This pad must be connected to a (-Vcc) copper area on the PCB
This pad must be connected to a (-Vcc) copper area on the PCB
2
-
-
+
+
3
3
VCC -
VCC -
4
4
Cross Section View Showing Exposed-Pad.
Cross Section View Showing Exposed-Pad.
VCC +
VCC +
8
8
7
7
Inverting Input2
Inverting Input2
6
6
-
-
+
+
Non Inverting Input2
Non Inverting Input2
5
5
dice
dice
Pad
Pad
Description
The TS616 is a dual operational amplifier
featuring a high output current of 410 mA. This
driver can be configured differentially for driving
signals in telecommunication systems using
multiple carriers. The TS616 is ideally suited for
xDSL (high speed asymmetrical digital subscriber
line) applications. This circuit is capable of driving
a 10 Ω or 25 Ω load on a range of power supplies: ±2.5 V, 5 V, ±6 V or +12 V. The TS616 is capable
of reaching a -3 dB bandwidth of 40 MHz on 25 Ω
load with a 12 dB gain. This device is designed for
high slew rates and demonstrates low harmonic
distortion and intermodulation.
Figure 1 shows a schematic of a typical xDSL application using the TS616.
Figure 1.Differential line driver for xDSL applications
8
8
3
3
2
2
Vi
Vi
Vi
Vi
R1
R1
R4
R4
ViVo
ViVo
ViVo
ViVo
4
4
5
5
+
+
+
+
1/2TS615
1/2TS616
1/2TS615
1/2TS61 6
_
_
_
_
R2
R2
GND
GND
R3
R3
_
_
_
_
1/2TS615
1/2TS616
1/2TS615
1/2TS616
+
+
+
+
4
4
+Vcc
+Vcc
+Vcc
+Vcc
-Vcc
-Vcc
-Vcc
-Vcc
Ω
Ω
Ω
Ω
12.5
12.5
12.5
12.5
1
1
1
1
Vo
Vo
Vo
12.5
12.5
12.5
12.5
Vo
Ω
Ω
Ω
Ω
25
25
25
25
1:2
1:2
1:2
1:2
Ω
Ω
Ω
Ω
Ω
Ω
Ω
100
100
100
100
Ω
3/37
Absolute maximum ratings and operating conditionsTS616
2 Absolute maximum ratings and operating conditions
Table 1.Absolute maximum ratings
SymbolParameterValueUnit
V
CC
V
id
V
in
T
oper
T
std
T
j
R
thjc
R
thja
P
max
ESD
only pins
1, 4, 7, 8
ESD
only pins
2, 3, 5, 6
Supply voltage
Differential input voltage
Input voltage range
Operating free air temperature range-40 to + 85°C
Storage temperature-65 to +150°C
Maximum junction temperature150°C
Thermal resistance junction to case16°C/W
Thermal resistance junction to ambient area60°C/W
Maximum power dissipation (at T
=150°C
T
j
HBM: human body model
MM: machine model
CDM: charged device model
HBM: human body model
MM: machine model
CDM: charged device model
Output short circuit
(1)
(3)
(5)
(5)
(2)
(4)
(4)
(6)
(6)
= 25° C) for
amb
±7V
±2V
±6V
2W
1.5
2
200
1.5
2
100
(7)
kV
kV
V
kV
kV
V
1. All voltage values, except differential voltage are with respect to network terminal.
2. Differential voltages are non-inverting input terminal with respect to the inverting input terminal.
3. The magnitude of input and output voltage must never exceed VCC +0.3 V.
4. Human body model: a 100 pF capacitor is charged to the specified voltage, then discharged through a
1.5 kΩ resistor between two pins of the device. This is done for all couples of connected pin combinations
while the other pins are floating.
5. Machine model: a 200 pF capacitor is charged to the specified voltage, then discharged directly between
two pins of the device with no external series resistor (internal resistor < 5 Ω). This is done for all couples of
connected pin combinations while the other pins are floating.
6. Charged device model: all pins and the package are charged together to the specified voltage and then
discharged directly to the ground through only one pin. This is done for all pins.
7. An output current limitation protects the circuit from transient currents. Short-circuits can cause excessive
heating. Destructive dissipation can result from short-circuits on amplifiers.
