The TS616 is a dual operational am plifier featuring a high output current o f 410m A. T he drivers
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 c apable of driving a 10 Ω
or 25Ω load at ±2.5V, 5V, ±6V or +12V power
supply. The TS616 is able to reach a -3dB bandwidth of 40MHz on 25Ω load with a 12dB gain.
This device is designed for high slew rates supporting low harmonic distortion and intermodulation.
DW
SO8 Exposed-Pad
(Plastic Micro package)
ORDER CODE
Part NumberTemperature RangePackage
TS616IDW-40, +85°CDW
TS616IDWT-40, +85°CDW
DW = Small Outline Package with Exposed-Pad, T = Tape & Real
PIN CONNECTIONS (top view)
Output1
Output1
1
1
2
VCC -
VCC -
2
-
-
+
+
3
3
4
4
Inverting Input1Output2
Inverting Input1Output2
Non Inverting Input1
Non Inverting Input1
VCC +
VCC +
8
8
7
7
Inverting Input2
Inverting Input2
6
6
-
-
+
+
Non Inverting Input2
Non Inverting Input2
5
5
APPLICATION
■ Line driver for xDSL
■ Multiple Video Line Driver
December 2002
Cross Section View Showing Exposed-Pad
Cross Section View Showing Exposed-Pad
This pad can be connected to a (-Vcc) copper area on the PCB
This pad can be connected to a (-Vcc) copper area on the PCB
1/27
TS616
ABSOLUTE MAXIMUM RATINGS
SymbolParameterValueUnit
V
T
T
R
R
P
ESD
only pins
1, 4, 7, 8
ESD
only pins
2, 3, 5, 6
Supply voltage
CC
V
Differential Input Voltage
id
V
Input Voltage Range
in
Operating Free Air Temperature Range-40 to + 85°C
oper
Storage Temperature-65 to +150°C
std
T
Maximum Junction Temperature150°C
j
Thermal Resistance Junction to Case16°C/W
thjc
Thermal Resistance Junction to Ambient Area60°C/W
thja
Maximum Power Dissipation (@Ta=25°C) for Tj=150°C2W
max.
CDM : Charged Device Model
HBM : Human Body Model
MM : Machine Model
CDM : Charged Device Model
HBM : Human Body Model
MM : Machine Model
Output Short Circuit
1.All voltage values, except differential voltage are with respect to network terminal.
2.Differential voltage are non-inverting input terminal with respect to the inverting input terminal.
3.The magnitude of input and output voltage must never exceed V
4.An output current limitation protects the circuit from transient currents. Short-circuits can cause excessive heating.
Destructive dissipation can result from short circuit on amplifiers.
1)
2)
3)
±7V
±2V
±6V
1.5
2
200
1.5
2
100
4)
+0.3V.
CC
kV
kV
V
kV
kV
V
OPERATING CONDITIONS
SymbolParameterValueUnit
V
V
Power Supply Voltage±2.5 to ±6V
CC
+1.5V to +VCC-1.5V
Common Mode Input Voltage
icm
-V
CC
TYPICAL APPLICATION:
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
1/2TS616
_
_
_
_
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
25
25
25
25
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω
1:2
1:2
1:2
1:2
100
100
100
100
Ω
Ω
Ω
Ω
V
2/27
TS616
ELECTRICAL CHARACTERISTICS
V
= ±6Volts, Rfb=910Ω,T
CC
Note: As described on page 24 (table 71), the TS616 requires a 620Ω feedback resistor for an optimized bandwidth with a gain of 12B for
a 12V power supply. Nevertheless, due to production test constraints, the TS616 is tested with the same feedback resistor for 12V and 5V
power su ppl i es (910Ω).
