FEATURES
D
VERY LOW NOISE: 0.7nV/
/
Hz
D
LOW-NOISE PREAMP (LNP)
- Active Termination
- Programmable Gains: 3, 12, 18, 22dB
- Programmable Input Impedance (R
F
)
- Buffered, Differential Outputs for CW
Processing
- Excellent Input Signal Handling
Capabilities
D
LOW-NOISE VARIABLE-GAIN AMPLIFIER
- High/Low-Mode (0/+6dB)
- 52dB Gain Control Range
- Linear Control Response: 22dB/V
- Switchable Differential Inputs
- Adjustable Output Clipping-Level
D
BANDWIDTH: 42MHz
D
HARMONIC DISTORTION: -55dB
D
5V SINGLE SUPPLY
D
LOW-POWER: 154mW/Channel
D
POWER-DOWN MODES
D
SMALL QFN-48 PACKAGE (7x7mm)
APPLICATIONS
D
MEDICAL AND INDUSTRIAL ULTRASOUND
SYSTEMS
- Suitable for 10-Bit and 12-Bit Systems
D
TEST EQUIPMENT
DESCRIPTION
The VCA2615 is a dual-channel, variable gain amplifier
consisting of a Low-Noise Preamplifier (LNP) and a Variable-
Gain Amplifier (VGA). This combination along with the device
features makes it well-suited for a variety of ultrasound
systems.
The LNP offers a high level of flexibility to adapt to a wide range
of systems and probes. The LNP gain can be programmed to
one of four settings (3, 12, 18, 22dB), while maintaining
excellent noise and signal handling characteristics. The input
impedance of the LNP can be controlled by selecting one of
the built-in feedback resistors.This active termination allows
the user to closely match the LNP to a given source
impedance, resulting in optimized overall system noise
performance. The differential LNP outputs are provided either
as buffered outputs for further CW processing, or fed directly
into the variable-gain amplifier (VGA). Alternatively, an
external signal can be applied to the differential VGA inputs
through a programmable switch.
Following a linear-in-dB response, the gain of the VGA can be
varied over a 52dB range with a 0.2V to 2.5V control voltage
common to both channels of the VCA2615. In addition, the
overall gain can be switched between a 0dB and +6dB
postgain, allowing the user to optimize the output swing of
VCA2615 for a variety of high-speed Analog-to-Digital
Converters (ADCs). As a means to improve system overload
recovery time, the VCA2615 provides an internal clipping
function where an externally applied voltage sets the desired
clipping level.
The VCA2615 operates on a single +5V supply and is
available in a small QFN-48 package (7x7mm).
MUX
52dB
Range
Feedback
Resistors
(3, 12, 18, 22dB)
LNP
+1
1/2 VCA2615
LNP
IN
+
LNP
OUT
-
FB1 FB2 FB3 FB4
+1
LNP
OUT
+
VCA
IN
+
VCA
IN
-
H/L
(0dB or
+6dB)
G1 G1
V
CNTL
V
CLMP
VCA
IN
SEL
LNP
IN
-
VCA
OUT
+
VCA
OUT
-
VGA
VCA2615
SBOS316C - JULY 2005 - REVISED SEPTEMBER 2005
Dual, Low-Noise
Variable-Gain Amplifier with Preamp
www.ti.com
Copyright
2005, Texas Instruments Incorporated
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 Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
All trademarks are the property of their respective owners.
VCA2615
SBOS316C - JULY 2005 - REVISED SEPTEMBER 2005
www.ti.com
2
ABSOLUTE MAXIMUM RATINGS
(1)
Power Supply (VDD)
+6V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Analog Inputs
-0.3V to (+VS + 0.3V)
. . . . . . . . . . . . . . . . . . . . . . . .
Logic Inputs
-0.3V to (+VS + 0.3V)
. . . . . . . . . . . . . . . . . . . . . . . . . .
Case Temperature
+100
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Junction Temperature
+150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage Temperature
-40
C to +150
C
. . . . . . . . . . . . . . . . . . . . . . .
(1) Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage. Exposure to absolute maximum
conditions for extended periods may affect device reliability.
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.
