IMD2 − dBc
−50
−60
−70
-90
RL = 499 W
−80
RL = 1 kW
R L = 1 kW
−90
RL = 200 W
-80
-100
RL = 499 W
-110
−100
0
50
100
150
0
200
50
Figure 14.
IMD3 vs FREQUENCY
-60
G = 10 dB,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
RL = 100 W
G = 10 dB,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
-65
RL = 200 W
RL = 100 W
-70
IMD3 - dBc
-50
IMD2 - dBc
200
Figure 15.
IMD2 vs FREQUENCY
-40
150
f - Frequency - MHz
f − Frequency − MHz
-30
100
-60
-70
RL = 499 W
-80
-75
RL = 200 W
-80
-85
RL = 1 kW
-90
RL = 1 kW
-90
-95
-100
-100
RL = 499 W
0
50
100
150
200
0
100
150
200
f - Frequency - MHz
f - Frequency - MHz
Figure 16.
10
50
Figure 17.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
IMD2 vs FREQUENCY
IMD3 vs FREQUENCY
-60
-40
RL = 100 W
-50
-70
RL = 200 W
RL = 200 W
-75
IMD3 - dBc
-60
RL = 1 kW
IMD2 - dBc
RL = 100 W
-65
-70
RL = 499 W
-80
-80
-85
RL = 1 kW
-90
-95
G = 14 dB,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
-100
G = 14 dB,
VOD = 2 VPP Envelope,
-90
RL = 499 W
-105
200 kHz Tone Spacing
-110
-100
0
50
100
150
0
200
50
f - Frequency - MHz
150
200
f - Frequency - MHz
Figure 18.
Figure 19.
OIP2 vs FREQUENCY
90
100
OIP3 vs FREQUENCY
50
G = 10 dB
85
80
45
G = 14 dB
G = 10 dB
OIP3 - dBm
OIP2 - dBm
75
70
65
G = 6 dB
60
G = 6 dB
40
G = 14 dB
35
55
RL = 100 W,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
50
45
40
0
50
RL = 100 W,
VOD = 2 VPP Envelope,
200 kHz Tone Spacing
30
100
150
200
25
0
f - Frequency - MHz
50
100
150
200
f - Frequency - MHz
Figure 20.
Figure 21.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
S-PARAMETERS vs FREQUENCY
TRANSITION RATE vs OUTPUT VOLTAGE
20
8000
7000
S21
0
-20
Transition Rate - V/ms
s-Parameters - dB
-10
S11
-30
-40
S22
-50
-60
S12
-70
Rising
Gain = 10 dB,
RL = 200 W
20 % - 80%
10
6000
Falling
5000
4000
3000
2000
1000
-80
-90
100 k
10 M
1M
100 M
1G
0
10 G
0
0.5
1
f - Frequency - Hz
1.5
2.5
2
Figure 22.
TRANSIENT RESPONSE
SETTLING TIME
VOD = 2 V step
3.5
0.3
3.25
3
Gain = 10 dB,
RL = 200 W,
VOD = 2 VPP
2.75
2.5
2.25
2
1.75
1.5
Percent of Final Value - %
VOD - Differential Output Voltage - V
4
0.5
3.75
0.1
-0.1
-0.3
1.25
-0.5
1
t - Time - (250 psec/div)
t - Time - 1 ns/div
Figure 24.
Figure 25.
0.1-dB FLATNESS
REJECTION RATIO vs FREQUENCY
10.5
10.4
100
90
VOD = 100 mVPP
Rejection Ratio - dB
10.2
10.1
10
9.9
9.8
70
CMRR
60
50
40
30
20
9.7
9.6
100 k
PSRR+
80
10.3
Signal Gain - dB
3.5
Figure 23.
4
VCM = VS / 2,
RL = 200 W
10
0
1M
10 M
100 M
1G
10 k
100 k
1M
10 M
100 M
1G
f - Frequency - Hz
f - Frequency - Hz
Figure 26.
12
3
VO - Output Voltage - V
Figure 27.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
OUTPUT IMPEDANCE vs FREQUENCY
OVERDRIVE RECOVERY
5.75
2
Input
1.5
3.75
VO - Output Voltage - V
ZO - Output Impedance - W
4.75
10
1
2.75
1
Output
1.75
0.5
0.75
-0.25
0
-1.25
-0.5
-2.25
Gain = 10 dB,
RL = 200 W
-3.25
-4.25
0.1
100 k
-1
-1.5
-5.25
1M
10 M
100 M
VI - Input Voltage - V
100
t - Time - 100 ns/div
1G
f - Frequency - Hz
Figure 28.