SymbolParameterTest ConditionMin.Typ.Max.Unit
DC PERFORMANCE
V
Input Offset Voltage
io
V
∆
Z
C
CMR
SVR
Differential Input Offset Voltage
io
I
Positive Input Bias Current
ib+
I
Negative Input Bias Current
ib-
Input(+) Impedance82k
IN+
Z
Input(-) Impedance54
IN-
Input(+) Capacitance1pF
IN+
Common Mode Rejection Ratio
20 log (∆V
/∆Vio)
ic
Supply Voltage Rejection Ratio
20 log (∆V
I
Total Supply Current per OperatorNo load13.517mA
CC
/∆Vio)
cc
DYNAMIC PERFORMANCE and OUTPUT CHARACTERISTIC
R
Open Loop Transimpedance
OL
-3dB Bandwidth
Full Power Bandwidth
BW
Gain Flatness @ 0.1dB
TrRise Time
TfFall Time
TsSettling Time
SRSlew Rate
V
High Level Output Voltage
OH
V
Low Level Output Voltage
OL
Output Sink Current
I
out
Output Source Current
= 25°C (unless otherwise specified)
amb
T
amb
< T
T
min.
T
amb
T
amb
T
min.
T
amb
T
min.
V
∆
ic
T
min.
V
∆
cc
T
min.
V
out
T
min.
< T
amb
= 25°C
< T
< T
amb
< T
< T
amb
= ±4.5V
< T
< T
amb
=±2.5V to ±6V
< T
< T
amb
= 7Vp-p, RL = 25
< T
amb.
Small Signal V
A
= 12dB, RL = 25
V
Large Signal V
= 12dB, RL = 25
A
V
Small Signal V
= 12dB, RL = 25
A
V
V
= 6Vp-p, AV = 12dB, RL
out
= 25
Ω
= 6Vp-p, AV = 12dB, RL
V
out
= 25
Ω
= 6Vp-p, AV = 12dB, RL
V
out
= 25
Ω
= 6Vp-p, AV = 12dB, RL
V
out
= 25
Ω
R
=25Ω Connected to GND
L
R
=25Ω Connected to GND
L
V
= -4Vp
out
< T
T
min.
V
out
T
min.
amb
= +4Vp
< T
amb
< T
< T
< T
max.
max.
max.
max.
max.
max.
<20mVp
out
Ω
=3Vp
out
Ω
<20mVp
out
Ω
max.
max.
13.5
1.6
mV
2.5mV
530
7.2
315
3.1
A
µ
A
µ
Ω
Ω
5864
62
7281
80
Ω
513.5
5.7
dB
dB
M
Ω
2540
MHz
26
7MHz
10.6ns
12.2ns
50ns
330420V/µs
4.85.05V
-5.3-5.1V
-320-490
-395
330420
mA
370
3/27
TS616
Note: As described on page 24 (table 71), the TS616 requires a 620Ω feedback resistor for an optimized bandwidth with a gain of 12B for
a 12V power supply. Nevertheless, due to production test constraints, the TS616 is tested with the same feedback resistor for 12V and 5V
power su ppl i es (910Ω).
SymbolParameterTest ConditionMin.Typ.Max.Unit
NOISE AND DISTORTION
eNEquivalent Input Noise VoltageF = 100kHz2.5nV/√Hz
iNpEquivalent Input Noise Current (+)F = 100kHz15pA/√Hz
iNnEquivalent Input Noise Current (-)F = 100kHz21pA/√Hz
Figure 44 shows the safe operating condition. This
curve shows the input level vs. the i nput frequen-
cy. It’s necessary to consider this characteristic to
guarantee the design . In the dash-lined zone, the
consumption increases . Moreover, this increas ed
consumption could do dam age to the chip if the
temperature increases.
14/27
TS616
INTERMODULATION DISTORTION PRODUCT
Non-ideal output of the amplifier can be described
by the following series:
VoutC0C1VinC2V
++ +=
2
in
…
CnV
n
in
due to non-li nearity in the input-output am plitude
transfer, where the input is V
DC component, C
) is the fundamental and C
1(Vin
=Asinωt, C0 is the
in
is the amplitude of the harmonics of the output sig-
out
.
nal V
A one-frequency (one-tone) input signal contrib-
utes to harmonic distortion. A two-tone input signal contributes to harmonic distortion and intermodulation product.
The study of the intermodulation/distortionfor a
two-tone input signal is the first step in characterizing the driving capability of multi-tone input signals.
