VCA2618YT [BB]
Dual, VARIABLE GAIN AMPLIFIER with Input Buffer; 双可变增益放大器，具有输入缓冲器
| 型号： | VCA2618YT |
| 厂家： | 
BURR-BROWN CORPORATION |
| 描述： | Dual, VARIABLE GAIN AMPLIFIER with Input Buffer |
| 文件： | 总14页 (文件大小：324K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
VCA2618
VCA2618
SBOS254B – JULY 2002 – REVISED NOVEMBER 2003
Dual, VARIABLE GAIN AMPLIFIER
with Input Buffer
FEATURES
z GAIN RANGE: up to 43dB
DESCRIPTION
The VCA2618 is a highly integrated, dual receive channel,
Variable Gain Amplifier (VGA) with analog gain control.
z 30MHz BANDWIDTH
The VCA2618’s VGA section consists of two parts: the Volt-
age Controlled Attenuator (VCA) and the Programmable Gain
Amplifier (PGA). The gain and gain range of the PGA can be
digitally programmed. The combination of these two program-
mable elements results in a variable gain ranging from 0dB up
to a maximum gain as defined by the user through external
connections. The single-ended unity gain input buffer provides
predictable high input impedance. The output of the VGA can
be used in either a single-ended or differential mode to drive
high-performance Analog-to-Digital (A/D) converters. A sepa-
rate power-down pin reduces power consumption.
z LOW CROSSTALK: 65dB at Max Gain, 5MHz
z HIGH-SPEED VARIABLE GAIN ADJUST
z POWER SHUTDOWN MODE
z HIGH IMPEDANCE INPUT BUFFER
APPLICATIONS
z ULTRASOUND SYSTEMS
z WIRELESS RECEIVERS
z TEST EQUIPMENT
z RADAR
The VCA2618 also features low crosstalk and outstanding
distortion performance. The combination of low noise
and gain range programmability make the VCA2618 a versa-
tile building block in a number of applications where
noise performance is critical. The VCA2618 is available in a
TQFP-32 package.
CP2A
CP1A
VCA2618
(1 of 2 Channels)
NOUTA
Voltage
Control
Attenuator
Programmable
Gain Amplifier
Buffer
INA
POUTA
MGS1
Maximum
Gain Select
Analog
Control
Maximum Gain
Select
MGS2
VCACNTL
MGS3
NOUTB
Voltage
Control
Attenuator
Programmable
Gain Amplifier
Buffer
INB
POUTB
CP2B
CP1B
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.
All trademarks are the property of their respective owners.
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.
Copyright © 2002–2003, Texas Instruments Incorporated
www.ti.com
ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be handled
with appropriate precautions. Failure to observe proper han-
dling and installation procedures can cause damage.
Power Supply (+VS) ............................................................................. +6V
Analog Input ............................................................. –0.3V to (+VS + 0.3V)
Logic Input ............................................................... –0.3V to (+VS + 0.3V)
Case Temperature ......................................................................... +100°C
Junction Temperature .................................................................... +150°C
Storage Temperature ...................................................... –40°C to +150°C
NOTE: (1) Stresses above those listed under “Absolute Maximum Ratings”
may cause permanent damage to the device. Exposure to absolute maximum
conditions for extended periods may affect device reliability.
ESD damage can range from subtle performance degrada-
tion 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
SPECIFIED
PACKAGE
DESIGNATOR(1)
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
PRODUCT
PACKAGE-LEAD
VCA2618Y
TQFP-32 Surface-Mount
PBS
–40°C to +85°C
VCA2618Y
VCA2618YT
VCA2618YR
Tape and Reel, 250
Tape and Reel, 2000
"
"
"
"
"
NOTE: (1) For the most current specifications and package information, refer to our web site at www.ti.com.
ELECTRICAL CHARACTERISTICS
At TA = +25°C, VDD = 5V, load resistance = 500Ω on each output to ground differential output (2VPP), MGS = 111, and fIN = 5MHz, unless otherwise noted.