Figure 29.
6
5
4
3
2
1
0
10
100
3
2.8
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Output
PD Input
Gain = 10 dB,
RL = 200 W
1000
6.4
6
5.6
5.2
4.8
4.4
4
3.6
3.2
2.8
2.4
2
1.6
1.2
0.8
Powerdown Input - V
TURN-OFF TIME
3.2
VO - Output Voltage - V
VOD - Differential Output Voltage Swing - V
VOD SWING vs LOAD RESISTANCE
7
0.4
0
t - Time - (2.5 ms/div)
RL - Load Resistance - kW
Figure 30.
Figure 31.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
INPUT OFFSET VOLTAGE vs CM INPUT VOLTAGE
PD Input
Output
Gain = 10 dB,
RL = 200 W
10
9
VOS - Input Offset Voltage - mV
6.4
6
5.6
5.2
4.8
4.4
4
3.6
3.2
2.8
2.4
2
1.6
1.2
0.8
0.4
0
Powerdown Input - V
VO - Output Voltage - V
TURN-ON TIME
3
2.8
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
8
7
6
5
4
3
2
1
0
-0.5
t - Time - (2.5 ms/div)
0
0.5
1
2
1.5
2.5
3
VIC - Commom-Mode Input Voltage - V
Figure 32.
Figure 33.
OPEN LOOP GAIN AND PHASE vs FREQUENCY
INPUT-REFERRED NOISE vs FREQUENCY
100
50
90
Open Loop Gain − dB
Phase
Gain
60
−50
50
40
−100
30
−150
20
10
−200
Vn - Voltage Noise - nVÖHz
In - Current Noise - pAÖHz
0
70
Open Loop Phase − degrees
80
10
In
Vn
0
−250
−10
1
100
10 k
1M
100 M
10 G
1
10k
f − Frequency − Hz
1M
10M
f - Frequency - Hz
Figure 34.
14
100k
Figure 35.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
NOISE FIGURE vs FREQUENCY
QUIESCENT CURRENT vs SUPPLY VOLTAGE
22
44
21
G = 6 dB
IQ - Quiescent Current - mA
Noise Figure - dB
20
19
G = 10 dB
18
17
G = 14 dB
50-W System
16
15
14
TA = 25oC
42
G = 20 dB
TA = 85oC
40
38
36
o
TA = -40 C
34
32
30
13
28
3.75
12
0
20
40
60
80 100 120 140
160 180
200
4
4.25
Figure 36.
OUTPUT BALANCE ERROR vs FREQUENCY
5.25
CM INPUT IMPEDANCE vs FREQUENCY
100 k
Gain = 10 dB,
VCOM = VS / 2,
Common-Mode Input Impedance - W
Output Balance Error - dB
-20
5
4.75
Figure 37.
0
-10
4.5
VS - Supply Voltage - V
f - Frequency - MHz
RL = 200 W,
VOD = 2 VPP
-30
-40
-50
-60
100 k
1M
10 M
100 M
1G
10 k
1k
100
10
100 k
f - Frequency - Hz
1M
10 M
100 M
1G
f - Frequency - Hz
Figure 38.
Figure 39.
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Test conditions unless otherwise noted: VS+ = 5 V, VS– = 0 V, G = 10 dB, CM = open, VO = 2 VPP, RF = 349 Ω, RL = 200 Ω
Differential, Single-Ended Input, Input Referenced to Ground and Output Referenced to Midrail
CM SMALL-SIGNAL FREQUENCY RESPONSE
CM BIAS CURRENT vs CM INPUT VOLTAGE
5
Common-Mode Input-Bias Current - mA
200
0
Gain - dB
-5
-10
-15
-20
-25
-30
100 k
1M
10 M
100 M
100
0
-100
-200
-300
1G
0
0.5
f - Frequency - Hz
2
2.5
3
3.5
4
5
4.5
Figure 40.
Figure 41.