Table 2.Operating conditions
SymbolParameterValueUnit
V
CC
V
icm
Power supply voltage±2.5 to ±6V
Common mode input voltage-VCC+1.5 V to +VCC-1.5 VV
4/37
TS616Electrical characteristics
3 Electrical characteristics
Table 3.V
= ±6 V, Rfb= 910 Ω, T
CC
= 25° C (unless otherwise specified)
amb
SymbolParameterTest conditionsMin.Typ. Max.Unit
DC performance
V
io
ΔV
I
ib+
I
ib-
Z
IN+
Z
IN-
C
IN+
CMR
SVR
I
CC
T
Input offset voltage
Differential input offset voltageT
io
Positive input bias current
Negative input bias current
amb
< T
T
T
T
T
T
min
amb
amb
min
amb
min
< T
amb
max
= 25°C2.5mV
530
< T
< T
amb
max
315
< T
< T
amb
max
Input(+) impedance82kΩ
Input(-) impedance54Ω
Input(+) capacitance1pF
ΔV
Common mode rejection ratio
20 log (ΔV
/ΔVio)
ic
Supply voltage rejection ratio
20 log (ΔVCC/ΔVio)
= ±4.5V5864
ic
< T
T
ΔV
T
min
CC
min
< T
amb
max
= ±2.5V to ±6V7281
< T
< T
amb
max
Total supply current per operatorNo load13.517mA
13.5
1.6
7.2
3.1
62
80
Dynamic performance and output characteristics
mV
µA
µA
dB
dB
R
Open loop transimpedance
OL
-3dB bandwidth
BW
Full power bandwidth
Gain flatness @ 0.1dB
Rise timeV
T
r
T
Fall timeV
f
Settling timeV
T
s
SRSlew rateV
V
V
High level output voltageRL = 25Ω connected to GND4.85.05V
OH
Low level output voltageRL = 25Ω Connected to GND-5.3-5.1V
Figure 20. Input voltage noise levelFigure 21. ICC vs. power supply
AV = +92, Rfb = 910 Ω
Input+ connected to GND via 25 Ω
5.0
+
+
+
4.5
4.0
3.5
3.0
Input Voltage Noise (nV/√Hz)
2.5
2.0
1001k10k100k1M
(Frequency (Hz)
+
_
_
_
_
10
10
10
10
+ 6V
+ 6V
+ 6V
+ 6V
Output
Output
Output
Output
6VΩ-
6VΩ-
-6V
-6V
910
910
Ω
Ω
910
910
Ω
Ω
Ω
Ω
Open loop, no load
30
20
10
0
(mA)
CC
I
-10
-20
-30
0123456789101112
Icc(+)
Icc(-)
VCC (V)
Figure 22. Iib vs. power supplyFigure 23. VOH & VOL vs. power supply
Open loop, no load
7
7
Iib+
Iib+
IB+
IB+
6
6
5
5
4
4
(μA)
(μA)
B
B
3
3
I
I
ib
I
Iib-
IB-
IB-
2
2
1
1
0
0
56789101112
56789101112
Vcc (V)
Vcc (V)
Open loop, RL = 25 Ω
6
5
4
3
2
(V)
1
OL
0
& V
-1
OH
V
-2
-3
-4
-5
-6
56789101112
VOH
VOL
Vcc (V)
Figure 24. I
source
vs. output amplitudeFigure 25. I
VCC = ±6 V, open loop, no load
700
600
500
400
300
Isource (mA)
200
100
0
0123456
Vout (V)
12/37
vs. output amplitude
source
VCC = ±2.5 V, open loop, no load
700
600
500
400
300
Isource (mA)
200
100
0
0.00.51.01.52.02.5
Vout (V)
TS616Electrical characteristics
Figure 26. I
VCC = ±6 V, open loop, no load
Isink (mA)
vs. output amplitudeFigure 27. I
sink
0
-100
-200
-300
-400
-500
-600
-700
-6-5-4-3-2-10
Vout (V)
vs. output amplitude
sink
VCC = ±2.5 V, open loop, no load
0
-100
-200
-300
-400
Isink (mA)
-500
-600
-700
-2.5-2.0-1.5-1.0-0.50.0
Vout (V)
Figure 28. Maximum output amplitude vs. load Figure 29. Bandwidth vs. temperature
AV = +4, Rfb = 620 Ω, VCC = ±6 V
12
10
)
8
P-P
(V
6
OUT-MAX
V
4
2
Vcc=±6V
Vcc=±2.5V
AV = +4, Rfb = 910 Ω
50
45
40
35
Bw (MHz)
30
