Maxim MAX499CWG Datasheet

19-1143; Rev 0; 10/96

EVALUATION KIT

AVAILABLE

Quad/Triple, SPDT, RGB Switches

with 250MHz Video Buffer Amplifiers

_______________General Description

The MAX498/MAX499 are high-speed, quad/triple, single-pole/double-throw video switches with on-board closed-loop buffer amplifiers. The buffer amplifiers feature +6dB gain (A

= 2V/V), 250MHz -3dB band-

VCL

width, 70MHz 0.1dB gain flatness, and 1250V/µs slew rate. Fast switching time (3ns) and fast settling time (12ns for a 4V step) make these devices excellent choices for a wide variety of video applications. The low differential gain/phase errors (0.03%/0.06°) and wide bandwidth make them ideal for both composite-video and RGB applications. The amplifiers are capable of delivering ±2.5V into back-terminated 50Ω or 75Ω cables, and they deliver ±2V to a 75Ω load, allowing multiple cables to be driven from a single output.

For implementation of large switch arrays, a low-power disable mode places the amplifier outputs in a highimpedance state. Channel selection and output enable/disable are controlled by four TTL/CMOScompatible logic inputs. Each video input is isolated by an AC-ground pin, which minimizes channel-to-channel capacitance and reduces crosstalk to 90dB at 10MHz.

The four-channel MAX498 dissipates 390mW (typical) from ±5VDC power supplies with all output buffers enabled. Power consumption is reduced to 130mW with all buffers disabled. The corresponding dissipation for the three-channel MAX499 is 300mW enabled and 100mW disabled.

________________________Applications

Video Switching and Routing Broadcast-Quality Composite-Video Multiplexing Workstations Video Editing Broadcast and High-Definition TV Systems Multimedia Products Medical Imaging

____________________________Features

♦ High Speed:

250MHz Small-Signal -3dB Bandwidth 135MHz Full-Power -3dB Bandwidth

♦ 70MHz 0.1dB Gain Flatness ♦ 1250V/µs Slew Rate ♦ 12ns to 0.1% Settling Time ♦ 0.03°/0.06% Differential Phase/Gain Error ♦ 2pF Input Capacitance ♦ 3ns Channel-Switching Time ♦ 120mVp-p Channel-Switching Transient ♦ Three-State Output Allows Large Switch Arrays ♦ Directly Drives 50Ω or 75Ω Back-Terminated

Cables

______________Ordering Information

PART

MAX498CWI MAX499CWG

TEMP. RANGE PIN-PACKAGE

0°C to +70°C 0°C to +70°C

28 SO 24 SO

_________________Pin Configurations

TOP VIEW

MAX498 appears at end of data sheet.

IN1A GND IN2A GND IN3A

V

IN1B GND IN2B GND IN3B

1 2 3 4

MAX499

5 6

CC

V

7

EE

8

9 10 11 12

SO

GND

24 23

LE

22

EN

21

A0

20

CS OUT1

19

V

18

CC

V

17

EE

OUT2

16

N.C.

15

OUT3

14

N.C.

13



MAX498/MAX499

________________________________________________________________

Maxim Integrated Products

1

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (VCCto VEE)................................................+12V

Voltage on IN__ to GND..................(V

Voltage on Digital Inputs

(LE, EN, A0, CS).........................................-0.3V to (V

Voltage on OUT_ (disabled)..................................................±4V

Output Short-Circuit Duration

to -4V ≤ OUT_ ≤ +4V ..................................................Continuous

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

- 0.3V) to (VCC+ 0.3V)

EE

CC

+ 0.3V)

Continuous Power Dissipation (T

24-Pin SO (derate 11.76mW/°C above +70°C).............941mW

28-Pin SO (derate 12.5mW/°C above +70°C)......................1W

Operating Temperature Range .................................0°C to +70°

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10sec).............................+300°C

DC ELECTRICAL CHARACTERISTICS

(VCC= +5V, VEE= -5V, VIN__ = 0V, RL= 150Ω, LE = EN = CS = 0V, TA= 0°C to +70°C, unless otherwise noted. Typical values are at

= +25°C.)

T

A

MAX498/MAX499

Input Voltage Range Voltage Gain Input Offset Voltage

Input Offset Voltage Drift Input Bias Current Input Resistance Input Capacitance Output Short-Circuit Current Output Current ±27 ±40 On Output Resistance

Negative Power-Supply Rejection

Logic Low Voltage Logic High Voltage Logic Input Current

Positive Supply Current

Negative Supply Current

Note 1: Limited by package power dissipation.

