LT1794
Dual 500mA, 200MHz
xDSL Line Driver Amplifier
FEATURES
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
Exceeds All Requirements For Full Rate,
Downstream ADSL Line Drivers
±500mA
Minimum I
OUT
±11.1V
Output Swing, V
S
=
±12V,
R
L
= 100Ω
±10.9V
Output Swing, V
S
=
±12V,
I
L
= 250mA
Low Distortion: – 82dBc at 1MHz, 2V
P-P
Into 50Ω
Power Saving Adjustable Supply Current
Power Enhanced Small Footprint Packages:
20-Lead TSSOP and 20-Lead SW
200MHz Gain Bandwidth
500V/µs Slew Rate
Specified at
±15V, ±12V
and
±5V
The LT
®
1794 is a 500mA minimum output current, dual op
amp with outstanding distortion performance. The ampli-
fiers are gain-of-ten stable, but can be easily compensated
for lower gains. The extended output swing allows for
lower supply rails to reduce system power. Supply current
is set with an external resistor to optimize power dissipa-
tion. The LT1794 features balanced, high impedance in-
puts with low input bias current and input offset voltage.
Active termination is easily implemented for further sys-
tem power reduction. Short-circuit protection and thermal
shutdown insure the device’s ruggedness.
The outputs drive a 100Ω load to
±11.1V
with
±12V
supplies, and
±10.9V
with a 250mA load. The LT1794,
with its increased swing on lower supplies, can be used to
upgrade LT1795 line driver applications.
The LT1794 is available in the very small, thermally
enhanced, 20-lead TSSOP for maximum port density in
line driver applications. The 20-lead SW is also available.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
High Density ADSL Central Office Line Drivers
High Efficiency ADSL, HDSL2, G.lite,
SHDSL Line Drivers
Buffers
Test Equipment Amplifiers
Cable Drivers
TYPICAL APPLICATIO
High Efficiency
±12V
Supply ADSL Central Office Line Driver
12V
R
BIAS
24.9k
SHDN
12.7Ω
+IN
+
1/2
LT1794
–
1k
110Ω
1000pF
1:2*
•
•
110Ω
1k
*COILCRAFT X8390-A OR EQUIVALENT
I
SUPPLY
= 10mA PER AMPLIFIER
WITH R
BIAS
= 24.9k
1794 TA01
–
1/2
LT1794
–IN
12.7Ω
SHDNREF
+
–12V
U
100Ω
U
U
1
LT1794
ABSOLUTE
MAXIMUM
RATINGS
Supply Voltage (V
+
to V
–
) ....................................
±18V
Input Current .....................................................
±10mA
Output Short-Circuit Duration (Note 2) ........... Indefinite
Operating Temperature Range ............... – 40°C to 85°C
PACKAGE/ORDER INFORMATION
TOP VIEW
V
–
1
NC 2
–IN 3
+IN 4
SHDN 5
SHDNREF 6
+IN 7
–IN 8
NC 9
V
–
10
20 V
–
19 NC
18 OUT
17 V
+
16 NC
15 NC
14
V
+
ORDER PART
NUMBER
NC 1
LT1794CFE
LT1794IFE
13 OUT
12 NC
11 V
–
FE PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 40°C/W,
θ
JC
= 3°C/W (Note 4)
UNDERSIDE METAL CONNECTED TO V
–
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full specified temperature range, otherwise specifications are at T
A
= 25°C.
V
CM
= 0V, pulse tested,
±5V ≤
V
S
≤ ±15V,
V
SHDNREF
= 0V, R
BIAS
= 24.9k between V
+
and SHDN unless otherwise noted. (Note 3)
SYMBOL
V
OS
PARAMETER
Input Offset Voltage
q
CONDITIONS
Input Offset Voltage Matching
q
Input Offset Voltage Drift
I
OS
I
B
Input Offset Current
Input Bias Current
q
Input Bias Current Matching
q
e
n
i
n
R
IN
Input Noise Voltage Density
Input Noise Current Density
Input Resistance
f = 10kHz
f = 10kHz
V
CM
= (V
+
– 2V) to (V
–
+ 2V)
Differential
q
2
U
U
W
W W
U
W
(Note 1)
Specified Temperature Range (Note 3) .. – 40°C to 85°C
Junction Temperature .......................................... 150°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
20 NC
19 V
+
18 OUT
17 V
–
16 V
–
15 V
–
14 V
–
13 –IN
12 +IN
11 SHDNREF
SW PACKAGE
20-LEAD PLASTIC SO
ORDER PART
NUMBER
LT1794CSW
LT1794ISW
V
+
2
OUT 3
V
–
4
V
–
5
V
–
6
V
–
7
–IN 8
+IN 9
SHDN 10
T
JMAX
= 150°C,
θ
JA
= 40°C/W,
θ
JC
= 3°C/W (Note 4)
MIN
TYP
1
0.3
MAX
5.0
7.5
5.0
7.5
500
800
±4
±6
500
800
UNITS
mV
mV
mV
mV
µV/°C
nA
nA
µA
µA
nA
nA
nV/√Hz
pA/√Hz
MΩ
MΩ
q
q
10
100
±0.1
100
8
0.8
5
50
6.5
LT1794
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full specified temperature range, otherwise specifications are at T
A
= 25°C.
