August 2003
User’ s G uide
SBOU020A
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EVM IMPORTANT NOTICE
Texas Instruments (TI) provides the enclosed product(s) under the following conditions:
This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION
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Should this evaluation kit not meet the specifications indicated in the EVM User’s Guide, the kit may be returned
within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE
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Copyright 2003, Texas Instruments Incorporated
EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the specified input and output ranges described in
the EVM User’s Guide.
Exceeding the specified input range may cause unexpected operation and/or irreversible
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field representative prior to connecting the input power.
Applying loads outside of the specified output range may result in unintended operation and/or
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please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than
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as the input and output ranges are maintained. These components include but are not limited
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types of devices can be identified using the EVM schematic located in the EVM User’s Guide.
When placing measurement probes near these devices during operation, please be aware
that these devices may be very warm to the touch.
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Copyright 2003, Texas Instruments Incorporated
1
VCA2614/18/19EVM
VCA2614/18/19EVM
The VCA2614/18/19EVM is designed to provide ease of use in evaluating the
performance of the VCA2614, VCA2618 or VCA2619 variable gain amplifier.
Topic Page
1.1 Initial Configuration 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Power Supply 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Signals 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Output Configuration 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Switches 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 User-Selectable Capacitors 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7 Schematic and PCB 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8 Component List 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Initial Configuration
2
1.1 Initial Configuration
By using simple slide switches and DIP switches, the VCA2614/18/19EVM
can be configured to accommodate several different modes of operation. Be-
fore using the evaluation board, each user should determine the configuration
and setting needed for the specific evaluation. The demonstration board
comes from the factory with the following factory settings:
-Switches SW1, SW2, SW3, and SW4 are all set to positions 2−3. (See
Table 1.)
-DIP−switch S1 has the following settings:
JMGS1, MGS2, and MGS3 are set to the off position.
J/PD is set to off position.
-Components C9 and C16 are not populated.
1.2 Power Supply
The VCA2614/18/19EVM requires +5V supplies (connector J4) for the output
amplifiers (U2 and U3) and a separate +5V supply (connector J1) for the
VCA2614/18/19. This configuration allows for the monitoring of supply cur-
rents to the VCA2614/18/19 independent of the rest of the evaluation board.
If monitoring of the supplies is not required, a single +5V supply can be substi-
tuted for the two separate +5V supplies. In this case, the −5V supply is still re-
quired.
Signals
3
VCA2614/18/19EVM
1.3 Signals
1.3.1 Input Signals
The input signals are applied to SMA connectors J2 and J3. The input signals
should be provided from a low impedance source. The inputs are ac coupled
into the VCA2614/18/19 through 0.01µF capacitors.
1.3.2 VCACNTL
The gain control signal is applied to the input SMA connector J7. This can be
a dc voltage or a customer-specific waveform. The source for the control input
should also be low impedance. The range for the control voltage, as specified
in the VCA2614, VCA2618, or VCA2619 data sheet, is from 0.2V to 3V.
1.3.3 Output Signals
The outputs of the evaluation board are located at SMA connectors J5 and J6.
When testing the EVM board, the outputs J5 and J6 should be terminated into
50Ω loads such as that of the inputs to a spectrum analyzer. This will result in
a 6dB loss of the signal magnitude. This loss should be taken into account
when taking all measurements.
1.4 Output Configuration
By utilizing the switches provided at the inputs to amplifiers U2 and U3, the out-
puts of the VCA2614/18/19 can be monitored on SMA connectors J5 and J6.
Amplifiers U2 and U3 are configured to have a gain of 1/2 in all modes except
where the signals are terminated to ground through a 5 0 0Ω equivalent resist-
ance. Table 1 lists the switch combinations and the resulting output:
Table 1. VCA2614/18/19 Switch Combinations
Single-Ended
Noninverting Single-Ended
Inverting Difference(1)
No Output at
J5 and J6
(output at
test points)
U2
SW1 1−2 2−3 2−3 1−2
SW3 2−3 1−2 2−3 1−2
U3
SW2 1−2 2−3 2−3 1−2
SW4 2−3 1−2 2−3 1−2
1) Denotes factory preset.
The outputs of the VCA2614/18/19 can be terminated through 500Ω on each
output and the output signals can then be observed at test points TP1 and TP4
and test points TP2 and TP3 respectively.