2 _______________________________________________________________________________________

IN

A

V

OS

OS B IN IN

OUT(SC)

OUT_

OUT

INLL INLH

INL

I

CC

I

EE

RL= 150Ω, -1.25V ≤ VIN≤ +1.25V RL= 75Ω, -1.0V ≤ VIN≤ +1.0V

-1.25V ≤ VIN≤ +1.25V Channel on or off

-3.5V ≤ OUT_ ≤ +3.5V (Note 1)

-2.0V ≤ V

f = 10MHz

-2.50V ≤ V

4.50V ≤ VCC≤ 5.50V, VEE= -5.0V

-5.50V ≤ VEE≤ -4.5V, VCC= +5.0V

0V ≤ V

INL

EN = 0

EN = 1

EN = 0

EN = 1

CONDITIONS

≤ +2.0V, RL= 75Ω

OUT_

≤ +2.50V

OUT

≤ V

CC

MAX498 MAX499 31 41 MAX498 MAX499 MAX498 MAX499 MAX498 MAX499

= +70°C)

A

1.985 2.030

1.965 2.030

40 52

14 17 11 14 38 50 29 39 12 15

912

UNITSMIN TYP MAXSYMBOLPARAMETER

µV/°C±50TCV

V±1.25 ±1.70V V/V mV±2 ±9V

µA±1 ±7I kΩ200 700R

pF2C mA120I mAI

Ω0.15R Ω3.0On Output Impedance

kΩ1.0 1.2Off Output Resistance

V±4.50 ±5.50Operating Supply-Voltage Range

dB55 72PSR+Positive Power-Supply Rejection

dB55 72PSR-

V0.8V V2V

µA-10 130I

mA

Quad/Triple, SPDT, RGB Switches

with 250MHz Video Buffer Amplifiers

AC ELECTRICAL CHARACTERISTICS

(VCC= +5V, VEE= -5V, V

Small-Signal, -3dB Bandwidth

Settling Time

= 0V, RL= 100Ω, LE = EN = CS = 0V, TA= +25°C, unless otherwise noted.)

IN__

CONDITIONS

VIN≤ 100mVp-p MHz250BW

-3dB

VIN≤ 100mVp-p MHz70±0.1dB Gain Flatness V

= ±2V MHz135FPBWFull-Power, -3dB Bandwidth

OUT

V

= 4V step V/µs1250SRSlew Rate

OUT

0.1%, V

s

f = 100kHz f = 100kHz f = 10MHz fC= 3MHz f = 10MHz (Note 2) f = 10MHz (Note 3) EN = 1, f = 10MHz (Note 4) f = 3.58MHz (Note 5), RL= 150Ω f = 3.58MHz (Note 5), RL= 150Ω

OUT

= 4V step ns12t

UNITSMIN TYP MAXSYMBOLPARAMETER

7.8Input Voltage Noise Density

2.6Input Current Noise Density

0.06Diff PhaseDifferential Phase

nV/√Hz

pA/√Hz

dB-50THDTotal Harmonic Distortion

dBc-66SFDRSpurious-Free Dynamic Range

dB90Adjacent-Channel Crosstalk dB62All-Hostile Crosstalk dB81Off-Isolation

%0.03Diff GainDifferential Gain

degrees

TIMING CHARACTERISTICS

(VCC= +5V, VEE= -5V, V otherwise noted.)

A0/EN to CS Setup Time A0/EN to CS Hold Time CS Pulse Width

Channel-Switching Propagation Delay

Channel-Switching Time Channel-Switching Transient

Enable/Disable Switching Transient

Amplifier-Disable Time Amplifier-Enable Time

Note 2: Test-channel input grounded through a 50Ω resistor. Adjacent channel driven to a 2Vp-p output with a 10MHz sine wave

Note 3: Same as Note 2, except all channels but the test channel are driven to a 2Vp-p output with a 10MHz sine wave (Figure 9). Note 4: Test-channel input connected to a 2V

Note 5: Input test signal is a 3.58MHz sine wave of 40IRE amplitude, superimposed on a 0IRE to 100IRE linear ramp (Figure 10). Note 6: Guaranteed by design. Note 7: V Note 8: V Note 9: Delay from EN to 90% of V Note 10: Delay from EN to 10% of V

(Figure 9).

disabled (Figure 9).