In this case :
C
+A
()
2
C
A
+
…
()
n
VinA
V
outC0C1
+=
tsinB
ω
1
tsinB
ω
1
tsinB
ω
1
A
ω
()
1
2
tsin+
ω
2
n
tsin+
ω
2
tsin+=
ω
2
tsinB
tsin+
ω
2
and :
C+
A
()
1
C
2
2
–
2+C2AB
cost B
------- A
2
()
3
C
A
+
3
tsinB
ω
1
2
ω
1
–
ω1ω
()
+
t
2
C
3
3
------4
3
tsinB33
ω
1
tsin+
ω
2
2
cos–tcos
tcos+
2
ω
2
–
ω
()
1
tsin+
ω
2
ω
2
In this expression, we recognize the second order
intermodulation IM2 by the frequencies (ω
and (ω
IM3 by the frequencies (2ω
+2ω2) and (ω1+2ω2).
(−ω
1
) and the third order intermodulation
1+ω2
1-ω2
The measurement of the intermodulation product
of the driver is achieved by using the driver as a
n
mixer by a summing amplifier configuration. In this
way, the non-linearity probl em of an ex ternal m ixing device is avoided.
Figure 45: Non-inverting Summing Amplifier for
Intermodulation measurem ents
1kΩ
1kΩ
1kΩ
1kΩ
49.9Ω
Vin1
Vin1
1:√2
1:√2
50Ω100Ω
50Ω100Ω
49.9Ω
Vin1
Vin1
1:√2
1:√2
50Ω100Ω
50Ω100Ω
49.9Ω
49.9Ω
49.9Ω
49.9Ω
49.9Ω
49.9Ω
1kΩ
1kΩ
+
+
1/2TS616
1/2TS616
_
_
910Ω
910Ω
300Ω
300Ω
300Ω
300Ω
910Ω
910Ω
_
_
1/2TS616
1/2TS616
1kΩ
1kΩ
+
+
+Vcc
+Vcc
-Vcc
-Vcc
Voutdiff.
Vout diff.
49.9Ω
49.9Ω
Rout1
Rout1
Rout2
Rout2
49.9Ω
49.9Ω
The following graphs show the IM2 and the IM3 of
the amplifier in different configurations. The
two-tone input signal was generat ed by the multisource generator Marconi 2026. Each tone has
the same amplitude. The measurement was performed using a HP3585A spectrum analyzer.
In the ADSL frequency range, printed circuit board
parasites can affect the closed-loop performance.
The implementation of a proper ground plane on
both sides of the PCB is mandatory to provide low
inductance and low resistance common return.
The most imp ortant factors affecting gai n f latness
and bandwidth are stray capa citances at the output and inverting input. To minimize these capacitances, the space between signal lines and
ground plane should be increased. Feedback
components 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 c hoose the smallest pos sible
external components, for example, surface
mounted devices (SMD) in order to minimize the
size of all DC and AC connections.
THERMAL INFORMATION
The TS616 is housed in an Exposed-Pad plastic
package. As depicted in figure 55, this package
uses a lead frame upon which the die is mounted.
This lead frame is exposed as a thermal pa d on
the underside of the package. The thermal contact
is direct with the dice. This thermal path provides
excellent colling.
Figure 55: Exposed-Pad Package
DICE
DICE
Bottom View
Side View
Side View
Bottom View
DICE
DICE
Cross Section View
Cross Section View
Figure 56: Evaluation Board
1
1
The thermal pad is electrically isolated from all
pins in the package. It should be soldered to a
copper area o f th e PC B underneath the package.
Through these thermal paths within this copper area, heat can b e conducted away from the pack age. In this case, the copp er area should be connected to (-
V
).