VCA2618Y
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BUFFER
Input Resistance
600
5
kΩ
pF
Input Capacitance
Input Bias Current
Maximum Input Voltage
Input Voltage Noise
Input Current Noise
Noise Figure
1
nA
1
VPP
PGA Gain = 45dB, RS = 50Ω
Independent of Gain
5.4
350
13
100
nV/Hz
fA/Hz
dB
RF = 550Ω, PGA Gain = 45dB, RS = 75Ω
Bandwidth
MHz
PROGRAMMABLE VARIABLE GAIN AMPLIFIER
Peak Input Voltage
1
30
VPP
MHz
V/µs
V
–3dB Bandwidth
Slew Rate
300
Output Signal Range
Output Impedance
Output Short-Circuit Current
3rd-Harmonic Distortion
2nd-Harmonic Distortion
RL > 500Ω Each Side to Ground
2.5 ±1
1
Ω
±40
mA
dBc
dBc
dBc
dB
VOUT = 2VPP, VCACNTL = 3.0V
VOUT = 2VPP, VCACNTL = 3.0V
–45
–42
–50
–50
2nd-Harmonic Distortion
Overload Performance (2nd-Harmonic
Distortion)
VOUT = 2VPP, VCACNTL = 3.0V, MGS = 011
Input Signal = 1VPP, VCACNTL = 2V
–60
–40 to –45
Time Delay
5
ns
dBc
dB
ns
IMD, 2-Tone
VOUT = 2VPP, f = 9.95MHz
–59
65
Crosstalk
Group Delay Variation
1MHz < f < 10MHz, Full Gain Range
13
ACCURACY
Gain Slope
Gain Error(1)
VCACNTL = 0.2V to 3.0V
VCACNTL = 0.2V to 3.0V
VCACNTL = 0.4V to 2.9V
16
dB/V
dB
±2.0
±1.3
±50
±2
dB
Output Offset Voltage
mV
GAIN CONTROL INTERFACE
Input Voltage (VCACNTL) Range
0.2 to 3.0
V
Input Resistance
Response Time
1
MΩ
µs
45dB Gain Change
0.2
POWER SUPPLY
Specified Operating Range
Power Dissipation
Power-Down
4.75
5.0
120
9.2
5.25
150
V
mW
mW
Operating, Each Channel
NOTE: (1) Referenced to best fit dB-linear curve.
VCA2618
2
SBOS254B
www.ti.com
PIN CONFIGURATION
Top View
TQFP
+INA
NC
1
2
3
4
5
6
7
8
24 VCACNTL
23 MGS3
22 MGS2
21 MGS1
20 PD
VDDR
VBIAS
VCM
VCA2618
GNDR
NC
19 NC
18 NC
+INB
17 DNC
PIN DESCRIPTIONS
PIN
DESIGNATOR
DESCRIPTION
PIN
DESIGNATOR
DESCRIPTION
1
2
+INA
NC
Noninverting Input Channel A
No Internal Connection
Internal Reference Supply
Bias Voltage
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
DNC
NC
Do Not Connect
No Internal Connection
3
VDDR
VBIAS
VCM
NC
No Internal Connection
4
PD
Power-Down (Active LOW)
Maximum Gain Select 1 (MSB)
Maximum Gain Select 2
Maximum Gain Select 3 (LSB)
VCA Analog Control
5
Common-Mode Voltage
Internal Reference Ground
Not Connected
MGS1
MGS2
MGS3
VCACNTL
NOUTA
POUTA
GNDA
VDDA
CP1A
6
GNDR
NC
7
8
+INB
NC
Noninverting Input Channel B
No Internal Connection
Do Not Connect
9
Negative VCA Output Channel A
Positive VCA Output Channel A
Ground Channel A
10
11
12
13
14
15
16
DNC
CP2B
CP1B
VDDB
GNDB
POUTB
NOUTB
Coupling Capacitor Channel B
Coupling Capacitor Channel B
+5V Supply Channel B
Ground Channel B
+5V Supply Channel A
Coupling Capacitor Channel A
Coupling Capacitor Channel A
Do Not Connect
CP2A
Positive Output Channel B
Negative Output Channel B
DNC
NC
No Internal Connection
VCA2618
SBOS254B
3
www.ti.com
TYPICAL CHARACTERISTICS
At TA = +25°C, VDD = 5V, load resistance = 500Ω on each output to ground, differential output (2VPP) MGS = 111, and fIN = 5MHz, unless otherwise noted.