VOD OFFSET VOLTAGE vs CM INPUT VOLTAGE
VOC OFFSET VOLTAGE vs CM INPUT VOLTAGE
4
3
2
1
0
-1
0
0.5
1
1.5
2
2.5
3
3.5
4.5
4
VIC - Common-Mode Input Voltage - V
5
VOC - Common-Mode Output Offset Voltage - mV
Differential Output Offset Voltage - mV
1.5
VIC - Common-Mode Input Voltage - V
5
50
40
30
20
10
0
-10
-20
-30
-40
-50
0
Figure 42.
16
1
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
VIC - Common-Mode Input Voltage - V
Figure 43.
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TEST CIRCUITS
The THS4508 is tested with the following test circuits
built on the EVM. For simplicity, the power supply
decoupling is not shown—see the layout in the
Application Information section for recommendations.
Depending on the test conditions, component values
are changed per the following tables, or as otherwise
noted. The signal generators used are ac-coupled
50-Ω sources, and a 0.22-µF capacitor and a 49.9-Ω
resistor to ground are inserted across RIT on the
alternate input to balance the circuit.
The output is probed using a high-impedance
differential probe across the 100-Ω resistor. The gain
is referred to the amplifier output by adding back the
6-dB loss due to the voltage divider on the output.
From
50 W
Source
VIN
RF
RG
RIT
5V
49.9 W
RG
0.22 mF
THS4508
49.9 W
CM
RIT
RF
GAIN
RF
RG
RIT
6 dB
348 Ω
165 Ω
61.9 Ω
10 dB
348 Ω
100 Ω
69.8 Ω
14 dB
348 Ω
56.2 Ω
88.7 Ω
20 dB
348 Ω
16.5 Ω
287 Ω
Note the gain setting includes 50-Ω source
impedance. Components are chosen to achieve
gain and 50-Ω input termination.
Table 2. Load Component Values
RL
RO
ROT
Output Measured
Here With High
Impedance
Differential Probe
Open
0.22 mF
49.9 W
Table 1. Gain Component Values
100 W
Atten.
100 Ω
25 Ω
Open
6 dB
200 Ω
86.6 Ω
69.8 Ω
16.8 dB
499 Ω
237 Ω
56.2 Ω
25.5 dB
1k Ω
487 Ω
52.3 Ω
31.8 dB
Note the total load includes 50-Ω termination by
the test equipment. Components are chosen to
achieve load and 50-Ω line termination through a
1:1 transformer.
Due to the voltage divider on the output formed by
the load component values, the amplifier output is
attenuated. The column Atten in Table 2 shows the
attenuation expected from the resistor divider. When
using a transformer at the output as shown in
Figure 45, the signal will see slightly more loss, and
these numbers will be approximate.
Figure 44. Frequency Response Test Circuit
Distortion and 1 db Compression
The circuit shown in Figure 45 is used to measure
harmonic distortion, intermodulation distortion, and
1-db compression point of the amplifier.
A signal generator is used as the signal source and
the output is measured with a spectrum analyzer. The
output impedance of the signal generator is 50 Ω. RIT
and RG are chosen to impedance-match to 50 Ω, and
to maintain the proper gain. To balance the amplifier,
a 0.22-µF capacitor and 49.9-Ω resistor to ground are
inserted across RIT on the alternate input.
A low-pass filter is inserted in series with the input to
reduce harmonics generated at the signal source.
The level of the fundamental is measured, then a
high-pass filter is inserted at the output to reduce the
fundamental so that it does not generate distortion in
the input of the spectrum analyzer.
The transformer used in the output to convert the
signal from differential to single-ended is an
ADT1-1WT. It limits the frequency response of the
circuit so that measurements cannot be made below
approximately 1 MHz.
From
50 W
Source
VIN
RF
RG
RIT
5V
RO
Frequency Response
The circuit shown in Figure 44 is used to measure the
frequency response of the circuit.
A network analyzer is used as the signal source and
as the measurement device. The output impedance
of the network analyzer is 50 Ω. RIT and RG are
chosen to impedance match to 50 Ω, and to maintain
the proper gain. To balance the amplifier, a 0.22-µF
capacitor and 49.9-Ω resistor to ground are inserted
across RIT on the alternate input.
