Linear Technology LT1795 Datasheet

FEATURES

LT1795

Dual 500mA/50MHz

Current Feedback Line Driver

Amplifier

U

DESCRIPTIO

■

500mA Output Drive Current

■

50MHz Bandwidth, AV = 2, RL = 25

■

900V/µs Slew Rate, AV = 2, RL = 25

■

Low Distortion: –75dBc at 1MHz

■

High Input Impedance, 10MΩ

■

Wide Supply Range, ±5V to ±15V

■

Full Rate, Downstream ADSL Supported

■

Power Enhanced Small Footprint Packages

Ω

Ω

TSSOP-20, S0-20 Wide

■

Low Power Shutdown Mode

■

Power Saving Adjustable Supply Current

■

Stable with CL = 10,000pF

U

APPLICATIO S

■

ADSL HDSL2, G.lite Drivers

■

Buffers

■

Test Equipment Amplifiers

■

Video Amplifiers

■

Cable Drivers

U

TYPICAL APPLICATION

The LT®1795 is a dual current feedback amplifier with high
output current and excellent large signal characteristics.
The combination of high slew rate, 500mA output drive
and up to ±15V operation enables the device to deliver
significant power at frequencies in the 1MHz to 2MHz
range. Short-circuit protection and thermal shutdown
insure the device’s ruggedness. The LT1795 is stable with
large capacitive loads and can easily supply the large
currents required by the capacitive loading. A shutdown
feature switches the device into a high impedance, low
current mode, reducing power dissipation when the de­vice is not in use. For lower bandwidth applications, the
supply current can be reduced with a single external
resistor.

The LT1795 comes in the very small, thermally enhanced,
20-lead TSSOP package for maximum port density in line
driver applications.

, LTC and LT are registered trademarks of Linear Technology Corporation.

Low Loss, High Power Central Office ADSL Line Driver

+

V

+IN

+

1/2

LT1795

–

1k

165Ω

1k

–

1/2

–IN

* MIDCOM 50215 OR EQUIVALENT

LT1795

+

–

V

12.5Ω

1:2*

12.5Ω

100Ω

1795 TA01

1

LT1795

WW

W

ABSOLUTE AXI U RATI GS

U

(Note 1)

Supply Voltage ...................................................... ±18V

Input Current ...................................................... ±15mA

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

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

UUW

PACKAGE/ORDER I FOR ATIO

–IN
+IN

SHDN

SHDNREF

+IN
–IN

TOP VIEW

–

1

V

2

NC

3
4
5
6
7
8
9

NC

–

10

V

FE PACKAGE

20-LEAD PLASTIC TSSOP

T

= 150° C, θJA = 40°C/W (Note 4)

JMAX

–

20

V

19

NC

18

OUT

+

17

V

16

COMP

15

COMP

+

14

V

13

OUT

12

NC

–

11

V

ORDER PART

NUMBER

LT1795CFE
LT1795IFE

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

1

COMP

+

2

V

3

OUT

–

4

V

–

5

V

–

6

V

–

7

V

8

–IN

9

+IN

10

SHDN

S PACKAGE

20-LEAD PLASTIC SW

T

= 150° C, θJA ≈ 40°C/W (Note 4)

JMAX

20
19
18
17
16
15
14
13
12
11

COMP

+

V
OUT

–

V

–

V

–

V

–

V
–IN
+IN
SHDNREF

ORDER PART

NUMBER

LT1795CSW
LT1795ISW

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

I

I

e
+i
–i

OS

+

IN

–

IN

n

n
n

Input Offset Voltage ±3 ±13 mV

Input Offset Voltage Matching ±1 ±3.5 mV

Input Offset Voltage Drift ● 10 µV/°C
Noninverting Input Current ±2 ±5 µA

Noninverting Input Current Matching ±0.5 ±2 µA

Inverting Input Current ±10 ±70 µA

Inverting Input Current Matching ±10 ±30 µA

Input Noise Voltage Density f = 10kHz, RF =1k, RG = 10Ω, RS = 0Ω 3.6 nV/√Hz
Input Noise Current Density f = 10kHz, RF =1k, RG = 10Ω, RS = 10kΩ 2 pA/√Hz
Input Noise Current Density f = 10kHz, RF =1k, RG = 10Ω, RS = 10kΩ 30 pA/√Hz

SHDN

= 2.5V, V

SHDNREF

= 0V unless otherwise noted. (Note 3)

● ±4.5 ±17 mV

● ±1.5 ±5.0 mV

● ±8 ±20 µA

● ±1.5 ±7 µA

● ±20 ±100 µA

● ±20 ±50 µA

2

LT1795

ELECTRICAL CHARACTERISTICS

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

+

R

IN

+

C

IN

CMRR Common Mode Rejection Ratio VS = ±15V, VCM = ±12V ● 55 62 dB

PSRR Power Supply Rejection Ratio VS = ±5V to ±15V ● 60 77 dB

A

V

R

OL

V

OUT

I

OUT

I

S

HD2, HD

3

SR Slew Rate (Note 7) AV = 4, RL = 400Ω 400 900 V/µs

BW Small-Signal BW AV = 2, VS = ±15V, Peaking ≤ 1.5dB 65 MHz

Input Resistance VIN = ±12V, VS = ±15V ● 1.5 10 MΩ

Input Capacitance VIN = ±15V 2 pF
Input Voltage Range (Note 5) VS = ±15V ● ±12 ±13.5 V