25
Vcc=±6V
Load=25
Vcc=±2.5V
Load=10
Ω
Ω
0
050100150200
R
(Ω)
LOAD
20
-40-200 2040 6080
Temperature (°C)
Figure 30. Transimpedance vs. temperatureFigure 31. ICC vs. temperature
Open loop
30
25
Vcc=±6V
20
15
(MΩ)
OL
R
10
Vcc=±2.5V
5
0
-40-200 2040 6080
Temperature (°C)
Open loop, no load
14
12
10
Icc(+) for Vcc=±2.5V
8
Icc(+) for Vcc=±6V
6
4
2
0
(mA)
-2
CC
I
-4
-6
Icc(-) for Vcc=±6V
-8
-10
-12
-14
Icc(-) for Vcc=±2.5V
-40-20020406 080
Temperature (°C)
13/37
Electrical characteristicsTS616
Figure 32. Slew rate vs. temperatureFigure 33. Slew rate vs. temperature
AV = +4, Rfb = 910 Ω, VCC = ±6 V, RL=25Ω
600
500
400
300
200
100
-100
-200
Slew Rate (V/μs)
-300
-400
-500
-600
Positive&Negative SR
Ω
Rfb=620
0
-40-20020406080
Positive&Negative SR
Ω
Rfb=910
Temperature (°C)
AV = +4, Rfb = 910 Ω, VCC = ±2.5 V, RL=10Ω
200
150
100
Positive SR
50
0
-50
Slew Rate (V/μs)
Negative SR
-100
-150
-200
-40-20020406080
Temperature (°C)
Figure 34. Iib(+) vs. temperatureFigure 35. Iib(+) vs. temperature
Open loop, no load
8
7
6
5
4
(μA)
3
IB(+)
I
2
1
0
-1
-40-20 0 20406080
Vcc=±6V
Vcc=±2.5V
Temperature (°C)
Open loop, no load
5
4
3
(μA)
IB(-)
2
I
1
0
-40-20020406 080
Temperature (°C)
Vcc=±6V
Vcc=±2.5V
Figure 36. VOH vs. temperatureFigure 37. VOL vs. temperature
Open loop
6
5
4
3
(V)
OH
V
2
1
0
-40-200 20406080
Vcc=±6vV
Load=25
Vcc=±2.5V
Load=10
Ω
Ω
Temperature (°C)
14/37
Open loop
0
Vcc=±2.5V
-1
-2
-3
(V)
OL
V
-4
-5
-6
-40-200 2040 6080
Load=10Ω
Vcc=±6V
Ω
Load=25
Temperature (°C)
TS616Electrical characteristics
Figure 38. Differential Vio vs. temperatureFigure 39. Vio vs. temperature
Open loop, no load
450
400
350
(μV)
IO
ΔV
300
250
200
-40-20020406 080
Vcc=±6V
Temperature (°C)
Figure 40. I
vs. temperatureFigure 41. I
out
Open loop, VCC = ±6 V, RL=10Ω
300
250
200
150
100
Isource
50
0
-50
-100
-150
Iout (mA)
-200
-250
-300
-350
-400
-450
Isink
-40-20020406 080
Temperature (°C)
Vcc=±2.5V
Open loop, no load
2.0
1.5
1.0
(mV)
IO
V
0.5
0.0
-0.5
-40-200 2040 6080
Temperature (°C)
vs. temperature
out
Open loop, VCC = ±2.5 V, RL=25Ω
300
250
200
150
100
50
Isource
0
-50
-100
-150
Iout (mA)
-200
-250
-300
-350
-400
-450
Isink
-40-20020406080
Temperature (°C)
Vcc=±6V
Vcc=±2.5V
Figure 42. CMR vs. temperatureFigure 43. SVR vs. temperature
Open loop, no load
70
68
66
64
62
60
58
CMR (dB)
56
54
52
50
-40-200 2040 6080
Vcc=±2.5V
Temperature (°C)
Vcc=±6V
Open loop, no load
84
82
80
Vcc=±6V
SVR (dB)
78
76
Vcc=±2.5V
-40-200 2040 6080
Temperature (°C)
15/37
Safe operating areaTS616
4 Safe operating area
Figure 44 shows the safe operating zone for the TS616. The curve shows the input level vs.
the input frequency—a characteristic curve which must be considered in order to ensure a
good application design. In the dash-lined zone, the consumption increases, and this
increased consumption could do damage to the chip if the temperature increases.