RG
0.22 mF
RIT
THS4508
RO
1:1
VOUT
ROT
To 50 W
Test
Equipment
CM
Open
0.22 mF
49.9 W
RF
Figure 45. Distortion Test Circuit
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The 1-dB compression point is measured with a
spectrum analyzer with 50-Ω double termination or
100-Ω termination as shown in Table 2. The input
power is increased until the output is 1 dB lower than
expected. The number reported in the table data is
the power delivered to the spectrum analyzer input.
Add 3 dB to refer to the amplifier output.
at VOUT+ or VOUT– with the input injected at VIN, RCM =
0 Ω and RCMT = 49.9 Ω. The input impedance is
measured with RCM = 49.9 Ω with RCMT = open, and
calculated by measuring the voltage drop across RCM
to determine the input current.
0.22 mF
S-Parameter, Slew Rate, Transient Response,
Settling Time, Output Impedance, Overdrive,
Output Voltage, and Turn-On/Off Time
The circuit shown in Figure 46 is used to measure
s-parameters, slew rate, transient response, settling
time, output impedance, overdrive recovery, output
voltage swing, and turn-on/turn-off times of the
amplifier. For output impedance, the signal is injected
at VOUT with VIN left open and the drop across the
49.9 Ω resistor is used to calculate the impedance
seen looking into the amplifier output.
Because S21 is measured single-ended at the load
with 50-Ω double termination, add 12 dB to refer to
the amplifier output as a differential signal.
From V IN
50-W
Source
RG
R IT
RF
THS4508
49.9 W
VOUT-
R IT
49.9 W
49.9 W
VOUT–
RG
0.22 mF
THS4508
CM
49.9 W
To 50-W
Test
Equipment
VOUT+
To
50-W
Test
Equipment
RCM
VIN
49.9 W
RCMT
RF
From
50-W
source
Figure 47. CM Input Test Circuit
CMRR and PSRR
The circuit shown in Figure 48 is used to measure the
CMRR and PSRR of VS+ and VS–. The input is
switched appropriately to match the test being
performed.
348 W
PSRR+
From VIN
50 W
CMRR
Source
5V
49.9 W
100 W
100 W
PSRRVS-
Open
0.22 mF
49.9 W
CM
RIT
VS+
VOUT+
0.22 mF
5V
RIT
5V
49.9 W
RG
RF
RG
THS4508
CM
69.8 W
RF
49.9 W
100 W
Open
0.22 mF
Output
Measured
Here
With High
Impedance
Differential
Probe
348 W
Figure 46. S-Parameter, SR, Transient Response,
Settling Time, ZO, Overdrive Recovery, VOUT
Swing, and Turn-On/Off Test Circuit
Figure 48. CMRR and PSRR Test Circuit
CM Input
The circuit shown in Figure 47 is used to measure the
frequency response and input impedance of the CM
input. Frequency response is measured single-ended
18
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APPLICATION INFORMATION
APPLICATIONS
Single-Ended
Input
The following circuits show application information for
the
THS4508.
For
simplicity,
power-supply
decoupling capacitors are not shown in these
diagrams. For more detail on the use and operation
of fully differential operational amplifiers, refer to
application
report
Fully-Differential
Amplifiers
(SLOA054) , available for download at the TI web
site.
RF
Differential
Input
Differential
Output
5V
RG
+
V IN+
–
VOUT–
THS4508
RG
VIN–
– +
VOUT+
RF
Figure 49. Differential Input to Differential Output
Amplifier
Depending on the source and load, input and output
termination can be accomplished by adding RIT and
RO.
Single-Ended Input to Differential Output
Amplifier
The THS4508 can be used to amplify and convert
single-ended input signals to differential output
signals. A basic block diagram of the circuit is shown
in Figure 50 (CM input not shown). The gain of the
circuit is again set by RF divided by RG.
Differential
5V
Output
+
RG
–
VOUT–
THS4508
–
Differential Input to Differential Output Amplifier
The THS4508 is a fully differential operational
amplifier, and can be used to amplify differential input
signals to differential output signals. A basic block
diagram of the circuit is shown in Figure 49 (CM input
not shown). The gain of the circuit is set by RF
divided by RG.
RF
RG
+
VOUT+
RF
Figure 50. Single-Ended Input to Differential
Output Amplifier
Input Common-Mode Voltage Range
The input common-model voltage of a fully differential
operational amplifier is the voltage at the (+) and (–)
input pins of the operational amplifier.
