LINEAR TECHNOLOGY LT1794 Technical data

FEATURES

■

Exceeds All Requirements For Full Rate,
Downstream ADSL Line Drivers

■

±500mA Minimum I

■

±11.1V Output Swing, VS = ±12V, RL = 100Ω

■

±10.9V Output Swing, VS = ±12V, IL = 250mA

■

Low Distortion: –82dBc at 1MHz, 2V

■

Power Saving Adjustable Supply Current

■

Power Enhanced Small Footprint Packages:

OUT

P-P

20-Lead TSSOP and 20-Lead SW

■

200MHz Gain Bandwidth

■

500V/µs Slew Rate

■

Specified at ±15V, ±12V and ±5V

U

APPLICATIO S

■

High Density ADSL Central Office Line Drivers

■

High Efficiency ADSL, HDSL2, G.lite,
SHDSL Line Drivers

■

Buffers

■

Test Equipment Amplifiers

■

Cable Drivers

Into 50Ω

LT1794

Dual 500mA, 200MHz

xDSL Line Driver Amplifier

U

DESCRIPTIO

The LT®1794 is a 500mA minimum output current, dual op
amp with outstanding distortion performance. The ampli­fiers 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 dissipa­tion. The LT1794 features balanced, high impedance in­puts with low input bias current and input offset voltage.
Active termination is easily implemented for further sys­tem 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.

TYPICAL APPLICATIO

+IN

1000pF

–IN

U

High Efficiency ±12V Supply ADSL Central Office Line Driver

12V

R

BIAS

1k

1k

–12V

24.9k

SHDN

SHDNREF

12.7Ω

12.7Ω

1:2*

•

•

*COILCRAFT X8390-A OR EQUIVALENT

= 10mA PER AMPLIFIER

I

SUPPLY

WITH R

BIAS

= 24.9k

1794 TA01

110Ω

110Ω

+

LT1794

–

–

LT1794

+

1/2

1/2

100Ω

1

LT1794

WW

W

ABSOLUTE MAXIMUM RATINGS

U

(Note 1)

Supply Voltage (V+ to V–) .................................... ±18V

Input Current ..................................................... ±10mA

Output Short-Circuit Duration (Note 2)........... Indefinite

Operating Temperature Range ............... – 40°C to 85°C

U

W

PACKAGE/ORDER INFORMATION

TOP VIEW

–

1

V

2

NC

3

–IN

4

+IN

5

SHDN

SHDNREF

T

JMAX

6
7

+IN

8

–IN

9

NC

–

10

V

FE PACKAGE

20-LEAD PLASTIC TSSOP

= 150°C, θJA = 40°C/W, θJC = 3°C/W (Note 4)
UNDERSIDE METAL CONNECTED TO V

20
19
18
17
16
15
14
13
12
11

V
NC
OUT
V
NC
NC
V
OUT
NC
V

–

+

+

–

–

ORDER PART

NUMBER

LT1794CFE
LT1794IFE

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

U

TOP VIEW

1

NC

+

2

V

3

OUT

–

4

V

–

5

V

–

6

V

–

7

V

8

–IN

9

+IN

10

SHDN

SW PACKAGE

20-LEAD PLASTIC SO

T

= 150°C, θJA = 40°C/W, θJC = 3°C/W (Note 4)

JMAX

20
19
18
17
16
15
14
13
12
11

NC

+

V
OUT

–

V

–

V

–

V

–

V
–IN
+IN
SHDNREF

ORDER PART

NUMBER

LT1794CSW
LT1794ISW

Consult factory for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C.
VCM = 0V, pulse tested, ±5V ≤ VS ≤ ±15V, V

SHDNREF

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OS

Input Offset Voltage 15.0 mV

Input Offset Voltage Matching 0.3 5.0 mV

Input Offset Voltage Drift ● 10 µV/°C

I

OS

I

B

Input Offset Current 100 500 nA

Input Bias Current ±0.1 ±4 µA

Input Bias Current Matching 100 500 nA

e

n

i

n

R

IN

Input Noise Voltage Density f = 10kHz 8 nV/√Hz
Input Noise Current Density f = 10kHz 0.8 pA/√Hz
Input Resistance V

= 0V, R

= (V+ – 2V) to (V–+ 2V) ● 550 MΩ

CM

= 24.9k between V+ and SHDN unless otherwise noted. (Note 3)

BIAS

● 7.5 mV

● 7.5 mV

● 800 nA

● ±6 µA

● 800 nA

Differential 6.5 MΩ

2

LT1794

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C.
VCM = 0V, pulse tested, ±5V ≤ VS ≤ ±15V, V

SHDNREF

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

C

IN

Input Capacitance 3pF
Input Voltage Range (Positive) (Note 5) ● V+ – 2 V+ – 1 V

Input Voltage Range (Negative) (Note 5)

CMRR Common Mode Rejection Ratio V

PSRR Power Supply Rejection Ratio VS = ±4V to ±15V 74 88 dB

A

V

I
I

VOL

OUT

OUT
S

Large-Signal Voltage Gain VS = ±15V, V

Output Swing VS = ±15V, RL = 100Ω 13.8 14.0 ±V

Maximum Output Current VS = ±15V, RL = 1Ω 500 720 mA
Supply Current per Amplifier VS = ±15V, R