Inverting Input Current VS = ±15V, VCM = ±12V ● 110µA/V
Common Mode Rejection V

Noninverting Input Current VS = ±5V to ±15V ● 30 500 nA/V
Power Supply Rejection

Inverting Input Current VS = ±5V to ±15V ● 15µA/V
Power Supply Rejection

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

Transresistance, ∆V

OUT

/∆I

–

IN

Maximum Output Voltage Swing VS = ±15V, RL = 25Ω±11.5 ±12.5 V

Maximum Output Current VS = ±15V, RL = 1Ω ● 0.5 1 A
Supply Current Per Amplifier VS = ±15V, V

Supply Current Per Amplifier, VS = ±15V 15 20 mA

= 51k, (Note 6) ● 25 mA

R

SHDN

Positive Supply Current, Shutdown VS = ±15V, V
Output Leakage Current, Shutdown VS = ±15V, V
Channel Separation VS = ±15V, V
2nd and 3rd Harmonic Distortion f = 1MHz, VO = 20V

Differential Mode

Slew Rate AV = 4, RL = 25Ω 900 V/µs

SHDN

= 2.5V, V

SHDNREF

= 0V unless otherwise noted. (Note 3)

V = ±2V, VS = ±5V ● 0.5 5 MΩ

VS = ±5V ● ±2 ±3.5 V

VS = ±5V, VCM = ±2V ● 50 60 dB

= ±5V, VCM = ±2V ● 110µA/V

S

= ±10V, RL = 25Ω ● 55 68 dB

= ±5V, V

V

S

VS = ±15V, V
VS = ±5V, V

OUT

= ±2V, RL = 12Ω ● 55 68 dB

OUT

= ±10V, RL = 25Ω ● 75 200 kΩ

OUT

= ±2V, RL = 12Ω ● 75 200 kΩ

OUT

● ±10.0 ±11.5 V

VS = ±5V, RL = 12Ω±2.5 ±3V

● ±2.0 ±3V

= 2.5V 29 34 mA

SHDN

= 0.4V ● 1 200 µA

SHDN

= 0.4V 1 10 µA

SHDN

= ±10V, RL = 25Ω 80 110 dB

OUT

, RL = 50, AV = 2 –75 dBc

P-P

● 42 mA

RF = RG = 910Ω, RL = 100Ω
AV = 2, VS = ±15V, Peaking ≤ 1.5dB 50 MHz

= RG = 820Ω, RL = 25Ω

R

F

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 LT1795C 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
LT1795I 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

is connected between the SHDN pin and V+.

SHDN

Note 7: Slew rate is measured at ±5V on a ±10V output signal while
operating on ±15V supplies with R
R

= 400Ω.

L

= 1k, RG = 333Ω (AV = +4) and

F

3

LT1795

W

UU

SMALL-SIGNAL BANDWIDTH

RSD = 0Ω, IS = 30mA per Amplifer, VS = ±15V,
Peaking ≤ 1dB, RL = 25Ω

A

V

R

F

–1 976 976 44

1 1.15k — 53
2 976 976 48

10 649 72 46

R

G

–3dB BW

(MHz)

RSD = 51kΩ, IS = 15mA per Amplifer, VS = ±15V,
Peaking ≤ 1dB, RL = 25Ω

A

V

–1 976 976 30

1 1.15k — 32
2 976 976 32

10 649 72 27

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Supply Current vs Ambient
Temperature

40

VS = ±15V

= 1

A

35

V

= ∞

R

L

30

25

20

15

10

5

SUPPLY CURRENT PER AMPLIFIER (mA)

0

–50

–25 0

TEMPERATURE (°C)

RSD = 0Ω

RSD = 51kΩ

50 100 125

25 75

LT1795 G01

Output Saturation Voltage vs
Junction Temperature

+

V

VS = ±15V

–1
–2
–3
–4

4
3
2

OUTPUT SATURATION VOLTAGE (V)

1

RL = 2k

–

V

–50

–25

RL = 2k

50

25

0

TEMPERATURE (°C)

RL = 25Ω

RL = 25Ω

75

100

LT1795 G02

125

R

F

R

G

Output Short-Circuit Current vs
Junction Temperature

2.0

1.8

1.6

1.4

1.2

–50

SINKING

–25 0

1.0

0.8

OUTPUT SHORT-CIRCUIT CURRENT (A)

0.6

SOURCING

25 75

TEMPERATURE (°C)

–3dB BW

(MHz)

VS = ±15V

50 100 125

LT1795 G03

SHDN Pin Current vs Voltage

0.6
VS = ±15V

= 0V

V

SHDNREF

0.5

0.4

0.3

0.2

CURRENT INTO SHDN PIN (mA)

0.1

0

0

1 2 3 4 5

VOLTAGE APPLIED AT SHDN PIN (V)

4

1795 G04

Second Harmonic Distortion vs
Frequency

–40

AV = 2 DIFFERENTIAL

= 20V

V

OUT

–50

VS = ±15V
R
I

Q

–60

–70

–80

DISTORTION (dBc)

–90

–100

10k

P-P

= 50Ω

LOAD

PER AMPLIFIER

FREQUENCY (Hz)

IQ = 10mA

100k 1M

IQ = 5mA

IQ = 15mA

IQ = 20mA

LT1795 G05

Third Harmonic Distortion vs
Frequency

–40

AV = 2 DIFFERENTIAL
V

= 20V

OUT

–50

VS = ±15V
R

I

Q

–60

–70

–80

DISTORTION (dBc)

–90

–100

10k

P-P

= 50Ω

LOAD

PER AMPLIFIER

IQ = 20mA

FREQUENCY (Hz)

IQ = 10mA

100k 1M

IQ = 5mA

IQ = 15mA

LT1795 G06