= +1V, V

INA

= +1V, V

INA

= 0V, RL= 150Ω, LE = EN = CS = 0V, TA= 0°C to +70°C. Typical values are at TA= +25°C, unless

IN_ _

CONDITIONS

LE = high (Note 6)

SU

LE = high (Note 6)

H

(Note 6)

CS

(Note 7)

PD

(Note 8)

SW

V

INA

V

INA

(Note 9) 16 nst

OFF

(Note 10) 24 nst

ON

p-p

= -1V, delay from CS to 10% of V

INB

= -1V, delay from CS to 10% of V

INB

OUT. OUT.

= V

= 0V

INB

= V

= 0V

INB

sine wave at 10MHz. The test channel’s output is measured with the outputs

OUT. OUT.

Positive Negative 50 Positive Negative

70

10

150

UNITSMIN TYP MAXSYMBOLPARAMETER

ns8t ns4t ns15t

ns20t ns3t

mV

MAX498/MAX499

_______________________________________________________________________________________ 3

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

__________________________________________Typical Operating Characteristics

(VCC= +5V, VEE= -5V, RL= 100Ω, TA = +25°C, unless otherwise noted.)

SMALL-SIGNAL GAIN

V

= 20mVp-p

IN

LARGE-SIGNAL GAIN

RL = 50Ω

= 2Vp-p

V

OUT

vs. FREQUENCY

100M

FREQUENCY (Hz)

vs. FREQUENCY

100M

FREQUENCY (Hz)

8 7 6 5 4 3

GAIN (dB)

2 1

MAX498/MAX499

0

-1 1M 10M 1G

8 7

6 5 4

GAIN (dB)

3 2 1 0

1M 10M 500M

MAX498/499-01

MAX498/499-04

GAIN (dB)

GAIN FLATNESS

V

= 20mVp-p

IN

LARGE-SIGNAL GAIN 

vs. FREQUENCY

V

= 2Vp-p

OUT

vs. FREQUENCY

100M

FREQUENCY (Hz)

OUT0–OUT1

OUT0–OUT3

OUT0–OUT2

FREQUENCY (Hz)

6.2

6.1

6.0

5.9

5.8

5.7

GAIN (dB)

5.6

5.5

5.4

5.3 1M 10M 1G

0.14

0.10

0.06

0.02

-0.02

-0.06

-0.10 1M 10M

100M

LARGE-SIGNAL GAIN

8 7

MAX498/499-02

6 5 4

GAIN (dB)

3 2 1 0

1M 10M 1G

1000

MAX498/499-05

100

10

1

IMPEDANCE (Ω)

0.1

0.01 10k 100k 1M 10M 100M

vs. FREQUENCY

V

= 2Vp-p

OUT

FREQUENCY (Hz)

OUTPUT IMPEDANCE 

vs. FREQUENCY

FREQUENCY (Hz)

MAX498/499-03

100M

MAX498/499 TOC-06

OFF-ISOLATION

-20

-30

-40

-50

-60

-70

OFF-ISOLATION (dB)

-80

-90

-100 1M 10M 1G

vs. FREQUENCY

100M

FREQUENCY (Hz)

MAX498/499-07

CROSSTALK (dB)

-100

-120

-140

20

= 2Vp-p

V

OUT

0

-20

-40

-60

-80

1M 10M

CROSSTALK

vs. FREQUENCY

ALL HOSTILE

FREQUENCY (Hz)

ADJACENT

100M

MAX498/499-08

PSR (dB)

POWER-SUPPLY REJECTION

-15

-25

-35

-45

-55

-65

-75

-85

-95

vs. FREQUENCY

1M0.1M30k 10M

FREQUENCY (Hz)

4 _______________________________________________________________________________________

MAX498/499-09

PSR-

PSR+

100M

Quad/Triple, SPDT, RGB Switches

with 250MHz Video Buffer Amplifiers

____________________________Typical Operating Characteristics (continued)

(VCC= +5V, VEE= -5V, RL= 100Ω, TA = +25°C, unless otherwise noted.)