GAIN vs VCA
GAIN ERROR vs TEMPERATURE
50
45
40
35
30
25
20
15
10
5
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
0
–5
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
GAIN ERROR vs VCACNTL
GAIN ERROR vs VCACNTL
2.5
2.0
2.5
2.0
1.5
1.5
1.0
1.0
0.5
0.5
0
0
–0.5
–1.0
–1.5
–2.0
–2.5
–0.5
–1.0
–1.5
–2.0
–2.5
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
GAIN MATCH: CHA to CHB, VCACNTL = 0.2V
GAIN MATCH: CHA to CHB, VCACNTL = 3.0V
50
45
40
35
30
25
20
15
10
5
45
40
35
30
25
20
15
10
5
0
0
Delta Gain (dB)
Delta Gain (dB)
VCA2618
4
SBOS254B
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VDD = 5V, load resistance = 500Ω on each output to ground, differential output (2VPP) MGS = 111, and fIN = 5MHz, unless otherwise noted.
GAIN vs FREQUENCY
(VCACNTL = 3.0V)
GAIN vs FREQUENCY
50
45
40
35
30
25
20
15
10
5
50
40
30
20
10
0
VCACNTL = 3.0V
MGS = 111
MGS = 011
VCACNTL = 1.6V
MGS = 001
VCACNTL = 0.2V
0
–10
100k
1M
10M
100M
100k
1M
10M
100M
Frequency (Hz)
Frequency (Hz)
INPUT REFERRED NOISE vs VCACNTL
OUTPUT REFERRED NOISE vs VCACNTL
600
550
500
450
400
350
300
250
200
150
100
50
500
450
400
350
300
250
200
150
100
50
RS= 50Ω
RS= 50Ω
MGS = 111
MGS = 111
MGS = 011
MGS = 011
0
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
NOISE FIGURE vs RS
INPUT REFERRED NOISE vs RS
24
22
20
18
16
14
12
10
8
100
10
1
6
4
2
10
100
1k
1
10
100
1k
RS (Ω)
RS (Ω)
VCA2618
SBOS254B
5
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VDD = 5V, load resistance = 500Ω on each output to ground, differential output (2VPP) MGS = 111, and fIN = 5MHz, unless otherwise noted.