It is important to not violate the input common-mode
voltage range (VICR) of the operational amplifier.
Assuming the operational amplifier is in linear
operation the voltage across the input pins is only a
few millivolts at most. So finding the voltage at one
input pin determines the input common-mode voltage
of the operational amplifier.
Treating the negative input as a summing node, the
voltage is given by Equation 1:
ö æ
æ
ö
RG
RF
÷ + ç VIN- ´
÷
VIC = çç VOUT + ´
÷
ç
R G + R F ÷ø
R G + RF ø è
è
(1)
To determine the VICR of the operational amplifier, the
voltage at the negative input is evaluated at the
extremes of VOUT+.
As the gain of the operational amplifier increases, the
input common-mode voltage becomes closer and
closer to the input common-mode voltage of the
source.
Setting the Output Common-Mode Voltage
The output common-mode voltage is set by the
voltage at the CM pin(s). The internal common-mode
control circuit maintains the output common-mode
voltage within 5-mV offset (typical) from the set
voltage, when set within 0.5 V of mid-supply. If left
unconnected, the common-mode set point is set to
mid-supply by internal circuitry, which may be
over-driven from an external source. Figure 51 is
representative of the CM input. The internal CM
circuit has about 700 MHz of –3-dB bandwidth, which
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is required for best performance, but it is intended to
be a dc-bias input pin. Bypass capacitors are
recommended on this pin to reduce noise at the
output. The external current required to overdrive the
internal resistor divider is given by Equation 2:
IEXT =
RS
RG
VSignal
RIT
RF
RPD
VS+ = 3.75 V to 5 V
RO
VOUT-
2VCM - (VS + - VS - )
50 kW
THS4508
RG
RO
VOUT+
(2)
CM
RS
RIT
RPD
VS–
where VCM is the voltage applied to the CM pin, and
VS+ ranges from 3.75 V to 5 V, and VS– is 0 V
(ground).
VCM
RF
Figure 52. THS4508 DC-Coupled Single-Source
Supply Range From 3.75 V to 5 V With RPD Used
To Set VIC
VS+
50 kW
to internal
CM circuit
I EXT
CM
Note that in Figure 52, the source is referenced to
ground as is the input termination resistor RIT. The
proper value of resistance to add can be calculated
from Equation 3:
50 kW
RPD =
V S–
Figure 51. CM Input Circuit
1
é
1 ê
1 .6
ê
R F ê V S + - 1 .6
êë 2
ù
ú
1
ú R
I
ú
úû
Device Operation with Single Power Supplies
Less than 5 V
The THS4508 is optimized to work in systems using a
5-V single supply, and the characterization data
presented in this data sheet were taken with 5-V
single-supply inputs. For ac-coupled systems or
dc-coupled systems operating with supplies less than
5 V and greater than 3.75 V, the amplifier input
common-mode range is maximized by adding
pull-down resistors at the device inputs. The
pull-down resistors provide additional loading at the
input, and lower the common-mode voltage that is fed
back into the device input through resistor RF.
Figure 52 shows the circuit configuration for this
mode of operation where RPD is added to the
dc-coupled circuit to avoid violating the VICR of the
operational amplifier. Note RS and RIT are added to
the alternate input from the signal input to balance
the amplifier. One resistor that is equal to the
combined value RI = RG + RS || RIT can be placed at
the alternate input.
(3)
where RI = RG + RS || RIT.
VS+ is the power-supply voltage, RF is the feedback
resistance, RG is the gain-setting resistance, RS is the
signal source resistance, and RIT is the termination
resistance.
Table 3 is a modification of Table 1 to add the proper
values with RPD assuming VS+ = 3.75 V, a dc-coupled
50-Ω source impedance, and setting the output
common-mode voltage to mid-supply.
Table 3. RPD Values for Various Gains,
VS+ = 3.75 V, DC-Coupled Signal Source
Gain
RF
RG
RIT
RPD
6 dB
348 Ω
169 Ω
64.9 Ω
86.6 Ω
10 dB
348 Ω
102 Ω
78.7 Ω
110 Ω
14 dB
348 Ω
61.9 Ω
115 Ω
158 Ω
20 dB
348 Ω
40.2 Ω
221 Ω
226 Ω
If the signal originates from an ac-coupled 50-Ω
source (see Figure 53), the equivalent dc-source
resistance is an open circuit and RI = RG + RIT.