Supply Current in Shutdown V
Output Leakage in Shutdown V
Channel Separation VS = ±12V, V

SR Slew Rate VS = ±15V, AV = –10, (Note 7) 300 600 V/µs

HD2 Differential 2nd Harmonic Distortion VS = ±12V, AV = 10, 2V
HD3 Differential 3rd Harmonic Distortion VS = ±12V, AV = 10, 2V
GBW Gain Bandwidth f = 1MHz 200 MHz

= 0V, R

= (V+ – 2V) to (V– + 2V) 74 83 dB

CM

VS = ±12V, V

VS = ±5V, V

= 24.9k between V+ and SHDN unless otherwise noted. (Note 3)

BIAS

● V

● 66 dB

● 66 dB

= ±13V, RL = 100Ω 70 82 dB

OUT

= ±10V, RL = 40Ω 63 76 dB

OUT

= ±3V, RL = 25Ω 60 70 dB

OUT

● 64 dB

● 57 dB

● 54 dB

● 13.6 ±V

–

+ 1 V– + 2 V

VS = ±15V, IL = 250mA 13.6 13.9 ±V

● 13.4 ±V

VS = ±12V, RL = 100Ω 10.9 11.1 ±V

● 10.7 ±V

VS = ±12V, IL = 250mA 10.6 10.9 ±V

● 10.4 ±V

VS = ±5V, RL = 25Ω 3.7 4.0 ±V

● 3.5 ±V

VS = ±5V, IL = 250mA 3.6 3.9 ±V

● 3.4 ±V

= 24.9k (Note 6) 10 13 18 mA

BIAS

VS = ±12V, R

V

= ±12V, R

S

V

= ±12V, R

S

= ±12V, R

V

S

VS = ±5V, R

= 0.4V 0.1 1 mA

SHDN

= 0.4V 0.3 1 mA

SHDN

= 24.9k (Note 6) 8.0 10 13.5 mA

BIAS

= 32.4k (Note 6) 8 mA

BIAS

= 43.2k (Note 6) 6 mA

BIAS

= 66.5k (Note 6) 4 mA

BIAS

= 24.9k (Note 6) 2.2 3.4 5.0 mA

BIAS

= ±10V, RL = 40Ω 80 110 dB

OUT

● 820mA

● 6.7 15.0 mA

● 1.8 5.8 mA

● 77 dB

VS = ±5V, AV = –10, (Note 7) 100 200 V/µs

, RL = 50Ω, 1MHz –85 dBc

P-P

, RL = 50Ω, 1MHz – 82 dBc

P-P

3

LT1794

TEMPERATURE (°C)

–50

OUTPUT SATURATION VOLTAGE (V)

–0.5

10

1794 G06

1.0

–30 –10 30

0.5

V

–

V

+

–1.0

–1.5

1.5

50 70 90

VS = ±12V

RL = 100Ω

RL = 100Ω

I

LOAD

= 250mA

I

LOAD

= 250mA

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

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

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.

LT1794I is guaranteed to meet the extended temperature limits.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Supply Current
vs Ambient Temperature

15

VS = ±12V

14
13
12

10

PER AMPLIFIER (mA)

SUPPLY

I

= 24.9k TO SHDN

R

BIAS

= 0V

V

SHDNREF

11

9
8
7
6
5

–30 –10 10 30 50 70 90

–50

TEMPERATURE (

°C)

1794 G01

Input Common Mode Range
vs Supply Voltage

+

V

TA = 25°C

> 1mV

∆V

–0.5

OS

–1.0
–1.5
–2.0

2.0

1.5

COMMON MODE RANGE (V)

1.0

0.5

–

V

4

2

SUPPLY VOLTAGE (±V)

6

810

is connected between V+ and the SHDN pin.

Input Bias Current
vs Ambient Temperature

200

VS = ±12V

180

PER AMPLIFIER = 10mA

I

S

160
140
120

(nA)

100

BIAS

±I

80
60
40
20

0

–30

12

14

1794 G02

–50

10 30

–10

TEMPERATURE (°C)

50

70 90

1794 G03

Input Noise Spectral Density

100

TA = 25°C

= ±12V

V

S

PER AMPLIFIER = 10mA

I

S

10

1

INPUT VOLTAGE NOISE (V/VHz)

0.1
1 100 1k 10k

4

10

FREQUENCY (Hz)

e

n

i

n

1794 G04

800
780

INPUT CURRENT NOISE (pA/VHz)

760
740
720
700

(mA)

SC

I

680
660
640

620

600

100k

100

10

1

0.1

Output Short-Circuit Current
vs Ambient Temperature

VS = ±12V

PER AMPLIFIER = 10mA

I

S

SOURCING

–50

–30 10

–10

TEMPERATURE (°C)

30

50

SINKING

70

1794 G05

Output Saturation Voltage
vs Ambient Temperature

90

UW

FREQUENCY (Hz)

1k 10k

0

GAIN (dB)

5

10

15

20

100k 1M 10M 100M

1794 G12

–5
–10
–15
–20

25

30

VS = ±12V
A

V

= 10

2mA PER AMPLIFIER

10mA PER AMPLIFIER
15mA PER AMPLIFIER

TYPICAL PERFOR A CE CHARACTERISTICS

LT1794

Open-Loop Gain and Phase
vs Frequency

120
100

80
60
40
20

GAIN (dB)

0

–20

TA = 25°C

= ±12V

V

S

–40

= –10

A

V

= 100Ω

R

L

–60

PER AMPLIFIER = 10mA

I

S

–80

100k 10M 100M

GAIN

1M

FREQUENCY (Hz)

PHASE

1794 G07

120
80
40
0
–40
–80
–120
–160
–200
–240
–280

PHASE (DEG)

–3dB Bandwidth
vs Supply Current Slew Rate vs Supply Current

45

TA = 25°C

= ±12V

V

40

S

= 10

A

V

= 100Ω

R

35

L

30

25

20

15

–3dB BANDWIDTH (MHz)

10

5

0

4

2

SUPPLY CURRENT PER AMPLIFIER (mA)

CMRR vs Frequency PSRR vs Frequency

100

90
80
70
60

50
40
30
20
10

COMMON MODE REJECTION RATIO (dB)

0

0.1

TA = 25°C

= ±12V

V

S

= 10mA PER AMPLIFIER

I

S

1 10 100

FREQUENCY (MHz)

1794 G10

100

90
80
70
60
50
40

30

20
10

POWER SUPPLY REJECTION (dB)

0

–10

0.01 1 10 100

(+) SUPPLY

0.1

6 8 10 12 14

VS = ±12V

= 10

A

V

= 10mA PER AMPLIFIER

I

S

(–) SUPPLY

FREQUENCY (MHz)

1794 G08

1794 G11

1000

TA = 25°C

900

= ±12V

V

S

= –10

A

V

800

R

= 1k

L

700

600
500

400

SLEW RATE (V/µs)

300
200
100

0

345

2

SUPPLY CURRENT PER AMPLIFIER (mA)

67

Frequency Response
vs Supply Current

RISING

FALLING

8910

11 12

13 14

1794 G09

15

1000

100

10

1

OUTPUT IMPEDANCE (Ω)

0.1

0.01

Output Impedance vs Frequency I

TA = 25°C

±12V

V

S

AMPLIFIER = 2mA

AMPLIFIER = 10mA

0.01 0.1

IS PER

IS PER

IS PER
AMPLIFIER = 15mA

1 10 100

FREQUENCY (MHz)

1734 G13

(mA)

SHDN

I

2.5

2.0

1.5

1.0

0.5

0

0

vs V

SHDN

TA = 25°C

= ±12V

V

S

V

SHDNREF

0.5

1.0

= 0V

1.5

SHDN

2.0
V

2.5

SHDN

(V)

3.0

3.5

4.0

4.5

1794 G14

5.0

Supply Current vs V

35

TA = 25°C

= ±12V

V

S

30

25

20

15

10

5

SUPPLY CURRENT PER AMPLIFIER (mA)

0

0

V

SHDNREF

0.5

1.0

= 0V

1.5

2.0
V

2.5

SHDN

SHDN

3.0

(V)

3.5

4.0

4.5

1794 G14

5

5.0

LT1794

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Differential Harmonic Distortion
vs Output Amplitude

–40

f = 1MHz

= 25°C

T

A

–50

= ±12V

V

S

A

= 10

V

= 50Ω

R

L

–60

PER AMPLIFIER = 10mA

I

S

–70

–80

DISTORTION (dBc)

–90

–100

02

6

4 8 10 12 14 16 18

V

OUT(P-P)

HD3

HD2

Differential Harmonic Distortion
vs Supply Current

–40

–45

–50

–55

–60

–65

–70

DISTORTION (dBc)

–75

–80

–85

23456 11

I

SUPPLY

f = 1MHz, HD3

f = 100kHz, HD2

f = 100kHz, HD3

f = 1MHz, HD2

PER AMPLIFIER (mA)

VO = 10V
VS = ±12V

= 10

A

V

= 50Ω

R

L

78910

1794 G16

P-P

1794 G18

Differential Harmonic Distortion
vs Frequency

–40

VO = 10V

–45
–50
–55
–60
–65
–70

DISTORTION (dBc)

–75
–80
–85
–90

P-P

TA = 25°C
V

= ±12V

S

= 10

A

V

= 50Ω

R

L

PER AMPLIFIER = 10mA

I

S

200100

400300

500

FREQUENCY (kHz)

600 700 900

Undistorted Output Swing
vs Frequency

20

)

15

P-P

10

SFDR > 40dB

= 25°C

T

A

5

OUTPUT VOLTAGE (V

= ±12V

V

S

= 10

A

V

= 50Ω

R

L

PER AMPLIFIER = 10mA

I

S

0

100k

300k 1M 3M 10M

FREQUENCY (Hz)

HD3

800

HD2

1000

1794 G17

1794 G19

6