CC
18/27
Figure 57: Schematic Diagram
J205
J205
J205
J206
J206
J206
J207
J207
J207
J208
J208
J208
J209
J209
J209
R206
R206
R206
3
3
R207
R207
R207
R202R201
R202R201
R202R201
R203
R203
R203
R208
R208
R208
R209
R209
R209
R204
R204
R204
R210
R210
R210
R205
R205
R205
3
+
+
+
1/2TS616
1/2TS616
1/2TS616
_
_
_
1
1
1
2
2
2
R214
R214
R214
R211
R211
R211
R212
R212
R212
R215
R215
R215
6
6
6
_
_
_
1/2TS616
1/2TS616
1/2TS616
7
7
7
+
+
+
5
5
5
R213
R213
R213
TS616
Non-Inverting
Non-Inver ti ng
3
R207
J206
R218
R218
R218
R216
R216
R216
R219
R219
R219
R217
R217
R217
J210
J210
J210
R220
R220
R220
J211
J211
J211
R221
R221
R221
J206
Inverting
Inverting
J208
J208
Summing Am plifier
Summing Am plifier
R207
R202
R202
R209
R209
R204
R204
3
+
+
1/2TS616
1/2TS616
_
_
1
1
2
2
R214
R214
R211
R211
R215
R215
_
_
6
6
1/2TS616
1/2TS616
7
7
+
+
5
5
R213
R213
R218
R218
R216
R216
R219
R219
R217
R217
J210
J210
R220
R220
J211
J211
R221
R221
Differential Amplifier
Differential Amplifier
Differential Amplifier
J206
J206
J206
R202
R202
R202
J209
J209
J209
R205
R205
R205
R207
R207
R207
R210
R210
R210
J205
J205
J206
J206
3
3
3
+
+
+
1/2TS616
1/2TS616
1/2TS616
_
_
_
1
1
1
2
2
2
R214
R214
R214
R211
R211
R211
R212
R212
R212
R215
R215
R215
6
6
6
_
_
_
1/2TS616
1/2TS616
1/2TS616
7
7
7
+
+
+
5
5
5
R213
R213
R213
R218
R218
R218
R216
R216
R216
R219
R219
R219
R217
R217
R217
J210
J210
J210
R220
R220
R220
Power Supply
Power Supply
Power Supply
J211
J211
J211
R221
R221
R221
J201
J201
J201
J201
+Vcc
+Vcc
+Vcc
+Vcc
J202
J202
J202
J202
GND
GND
GND
GND
J303
J303
J303
J303
-Vcc
-Vcc
-Vcc
-Vcc
J20412
J20412
J20412
J20412
R206
R206
3
R207
R207
R202R201
R202R201
C202
C202
C202
C202
100nF
100nF
100nF
100nF
C203
C203
C203
C203
C203
100nF
100nF
100nF
100nF
100nF
3
3
3
3
3
+
+
1/2TS616
1/2TS616
_
_
1
1
2
2
R214
R214
R211
R211
+Vcc
+Vcc
+Vcc
+Vcc
C205
C205
C205
C205
+Vcc
+Vcc
+Vcc
+Vcc
100nF
100nF
100nF
C201
C201
C201
C201
100uF
100uF
100uF
100uF
C204
C204
C204
C204
100uF
100uF
100uF
100uF
+Vcc
+Vcc
+Vcc
+Vcc
-Vcc
-Vcc
-Vcc
-Vcc
100nF
8
8
8
8
3
3
3
3
+
+
+
+
1/2TS616
1/2TS616
1/2TS616
1/2TS616
_
_
_
_
2
2
2
2
4
4
4
4
C206
C206
C206
C206
100nF
100nF
100nF
100nF
-Vcc
-Vcc
-Vcc
-Vcc
-Vcc
-Vcc
-Vcc
-Vcc
_
_
_
_
6
6
6
6
1/2TS616
1/2TS616
1/2TS616
1/2TS616
+
+
+
+
5
5
5
5
R218
R218
R216
R216
1
1
1
1
-Vcc
-Vcc
-Vcc
-Vcc-Vcc
Exposed-Pad
Exposed-Pad
Exposed-Pad
Exposed-Pad
7
7
7
7
J210
J210
R220
R220
19/27
TS616
Figure 58: Component Locations - Top Side
Figure 59: Component Locations - Bottom Side
Figure 60: Top Side Board Layout
Figure 61: Bottom Side Board Layout
20/27
TS616
g
NOISE MEASUREMENT
Figure 62: Noise Model
+
eN
eN
+
TS616
TS616
_
_
R2
R2
iN+
N3
N3
iN+
iN-
iN-
N2
N2
R1
R1
N1
N1
R3
R3
output
output
HP3577
HP3577
Input noise:
Input noise:
8nV/√Hz
8nV/√Hz
eN : input voltage noise of the amplifier
iNn : negative input current noise of the amplifier
iNp : positive input current noise of the amplifier
The closed loop gain is :
R
AVg1
The six noise sources are :
=
V1eN
×
fb
--------- -+==
R
2
R
------ -
1
+
1
R
k is the Boltzmann’s constant, equal to
1,374.10-23J/°K. T is the temperature (°K).