Table 4 is a modification of Table 1 to add the proper
values with RPD assuming VS+ = 3.75 V, an
ac-coupled 50-Ω source impedance, and setting the
output common-mode voltage to mid-supply.
20
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Table 4. RPD Values for Various Gains,
VS+ = 3.75 V, AC-Coupled Signal Source
RF
RG
RIT
RPD
6 dB
348 Ω
169 Ω
64.9 Ω
80.6 Ω
10 dB
348 Ω
102 Ω
78.7 Ω
90.9 Ω
14 dB
348 Ω
61.9 Ω
115 Ω
90.9 Ω
20 dB
348 Ω
40.2 Ω
221 Ω
77.6 Ω
C
RS
0.6
0.4
Voltage - V
Gain
0.8
0.2
0
RF
RG
-0.2
RIT
V Signal
RPD
VS+ = 3.75 V to 5 V
-0.4
0
RO
5
V OUTTHS4508
RG
CM
RIT
RS
RPD
V S-
1.5
Video Buffer
Figure 54 shows a possible application of the
THS4508 as a dc-coupled video buffer with a gain of
2. Figure 55 shows a plot of the Y' signal originating
from a HDTV 720p video system. The input signal
includes a 3-level sync (minimum level at –0.3 V),
and the portion of the video signal with maximum
amplitude of 0.7 V. Although the buffer draws its
power from a 5-V single-ended power supply, internal
level shifters allow the buffer to support input signals
which are as much as –0.3 V below ground. This
allows maximum design flexibility while maintaining a
minimum parts count. Figure 56 shows the differential
output of the buffer. Note that the dc-coupled
amplifier can introduce a dc offset on a signal applied
at its input
Video
Source
VSignal
348 W
175 W
130 W
VS+ = 5 V
RO
THS4508
175 W
75 W
130 W
VS-
RO
VOD
VCM
348 W
Figure 54. Single-Supply Video Buffer, Gain = 2
VOD - Video Buffer Output - V
Figure 53. THS4508 AC-Coupled Single-Source
Supply Range From 3.75 V to 5 V With RPD Used
To Set VIC
VIN
20
Figure 55. Y' Signal With 3-Level Sync and Video
Signal
RF
RS = 75 W
15
RO
V OUT+
C
10
t - Time - ms
1
0.5
0
-0.5
-1
0
5
10
15
20
t - Time - ms
Figure 56. Video Buffer Differential Output Signal
THS4508 + ADS5500 Combined Performance
The THS4508 is designed to be a high-performance
drive amplifier for high-performance data converters
such as the ADS5500 14-bit 125-MSPS ADC.
Figure 57 shows a circuit combining the two devices,
and Figure 58 shows the combined SNR and SFDR
performance versus frequency with –1 dBFS input
signal level sampling at 125 MSPS. The THS4508
amplifier circuit provides 10 dB of gain, and converts
the single-ended input signal to a differential output
signal. The default common-mode output of the
THS4508 (2.5 V) is not compatible with the required
common-mode input of the ADS5500 (1.55 V), so
dc-blocking capacitors are added (0.22 µF). Note that
a biasing circuit (not shown in Figure 57) is needed to
provide the required common-mode, dc-input for the
ADS5500. The 100-Ω resistors and 2.7-pF capacitor
between the THS4508 outputs and ADS5500 inputs
along with the input capacitance of the ADS5500 limit
the bandwidth of the signal to 115 MHz (–3 dB). For
testing, a signal generator is used for the signal
source. The generator is an ac-coupled 50-Ω source.
A band-pass filter is inserted in series with the input
to reduce harmonics and noise from the signal
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source. Input termination is accomplished via the
69.8-Ω resistor and 0.22-µF capacitor to ground in
conjunction with the input impedance of the amplifier
circuit. A 0.22-µF capacitor and 49.9-Ω resistor is
inserted to ground across the 69.8-Ω resistor and
0.22-µF capacitor on the alternate input to balance
the circuit. Gain is a function of the source
impedance, termination, and 348-Ω feedback resistor.
See Table 1 for component values to set proper 50-Ω
termination for other common gains.