MAX498 

SUPPLY CURRENT

50

45

40

SUPPLY CURRENT (mA)

35

30

vs. TEMPERATURE

I

CC

I

EE

-55 -35 -15 5 25 45 65 85 TEMPERATURE (°C)

INPUT OFFSET VOLTAGE

vs. TEMPERATURE

-55-35-15 5 25 45 65 85

(mV)

OS

V

12 10

8 6 4 2 0

-2

-4

-6

-8

-10

-12

MAX498/499-10

CURRENT (mA)

TEMPERATURE (°C)

DISABLED SUPPLY CURRENT

15

14

13 12

11

10

9

8

-55-35-15 5 25 45 65 85

vs. TEMPERATURE

EN = HIGH (OUTPUTS DISABLED)

I

CC

I

EE

TEMPERATURE (°C)

MAX498/499-13

2.0200

MAX498/499-11

2.0175

2.0150

SUPPLY CURRENT (mA)

2.0125

2.0100

INPUT BIAS CURRENT

10

8 6 4 2 0

-2

-4

INPUT BIAS CURRENT (µA)

-6

-8

-10

vs. TEMPERATURE

-55-35-15 5 25 45 65 85 TEMPERATURE (°C)

GAIN vs. TEMPERATURE

-55 -35 -15 5 25 45 65 85

V

IN

TEMPERATURE (°C)

= +1V

MAX498/499-14

V

= -1V

IN

MAX498/MAX499

MAX498/499-12

+1

0

IN

-1

+2

VOLTAGE (V)

OUT

0

-2



LARGE-SIGNAL

PULSE RESPONSE

TIME (10ns/div)

MAX498/499 TOC-16

VOLTAGE (V)

OUT

+1

0

IN

-1

+2

0

-2



LARGE-SIGNAL

PULSE RESPONSE (C

TIME (10ns/div)

= 47pF)

L

MAX498/499 TOC-17

VOLTAGE (V)

OUT

+1

0

IN

-1

+2

0

-2



LARGE-SIGNAL

PULSE RESPONSE (C

TIME (10ns/div)

L

_______________________________________________________________________________________

= 100pF)

MAX498/499 TOC-18

5

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

____________________________Typical Operating Characteristics (continued)

(VCC= +5V, VEE= -5V, RL= 100Ω, TA = +25°C, unless otherwise noted.)

SMALL-SIGNAL

PULSE RESPONSE

+100

IN

0



-100

+200

VOLTAGE (mV)

0

OUT

-200

MAX498/MAX499

TIME (10ns/div)

CHANNEL SWITCHING

+2

OUT_

0

-2 +5

VOLTAGE (V)

A0

0

TIME (10ns/div)

IN_A = -1V 



IN_B = +1V

ENABLE/DISABLE

SWITCHING TRANSIENT

+5

ENABLE 

0



+100m

0

OUT_ 

VOLTAGE (V)



-100m

TIME 50ns/div



MAX498/499 TOC-19

VOLTAGE (mV)

OUT

MAX498/499 TOC-22

VOLTAGE (V)

ENABLE

IN

+100

0

-100

+200

0

-200

+2

OUT

0

+5

0

SMALL-SIGNAL

PULSE RESPONSE (C

TIME (10ns/div)

ENABLE/DISABLE 

SWITCHING

TIME (10ns/div)



MAX498/499 TOC-25

= 47pF)

L

SMALL-SIGNAL

PULSE RESPONSE (C

+100

IN

MAX498/499 TOC-20

MAX498/499 TOC-23

300 280 260 240 220 200 180

BANDWIDTH (MHz)

160 140 120

0.01 0.1 10

0

-100

+200

VOLTAGE (mV)

OUT

0

-200

+5

A0

0

+100m

VOLTAGE (V) OUT_

0

-100m

vs. INPUT VOLTAGE

INPUT VOLTAGE (Vp-p)



CHANNEL-SWITCHING 



BANDWIDTH

TIME (10ns/div)

TRANSIENT

TIME (50ns/div)

1

= 100pF)

L

MAX498/499-26

MAX498/499 TOC-21

MAX498/499 TOC-24

6 _______________________________________________________________________________________

Quad/Triple, SPDT, RGB Switches

with 250MHz Video Buffer Amplifiers

______________________________________________________________Pin Description

MAX498

1, 3, 5, 11, 13,

7, 22 V

9, 21 V

15, 17 N.C. No Connect. Not internally connected; connect to GND.

MAX499

2, 4, 9,

19

10 IN1B Signal Input 1, Channel B 12 IN2B Signal Input 2, Channel B 14 IN3B Signal Input 3, Channel B

16 OUT3 Output 3 18 OUT2 Output 2 20 OUT1 Output 1 23 OUT0 Output 0

24

25 A0

26

27 LE

28 IN0A Signal Input 0, Channel A

11, 24

2 IN1A Signal Input 1, Channel A 4 IN2A Signal Input 2, Channel A 6 IN3A Signal Input 3, Channel A

6, 18

8 IN0B Signal Input 0, Channel B

7, 17

10 12

13, 15

14 16 19

20

21

22

23

NAME FUNCTION

GND

1 3 5

—

8

—

Analog Ground. All ground pins are internally connected. Connect all ground pins externally to ground to minimize impedance.