The output noise eNo is c alculated using the Su-
perposition Theorem. However it is not the simple
sum of all noi se sources. The squ are root of the
sum of the square of each noise source.
eNoV12V22V32V42V52V6
+++++ eq1
2
,=
()
2
2
=
eNo2eN2g2iNn2R
2
2
R
------ -
+
4
×eq2(),
1
R
+
×R
kTR
14
21
++
kTR
2
+
×
iNp
2
R
-------
+
1
R
×g2×
2
4
kTR
×
2
3
3
The input noise of the instrumentation must be extracted from the measured noise value. Th e real
output noise value of the driver is:
eNoMeasured
()
2
instrumentation
–eq3
()
2
,=
()
The input noise is called the Equivalent Input
Noise as it is not directly measured but it is evaluated from the meas urement of the output divided
by the closed loop gain (eNo/g).
After simplification of the fourth and the fifth term
of (eq2) we obtain:
2
2
=
eNo2eN2g2iNn2R
+
… g4kTR
×eq4(),
+
×R
21
×
2
R
------ -
+
+
1
R
2
+
iNp
2
4
kTR
×
3
×g2×
3
2
2
=
V
iNn R2×
2
R
-------
+
××
1
R
4
1
kTR
2=
kTR
4
3=
kTR
=
V3iNp R
2
R
------ -
4
–=
V
61
V
1
R
54
V
+
31
×
2
R
------ -
1
R
We assume that the thermal noise of a resistance
R is:
4kTR∆F
wher ∆F is the specified bandwidth.
On 1Hz bandwidth the thermal noise is reduced to
4kTR
Measurement of eN:
We assume a short-circuit on the non-inverting input (R3=0). (eq4) comes:
=
eNoeN2g2iNn2R
+
×eq5(),
×
2
+
g4kTR
2
×
2
In order to easily extract the value of eN, the resistance R2 will be chosen as low as possible. In the
other hand, the gain must be large enough.
R1=10Ω, R2=910Ω, R3=0, Gai n=92
Equivalent Input Noise: 2.57nV/√Hz
Input Voltage Noise: eN=2.5nV/√Hz
Measurement of iNn:
R3=0 and the output noise equation is still the
(eq5). This time the gain must be decreased to decrease the thermal noise contribution.
R1=100Ω, R2=910Ω, R3=0, Gain=10.1
Equivalent Input Noise: 3.40nV/√Hz
Negative Input Current Noise: iNn =21pA/√Hz
Measurement of iNp:
To extract iNp from (eq3), a resist ance R3 is connected to the non-inverting input. The val ue of R3
must be chose n in o rder to keep i ts therm al noise
21/27
TS616
+
-VCC
+VCC
10µF
+
10nF
TS616
10µF
+
10nF
-
+
-VCC
+VCC
10µF
+
10nF
TS616
10µF
+
10nF
-
contribution as low as possible against the iNp
contribution.
R1=100Ω, R2=910Ω, R3=100Ω, Gain=10.1
Equivalent Input Noise: 3.93nV/√Hz
Positive Input Current Noise: iNp=15pA/√Hz
Condit i ons: frequency=100kHz, V
Instrumentation: Spectrum Analyz er HP3585A
(input noi se of the HP3585A: 8nV/√Hz)
CC
=±2.5V
POWER SUPPLY BYPASSIN G
Correct power supply by pa ssing is very important
for optimizing the performance in high frequency
ranges. Bypass capacitors should be placed as
close as pos sible to the IC pins t o improve high
frequency bypassing. A capacitor greater than
1µF is necessary to minim ize the distortion. For a
better quality bypassing a capac itor of 10nF can
be added usin g the same implementation con ditions. Bypass capacit ors mu st be incorporat ed f or
both the negative and the positive supply.