VIN
100 W
From
50-W
source
When the THS4508 is operated from a single power
supply with VS+ = 5 V and VS– = ground, the 2.5-V
output common-mode voltage is compatible with the
recommended value of the ADS5424 input
common-mode voltage (2.4 V).
From
50-W
source
348 W
5V
69.8 W
The 225-Ω resistors and 2.7-pF capacitor between
the THS4508 outputs and ADS5424 inputs (along
with the input capacitance of the ADC) limit the
bandwidth of the signal to about 100 MHz (–3 dB).
0.22 mF
V IN
69 .8 W
49.9 W
5V
14-bit,
125 MSPS
100 W
225 W
A IN +
THS4508
100
ADS5500
2.7 pF
100 W
348 W
100 W
THS4508
225 W
2 .7 pF
A IN - CM
CM
69.8 W
0.22 mF
49 .9 W
100 W
CM
69 .8 W
49.9 W
0.22 mF
0.22 mF
0.1 mF
0.1 mF
348 W
348 W
14-bit,
105 MSPS
A IN+
ADS5424
A IN– VBG
0.1 mF
Figure 59. THS4508 + ADS5424 Circuit
Figure 57. THS4508 + ADS5500 Circuit
95
95
SFDR
90
90
85
85
SFDR
80
80
75
75
SNR
SNR
70
70
65
60
10
65
10
20
30
40
50
60
70
80
90
100
20
30
40
50
60
110
Input Frequency - MHz
Input Frequency - MHz
Figure 58. THS4508 + ADS5500 SFDR and SNR
Performance versus Frequency
Figure 60. THS4508 + ADS5424 SFDR and SNR
Performance vs Frequency
THS4508 + ADS5424 Combined Performance
Figure 59 shows the THS4508 driving the ADS5424
ADC, and Figure 60 shows the combined SNR and
SFDR performance versus frequency with –1 dBFS
input signal level and sampling at 80 MSPS.
As before, the THS4508 amplifier provides 10 dB of
gain, converts the single-ended input to differential,
and sets the proper input common-mode voltage to
the ADS5424. Input termination and circuit testing is
the same as described above for the THS4508 +
ADS5500 circuit.
22
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Layout Recommendations
It is recommended to follow the layout of the external
components near the amplifier, ground plane
construction, and power routing of the EVM as
closely as possible. General guidelines are:
1. Signal routing should be direct and as short as
possible into and out of the operational amplifier
circuit.
2. The feedback path should be short and direct
avoiding vias.
3. Ground or power planes should be removed from
directly under the amplifier’s input and output
pins.
4. An output resistor is recommended on each
output, as near to the output pin as possible.
5. Two 10-µF and two 0.1-µF power-supply
decoupling capacitors should be placed as near
to the power-supply pins as possible.
6. Two 0.1-µF capacitors should be placed between
the CM input pins and ground. This limits noise
coupled into the pins. One each should be placed
to ground near pin 4 and pin 9.
7. It is recommended to split the ground pane on
layer 2 (L2) as shown below and to use a solid
ground on layer 3 (L3). A single-point connection
should be used between each split section on L2
and L3.
8. A single-point connection to ground on L2 is
recommended for the input termination resistors
R1 and R2. This should be applied to the input
gain resistors if termination is not used.
9. The THS4508 recommended printed circuit board
(PCB) footprint is shown in Figure 61.
0.144
0.049
0.012
Pin 1
0.0095
0.015
0.144
0.0195 0.0705
0.010
vias
0.032
0.030
0.0245
Top View
Figure 61. QFN Etch and Via Pattern
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THS4508 EVM
Figure 62 is the THS4508 EVAL1 EVM schematic. Layers 1 through 4 of the PCB are shown in Figure 63
through Figure 66 , and Table 5 lists the bill of material for the EVM as supplied from TI.