Positive Power-Supply Voltage. Connect VCCto +5V. VCCpins are internally connected. Connect both pins externally to +5V to minimize supply impedance. Bypass each pin to

CC

ground with a 0.1µF ceramic capacitor.

Negative Power-Supply Voltage. Connect VEEto -5V. VEEpins are internally connected. Connect both pins to -5V externally to minimize supply impedance. Bypass each pin to

EE

ground with a 0.1µF ceramic capacitor.

Chip-Select Input. When CS is low, the A0 and EN latches are transparent. The data present at A0

CS

is latched when CS goes high. LE’s status determines whether EN is latched along with A0, or if the EN latch remains transparent independently of CS.

Address Input. A0 = 0 selects channel A, and A0 = 1 selects channel B if CS is low. A0 is latched on CS’s low-to-high transition.

Output Buffer-Enable Input. EN = 0 enables the output buffer amplifiers, and EN = 1 disables

EN

the output buffers if CS is low. EN is latched during CS’s low-to-high transition if LE is high. EN is not latched if LE is low.

Latch-Enable Input. With LE = 1, EN is latched along with A0 when CS goes high. When LE = 0, the EN latch is transparent independently of CS’s state.

MAX498/MAX499

_______________________________________________________________________________________ 7

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

MAX498/MAX499

+5V

DC

10µF

-5V

DC

10µF

0.1µF

1

GND

2

IN1A

3

GND

4

IN2A

5

GND

6

IN3A

7

V

CC

8

IN0B

9

V

EE

10

IN1B

MAX498

IN0A

OUT0

V

OUT1

GND

28

27

LE

26

EN

25

A0

24

CS

23

22

CC

21

V

EE

20

19

0.1µF

+5V

-5V

DC

11

GND

12

IN2B

13

GND

14

IN3B

EIGHT-IN/FOUR-OUT

VIDEO MUX AMP

18

OUT2

17

N.C.

16

OUT3

15

N.C.

NOTE: ALL RESISTORS ARE 50Ω OR 75Ω

Figure 1a. MAX498 Typical Application Circuit

8 _______________________________________________________________________________________

Quad/Triple, SPDT, RGB Switches

with 250MHz Video Buffer Amplifiers

MAX498/MAX499

+5V

1

IN1A

2

GND

3

IN2A

4

GND

5

IN3A

6

DC

10µF

DC

10µF

0.1µF

V

CC

7

V

EE

8

IN1B

9

GND

10

IN2B

MAX499

GND

OUT1

V

OUT2

N.C.

24

23

LE

22

EN

21

A0

20

CS

19

18

CC

17

V

EE

16

15

0.1µF

+5V

-5V

DC

Figure 1b. MAX499 Typical Application Circuit

_______________________________________________________________________________________ 9

11

GND

12

IN3B

SIX-IN/THREE-OUT

VIDEO MUX AMP

14

OUT3

13

N.C.

NOTE: ALL RESISTORS ARE 50Ω OR 75Ω

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

______________ Detailed Description

The MAX498/MAX499 are quad/triple video switches with high-speed, closed-loop, voltage-feedback amplifiers set to a 2V/V gain. Figure 1 shows typical application circuits. The amplifiers use a unique two-stage, voltage-feedback architecture that combines the benefits of conventional voltage-feedback and currentfeedback topologies to achieve wide bandwidths and high slew rates while maintaining precision.

Figure 2 is a simplified block diagram of the MAX498/ MAX499. All four amplifier/switch blocks are identical to that shown for Ch_0. A common control logic block accepts external logic inputs A0, EN, CS, and LE, and controls the status of switches S1, S2, and S3 of each amplifier in parallel, as described in the

Interface

MAX498/MAX499

section.

S3 is open in the enabled state, and if Ch_A is selected, S1 is connected to IN_A and S2 is connected to GND. If Ch_B is selected, S1 is connected to GND and S2 is connected to IN_B. Connecting the deselected GM_ block to GND ensures minimum feedthrough.

S3 is closed in the disabled state, and both S1 and S2 are connected to GND. Disconnecting both inputs and connecting the amplifier’s inputs to GND significantly improves off-isolation.