Figure 63: Circuit for Power Supply Bypassing
The following figure shows the case of a 5V single
power suppl y configuration
Figure 64: Circuit for +5V single supply
+5V
+5V
10µF
10µF
+
IN
IN
+5V
+5V
R1
R1
820Ω
820Ω
R2
R2
820Ω
820Ω
Rin
Rin
1kΩ
1kΩ
+ 1µF
+ 1µF
10nF
10nF
+
½ TS616
½ TS616
_
_
fb
fb
R
R
R
G
G
+
+
CG
CG
R
The TS616 operates with power supplies from
12V down to 5V. This can be achieved by either a
dual power sup plies of ±6V or ±2.5V or a single
power supply of 12V or 5V referenced to the
ground. In the case of asymmetrical supply, a new
biasing is necessary to assume a positive output
dynamic range between 0V and +V
Considering the values of V
OH and VOL, the ampli-
fier will provide an output dynamic from +0.5V to
10.6V on 25Ω load for a 12V supply and from
0.45V to 3.8V on 10Ω load for a 5V supply.
100µF
100µF
OUT
OUT
supply rails.
CC
10Ω
10Ω
SINGLE POWER SUPPLY
22/27
The amplifier must be biased with a mid-supply
(nominally +V
/2), in order to maintain the DC
CC
component of the signa l at this val ue. Several options are possible to provide this bias supply, such
as a virtual ground using an o perational amplifier
or a two-resistance di vider (whi ch is the cheapest
solution). A high resistance value is required to
limit the current cons umption. O n the other hand,
the current must be high enough to bias the
non-inverting input of t he am plifier. If we consider
TS616
this bias current (30µA max.) as the 1% of the current through the resist ance divider to keep a stable mid-supply, two resistances of 2.2kΩ can be
used in the case of a 12V power supply and two
resistances of 820Ω can be u sed in the case of a
5V power supply.
The input provides a high pass filter with a break
frequency below 10Hz which is necessary to remove the original 0 volt DC component of the input
signal, and to fix it at +V
CC
/2.
CHANNEL SEPARATION - CROSSTALK
The following figure shows the crosstalk from an
amplifier to a second amplifier. This phenomenon,
accentuated at high frequencies, is unavoidable
and intrinsic to the circuit.
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 fact o rs.
Figure 65: Crosstalk vs. Frequency
AV=+4, Rfb=620Ω, VCC=±6V, Vout=2Vp
-50
-60
-70
-80
-90
-100
CrossTal k (dB)
-110
-120
-130
10k100k1M10M
Frequency (Hz)
CHOICE OF THE FEEDBACK CIRCUIT
Table 1: Closed-Loop Gain - Feedback Compo-
nents
V
CC
±6
±2.5
(V)
Gain
+1750
+2680
+4620
+8510
-1680
-2680
-4620
-8510
+11.1k
+21k
+4910
+8680
-11k
-21k
-4910
-8680
Rfb (Ω)
INVERTING AMPLIFIER BIASING
In this case a resistance R is necessary to achieve
good input biasing, see Figure 66.
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 comes: R = R
in, Rfb and a zero
in // Rfb .
Figure 66: Compensation of the Input Bias
Current
fb
fb
R
R
Ib-
Ib-
Rin
Rin
Ib+
Ib+
_
_
+
+
TS616
TS616
Vcc+
Vcc+
Vcc-
Vcc-
Output
Output
Load
Load
R
R
23/27
TS616
ACTIVE FI LT ER I N G
Figure 67 : Low-Pass Active Filtering. Sallen-Key
C1
C1
R
R
1R2
1R2
IN
IN
The resistors R
fb and RG give the gain of the f ilter
+
+
C2
C2
TS616
TS616
_
_
R
R
fb
fb
910Ω
RG
RG
910Ω
OUT
OUT
25Ω
25Ω
as a classical non-inverting am plification configuration :
R
AVg1
fb
--------- -+==
R
g
Assume the following expression i s the response
of the system:
preferable to use very stabl e resisto rs and c apacitances values.
In the case of R1=R2:
R
2C2C
------------------------------------=
ζ
2C1C
fb
--------- -–
1
R
g
2
INCREASING THE LINE LEVEL BY USING AN
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, active
matching impedance can be used. W ith this t echnique, it is possible to keep good impedance
matching with an amplitude on the load higher
than half of the output driver amplitude. This c oncept is shown in Figure 68 for a differential line.