PACKAGE/ORDERING INFORMATION
(1)
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING NUMBER
TRANSPORT MEDIA,
QUANTITY
VCA2615
QFN-48
RGZ
-40
C to +85
C
VCA2615
VCA2615RGZR
Tape and Reel, 2500
VCA2615
QFN-48
RGZ
-40
C to +85
C
VCA2615
VCA2615RGZT
Tape and Reel, 250
(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website
at www.ti.com.
FUNCTIONAL BLOCK DIAGRAM
INP UT
B
Fee db ack
Network
Ga in
Co ntrol
Logic
LNP
OUT
-
B
VC A
IN
-
B
LN P
OUT
+B
LN P
V CA
IN
+B
H /L V
CLMP
V
CNTL
VC A
OUT
+B
VC A
OUT
-
B
VC A
OUT
+A
VC A
OUT
-
A
VC A
IN
SEL
C
EXT
B2
C
EXT
B1
C
EXT
A2
C
EXT
A1
VGA
INP UT
A
F B1
F B2
F B3
F B4
G1
G2
Fee db ack
Network
Ga in
Co ntrol
Logic
LNP
OUT
-
A
VC A
IN
-
A
LN P
Buffer
Buffe r
V CA
IN
+A
LNP
O UT
+A
VGA
Buffer
B uffer
VCA2615
SBOS316C - JULY 2005 - REVISED SEPTEMBER 2005
www.ti.com
3
ELECTRICAL CHARACTERISTICS
All specifications at T
A
= +25
C, V
DD
= 5V, load resistance = 500
on each output to ground; the input to the preamp (LNP) is single-ended;
fIN = 5MHz, LNP Gain (G1, G2) = 10, H/L = 0, V
CNTL
= 2.5V; VCA output is 1VPP differential; CA, CB = 3.9
F, unless otherwise noted.
VCA2615
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
PREAMPLIFIER (LNP and Buffer)
Input Resistance, RIN
With Active Feedback Termination
See Note
(1)
k
Input Resistance
Feedback Termination Open
100
k
Input Capacitance
45
pF
Maximum Input Voltage
LNP Gain (G1, G2) = 00 - Linear Operation(2)
2.3
VPP
LNP Gain (G1, G2) = 01 - Linear Operation(2)
0.78
VPP
LNP Gain (G1, G2) = 10 - Linear Operation(2)
0.39
VPP
LNP Gain (G1, G2) = 11 - Linear Operation(2)
0.23
VPP
Maximum Input Voltage
Any LNP Gain - Overload (symmetrical clipping)
5
VPP
Input Voltage Noise
RS = 0
; Includes Buffer Noise, LNP Gain = 11
0.8
nV/
Hz
Input Current Noise
1
pA/
Hz
Bandwidth
50
MHz
2nd-Harmonic Distortion
fIN = 5MHz
-55
dBc
3rd-Harmonic Distortion
fIN = 5MHz
-55
dBc
LNP Gain Change Response Time
LNP Gain 00 to 11; to 90% Signal Level
0.1
s
BUFFER (LNPOUT+A/B, LNPOUT-A/B)
Output Signal Range(2)
RL > = 500
3.3
VPP
Output Common-Mode Voltage
1.85
V
Output Short-Circuit Current
60
mA
Output Impedance
3
ACTIVE TERMINATION
Feedback Resistance(3), RF
FB (1-4) = 0111
1500
FB (1-4) = 1011
1000
FB (1-4) = 1101
500
FB (1-4) = 1110
250
FB (1-4) = 0000
130
VARIABLE-GAIN AMPLIFIER (VGA)
Peak Input Voltage
Linear Operation(2), V
CNTL
= 0.7V
2
V
PP
Upper -3dB Bandwidth
50
MHz
2nd-Harmonic Distortion
V
CNTL
= 2.5V, 1V
PP
Differential Output
-60
dBc
3rd-Harmonic Distortion
V
CNTL
= 2.5V, 1V
PP
Differential Output
-63
dBc
Slew-Rate
100
V/
s
PREAMPLIFIER AND VARIABLE-GAIN
AMPLIFIER (LNP AND VGA)
Input Voltage Noise
0.7
nV/
Hz
Clipping Voltage Range (VCLMP)
0.25 to 2.6
V
Clipping Voltage Variation
V
CLMP
= 0.5V, VCA
OUT
= 1.0V
PP
50
mV
Output Impedance
fIN = 5MHz, Single-Ended, Either Output
3
Output Short-Circuit Current
60
mA
Overload Distortion (2nd-Harmonic)
V
IN
= 250mV
PP
-44
dBc
Crosstalk
fIN = 5MHz
-70
dBc
Delay Matching
1
ns
Overload Recovery Time
25
ns
Maximum Output Load
100
Maximum Capacitive Output Loading
50
in Series
80
pF
Maximum Output Signal(2)
6
V
PP
Output Common-Mode Voltage
2.5
V
2nd-Harmonic Distortion
Input Signal = 5MHz, V
CNTL
= 1V
-45
-55
dB
3rd-Harmonic Distortion
Input Signal = 5MHz, V
CNTL
= 1V
-45
-55
dB
Upper -3dB Bandwidth
V
CNTL
= 2.5V
42
MHz
(1)
R
IN
+
R
F
(1
)
A
LNP
2
)
(2) 2nd, 3rd-harmonic distortion less than or equal to -30dBc.