__________Applications Information

The MAX498/MAX499’s maximum output current is limited by the package’s maximum allowable power dissipation. The maximum junction temperature should not exceed +150°C. Power dissipation increases with load, and this increase can be approximated by one of the following equations:

For V

OUT

> 0V: |V < 0V: |V

CC

EE

These devices can drive 100Ω loads connected to each of the outputs over the entire rated output swing and temperature range. While the output is short-circuit protected to 120mA, this does not necessarily guarantee that under all conditions, the maximum junction temperature will not be exceeded. Do not exceed the derating values given in the section.

Power Dissipation

- V

OUT|ILOAD

OR

- V

OUT|ILOAD

.

Absolute Maximum Ratings

Digital

IN0A

S1

C

IN0B

S2

R

G

S1 S2 S3

A0 EN CS

LE

Figure 2. Block Diagram

The MAX498/MAX499’s low 2.6pA/√Hz input current noise and 7.8nV/√Hz voltage noise provide for lower total noise compared to typical current-mode feedback amplifiers, which usually have significantly higher input current noise. The input current noise multiplied by the feedback resistor is the dominant noise source of current-mode feedback amplifiers.

Differential Gain and Phase Errors

Differential gain and phase errors are critical specifications for a buffer in composite (NTSC, PAL, SECAM) video applications, because these errors correspond directly to color changes in the displayed picture of composite video systems. The MAX498/MAX499’s low differential gain and phase errors (0.03%/0.06°) make them ideal in broadcastquality, composite video applications.

GM_A

C

R

GM_B

CONTROL LOGIC

MAX498 MAX499

0

R

FB



X1

CHANNEL 0

OUT0

X1

S3

CHANNEL 1

CHANNEL 2

CHANNEL 3

Total Noise

10 ______________________________________________________________________________________

Quad/Triple, SPDT, RGB Switches

MAX186/MAX188

with 250MHz Video Buffer Amplifiers

FULL POWER-DOWN



14

R

= 0Ω

ISO

12 10

8 6 4

GAIN (dB)

2 0

-2

-4

-6 1M

100pF

47pF

0pF

10M 1G

FREQUENCY (Hz)

100M



Figure 3a. Small-Signal Gain vs. Frequency and Load Capacitor (R

V

VOLTAGE (V)

= 100Ω, R

L

+1

V

IN

-1

+2

OUT

-2

ISO

= 0Ω)



MAX498/MAX499

FULL POWER-DOWN

14

R

= 6.8Ω

ISO

12 10

8 6 4

GAIN (dB)

2 0

-2

-4

-6

150pF

1M

10M 1G

FREQUENCY (Hz)

100pF

47pF

0pF



100M

Figure 3b. Small-Signal Gain vs. Frequency and Load Capacitor (R



= 100Ω, R

L

+100

V

IN

-100

+200

V

OUT

VOLTAGE (mV)

-200

ISO

= 6.8Ω)

TIME (10ns/div)

Figure 4a. Large-Signal Pulse Response with CL= 100pF and

= 5.1Ω

R

ISO

Coaxial Cable Drivers

High-speed performance, excellent output current capability, and an internally fixed gain of +2 make the MAX498/MAX499 ideal for driving back-terminated 50Ω or 75Ω coaxial cables to ±2.5V.

In a typical application, the MAX498/MAX499 drive a back-terminated cable (Figure 1). The back-termination resistor, at the output, matches the impedance of the cable’s driven end to the cable’s impedance, eliminating signal reflections. This resistor, along with the loadtermination resistor, forms a voltage divider with the load impedance, which attenuates the signal at the cable’s output by one-half. The MAX498/MAX499 operate with an internal +2V/V closed-loop gain to provide unity gain at the cable’s output.

______________________________________________________________________________________ 11

TIME (10ns/div)

Figure 4b. Small-Signal Pulse Response with CL= 100pF and

= 5.1Ω

R

ISO

Capacitive-Load Driving

In most amplifier circuits, driving large capacitive loads increases the likelihood of oscillation. This is especially true for circuits with high loop gains, such as voltage followers. The amplifier’s output resistance and the capacitive load form an RC filter that adds a pole to the loop response. If the pole frequency is low enough (as when driving a large capacitive load), the circuit-phase margin is degraded and oscillation may occur.

The MAX498/MAX499 drive capacitive loads up to 100pF without sustained oscillation, although some peaking may occur (Figures 3a and 3b). When driving larger capacitive loads, or to reduce peaking, add an isolation resistor (R

) between the output and the

ISO

capacitive load (Figures 4a, 4b, and 5).