HARMONIC DISTORTION vs FREQUENCY
(Differential, 2Vp-p, MGS = 001)
NOISE FIGURE vs VCACNTL
60
55
50
45
40
35
30
25
20
15
10
5
–30
–35
–40
–45
–50
–55
–60
–65
–70
VCA
VCA
VCA
VCA
= 0.2V, H2
CNTL
= 0.2V, H3
CNTL
= 3.0V, H2
CNTL
= 3.0V, H3
CNTL
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
100k
1M
10M
Frequency (Hz)
HARMONIC DISTORTION vs FREQUENCY
(Differential, 2Vp-p, MGS = 011)
HARMONIC DISTORTION vs FREQUENCY
(Differential, 2Vp-p, MGS = 111)
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
VCA
VCA
VCA
VCA
= 0.2V, H2
= 0.2V, H3
= 3.0V, H2
= 3.0V, H3
CNTL
CNTL
CNTL
CNTL
VCACNTL = 0.2V, H2
VCACNTL = 0.2V, H3
VCACNTL = 3.0V, H2
VCACNTL = 3.0V, H3
100k
1M
10M
100k
1M
Frequency (MHz)
10M
Frequency (Hz)
HARMONIC DISTORTION vs FREQUENCY
(Single-Ended, 1Vp-p, MGS = 001)
HARMONIC DISTORTION vs FREQUENCY
(Single-Ended, 1Vp-p, MGS = 011)
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
VCACNTL = 0.2V, H2
VCA
VCA
VCA
VCA
= 0.2V, H2
= 0.2V, H3
= 3.0V, H2
= 3.0V, H3
CNTL
CNTL
CNTL
CNTL
VCACNTL = 0.2V, H3
VCACNTL = 3.0V, H2
VCACNTL = 3.0V, H3
100k
1M
10M
100k
1M
10M
Frequency (Hz)
Frequency (Hz)
VCA2618
6
SBOS254B
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VDD = 5V, load resistance = 500Ω on each output to ground, differential output (2VPP) MGS = 111, and fIN = 5MHz, unless otherwise noted.
HARMONIC DISTORTION vs FREQUENCY
(Single-Ended, 1Vp-p, MGS = 111)
HARMONIC DISTORTION vs VCACNTL
(Differential, 2Vp-p)
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
0
–5
MGS = 001, H2
MGS = 011, H2
MGS = 111, H2
MGS = 001, H3
MGS = 011, H3
MGS = 111, H3
–10
–15
–20
–25
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
VCA
VCA
VCA
VCA
= 0.2V, H2
CNTL
CNTL
CNTL
CNTL
= 0.2V, H3
= 3.0V, H2
= 3.0V, H3
100k
1M
10M
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
Frequency (Hz)
INTERMODULATION DISTORTION
(Single-Ended, 1Vp-p, fIN = 10MHz, VCACNTL = 3.0V)
HARMONIC DISTORTION vs VCACNTL
(Single-Ended, 1Vp-p)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–5
MGS = 001, H2
MGS = 011, H2
MGS = 111, H2
MGS = 001, H3
MGS = 011, H3
MGS = 111, H3
–10
–15
–20
–25
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
9.5 9.6 9.7 9.8 9.9 10.0 10.1 10.2 10.3 10.4 10.5
Frequency (MHz)
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VCACNTL (V)
INTERMODULATION DISTORTION
(Differential, 2Vp-p, fIN = 10MHz, VCACNTL = 3.0V)
CROSS TALK vs FREQUENCY
(Differential, 2Vp-p, MGS = 011)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
VCACNTRL = 0V
VCACNTRL = 1.5V
VCACNTRL = 3.0V
9.5 9.6 9.7 9.8 9.9 10 10.1 10.2 10.3 10.4 10.5
Frequency (MHz)
1
6
11
16
21
Frequency (MHz)
VCA2618
SBOS254B
7
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VDD = 5V, load resistance = 500Ω on each output to ground, differential output (2Vp-p) MGS = 111, and fIN = 5MHz, unless otherwise noted.
OVERLOAD DISTORTION vs FREQUENCY
I
CC vs TEMPERATURE
0
–10
–20
–30
–40
–50
–60
59
57
55
53
51
49
47
45
0.1V
0.25V
0.5V
1V
1M
10M
–40
–25
–10
5
20
35
50
65
80
95
Frequency (Hz)
Temperature (°C)
GROUP DELAY
(1MHz Aperture)
15
14
13
12
11
10
9
VCACNTL = 3.0V
8
7
6
VCACNTL = 0.2V
5
4
3
2
1
0
1M
10M
100M
Frequency (Hz)
VCA2618
8
SBOS254B
www.ti.com
power-on time of the VCA2618 would be increased. If a
decrease in the power-on time is needed, the value can be
decreased to no less than 100pF.