Figure 68: TS616 as a differential line driver with
an active impedance matching
the cut-off frequency is not gai n-dependent a nd it
becomes:
1
------------------------------------- -=
ω
c
R1R2C1C2
The damping factor becomes:
1
-- -
=
ζ
ω
()
cC1R1C1R2C2R1C1R1
2
g–++
The higher the gain, the more sensitive the damping factor is. When the gain is higher than 1 it is
100n
Vcc+
1k
Vi
100n
100n
10µ
1k
GND
ViVo
1/2 R1
1/2 R1
+
_
+
_
Vcc/2
Vcc+
Rs1
GND
R2
R3
R5
R4
Vcc+
GND
Vo°
Vo°
Rs2
µ
1
10n
Vo
1:n
Hybrid
&
RL
Transformer
100Ω
24/27
TS616
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
Vo°
Vo°
Rs1
Rs1
-1
-1
-1
-1
Vo
Vo
½ RL
½ RL
Let us consider the unloaded system . Assumi ng
the currents through R1, R2 and R3
are respect ively:
2Vi
Vi Vo°–
()
---------
---------------------------and
R1
° equals Vo without load, the gain in this
as Vo
R2
Vi Vo+
()
------------------------,
R3
case becomes :
2R2
----------R1
R2
–
1
------- R3
R2
------- -++
R3
G
Vo noload
()
--------------------------------Vi
1
------------------------------------==
2R2
----------R1
R2
------- -–
R3
R2
------- -++
R3
Rs1Iout
----------------------- e q 3
1
R2
------- -–
R3
,–=
()
Vi 1
Vo
------------------------------------------------
1
By identification of both equations (eq2) and
(eq3), the synthesized impedance is, with
Rs1=Rs2=Rs:
Ro
Rs
----------------- e q 4
,=
()
R2
1
------- -–
R3
Figure 70: Equivalent schematic. Ro is the
synthesized impedance .
Iout
1/2RL
° required for a passive imped-
Vi.Gi
Unlike the level Vo
ance, Vo
us write Vo
° will be smaller than 2Vo in our case. Let
°=kVo with k the m at ching f actor vary -
Ro
ing between 1 and 2. Assum ing that the current
through R3 is negligible, (eq4) becomes the following :
Ro
kVoRL
----------------------------- -=
RL 2R s1+
The gain, for the loaded system will be (eq1):
2R2
----------R1
R2
1
------- -–
R3
R2
------- -++
R3
,==
()
GL
Vo withload
()
-------------------------------------Vi
1
1
-- -
------------------------------------ e q 1
2
As shown in Figure70, this system is an ideal generator with a synthesized impedance as the internal impedance of the system. From this, the output voltage becomes:
VoViG
()
RoIout
–=eq2
()
,
()
with Ro the synthesized impedance and Iout the
output current. On the other hand Vo can be expressed as:
After choosing the k factor, Rs will equal to
1/2RL(k-1).
A good impedance matching assume s:
1
Ro
-- -RL eq5
,=
()
2
(eq4) and (eq5) give :
R2
------- -1
R3
2Rs
----------- e q 6
,–=
()
RL
By fixing an arbitrary value of R2, (eq6) becomes :
R3
R2
-------------------- -=
2Rs
1
-----------–
RL
Finally, the values of R2 and R3 allow us to extract
R1 from (eq1), and it becomes:
25/27
TS616
R1
----------------------------------------------------------- e q 7
21
2R2
R2
------- -–
R3
GL 1–
,=
()
R2
------- -–
R3
with GL the required gain.
Table 2 : Components Calculation for Impedance
Matching Implementa tion
GL (gain for the
loaded system)
R12R2/[2(1-R2/R3)GL-1-R2/R3]
R2 (=R4)Abritra ry fixed
R3 (=R5)R2/(1-Rs/0.5RL)
Rs0.5RL(k-1)
Load view ed by
each driv er
GL is fixed for the application requirements
GL=Vo/Vi=0.5(1+2R2/R1+R2/R3)/(1-R2/R3)
kRL/2
26/27
PACKAGE MECHANICAL DATA
8 PINS - PLASTIC MICROPACKAGE (SO Exposed-Pad)
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