Quad/Triple, SPDT, RGB Switches

MAX186/MAX188

COMPARATOR INPUT BIAS CURRENT

with 250MHz Video Buffer Amplifiers

8

7

6

5

4

ISOLATION RESISTOR (Ω)

3

2

MAX498/MAX499

Figure 5. Isolation Resistor vs. Capacitive Load

vs. SUPPLY VOLTAGE

47

100 150 200 270 390 510

CAPACITANCE (pF)



Switching Audio Signals

(Audio-Distortion Measurement)

When switching audio signals, distortion is the prime consideration in performance. Figure 6 shows total harmonic distortion vs. frequency, in the audio range, for the MAX498/MAX499.

Large Switch Arrays

Large crosspoint switch arrays are possible with the MAX498/MAX499 using the enable function EN. When the amplifiers are disabled, output impedance is typically 1.2kΩ, due to the feedback and gain resistors. This limits the number of outputs that can be paralleled without a buffer. Since each output can drive 100Ω, eight outputs can typically be connected together. If additional outputs must be connected in parallel, a MAX4178 (single), MAX496 (quad), or equivalent unitygain buffer can be used.

Whether enabled or disabled, each input represents more than 200kΩ of resistance. Capacitance is the prime consideration limiting the number of inputs that can be connected to a single output. Since each output can drive 100pF of capacitance without an isolation resistor, 50 inputs (CIN= 2pF, typical) can be driven by a single output. However, peaking will occur as inputs are added (Figure 3), which reduces the 0.1dB bandwidth.



1k

10

FULL POWER-DOWN

100 10k

FREQUENCY (Hz)

-82

-84

-86

-88

-90

-92

DISTORTION (dBc)

-94

-96

-98

Figure 6. Total Harmonic Distortion (Audio) vs. Frequency

Digital Interface

The MAX498/MAX499 multiplexer architecture ensures that no input channels are ever connected together. Select a channel by changing A0’s state (A0 = 0 for channel A, and A0 = 1 for channel B) and pulsing CS low (see Tables 1a and 1b). Figure 7 shows the logic timing diagram.

When the enable input (E—N–) is driven to a TTL low state, it enables the MAX498/MAX499 amplifier outputs. When E—N is driven high, it disables the amplifier outputs. When disabled, the MAX498/MAX499 exhibit a 1.2kΩ disabled output resistance due to their internal feedback resistors.

LE determines whether E—N–is latched by CS or operates independently. When the latch-enable input (LE) is connected to V+, CS becomes the latch control for the E—N input register. If CS is low, both the E—N–and A0 latches are transparent; once CS returns high, both A0 and E—N are latched.

When LE is connected to ground, the E—N–latch is transparent and independent of CS. This allows all MAX498/MAX499 devices to be shut down simultaneously, regardless of CS’s input state. Simply connect LE to ground and connect all E—N–inputs together (Figure 8a). Hard wire LE to V+ or ground (rather than driving LE with a gate) to prevent crosstalk from the digital inputs to IN0A.

–

– –

12 ______________________________________________________________________________________

Quad/Triple, SPDT, RGB Switches

A0ENCE

ENCS

with 250MHz Video Buffer Amplifiers

Another option for output disable is to connect LE to V+, parallel the outputs of several MAX498/MAX499s, and use E—N–to individually disable all devices but the one in use (Figure 8b).

When the outputs are disabled, off-isolation from the analog inputs to the amplifier outputs is typically 81dB at 10MHz.

Grounding and Layout

The MAX498/MAX499 bandwidths are in the RF frequency range. Depending on the size of the PC board used and the frequency of operation, it may be necessary to use Micro-strip or Stripline techniques.

To realize the full AC performance of these high-speed buffers, pay careful attention to power-supply bypassing and board layout. The PC board should have at least two layers (wire-wrap boards are too inductive, and bread boards are too capacitive), with one side a signal layer and the other a large, low-impedance ground plane. With multilayer boards, locate the ground plane on the layer that is not dedicated to a specific signal trace. The ground plane should be as free from voids as possible. Connect all ground pins to the ground plane.

Connect both positive power-supply pins together and bypass with a 0.10µF ceramic capacitor at each powersupply pin, as close to the device as possible. Repeat for the negative power-supply pins. The capacitor lead lengths should be as short as possible to minimize lead inductance; surface-mount chip capacitors are ideal. A large-value (10µF or greater) tantalum or electrolytic bypass capacitor on each supply may be required for high-current loads. The location of this capacitor is not critical.