OVERVIEW
The VCA2618 is a dual-channel, VGA consisting of three
primary blocks, an Input Buffer, a VCA, and a PGA. All
stages are AC coupled, with the coupling into the PGA stage
being made variable by placing an external capacitor be-
tween the CP1 and CP2 pins. This will be discussed further in
the PGA section. By using the internal coupling into the PGA,
the result is a high-pass filter characteristic with cutoff at
approximately 75kHz. The output PGA naturally rolls off at
around 30MHz, making the usable bandwidth of the VCA2618
between 75kHz and 30MHz.
VOLTAGE-CONTROLLED ATTENUATOR
The magnitude of the VCA input signal from the input buffer
is reduced by a programmable attenuation factor, set by the
analog VCA Control Voltage (VCACNTL) at pin 24. The maxi-
mum attenuation is programmable by using the three MGS
bits (pins 21, 22, and 23). Figure 2 illustrates this dual-adjust
characteristic.
0
Minimum Attenuation
Channel A
Output
Channel A
Input
Buffer
VCA
PGA
–25
Maximum
Gain
Select
Analog
Control
VCA
Control
MGS
Channel B
Output
Channel B
Input
Buffer
VCA
PGA
Maximum Attenuation
–43
0
3.0V
Control Voltage
FIGURE 2. Swept Attenuator Characteristic.
FIGURE 1. Simplified Block Diagram of the VCA2618.
The MGS bits adjust the overall range of attenuation and
maximum gain while the VCACNTL voltage adjusts the actual
attenuation factor. At any given maximum gain setting, the
analog variable gain characteristic is linear in dB as a
function of the control voltage, and is created as a piecewise
approximation of an ideal dB-linear transfer function. The
VCA control circuitry is common to both channels of the
VCA2618. The range for the VCACNTL input spans from 0V to
3V. Although overdriving the VCACNTL input above the rec-
ommended 3V maximum will not damage the part, this
condition should be avoided.
INPUT BUFFER
The input buffer is a unity gain amplifier (gain of +1) with a
bandwidth of 100MHz with an input resistance of approxi-
mately 600kΩ. The input buffer isolates the circuit driving the
VCA2618 inputs from the internal VCA block, which would
present a varying impedance to the input circuitry. To allow
symmetrical operation of the input buffer, the input to the
buffer must be AC coupled through an external capacitor.
The recommended value of the capacitor is 0.01µF. It should
be noted that if the capacitor value were increased, the
RS
Input
Output
Q1A
Q1B
Q2A
Q2B
Q3A
Q3B
Q4A
Q4B
Q5A
Q5B
VCM
A1
A2
A3
A4
A5
B1
B2
FIGURE 3. Programmable Attenuator Section.
VCA2618
SBOS254B
9
www.ti.com
Attenuator
Input
A1 to A10 Attenuator Stages
QS
Attenuator
Output
RS
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
VCM
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
V1
V2
V3
V4
V5
V6
V7
V8
V9
V10
Control
Input
C1 to C10 Clipping Amplifiers
0dB
–4.3dB
Attenuation Characteristic of Individual FETs
VCM – VT
0
V1
V2
V3
V4
V5
V6
V7
V8
V9
V10
Characteristic of Attenuator Control Stage Output
OVERALL CONTROL CHARACTERISTICS OF ATTENUATOR
0dB
–43dB
0.3V
3V
Control Signal
FIGURE 4. Piecewise Approximation to Logarithmic Control Characteristics.
VCA2618
10
SBOS254B
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PGA POST-AMPLIFIER
MGS
SETTING
ATTENUATOR GAIN
VCACNTL = 0V to 3V
ATTENUATOR +
DIFFERENTIAL PGA GAIN
Figure 5 shows a simplified circuit diagram of the PGA block.