V
CM
= 0V, pulse tested,
±5V ≤
V
S
≤ ±15V,
V
SHDNREF
= 0V, R
BIAS
= 24.9k between V
+
and SHDN unless otherwise noted. (Note 3)
SYMBOL
C
IN
PARAMETER
Input Capacitance
Input Voltage Range (Positive)
Input Voltage Range (Negative)
CMRR
PSRR
A
VOL
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Large-Signal Voltage Gain
(Note 5)
(Note 5)
V
CM
= (V
+
– 2V) to (V
–
+ 2V)
q
q
q
CONDITIONS
MIN
V
+
– 2
74
66
74
66
70
64
63
57
60
54
13.8
13.6
13.6
13.4
10.9
10.7
10.6
10.4
3.7
3.5
3.6
3.4
500
q
TYP
3
V
+
– 1
V
–
+ 1
83
88
82
76
70
14.0
13.9
11.1
10.9
4.0
3.9
720
13
10
8
6
4
MAX
UNITS
pF
V
V
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
±V
±V
±V
±V
±V
±V
±V
±V
±V
±V
±V
±V
mA
V
–
+
2
V
S
=
±4V
to
±15V
q
V
S
=
±15V,
V
OUT
=
±13V,
R
L
= 100Ω
q
V
S
=
±12V,
V
OUT
=
±10V,
R
L
= 40Ω
q
V
S
=
±5V,
V
OUT
=
±3V,
R
L
= 25Ω
q
V
OUT
Output Swing
V
S
=
±15V,
R
L
= 100Ω
q
V
S
=
±15V,
I
L
= 250mA
q
V
S
=
±12V,
R
L
= 100Ω
q
V
S
=
±12V,
I
L
= 250mA
q
V
S
=
±5V,
R
L
= 25Ω
q
V
S
=
±5V,
I
L
= 250mA
q
I
OUT
I
S
Maximum Output Current
Supply Current per Amplifier
V
S
=
±15V,
R
L
= 1Ω
V
S
=
±15V,
R
BIAS
= 24.9k (Note 6)
V
S
=
±12V,
R
BIAS
= 24.9k (Note 6)
V
S
=
±12V,
R
BIAS
= 32.4k (Note 6)
V
S
=
±12V,
R
BIAS
= 43.2k (Note 6)
V
S
=
±12V,
R
BIAS
= 66.5k (Note 6)
V
S
=
±5V,
R
BIAS
= 24.9k (Note 6)
q
q
10
8
8.0
6.7
18
20
13.5
15.0
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
dB
dB
V/µs
V/µs
dBc
dBc
MHz
2.2
1.8
3.4
0.1
0.3
5.0
5.8
1
1
Supply Current in Shutdown
Output Leakage in Shutdown
Channel Separation
SR
HD2
HD3
GBW
Slew Rate
Differential 2nd Harmonic Distortion
Differential 3rd Harmonic Distortion
Gain Bandwidth
V
SHDN
= 0.4V
V
SHDN
= 0.4V
V
S
=
±12V,
V
OUT
=
±10V,
R
L
= 40Ω
q
80
77
300
100
110
600
200
–85
– 82
200
V
S
=
±15V,
A
V
= – 10, (Note 7)
V
S
=
±5V,
A
V
= –10, (Note 7)
V
S
=
±12V,
A
V
= 10, 2V
P-P
, R
L
= 50Ω, 1MHz
V
S
=
±12V,
A
V
= 10, 2V
P-P
, R
L
= 50Ω, 1MHz
f = 1MHz
3
LT1794
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Applies to short circuits to ground only. A short circuit between
the output and either supply may permanently damage the part when
operated on supplies greater than
±10V.
Note 3:
The LT1794C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at – 40°C and 85°C. The
LT1794I is guaranteed to meet the extended temperature limits.
Note 4:
Thermal resistance varies depending upon the amount of PC board
metal attached to the device. If the maximum dissipation of the package is
exceeded, the device will go into thermal shutdown and be protected.
Note 5:
Guaranteed by the CMRR tests.
Note 6:
R
BIAS
is connected between V
+
and the SHDN pin.
Note 7:
Slew rate is measured at
±5V
on a
±10V
output signal while
operating on
±15V
supplies and
±1V
on a
±3V
output signal while
operating on
±5V
supplies.