The MAX498/MAX499’s analog input pins are isolated with ground pins to minimize parasitic coupling, which can degrade crosstalk and/or amplifier stability. Keep signal paths as short as possible to minimize inductance. Ensure that all input channel traces are the same length, to maintain the phase relationship between the four channels. To further reduce crosstalk, connect the coaxial-cable shield to the ground side of the 75Ω terminating resistor at the ground plane, and terminate all unused inputs to ground and outputs with a 100Ωor 150Ω resistor to ground.

Table 1a. Amplifier and Channel Selection with LE = V+

A0

Enables amplifier outputs. Selects

000

channel A. Enables amplifier outputs. Selects

100

channel B. Disables amplifiers. Outputs high-Z.X10

XX1

Latches A0, EN. Outputs unchanged.

FUNCTION

Table 1b. Amplifier and Channel Selection with LE = GND

FUNCTION

Enables amplifier outputs. Selects

000

channel A. Enables amplifier outputs. Latches A0

to output A or B, according to A0’s

X01

state at C—S–’s last edge. Disables amplifiers. Outputs high-Z.

X1X

A0 latch = channel A. Enables amplifier outputs. Selects

100

channel B.

MAX498/MAX499

______________________________________________________________________________________ 13

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

t

CS

A0

CS

t

SU

t

H

t

SU

t

H

EN

MAX498/MAX499

OUTPUTS

LE = V+

Figure 7. Logic Timing Diagram

LE

SHUTDOWN

NOTE: ISOLATION RESISTORS

(IF REQUIRED) NOT SHOWN.

EN

LE

EN

MAX498 MAX499

(a)

t

PD

t

SW

t

OFF

EN AO CS

+5V

LE

EN



AO CS

+5V

LE



MAX498 MAX499

t

ON

(b)

Figure 8. (a) Simultaneous Shutdown of all MAX498/MAX499s; (b) Enable (–E—N–) Register Latched by –C—S

–

14 ______________________________________________________________________________________

Quad/Triple, SPDT, RGB Switches

with 250MHz Video Buffer Amplifiers

MAX498/MAX499



MAX498/MAX499

50Ω

VIN = 4Vp-p, f = 10MHz,

= 75Ω

R

S

a) ADJACENT CHANNEL b) ALL HOSTILE

50Ω

100Ω

VIN = 4Vp-p, f = 10MHz,

= 75Ω

R

S

Figure 9. Test Circuits for Measuring Crosstalk: a) Adjacent Channel; b) All Hostile

75Ω CABLE

75Ω

SOURCE: TEKTRONIX 1910 DIGITAL GENERATOR

75Ω CABLE

MAX499

DUT

75Ω

75Ω CABLE

50Ω

100Ω

75Ω

MEASUREMENT: TEKTRONIX VM700 VIDEO MEASUREMENT SET

Figure 10. Differential Phase and Gain Error Test Circuit

______________________________________________________________________________________ 15

Quad/Triple, SPDT, RGB Switches with 250MHz Video Buffer Amplifiers

____Pin Configurations (continued) ___________________Chip Information

TOP VIEW

GND

1

IN1A

2

GND

3

IN2A

4 GND IN3A

V

CC

IN0B

V

EE

MAX498/MAX499

IN1B GND IN2B GND IN3B

MAX498

5

6

7

8

9

10 11 12

13 14

28 27 26 25 24

23 22 21 20

19 18 17 16 15

IN0A LE EN A0 CS OUT0 V

CC

V

EE

OUT1 GND OUT2 N.C. OUT3 N.C.

SUBSTRATE CONNECTED TO: V TRANSISTOR COUNT: 813

SO

________________________________________________________Package Information

DIM

D

A

0.101mm

e

B

A1

0.004in.

C

0°- 8°

L



A

A1

B C E

e

H

L

EE

INCHES MILLIMETERS

MAX

MIN

0.093

0.004

0.014

0.009

0.291

0.394

0.016



0.050

0.104

0.012

0.019

0.013

0.299

0.419

0.050

MIN

2.35

0.10

0.35

0.23

7.40



10.00

0.40

1.27

MAX

2.65

0.30

0.49

0.32

7.60 

10.65

1.27

DIM

HE

Wide SO

SMALL-OUTLINE

PACKAGE

(0.300 in.)

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

16

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

16

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

16

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

16

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600



D D D D D

MIN

MAX

MIN

0.398

0.447

0.496

0.598

0.697

0.413

0.463

0.512

0.614

0.713

16 18 20 24 28

10.10

11.35

12.60

15.20

17.70

MAX

10.50

11.75

13.00

15.60

18.10

21-0042A

INCHES MILLIMETERS

PINS

Maxim MAX499CWG Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual