Linear Technology LT1675-1, LT1675 Datasheet

LT1675/LT1675-1

250MHz, Triple and Single

RGB Multiplexer with Current Feedback Amplifiers

FEATURES

■

100MHz Pixel Switching

■

– 3dB Bandwidth: 250MHz

■

Small 16-Pin SSOP Package

■

Channel Switching Time: 2.5ns

■

Expandable to Larger Arrays

■

Drives Cables Directly

■

High Slew Rate: 1100V/µs

■

Low Switching Transient: 50mV

■

Shutdown Supply Current: 0mA

■

Output Short-Circuit Protected

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APPLICATIONS

■

RGB Switching

■

Workstation Graphics

■

Pixel Switching

■

Coaxial Cable Drivers

■

High Speed Signal Processing

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DESCRIPTION

The LT®1675 is a high speed RGB multiplexer designed for
pixel switching and fast workstation graphics.
Included on chip are three SPDT switches and three
current feedback amplifiers. The current feedback ampli­fiers drive double-terminated 50Ω or 75Ω cables and are

configured for a fixed gain of 2, eliminating six external
gain setting resistors. The SPDT switches are designed to
be break-before-make to minimize unwanted signals cou­pling to the input.

The LT1675-1 is a single version with two inputs, a single
output and is ideal for a single channel application such as
video sync.

The key to the LT1675 fast switching speed is Linear
Technology’s proprietary high speed bipolar process. This
MUX can toggle between sources in excess of 100MHz,
has a slew rate over 1000V/µs and has a –3dB bandwidth
of 250MHz. The speed and ease of use of the LT1675 make
it ideal for high performance PCs, workstations and pro­fessional video monitors. The input-referred switching
transient is only 50mV

and lasts just 5ns, making it

P-P

virtually undetectable. Power supply requirements are
±4V to ±6V and power dissipation is only 300mW on ±5V,
or 100mW for the LT1675-1. The expandable feature uses
the disable pin to reduce the power dissipation to near
0mW in the off parts.

Unlike competitive solutions that are in bulky high pin
count packages, the LT1675 is in a 16-lead narrow body
SSOP. This small footprint, the size of an SO-8, results in
a very clean high performance solution. The LT1675-1 is
available in the tiny MSOP and the SO-8.

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

TYPICAL APPLICATION

High Speed RGB MUX

RED 1

75Ω

GREEN 1

75Ω

BLUE 1

75Ω

RED 2

75Ω

GREEN 2

75Ω

BLUE 2

75Ω

LT1675

+1

+1

+1

+1

+1

+1

+2

+2

+2

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75Ω

75Ω

75Ω

+

V

ENABLE

CABLE

CABLE

CABLE

–

V

SELECT RGB1/RGB2

V

75Ω

V

75Ω

V

75Ω

OUT RED

OUT GREEN

OUT BLUE

1675 TA01

Select Pin Switches Inputs at 100MHz

3V

SELECT

LOGIC

PIN 10

0V

1V
RED
OUT

0V

RED 1 = 0V, RED 2 = 1V, RL = 100Ω
MEASURED BETWEEN 50Ω BACK TERMINATION AND 50Ω LOAD

1V/DIV

500mV/DIV

1675 TA02

1

LT1675/LT1675-1

WW

W

ABSOLUTE MAXIMUM RATINGS

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(Note 1)

Supply Voltage ..................................................... ±6.3V

Inputs, ENABLE and SELECT, Current ................ ±20mA

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

Specified Temperature Range (Note 3)....... 0°C to 70°C

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W

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PACKAGE/ORDER INFORMATION

TOP VIEW

V

1

IN1

2

GND

3

V

IN2

–

4

V

MS8 PACKAGE

8-LEAD PLASTIC MSOP

T

= 150°C, θJA = 250°C/ W

JMAX

8

V

7

ENABLE

6

V

5

SELECT

+

OUT

V

IN1

GND
V

IN2

V

TOP VIEW

1

2

3

–

4

S8 PACKAGE

8-LEAD PLASTIC SO

T

= 150°C, θJA = 150°C/ W

JMAX

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

Storage Temperature Range ................. –65°C to 150°C

Junction Temperature (Note 4)............................ 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

TOP VIEW

8

7

6

5

+

V
ENABLE
V

OUT

SELECT

1

RED 1

GREEN 1

GREEN 2

2
3

BLUE 1

4

GND

5

GND

6

RED 2

7
8

BLUE 2

GN PACKAGE

16-LEAD PLASTIC SSOP NARROW

T

= 150°C, θJA = 120°C/W

JMAX

16
15
14
13
12
11
10

9

+

V
V

OUT RED

V

OUT GREEN

V

OUT BLUE
–

V

–

V
SELECT
ENABLE

ORDER PART

NUMBER

LT1675CMS8-1

MS8 PART

MARKING

LTGX

Consult factory for Industrial and Military grade parts.

ORDER PART

NUMBER

LT1675CS8-1

S8 PART

MARKING

16751

ORDER PART

NUMBER

LT1675CGN

GN PART

MARKING

1675

2

LT1675/LT1675-1

ELECTRICAL CHARACTERISTICS

0°C ≤ TA ≤ 70°C, VS = ±5V, RL = ∞

= 0V LT1675 (Pins 1, 2, 3, 6, 7, 8),

, VIN

LT1675-1 (Pins 1, 3), ENABLE = 0V, unless otherwise specified.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Output Offset Voltage Any Input Selected ● 20 40 mV
Output Offset Matching Between Outputs R1 to R2, G1 to G2, B1 to B2 ● 520 mV
Input Current Any Input Selected ● –12 –30 µA
Input Resistance VIN = ±1V ● 100 700 kΩ
PSRR VS =±2.6V to ±6V, Measured at Output ● 38 50 dB
DC Gain Error 0V to 1V VIN = 1V, R

V

= 1V, RL = 150Ω ● 48 %

IN

= 1V, RL = 75Ω ● 510 %

V

IN

DC Gain Error 0V to –1V VIN = –1V, R

= –1V, RL = 150Ω ● 48 %

V

IN

V

= –1V, RL = 75Ω ● 820 %

IN

Output Voltage VIN = 2V, R

V

= 2V, RL = 150Ω ● 2.8 3.0 V

IN

= 2V, RL = 75Ω ● 2.4 2.8 V

V

IN

VIN = –2V, R

= –2V, RL = 150Ω ● –2.7 – 3.0 V

V

IN

V

= –2V, RL = 75Ω ● – 2.3 – 2.6 V

IN

Disabled Output Impedance ENABLE Open ● 1.1 1.5 2.0 kΩ
Maximum Output Current VIN = ±1V, VO = 0V ● 50 70 mA
Supply Current LT1675 ENABLE = 0V ● 25 33 42 mA

ENABLE = 4.7V

LT1675-1 ENABLE = 0V ● 81114 mA

ENABLE = 4.7V

ENABLE Pin Current LT1675 ENABLE= 0V ● 450 600 µA

LT1675-1 ENABLE= 0V ● 150 200 µA

SELECT Pin Current LT1675 SELECT = 0V ● 90 180 µA

LT1675-1 SELECT = 0V ● 30 60 µA

SELECT Low SELECT (See Truth Table) ● 0.8 V
SELECT High SELECT (See Truth Table) ● 2V

= ∞ ● 36 %

L

= ∞ ● 36 %

L

= ∞ ● 3.1 3.4 V

L

= ∞ ● –3.1 –3.3 V

L

● 1 100 µA

● 0.3 33 µA

3

LT1675/LT1675-1

AC CHARACTERISTICS

0°C ≤ TA ≤ 70°C, VS = ±5V, RL = 150Ω

= 0V LT1675 (Pins 1, 2, 3, 6, 7, 8),

, VIN

LT1675-1 (Pins 1, 3), ENABLE = 0V, unless otherwise specified.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Slew Rate V
Full Power Bandwidth (Note 5) V
Small-Signal –3dB Bandwidth Less Than 1dB Peaking 250 MHz
Gain Flatness Less Than 0.1dB 70 MHz
Gain Matching R to G to B 0.10 dB

Channel-to-Channel Select Time R1 = 0V, R2 = 1V

Delay Time Measured from Time SELECT Pin Crosses Logic Threshold 5.0 ns

Switching Time Time for V
Enable Time 10 ns
Disable Time 100 ns
Input Pin Capacitance 2pF
SELECT Pin Capacitance LT1675 2.2 pF

LT1675-1 1.5 pF

ENABLE Pin Capacitance LT1675 2.1 pF

LT1675-1 1.5 pF
Output Pin Capacitance (Disabled) ENABLE Open 4.4 pF
Small-Signal Rise Time VIN = 300mV
Propagation Delay VIN = 300mV
Overshoot VIN = 300mV
On-Channel to Off-Channel Crosstalk Measured at 10MHz 60 dB
Chip Disable Crosstalk Measured at 10MHz, ENABLE Open 90 dB
Channel Select Output Transient Measured Between Back Termination and Load 50 mV
Differential Gain (Note 6) 0.07 %
Differential Phase (Note 6) 0.05 DEG

= 5V

OUT

P-P

=6V

OUT

P-P

R1 to R2, G1 to G2, B1 to B2, LT1675-1 V

to Go from 0V to 1V 2.5 ns

OUT

, RL = 100Ω 1.85 ns

P-P

, RL = 100Ω 3ns

P-P

, RL = 100Ω 10 %

P-P

IN1

to V

IN2

1100 V/µs

58 MHz

0.01 dB

P-P

The

● denotes specifications that apply over the specified temperature

range.
Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: May require a heat sink.
Note 3: The LT1675/LT1675-1 are guaranteed to meet specified

performance from 0°C to 70°C and are designed, characterized and
expected to meet these extended temperature limits, but are not tested at
–40°C and 85°C. Guaranteed I grade parts are available; consult factory.