Figure 44. Safe operating area
700
Vcc=+/-6V
Ta=25°C
600
G=12dB
RL=100Ω
500
)
RMS
400
(mV
300
INPUT
V
200
100
SAFE
OPERATING
AREA
0
1M10M100M
Frequency (Hz)
16/37
TS616Intermodulation distortion product
5 Intermodulation distortion product
The non-ideal output of the amplifier can be described by the following series, due to a nonlinearity in the input-output amplitude transfer:
V
C0C1VinC2V
out
++ +=
2
in
CnV
n
in
where the single-tone input is V
fundamental, C
is the amplitude of the harmonics of the output signal V
n
=Asinωt, and C0 is the DC component, C1(Vin) is the
in
out
.
A one-frequency (one-tone) input signal contributes to a harmonic distortion. A two-tone
input signal contributes to a harmonic distortion and an intermodulation product.
This intermodulation product, or rather, the study of the intermodulation distortion of a twotone input signal is the first step in characterizing the amplifiers capability for driving multitone signals.
The two-tone input is equal to:
V
Aω1tsinBω2tsin+=
in
giving:
C0C1Aω1tsinBω2tsin+()C2Aω1tsinBω2tsin+()
+++=
t
2
… CnAω1tsinBω2tsin+()
n
In this expression, we can extract distortion terms and intermodulation terms from a single
sine wave: second-order intermodulation terms IM2 by the frequencies (ω
with an amplitude of C2A
(2ω
- ω2), (2ω1+ω2), (−ω1+2ω2) and (ω1+2ω2) with an amplitude of (3/4)C3A3.
1
2
and third-order intermodulation terms IM3 by the frequencies
- ω2) and (ω1+ω2)
1
We can measure the intermodulation product of the driver by using the driver as a mixer via
a summing amplifier configuration. In doing this, the non-linearity problem of an external
mixing device is avoided.
Figure 45. Non-inverting summing amplifier for intermodulation measurements
Vin1
Vin1
50Ω
50Ω
1:√2
1:√2
100Ω
100Ω
Vin1
Vin1
50Ω
50Ω
49.9Ω
49.9Ω
1:√2
1:√2
49.9Ω
49.9Ω
100Ω
100Ω
1kΩ
1kΩ
1kΩ
1kΩ
49.9Ω
49.9Ω
49.9Ω
49.9Ω
1kΩ
1kΩ
1kΩ
1kΩ
300Ω
300Ω
300Ω
300Ω
+
+
1/2TS616
1/2TS616
_
_
910Ω
910Ω
910Ω
910Ω
_
_
1/2TS616
1/2TS616
+
+
+Vcc
+Vcc
-Vcc
-Vcc
Voutdiff.
Vout diff.
49.9Ω
49.9Ω
Rout1
Rout1
Rout2
Rout2
49.9Ω
49.9Ω
100Ω
100Ω
√2:1
√2:1
17/37
50Ω
50Ω
Intermodulation distortion productTS616
The following graphs show the IM2 and the IM3 of the amplifier in different configurations.
The two-tone input signal was generated by the multisource generator Marconi 2026. Each
tone has the same amplitude. The measurement was performed using a HP3585A
spectrum analyzer.
370 kHz & 400 kHz
AV = +4, Rfb = 620 kΩ, RL=50Ω diff., VCC = ±6 V
-30
-40
-50
-60
-70
-80
IM2 and IM3 (dBc)
-90
-100
-110
0 2 4 6 8 1012 1416182022
IM3
340kHz, 430kHz
Differential Output Voltage (Vp-p)
IM3
1140kHz, 1170kHz
Figure 53. Intermodulation vs. output
amplitude
100 kHz & 110 kHz
1.1M
= +4, Rfb = 620 kΩ, RL=50Ω diff., VCC = ±6 V
A
V
-30
-40
-50
-60
-70
-80
IM2 and IM3 (dBc)
-90
-100
-110
246810121416182022
IM3
90kHz, 120kHz, 310kHz, 320kHz
Differential Output Voltage (Vp-p)
IM2
30kHz
IM2
210kHz
IM2
770kHz
19/37
Printed circuit board layout considerationsTS616
6 Printed circuit board layout considerations
In the ADSL frequency range, printed circuit board parasites can affect the closed-loop
performance.
The use of a proper ground plane on both sides of the PCB is necessary to provide low
inductance and a low resistance common return. The most important factors affecting gain
flatness and bandwidth are stray capacitance at the output and inverting input. To minimize
capacitance, the space between signal lines and ground plane should be maximized.
Feedback component connections must be as short as possible in order to decrease the
associated inductance which affects high-frequency gain errors. It is very important to
choose the smallest possible external components—for example, surface mounted devices
(SMD)—in order to minimize the size of all DC and AC connections.
6.1 Thermal information
The TS616 is housed in an exposed-pad plastic package. As described in Figure 55, this
package has a lead frame upon which the dice is mounted. This lead frame is exposed as a
thermal pad on the underside of the package. The thermal contact is direct with the dice.
This thermal path provides an excellent thermal performance.
The thermal pad is electrically isolated from all pins in the package. It must be soldered to a
copper area of the PCB underneath the package. Through these thermal paths within this
copper area, heat can be conducted away from the package. The copper area
connected to -V
Figure 58. Component locations - top sideFigure 59. Component locations - bottom side
Figure 60. Top side board layoutFigure 61. Bottom side board layout
22/37
TS616Noise measurements
7 Noise measurements
The noise model is shown in Figure 62, where:
●eN: input voltage noise of the amplifier
●iNn: negative input current noise of the amplifier
●iNp: positive input current noise of the amplifier
Figure 62. Noise model
+
iN+
+
N3
N3
iN+
iN-
iN-
N2
N2
R1
R1
N1
N1
eN
eN
TS616
TS616
_
_
R2
R2
R3
R3
output
output
HP3577
HP3577
Input noise:
Input noise:
8nV/√Hz
8nV/√Hz
The closed loop gain is:
R
AVg1
fb
--------+==
R
g
The six noise sources are:
R2
V1eN1
⎛⎞
------- -+
×=
⎝⎠
R1
V2iNnR2×=
R2
V3iNpR31
R2
V4
------- -
R1
⎛⎞
------- -+
××=
⎝⎠
R1
4kTR1×–=
V54kTR2=
R2
⎛⎞
V61
------- -+
R1
4kTR3=
⎝⎠
We assume that the thermal noise of a resistance R is:
4kTR FΔ
ΔF is the specified bandwidth.
where
On a 1 Hz bandwidth the thermal noise is reduced to:
4kTR
where k is Boltzmann's constant, equal to 1374.10
23/37
-23
J/°K. T is the temperature (°K).
Noise measurementsTS616
The output noise eNo is calculated using the Superposition Theorem. However eNo is not
the sum of all noise sources, but rather the square root of the sum of the square of each
noise source, as shown in Equation 1.
Equation 1
oV12V22V32V42V52V6
+++++=
2
Equation 2
2
o2eN2g2iNn2R22iNp
2
R2
⎛⎞
------- -
…
⎝⎠
R1
4kTR1 4kTR21
+×+×R3
2
×g2×=
2
R2
⎛⎞
------- -+
⎝⎠
R1
4kTR3×++×+
The input noise of the instrumentation must be extracted from the measured noise value.
The real output noise value of the driver is:
Equation 3
eNoMeasured()
2
instrumentation()
–=
2
The input noise is called the Equivalent Input Noise as it is not directly measured but is
evaluated from the measurement of the output divided by the closed loop gain (eNo/g).
After simplification of the fourth and the fifth term of Equation 2 we obtain:
Equation 4
eN2g2iNn2R22iNp
+×+×R3
2
2
×g2×…g4kTR2 1
⎛⎞
⎝⎠
R2
------- -+
R1
2
4kT×+×+=
7.1 Measurement of eN
If we assume a short-circuit on the non-inverting input (R3=0), Equation 4 becomes:
Equation 5
oeN2g2iNn2R22g4kTR2×+×+×=
In order to easily extract the value of eN, the resistance R2 will be chosen as low as
possible. On the other hand, the gain must be large enough:
●R1=10 Ω, R2=910 Ω, R3=0, Gain=92
●Equivalent input noise: 2.57 nV/√Hz
●Input voltage noise: eN=2.5 nV/√Hz
24/37
TS616Noise measurements
7.2 Measurement of iNn
To measure the negative input current noise iNn, we set R3=0 and use Equation 5. This time
the gain must be lower in order to decrease the thermal noise contribution:
●R1=100 Ω, R2=910 Ω, R3=0, gain= 10.1
●Equivalent input noise: 3.40 nV/√Hz
●Negative input current noise: iNn =21 pA/√Hz
7.3 Measurement of iNp
To extract iNp from Equation 3, a resistance R3 is connected to the non-inverting input. The
value of R3 must be chosen in order to keep its thermal noise contribution as low as
possible against the iNp contribution.