(3) See Table 5.
(4) Referred to best-fit dB linear curve.
(5) Parameters ensured by design; not production tested.
(6) Do not leave inputs floating; no internal pull-up/pull-down resistors.
VCA2615
SBOS316C - JULY 2005 - REVISED SEPTEMBER 2005
www.ti.com
4
ELECTRICAL CHARACTERISTICS (continued)
All specifications at T
A
= +25
C, V
DD
= 5V, load resistance = 500
on each output to ground; the input to the preamp (LNP) is single-ended;
fIN = 5MHz, LNP Gain (G1, G2) = 10, H/L = 0, V
CNTL
= 2.5V; VCA output is 1VPP differential; CA, CB = 3.9
F, unless otherwise noted.
PARAMETER
UNIT
VCA2615
CONDITIONS
PARAMETER
UNIT
MAX
TYP
MIN
CONDITIONS
ACCURACY
Gain Slope
V
CNTL
= 0.4V to 2.0V
22
dB/V
Gain Error(4)
V
CNTL
= 0.4V to 2.0V
-1.5
0.9
+1.5
dB
Gain Range
V
CNTL
= 0.2V to 2.5V
52
dB
Gain Range
V
CNTL
= 0.4V to 2.0V
36.5
dB
Gain Range (H/L)
H/L = 0 (+6dB); VGA High Gain; V
CNTL
= 0.2V to 2.5V
-12 to +40
dB
H/L = 1 (0dB); VGA Low Gain; V
CNTL
= 0.2V to 2.5V
-18 to +34
dB
Output Offset Voltage, Differential
50
mV
Channel-to-Channel Gain Matching
V
CNTL
= 0.4V to 2.0V, CHA to CHB
0.33
dB
GAIN CONTROL INTERFACE (V
CNTL
)
Input Voltage Range
0.2 to 2.5
V
Input Resistance
Response Time
1
M
Input Resistance
Response Time
V
CNTL
= 0.2V to 2V; to 90% Signal Level
0.6
s
DIGITAL INPUTS(5), (6)
(G1, G2, PDL, PDV, H/L, FB1-FB4, VCAINSEL)
VIH, High-Level Input Voltage
2.0
V
VIL, Low-Level Input Voltage
0.8
V
Input Resistance
1
M
Input Capacitance
5
pF
POWER SUPPLY
Supply Voltage
4.75
5.0
5.25
V
Power-Up Response Time
25
s
Power-Down Response Time
2
s
Total Power Dissipation
PDV, PDL = 1
308
350
mW
VGA Power-Down
PDV = 0, PDL = 1
236
mW
LNP Power-Down
PDL = 0, PDV = 1
95
mW
THERMAL CHARACTERISTICS
Temperature Range
Ambient, Operating
-40
+85
C
Thermal Resistance,
q
JA
Soldered Pad; Four-Layer PCB with Thermal Vias
29.1
C/W
q
JC
2.2
C/W
(1)
R
IN
+
R
F
(1
)
A
LNP
2
)
(2) 2nd, 3rd-harmonic distortion less than or equal to -30dBc.