Truth Table

SELECT ENABLE RED OUT GREEN OUT BLUE OUT VOUT

1 0 RED 1 GREEN 1 BLUE 1 VIN1
0 0 RED 2 GREEN 2 BLUE 2 VIN2
X 1 OFF OFF OFF OFF

4

Note 4: TJ is calculated from the ambient temperature TA and power
dissipation P

LT1675CGN: T
LT1675CMS8-1: T
LT1675CS8-1: T

Note 5: Full power bandwidth is calculated from the slew rate
measurement:

FPBW = SR/2πV

Note 6: Differential Gain and Phase are measured using a Tektronix
TSG120 YC/NTSC signal generator and a Tektronix 1780R Video
Measurement Set. The resolution of this equipment is 0.1% and 0.1°. Nine
identical MUXs were cascaded giving an effective resolution of 0.011%
and 0.011°.

LT1675 LT1675-1

according to the following formula:

D

= TA + (PD)(120°C/W)

J

= TA + (PD)(250°C/W)

J

= TA + (PD)(150°C/W)

J

.

PEAK

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TYPICAL PERFORMANCE CHARACTERISTICS

LT1675/LT1675-1

Gain and Phase vs
Frequency

5
4
3
2
1
0

GAIN (dB)

–1
–2
–3

CL = 0pF

–4

R

L

–5

100k 10M 100M 1G

GAIN

= 150Ω

1M

FREQUENCY (Hz)

PHASE

–3dB Bandwidth vs
Supply Voltage

300

RL = 150Ω

280
260
240
220
200
180

FREQUENCY (MHz)

160
140
120
100

2

3

SUPPLY VOLTAGE (±V)

4

5

1675 G01

1675 G04

0
–20
–40
–60

PHASE (DEG)

–80
–100
–120
–140
–160
–180
–200

GAIN (dB)

Crosstalk Rejection vs Frequency

–30
–40
–50
–60
–70
–80
–90

–100

CROSSTALK REJECTION (dB)

–110
–120
–130

6

100k 10M 100M 1G

Frequency Response with
Capacitive Loads

6

RL = 150Ω

5
4
3
2
1

0
–1
–2
–3
–4

100k 10M 100M 1G

RS = 75Ω
R
R1 DRIVEN
R2 SELECTED

= 150Ω

L

1M

1M

FREQUENCY (Hz)

CL = 10pF

CL = 5pF

CL = 3pF

CL = 0pF

FREQUENCY (Hz)

1675 G02

1675 G05

Gain vs Frequency

6.5
RL = 100Ω

6.4

6.3

6.2

6.1

6.0

GAIN (dB)

5.9

5.8

5.7

5.6

5.5

10k 1M 10M 100M

100k

FREQUENCY (Hz)

R

Crosstalk Rejection vs Frequency

20

RS = 75Ω

10

= 150Ω

R

L

G1 DRIVEN

0

R1 SELECTED

–10
–20
–30
–40
–50

CROSSTALK REJECTION (dB)

–60
–70
–80

100k 10M 100M 1G

1M

FREQUENCY (Hz)

G

B

1675 G03

1675 G23

Crosstalk Rejection vs Frequency
(Disabled)

–10

RS = 75Ω

–20

= 150Ω

R

L

–30
–40
–50
–60
–70
–80

CROSSTALK REJECTION (dB)

–90
–100
–110

100k 10M 100M 1G

1M

FREQUENCY (Hz)

1675 G06

Power Supply Rejection Ratio
vs Frequency

70
60
50
40
30
20
10

0
–10
–20

POWER SUPPLY REJECTION RATIO (dB)

–30

100k 10M 100M 1G

–PSRR

1M

FREQUENCY (Hz)

+PSRR

VS = ±5V

= 25°C

T

A

= 150Ω

R

L

1675 G07

Undistorted Output Swing
vs Frequency

8

VS = ±5V

= 150Ω

R

L

7

)

P-P

6

5

4

OUTPUT VOLTAGE (V

3

2

1M

10M 100M 1G

FREQUENCY (Hz)

1675 G08

5