●R1=100 Ω, R2=910 Ω, R3=100 Ω, Gain=10.1
●Equivalent input noise: 3.93 nV/√Hz
●Positive input current noise: iNp=15 pA/√Hz
●Conditions: Frequency=100 kHz, V
●Instrumentation: HP3585A Spectrum Analyzer (the input noise of the HP3585A is
8nV/√Hz)
=±2.5V
CC
25/37
Power supply bypassingTS616
8 Power supply bypassing
Correct power supply bypassing is very important for optimizing performance in highfrequency ranges. Bypass capacitors should be placed as close as possible to the IC pins to
improve high-frequency bypassing. A capacitor greater than 1 µF is necessary to minimize
the distortion. For better quality bypassing, a capacitor of 10 nF is added using the same
implementation conditions. Bypass capacitors must be incorporated for both the negative
and the positive supply.
Figure 63. Circuit for power supply bypassing
+VCC
+
+
-
-
+VCC
TS616
TS616
-VCC
-VCC
+
+
10μF
10μF
10nF
10nF
10nF
10nF
10μF
10μF
+
+
8.1 Single power supply
The TS616 can operate with power supplies ranging from 12 V to 5 V. The power supply can
either be single (12 V or 5 V referenced to ground), or dual (such as ±6 V and ±2.5 V).
In the event that a single supply system is used, new biasing is necessary to assume a
positive output dynamic range between 0 V and +V
of V
and VOL, the amplifier will provide an output dynamic from +0.5 V to 10.6 V on 25 Ω
OH
load for a 12 V supply and from 0.45 V to 3.8 V on 10 Ω load for a 5 V supply.
The amplifier must be biased with a mid-supply (nominally +V
DC component of the signal at this value. Several options are possible to provide this bias
supply, such as a virtual ground using an operational amplifier or a two-resistance divider
(which is the cheapest solution). A high resistance value is required to limit the current
consumption. On the other hand, the current must be high enough to bias the non-inverting
input of the amplifier. If we consider this bias current (30 µA max.) as the 1% of the current
through the resistance divider to keep a stable mid-supply, two resistances of 2.2 kΩ can be
used in the case of a 12 V power supply and two resistances of 820 Ω can be used in the
case of a 5 V power supply.
The input provides a high-pass filter with a break frequency below 10 Hz which is necessary
to remove the original 0 volt DC component of the input signal, and to fix it at +V
Figure 64 shows a schematic of a 5 V single power supply configuration.
supply rails. Considering the values
CC
/2), in order to maintain the
CC
/2.
CC
26/37
TS616Power supply bypassing
Figure 64. Circuit for +5 V single supply
+5V
+5V
10µF
10µF
+
+
+
RG
RG
CG
CG
+
½ TS616
½ TS616
_
_
100µF
100µF
OUT
OUT
10Ω
10Ω
R
R
fb
fb
IN
IN
+5V
+5V
R1
R1
820Ω
820Ω
R2
R2
820Ω
820Ω
Rin
Rin
1kΩ
1kΩ
+ 1µF
+ 1µF
10nF
10nF
8.2 Channel separation and crosstalk
Figure 65 shows an example of crosstalk from one amplifier to a second amplifier. This
phenomenon, accentuated at high frequencies, is unavoidable and intrinsic to the circuit
itself.
Nevertheless, the PCB layout also has an effect on the crosstalk level. Capacitive coupling
between signal wires, distance between critical signal nodes and power supply bypassing
are the most significant factors.
Figure 65. Crosstalk vs. frequency: AV=+4, Rfb=620 Ω, VCC= ±6 V, V
-50
-60
-70
-80
-90
-100
CrossTalk (dB)
-110
-120
-130
10k100k1M10M
Frequency (Hz)
= 2 V
out
p
27/37
Choosing the feedback circuitTS616
9 Choosing the feedback circuit
As described in Figure 67 on page 29, the TS616 requires a 620Ω feedback resistor to
optimize the bandwidth with a gain of 12 dB for a 12 V power supply. Nevertheless, due to
production test constraints, the TS616 is tested with the same feedback resistor for 12 V and
5 V power supplies (910 Ω).
Table 5.Closed-loop gain - feedback components
VCC (V)GainRfb (Ω)
+1750
+2680
+4620
±6
+8510
-1680
-2680
-4620
-8510
+11.1k
+21k
±2.5
+4910
+8680
-11k
-21k
-4910
-8680
28/37
TS616Choosing the feedback circuit
9.1 The bias of an inverting amplifier
A resistance is necessary to achieve good input biasing, such as resistance R, shown in
Figure 66.
The magnitude of this resistance is calculated by assuming the negative and positive input
bias current. The aim is to compensate for the offset bias current, which could affect the
input offset voltage and the output DC component. Assuming Ib-, Ib+, R
volt output, the resistance R is:
R = R
in
// R
fb
Figure 66. Compensation of the input bias current
fb
fb
R
R
Ib-
Ib-
Rin
Rin
Ib+
Ib+
R
R
_
_
+
+
TS616
TS616
Vcc+
Vcc+
Vcc-
Vcc-
Output
Output
Load
Load
, Rfb and a zero
in
9.2 Active filtering
Figure 67. Low-pass active filtering - Sallen-Key
From the resistors Rfb and RG, we can directly calculate the gain of the filter in a classic noninverting amplification configuration:
We assume the following expression as the response of the system:
C1
C1
R
R
1R2
1R2
IN
IN
RG
RG
AVg1
Vout
---------------- -
Vin
jω
jω
T
jω
C2
C2
---------------------------------------- -==
12ζ
+
+
_
_
TS616
TS616
910Ω
910Ω
R
fb
--------+==
R
g
jω
-----
ω
OUT
OUT
25Ω
25Ω
fb
fb
R
R
g
2
jω()
----------- -++
2
c
ω
c
29/37
Choosing the feedback circuitTS616
The cutoff frequency is not gain-dependent and so becomes:
ω
c
1
------------------------------------ -=
R1R2C1C2
The damping factor is calculated by the following expression:
1
-- -
ζ
ωcC1R1C1R2C2R1C1R1g–++()=
2
The higher the gain the more sensitive the damping factor is. When the gain is higher than
1, it is preferable to use some very stable resistor and capacitor values. In the case of
R1 = R2:
R
fb
--------
–
2C
2C1
R
ζ
-------------------------------- -=
2C1C
g
2
30/37
TS616Increasing the line level using active impedance matching
10 Increasing the line level using active impedance
matching
With passive matching, the output signal amplitude of the driver must be twice the amplitude
on the load. To go beyond this limitation an active matching impedance can be used. With
this technique, it is possible to maintain good impedance matching with an amplitude on the
load higher than half of the output driver amplitude. This concept is shown in Figure 68 for a
differential line.
Figure 68. TS616 as a differential line driver with active impedance matching
1
μ
100n
Vcc+
1k
Vi
1/2
1/2
μ
GND
100n
ViVo
10
1k
100n
R1
R1
+
_
Vcc/2
+
_
R2
R3
R5
R4
Vcc+
GND
Vcc+
GND
Rs1
Vo°
Vo°
Rs2
10n
Vo
RL
1:n
Hybrid
&
Transformer
100
Ω
Component calculation
Let us consider the equivalent circuit for a single-ended configuration, as shown in
Figure 69.
Figure 69. Single-ended equivalent circuit
+
+
+
Vi
Vi
½ R1
½ R1
+
_
_
_
_
R2
R2
R3
R3
31/37
Vo°
Vo°
Rs1
Rs1
-1
-1
-1
-1
Vo
Vo
½ RL
½ RL
Increasing the line level using active impedance matchingTS616
First let’s consider the unloaded system. We can assume that the currents through R1, R2
and R3 are respectively:
2Vi
Vi Vo°–()
-------- -
---------------------------
,
R1
As Vo
° equals Vo without load, the gain in this case becomes:
Vo noload()
G
--------------------------------
R2
Vi
Vi Vo+()
------------------------
and
R3
2R2
1
-----------
R1
----------------------------------- -==
R2
1
------- -–
R3
R2
------- -++
R3
The gain, for the loaded system is given by Equation 6:
Equation 6
2R2
-----------
R1
1
R2
------- -–
R3
R2
------- -++
R3
1
Vo withload()
GL
------------------------------------ -
==
Vi
1
-- -
----------------------------------- -
2
The system shown in Figure 70 is an ideal generator with a synthesized impedance acting
as the internal impedance of the system. From this, the output voltage becomes:
Equation 7
VoViG()RoIout⋅()–=
where Ro is the synthesized impedance and Iout the output current.