Switches
4
1.5 Switches
The four dip switches (S1) control the gain range bits (MGS1, MGS2, and
MGS3) of the PGA and the power down (PD) function of the VCA2614/18/19.
Table 2, Table 3 and Table 4 show the MGS settings and the corresponding
gain ranges for each device.
Table 2. MGS Settings for the VCA2614
MGS Setting Attenuator Gain
VCACNTL = 0.02V to 3V Attenuator +
Differential PGA Gain
000 Not valid Not valid
001 −24.1dB to 0dB 2.6dB to 26.7dB
010 −26.9dB to 0dB 2.6dB to 29.5dB
011 −29.5dB to 0dB 3.0dB to 35.6dB
100 −32.4dB to 0dB 3.1dB to 35.5dB
101 −34.8dB to 0dB 3.4dB to 38.3dB
110 −37.3dB to 0dB 3.7dB to 44.1dB
111 −40.0dB to 0dB 4.1dB to 44.2dB
Table 3. MGS Settings for the VCA2618
MGS Setting Attenuator Gain
VCACNTL = 0V to 3V Attenuator +
Differential PGA Gain
000 Not valid Not valid
001 −27dB to 0dB 0dB to 27dB
010 −30dB to 0dB 0dB to 30dB
011 −33dB to 0dB 0dB to 33dB
100 −36dB to 0dB 0dB to 36dB
101 −39dB to 0dB 0dB to 39dB
110 −42dB to 0dB 0dB to 42dB
111 −45dB to 0dB 0dB to 45dB
Table 4. MGS Settings for the VCA2619
MGS Setting Attenuator Gain
VCACNTL = 0.2V to 3V Attenuator +
Differential PGA Gain
000 Not valid Not valid
001 Not valid Not valid
010 −41.0dB to 0dB −12dB to 29dB
011 −43.3dB to 0dB −11.5dB to 31.8dB
100 −46.4dB to 0dB −11.5dB to 34.9dB
101 −48.2dB to 0dB −10.6dB to 37.6dB
110 −50.2dB to 0dB −9.8dB to 40.4dB
111 −52.3dB to 0dB −9.3dB to 43.3dB
User-Selectable Capacitors
5
VCA2614/18/19EVM
1.6 User-Selectable Capacitors
Capacitors C 9 a nd C 16 a re user-selectable a nd o ptional. P lacing a n e xternal c a-
pacitor at these positions will lower the low frequency bandwidth of the
VCA2614/18/19. The following equation is used to calculate the low frequency
cutoff:
f(low*3dB)+1
2 p 500kW (220pF )CEXTERNAL)
Care must be taken not to select too large a value because the charging time
may exceed the time constant set by the input coupling capacitors, thus caus-
ing a longer-than-expected power-on delay. Please refer to the Input Buffer
section of the VCA2614, VCA2618 or VCA2619 data sheet, located at
www.ti.com, for further details.
Schematic and PCB
6
1.7 Schematic and PCB
Figure 1. VCA2614/18/19EVM Schematic
+INa
1
NC
2
Vddr
3
Vbias
4
Vcm
5
GNDr
6
NC
7
+INb
8
NC
9
NC
10
CP2B
11
CP1B
12
Vddb
13
GND b
14
Noutb
15 Poutb
16
NC 17
NC 18
NC 19
PD 20
MGS 1 21
MGS 2 22
MGS 3 23
VCA cntl 24
Pout
a25
Nout
a26
GND a 27
Vdda 28
Cp1a 29
Cp2a 30
NC 31
NC 32
U1
VCA2614/18/19
R8 332
R2 499
C22
330 pF
C23
330 pF
R6 49.9
C21
0.1uF
1
2
3
4
5
J6
21
3
SW4
2
1
3
SW2
R5
250
R15
169
R9
169
C27
0.1uF
C17
0.1uF
+
C26
2.2uF
+
C15
2.2uF
−5V
+5V
−4
+3
V+
5V− 2
1
U3
OPA642N
R7 332
R1 499
C20
330 pF
C19
330 pF
R3 49.9
C18
0.1uF
1
2
3
4
5
J5
21
3
SW3
2
1
3
SW1
R4
250
R16
169
R10
169
C25
0.1uF
C13
0.1uF
+
C24
2.2uF
+
C14
2.2uF
−5V
+5V
−4
+3
V+
5V− 2
1
U2
OPA642N
R12
10k
R13
10k
R14
10k
R11
10k
+5V
1
2
3
4 5
6
7
8
S1
SW−DIP4
1
2
3
4
5
J7
+
C29
1uF
C28
0.1uF
+5DUT
1
2
3
4
5
J3
1
2
3
4
5
J2
C12
0.01uF
C11
0.01uF
+
C8
1uF
C6
0.1uF
+5DUT
+
C4
1uF
C3
0.1uF
+
C7
1uF
C5
0.1uF
+
C31
1uF
C30
0.1uF
+5DUT
1
2
J1
1
2
3
J4
+C1
10 uF
+C10
10 uF
+C2
10 uF
+5V
−5V
+5DUT
C9
User Select
C16
User Select
TP3
TP2
TP4
TP1
Gain Control
Input
MGS
Switches
Input
Channel A
Output
Channel A
Output
Channel B
Input
Channel B
Schematic and PCB
7
VCA2614/18/19EVM
Figure 2. VCA2614/18/19EVM PCB Top Layer
Figure 3. VCA2614/18/19EVM PCB Ground Layer
Schematic and PCB
8
Figure 4. VCA2614/18/19EVM PCB Power Layer
Figure 5. VCA2614/18/19EVM PCB Bottom Layer
Component List
9
VCA2614/18/19EVM
1.8 Component List
Table 5. Component List
Qty Part Type Designator Footprint Mfg Part Number Description
11 0.1µFC3, C5, C6, C13, C17, C18,
C21, C25, C27, C28, C30 805 Kemet C0805C104M5UAC Multilayer ceramic − 0805 size
2 0.01µFC11, C12 805 Kemet C0805C103K5RAC Multilayer Ceramic − 0805 Size
5 1µFC4, C7, C8, C29, C31 3216 Kemet T491A105M016AS Low Profile Tantalum Capacitor
4 2.2µFC14, C15, C24, C26 3216 Kemet T491A225M016AS Low Profile Tantalum Capacitor
4 10kΩR11, R12, R13, R14 805 Dale CRCW0805103F 1/10W 0805 Chip Resistor
3 10µFC1, C2, C10 3528 Kemet T491B106M016AS Low Profile Tantalum Capacitor
2 49.9ΩR3, R6 805 Dale CRCW080549R9F 1/10W 0805 Chip Resistor
4 169ΩR9, R10, R15, R16 805 Dale CRCW08051690F 1/10W 0805 Chip Resistor
2 250ΩR4, R5 805 Dale CRCW08052490F 1/10W 0805 Chip Resistor
4 330pF C19, C20, C22, C23 805 Kemet C0805C331K3GAC Multilayer Ceramic − 0805 Size
2 332ΩR7, R8 805 Dale CRCW08053320F 1/10W 0805 Chip Resistor
2 499ΩR1, R2 805 Dale CRCW08054990F 1/10W 0805 Chip Resistor
1 CON_2TERM_SCREW J1 2P-TERM Digi-Key ED−1514−ND 2 Terminal Screw Connector
1 CON_3TERM_SCREW J4 3P-TERM Digi-Key ED−1515−ND 3 Terminal Screw Connector
2OPA642N (OPA842) U2, U3 SOT23−5 TI OPA642N High−Speed, Low THD Op Amp
5 SMA_PCB_MT_MOD J2, J3, J5, J6, J7 SMA_JACK_RIGHT_ANGLE Johnson 142−0801−301 Right−angle SMA
4 SPDT_SLIDE SW1, SW2, SW3, SW4 SPDT_SLIDE Digi-Key EG−1903−ND C&K / TS01−C−K−E
1 SW-DIP4 S1 4POS_SPST_DIP Digi-Key A5204−ND 4 Position SPST Dip Switch
2User Select(1) C9, C16 805 — User Select Multilayer Ceramic − 0805 Size
1 VCA2614
VCA2618
VCA2619
U1 32-TQFP TI VCA2614Y
VCA2618Y
VCA2619Y
Voltage Controlled Amplifier
1) Not populated on board. Optional component.