(3) See Table 5.
(4) Referred to best-fit dB linear curve.
(5) Parameters ensured by design; not production tested.
(6) Do not leave inputs floating; no internal pull-up/pull-down resistors.
VCA2615
SBOS316C - JULY 2005 - REVISED SEPTEMBER 2005
www.ti.com
5
PIN CONFIGURATION
V
DD
A
C
EXT
A1
C
EXT
A2
VCA
IN
-
A
VCA
IN
+A
LNP
OUT
-
A
LNP
OUT
+A
NC
VB
VDDAL
GNDAL
LNP
IN
-
A
V
DD
B
C
EXT
B1
C
EXT
B2
VCA
IN
-
B
VCA
IN
+B
LNP
OUT
-
B
LNP
OUT
+B
NC
NC
VDDBL
GNDBL
LNP
IN
-
B
1
2
3
4
5
6
7
8
9
10
11
12
36
35
34
33
32
31
30
29
28
27
26
25
VCA2615
(Thermal Pad tied to
Ground Potential)
G
NDA
VC
A
OU
T
-
A
VC
A
OU
T
+A
FB
4
VC
A
IN
SE
L
V
CNT
L
FB
3
FB
2
FB
1
VC
A
OU
T
+B
VC
A
OU
T
-
B
G
NDB
48
47
46
45
44
43
42
41
40
39
38
37
G1
G2
V
DD
A
LN
P
IN
+A
V
DD
R
V
CL
M
P
V
CM
GN
D
R
LN
P
IN
+B
PD
L
PD
V
H/
L
13
14
15
16
17
18
19
20
21
22
23
24
PIN CONFIGURATION
PIN
DESIGNATOR
DESCRIPTION
PIN
DESIGNATOR
DESCRIPTION
1
VDDA
Channel A + Supply
25
LNPIN-B
Channel B LNP Inverting Input
2
CEXTA1
External Capacitor
26
GNDBL
GND B Channel LNP
3
CEXTA2
External Capacitor
27
VDDBL
VDD B Channel LNP
4
VCAIN-A
Channel A VCA Negative Input
28
NC
Do Not Connect
5
VCAIN+A
Channel A VCA Positive Input
29
NC
Do Not Connect
6
LNPOUT-A
Channel A LNP Negative Output
30
LNPOUT+B
Channel B LNP Positive Output
7
LNPOUT+A
Channel A LNP Positive Output
31
LNPOUT-B
Channel B LNP Negative Output
8
NC
Do Not Connect
32
VCAIN+B
Channel B VCA Positive Input
9
VB
0.01
F Bypass
33
VCAIN-B
Channel B VCA Negative Input
10
VDDAL
VDD A Channel LNP
34
CEXTB2
External Capacitor
11
GNDAL
GND A Channel LNP
35
CEXTB1
External Capacitor
12
LNPIN-A
Channel A LNP Inverting Input
36
VDDB
Channel B + Supply
13
G1
LNP Gain Setting Pin (MSB)
37
GNDB
Channel B Ground
14
G2
LNP Gain Setting Pin (LSB)
38
VCAOUT-B
Channel B VCA Negative Output
15
VDDA
Supply Pin for Gain Setting
39
VCAOUT+B
Channel B VCA Positive Output
16
LNPIN+A
Channel A LNP Noninverting Input
40
FB1
Feedback Control Pin
17
VDDR
Supply for Internal Reference
41
FB2
Feedback Control Pin
18
VCLMP
VCA Clamp Voltage Setting Pin
42
FB3
Feedback Control Pin
19
VCM
0.1
F Bypass
43
VCNTL
VCA Control Voltage Input
20
GNDR
Ground for Internal Reference
44
VCAINSEL
VCA Input Select, Hi = External
21
LNPIN+B
Channel B LNP Noninverting Input
45
FB4
Feedback Control Pin
22
PDL
Power Down LNPs
46
VCAOUT+A
Channel A VCA Positive Pin
23
PDV
Power Down VCAs
47
VCAOUT-A
Channel A VCA Negative Pin
24
H/L
VCA High/Low Gain Mode
48
GNDA
Channel A Ground
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