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current
vs Ambient Temperature
V
S
=
±12V
14 R
BIAS
= 24.9k TO SHDN
V
SHDNREF
= 0V
13
12
11
10
9
8
7
6
5
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
15
V
+
–0.5
COMMON MODE RANGE (V)
–1.0
–1.5
±I
BIAS
(nA)
–2.0
I
SUPPLY
PER AMPLIFIER (mA)
Input Noise Spectral Density
100
T
A
= 25°C
V
S
=
±12V
I
S
PER AMPLIFIER = 10mA
e
n
100
OUTPUT SATURATION VOLTAGE (V)
INPUT VOLTAGE NOISE (V/VHz)
10
I
SC
(mA)
1
i
n
0.1
1
10
100
1k
FREQUENCY (Hz)
10k
4
U W
1794 G01
1794 G04
Input Common Mode Range
vs Supply Voltage
T
A
= 25°C
∆V
OS
> 1mV
Input Bias Current
vs Ambient Temperature
200
V
S
=
±12V
180 I
S
PER AMPLIFIER = 10mA
160
140
120
100
80
60
40
20
2.0
1.5
1.0
0.5
V
–
2
4
8
10
6
SUPPLY VOLTAGE (±V)
12
14
1794 G02
0
–50
–30
10
30
50
–10
TEMPERATURE (°C)
70
90
1794 G03
Output Short-Circuit Current
vs Ambient Temperature
800
780
INPUT CURRENT NOISE (pA/VHz)
Output Saturation Voltage
vs Ambient Temperature
V
+
–0.5
–1.0
–1.5
I
LOAD
= 250mA
V
S
=
±12V
R
L
= 100Ω
V
S
=
±12V
I
S
PER AMPLIFIER = 10mA
760
740
720
700
680
660
640
620
SOURCING
SINKING
10
1
1.5
1.0
0.5
V
–
– 50 –30
–10
I
LOAD
= 250mA
R
L
= 100Ω
0.1
100k
600
–50
–30
30
–10 10
50
TEMPERATURE (°C)
70
90
50
30
10
TEMPERATURE (°C)
70
90
1794 G06
1794 G05
LT1794
TYPICAL PERFOR A CE CHARACTERISTICS
Open-Loop Gain and Phase
vs Frequency
120
100
80
60
GAIN (dB)
40
20
0
GAIN
T
A
= 25°C
V
S
=
±12V
A
V
= –10
R
L
= 100Ω
I
S
PER AMPLIFIER = 10mA
1M
10M
FREQUENCY (Hz)
100M
1794 G07
PHASE
–3dB BANDWIDTH (MHz)
30
25
20
15
10
5
0
2
4
6
8
10
12
14
SUPPLY CURRENT PER AMPLIFIER (mA)
1794 G08
–40
–80
–120
–160
–200
–240
–280
SLEW RATE (V/µs)
–20
–40
–60
–80
100k
CMRR vs Frequency
100
COMMON MODE REJECTION RATIO (dB)
90
80
70
60
50
40
30
20
10
0
0.1
POWER SUPPLY REJECTION (dB)
T
A
= 25°C
V
S
=
±12V
I
S
= 10mA PER AMPLIFIER
GAIN (dB)
1
10
FREQUENCY (MHz)
Output Impedance vs Frequency
1000
T
A
= 25°C
V
S
±12V
I
S
PER
AMPLIFIER = 2mA
10
I
S
PER
AMPLIFIER = 10mA
I
S
PER
AMPLIFIER = 15mA
I
SHDN
(mA)
2.5
SUPPLY CURRENT PER AMPLIFIER (mA)
100
OUTPUT IMPEDANCE (Ω)
1
0.1
0.01
0.01
0.1
1
10
FREQUENCY (MHz)
U W
1794 G10
1734 G13
–3dB Bandwidth
vs Supply Current
120
80
40
0
PHASE (DEG)
Slew Rate vs Supply Current
1000
900
800
700
600
500
400
300
200
100
0
2 3 4 5 6 7 8 9 10 11 12 13 14 15
SUPPLY CURRENT PER AMPLIFIER (mA)
1794 G09
45
40
35
T
A
= 25°C
V
S
=
±12V
A
V
= 10
R
L
= 100Ω
T
A
= 25°C
V
S
=
±12V
A
V
= –10
R
L
= 1k
RISING
FALLING
PSRR vs Frequency
100
90
80
70
60
50
40
(–) SUPPLY
(+) SUPPLY
V
S
=
±12V
A
V
= 10
I
S
= 10mA PER AMPLIFIER
Frequency Response
vs Supply Current
30
25
20
15
10
5
0
–5
–10
–15
–20
2mA PER AMPLIFIER
10mA PER AMPLIFIER
15mA PER AMPLIFIER
V
S
=
±12V
A
V
= 10
30
20
10
0
–10
0.01
100
0.1
1
10
FREQUENCY (MHz)
100
1794 G11
1k
10k
100k
1M
10M
FREQUENCY (Hz)
100M
1794 G12
I
SHDN
vs V
SHDN
35
T
A
= 25°C
V
S
=
±12V
V
SHDNREF
= 0V
30
25
20
15
10
5
0
Supply Current vs V
SHDN
T
A
= 25°C
V
S
=
±12V
V
SHDNREF
= 0V
2.0
1.5
1.0
0.5
100
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
V
SHDN
(V)
1794 G14
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
V
SHDN
(V)
1794 G14
5
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