GND
VS+
J5
J6
10 mF
TP1
J1
C15
R12
49.9 W
PD
2
3
VO+
+
R4
100 W
4
VOPwrPad 10
R7
9
J3
T1
86.6 W
R8
6
R11
69.8 W
5
1
86.6 W
4
3
Vocm
R2
69.8 W
C13
R9
open
7
U1 11
0.22 mF
J2
12
0.1 mF
C12
VCC
VCC
8
6
5
0.1 mF
C5
J8
348 W
100 W
10 mF
C3
R5
R1
69.8 W
R3
VCC
C8
open
XFMR_ADT1-1WT
15 13
14 16
R10
open
R6
C1
open
C7
open
C2
open
J7
348 W
TP3
TP2
C14
0.1 mF
C11
0.1 mF
Figure 62. THS4508 EVAL1 EVM Schematic
24
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Table 5. THS4508RGT EVM Bill of Materials
ITEM
(1)
DESCRIPTION
SMD
SIZE
REFERENCE
DESIGNATOR
PCB
QTY
MANUFACTURER'S
PART NUMBER (1)
1
CAP, 10.0 F, Ceramic, X5R, 6.3V
0805
C3, C5
2
(AVX) 08056D106KAT2A
2
CAP, 0.1 µF, Ceramic, X5R, 10V
0402
C11, C12, C13, C14
4
(AVX) 0402ZD104KAT2A
3
CAP, 0.22 µF, Ceramic, X5R, 6.3V
0402
C15
1
(AVX) 04026D224KAT2A
4
OPEN
0402
C1, C2, C7, C8, C9, C10
6
5
OPEN
0402
R9, R10
2
6
Resistor, 49.9 Ω, 1/16W, 1%
0402
R12
1
(KOA) RK73H1ETTP49R9F
8
Resistor, 69.8 Ω, 1/16W, 1%
0402
R1, R2, R11
3
(KOA) RK73H1ETTP69R8F
9
Resistor, 86.6 Ω, 1/16W, 1%
0402
R7, R8
2
(KOA) RK73H1ETTP86R6F
10
Resistor, 100 Ω, 1/16W, 1%
0402
R3, R4
2
(KOA) RK73H1ETTP1000F
11
Resistor, 348 Ω, 1/16W, 1%
0402
R5, R6
2
(KOA) RK73H1ETTP3480F
12
Resistor, 0 Ω, 5%
0805
C4, C6
2
(KOA) RK73Z2ATTD
13
Transformer, RF
T1
1
(MINI-CIRCUITS) ADT1-1WT
14
Jack, banana receptance, 0.25" diameter
hole
J5, J6
15
OPEN
J1, J7, J8
3
16
Connector, edge, SMA PCB Jack
J2, J3
2
(JOHNSON) 142-0701-801
17
Test point, Red
TP1, TP2, TP3
3
(KEYSTONE) 5000
18
IC, THS4508
U1
1
(TI) THS4508RGT
19
Standoff, 4-40 HEX, 0.625" length
4
(KEYSTONE) 1808
20
SCREW, PHILLIPS, 4-40, 0.250"
4
SHR-0440-016-SN
21
Printed circuit board
1
(TI) EDGE# 6468901
2
(HH SMITH) 101
The manufacturer's part numbers were used for tesr purposes only.
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Figure 63. THS4508 EVM Top Layer
Figure 64. THS4508 EVM Layer 1
Figure 65. THS4508 EVM Layer 2
26
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Figure 66. THS4508 EVM Bottom Layer
EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the input and output voltage ranges as specified in the table provided
below.
Input Range, VS+ to VS–
3.0 V to 6.0 V
Input Range, VI
3.0 V to 6.0 V NOT TO EXCEED VS+ or VS–
Output Range, VO
3.0 V to 6.0 V NOT TO EXCEED VS+ or VS–
Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM. If
there are questions concerning the input range, please contact a TI field representative prior to connecting the
input power.
Applying loads outside of the specified output range may result in unintended operation and/or possible
permanent damage to the EVM. Please consult the product data sheet or EVM user's guide (if user's guide is
available) prior to connecting any load to the EVM output. If there is uncertainty as to the load specification,
please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than +30°C. The EVM is
designed to operate properly with certain components above +50°C as long as the input and output ranges are
maintained. These components include but are not limited to linear regulators, switching transistors, pass
transistors, and current sense resistors. These types of devices can be identified using the EVM schematic
located in the material provided. When placing measurement probes near these devices during operation, please
be aware that these devices may be very warm to the touch.
Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265
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Revision History
Changes from Revision D (May 2007) to Revision E ...................................................................................................... Page
•
•
28
Added Ordering Information table.......................................................................................................................................... 2
Changed Figure 35; corrected x-axis scale values.............................................................................................................. 14
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
THS4508RGTT
ACTIVE
VQFN
RGT
16
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
4508
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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