On the other hand Vo can be expressed as:
Equation 8
2R2
-----------
R1
R2
------- -–
R3
R2
------- -++
R3
Rs1Iout
----------------------–=
R2
1
------- -–
R3
⎛⎞
Vi 1
Vo
⎝⎠
-----------------------------------------------
1
By identification of both Equation 7 and Equation 8, the synthesized impedance is, with
Rs1 = Rs2 = Rs:
Equation 9
Ro
Rs
-----------------=
R2
1
------- -–
R3
32/37
TS616Increasing the line level using active impedance matching
Figure 70. Equivalent schematic - Ro is the synthesized impedance
Iout
Ro
Vi.Gi
1/2RL
Let us write Vo°=kVo, where k is the matching factor varying between 1 and 2. If we assume
that the current through R3 is negligible, we can calculate the output resistance, Ro:
Ro
kVoRL
---------------------------- -=
RL 2Rs1+
After choosing the k factor, Rs will be equal to 1/2RL(k-1).
For a good impedance matching we assume that:
Equation 10
1
-- -
Ro
RL=
2
From Equation 9 and Equation 10, we derive:
Equation 11
R2
------- -1
R3
2Rs
---------- -–=
RL
By fixing an arbitrary value of R2, Equation 11 becomes:
R3
R2
--------------------=
2Rs
1
---------- -–
RL
Finally, the values of R2 and R3 allow us to extract R1 from Equation 6, so that:
Table 6.Components calculation for impedance matching implementation
GL (gain for the loaded system)
R12R2/[2(1-R2/R3)GL-1-R2/R3]
R2 (= R4)Arbitrarily fixed
R3 (= R5)R2/(1-Rs/0.5RL)
Rs0.5RL(k-1)
Load viewed by each driverkRL/2
GL is fixed for the application requirements
GL= Vo/Vi= 0.5(1+2R2/R1+R2/R3)/(1-R2/R3)
33/37
Package informationTS616
11 Package information
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a Lead-free second level interconnect. The category of
second level interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com
34/37
TS616Package information
Figure 71. SO-8 exposed pad package mechanical drawing
Table 7.SO-8 exposed pad package mechanical data
Dimensions
MillimetersInches
Ref.
Min.Typ.Max.Min.Typ.Max.
A1.3501.7500.0530.069
A10.0000.1500.0010.0059
A21.1001.6500.0430.065
B0.3300.5100.0130.020
C0.1900.2500.0070.010
D4.8005.0000.1890.197
D13.100.122
E3.8004.0000.1500.157
E12.410.095
e1.2700.050
H5.8006.2000.2280.244
h0.2500.5000.0100.020
L0.4001.2700.0160.050
k0d8d0d8d
ddd0.1000.004
35/37
Ordering informationTS616
12 Ordering information
Table 8.Order codes
Part numberTemperature rangePackagePackagingMarking
TS616IDW
-40°C to +85°CSO-8
TS616IDWTTape & reelTS616
13 Revision history
DateRevisionChanges
1-Nov-20021First release.
03-Dec-20042
24-Oct-20063
16-Apr-20074Corrected package error in Table 8: Order codes.
26-Sep-20085Corrected package error in Table 8: Order codes.
TubeTS616
Moved note in Ta bl e 3 to Section 9: Choosing the feedback circuit on
page 28.
Figure 43 in Revision 1, entitled Group Delay, has been removed
because the results presented were not technically meaningful.
Simplified mathematical representations of the intermodulation
product in Section 5: Intermodulation distortion product on page 17.
In Section 6: Printed circuit board layout considerations on page 20,
change from “The copper area can be connected to (-Vcc) available
on pin 4.” to “The copper area
on pin 4.”.
In Section 9.1: The bias of an inverting amplifier on page 29, change
of section title, and correction of referred figure to Figure 66.
Format update.
Corrected package mechanical data for SO-8 exposed pad.
must be connected to -Vcc available
36/37
TS616
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