As stated before, the input to the PGA is AC coupled by an
internal capacitor. Provisions are made so that an external
capacitor can be placed in parallel with the internal capacitor,
thus lowering the usable low-frequency bandwidth. The low-
frequency bandwidth is set by the following equation:
000
001
010
011
100
101
110
111
Not Valid
Not Valid
–25dB to 0dB
–28dB to 0dB
–31dB to 0dB
–34dB to 0dB
–37dB to 0dB
–40dB to 0dB
–43dB to 0dB
0dB to 25dB
0dB to 28dB
0dB to 31dB
0dB to 34dB
0dB to 37dB
0dB to 40dB
0dB to 43dB
1
2 •π • 500kΩ• 220pF + C
(
(
EXTERNAL))
TABLE I. MGS Settings.
where CEXTERNAL is the external capacitor value in farads.
Care should be taken to avoid using too large a value of
capacitor, as this can increase the power-on delay time.
input buffer noise dominates; at maximum VCA attenuation
(large input signals), the PGA noise dominates. Note that if
the PGA output is used single-ended, the apparent gain will
be 6dB lower.
As described previously, the PGA gain is programmed with
the same MGS bits that control the VCA maximum attenua-
tion factor. Specifically, the maximum PGA gain at each
MGS setting is the inverse (reciprocal) of the maximum VCA
attenuation at that setting. Therefore, the VCA + PGA overall
gain will always be 0dB (unity) when the analog VCACNTL
input is set to 0V (the maximum attenuation for VCA). For
VCACNTL = 3V (no attenuation), the VCA + PGA gain will be
controlled by the programmed PGA gain (25dB to 43dB in
3dB steps). For clarity, the gain and attenuation factors are
detailed in Table I.
LAYOUT CONSIDERATIONS
The VCA2618 is an analog amplifier capable of high gain.
When working on a PCB layout for the VCA2618, it is
recommended to utilize a solid ground plane that is con-
nected to analog ground. This helps to maximize the noise
performance of the VCA2618.
Adequate power-supply decoupling must be used in order to
achieve the best possible performance. Decoupling capaci-
tors on the VCACNTL voltage should also be used to help
minimize noise. Recommended values can be obtained from
the layout diagram of Figure 6.
The PGA architecture converts the single-ended signal from
the VCA into a differential signal. Low input noise was also
a requirement of the PGA design due to the large amount of
signal attenuation that can be asserted before the PGA. At
minimum VCA attenuation (used for small input signals), the
VDD
To Bias
Circuitry
Q1
Q11
Q12
Q9
RL
RL
VCAOUT
P
VCAOUTN
Q3
Q8
VCM
VCM
RS1
RS2
Q13
Q4
Q7
+In
–In
Q14
Q2
Q10
Q5
Q6
To Bias
Circuitry
FIGURE 5. Simplified Block Diagram of the PGA Section with the VCA2618.
VCA2618
SBOS254B
11
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+5V
0.1µF
1µF
+5V
0.1µF
0.1µF
1µF
1µF
28
3
5
0.01µF
0.01µF
0.01µF
VDDA VDDR VCM
1
25
26
–OUTA
INA
INA
–OUTA
+OUTA
+OUTA
VCA2618
0.01µF
0.01µF
16
15
–OUTB
+OUTB
24
–OUTB
+OUTB
0.01µF
8
INB
INB
VDDB VBIAS VCNTL
13
4
1µF
0.1µF
0.1µF
+5V
1µF
0.1µF
VCACNTL
FIGURE 6. VCA2618 Layout.
VCA2618
12
SBOS254B
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PACKAGE DRAWING
PBS (S-PQFP-G32)
PLASTIC QUAD FLATPACK
0,23
0,17
M
0,50
0,08
24
17
25
32
16
9
0,13 NOM
1
8
3,50 TYP
Gage Plane
5,05
SQ
4,95
0,25
7,10
SQ
0,10 MIN
6,90
0°–7°
0,70
0,40
1,05
0,95
Seating Plane
0,08
1,20 MAX
4087735/A 11/95
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
VCA2618
SBOS254B
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