LMH6714MAXNOPB - NATIONAL SEMICONDUCTOR

August 2007

LMH6583

16x8 550 MHz Analog Crosspoint Switch, Gain of 2

General Description

The LMH® family of products is joined by the LMH6583, a high

speed, non-blocking, analog, crosspoint switch. The

LMH6583 is designed for high speed, DC coupled, analog

signals like high resolution video (UXGA and higher). The

LMH6583 has 16 inputs and 8 outputs. The non-blocking ar-

chitecture allows an output to be connected to any input,

including an input that is already selected. With fully buffered

inputs the LMH6583 can be impedance matched to nearly any

source impedance. The buffered outputs of the LMH6583 can

drive up to two back terminated video loads (75Ω load). The

outputs and inputs also feature high impedance inactive

states allowing high performance input and output expansion

for array sizes such as 16 x 16 or 32 x 8 by combining two

devices. The LMH6583 is controlled with a 4 pin serial inter-

face. Both single serial mode and addressed chain modes are

available.

The LMH6583 comes in a 64-pin thermally enhanced TQFP

package. It also has diagonally symmetrical pin assignments

to facilitate double sided board layouts and easy pin connec-

tions for expansion.

Features

■16 inputs and 8 outputs

■64-pin exposed pad TQFP package

■−3 dB bandwidth (VOUT = 2 VPP, RL = 1 kΩ) 550 MHz

■−3 dB bandwidth (VOUT = 2 VPP,RL = 150Ω) 450 MHz

■Fast slew rate 1800 V/μs

■Channel to channel crosstalk (10/ 100 MHz) −70/ −52 dBc

■All Hostile Crosstalk (10/ 100 MHz) −55/−45 dBc

■Easy to use serial programming 4 wire bus

■Two programming modes Serial & addressed modes

■Symmetrical pinout facilitates expansion.

■Output current ±60 mA

■Gainf of 1 version also available LMH6582

Applications

■Studio monitoring/production video systems

■Conference room multimedia video systems

■KVM (keyboard video mouse) systems

■Security/surveillance systems

■Multi antenna diversity radio

■Video test equipment

■Medical imaging

■Wide-band routers & switches

Connection Diagram

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Block Diagram

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LMH® is a registered trademark of National Semiconductor Corporation.

TRI-STATE® is a registered trademark of National Semiconductor Corporation.

LMH6583 16x8 550 MHz Analog Crosspoint Switch, Gain of 2

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

ESD Tolerance (Note 2)

Human Body Model 2000V

Machine Model 200V

VS±6V

IIN (Input Pins) ±20 mA

IOUT (Note 3)

Input Voltage Range V− to V+

Maximum Junction Temperature +150°C

Storage Temperature Range −65°C to +150°C

Soldering Information

Infrared or Convection (20 sec.) 235°C

Wave Soldering (10 sec.) 260°C

Operating Ratings (Note 1)

Temperature Range (Note 4) −40°C to +85°C

Supply Voltage Range ±3V to ±5.5V

Thermal Resistance θJA θJC

64–Pin Exposed Pad TQFP 27°C/W 0.82°C/W

±3.3V Electrical Characteristics (Note 5)

Unless otherwise specified, typical conditions are: TA = 25°C, AV = +2, VS = ±3.3V, RL = 100Ω; Boldface limits apply at the

temperature extremes.

Symbol Parameter Conditions Min

(Note 8)

Typ

(Note 7)

Max

(Note 8)

Units

Frequency Domain Performance

SSBW −3 dB Bandwidth VOUT = 0.5 VPP 425

MHz

LSBW VOUT = 2 VPP, RL = 1 kΩ 500

VOUT = 2 VPP, RL = 150Ω 450

GF 0.1 dB Gain Flatness VOUT = 2 VPP, RL = 150Ω 80 MHz

DG Differential Gain RL = 150Ω, 3.58 MHz/ 4.43 MHz 0.05 %

DP Differential Phase RL = 150Ω, 3.58 MHz/ 4.43 MHz 0.05 deg

Time Domain Response

trRise Time 2V Step, 10% to 90% 1.7 ns

tfFall Time 2V Step, 10% to 90% 1.4 ns

OS Overshoot 2V Step 4 %

SR Slew Rate 4 VPP, 40% to 60% (Note 6) 1700 V/µs

tsSettling Time 2V Step, VOUT within 0.5% 9 ns

Distortion And Noise Response

HD2 2nd Harmonic Distortion 2 VPP, 10 MHz −76 dBc

HD3 3rd Harmonic Distortion 2 VPP, 10 MHz −76 dBc

enInput Referred Voltage Noise >1 MHz 12 nV/

inInput Referred Noise Current >1 MHz 2 pA/

Switching Time 16 ns

XTLK Crosstalk All Hostile, f = 100 MHz −45 dBc

ISOL Off Isolation f = 100 MHz −60 dBc

Static, DC Performance

AVGain 1.986 2.00 2.014

VOS Output Offset Voltage ±3 ±17 mV

TCVOS Output Offset Voltage Average Drift (Note 10) 38 µV/°C

IBInput Bias Current Non-Inverting (Note 9) −5 µA

TCIBInput Bias Current Average Drift Non-Inverting (Note 10) -12 nA/°C

VOOutput Voltage Range RL = 100Ω ±1.75 ±2.1 V

VOOutput Voltage Range RL = ∞ (Note 11) +2.1

-2.05

±2.2 V

PSRR Power Supply Rejection Ratio 45 dB

ICC Positive Supply Current RL = ∞ 98 120 mA

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LMH6583

Symbol Parameter Conditions Min

(Note 8)

Typ

(Note 7)

Max

(Note 8)

Units

IEE Negative Supply Current RL = ∞ 92 115 mA

Tri State Supply Current RST Pin > 2.0V 17 25 mA

Miscellaneous Performance

RIN Input Resistance Non-Inverting 100 kΩ

CIN Input Capacitance Non-Inverting 1 pF

ROOutput Resistance Enabled Closed Loop, Enabled 300 mΩ

ROOutput Resistance Disabled Disabled 1100 1300 1450 Ω

CMVR Input Common Mode Voltage

Range

±1.3 V

IOOutput Current Sourcing, VO = 0 V ±50 mA

Digital Control

VIH Input Voltage High 2.0 V

VIL Input Voltage Low 0.8 V

VOH Output Voltage High >2.2 V

VOL Output Voltage Low <0.4 V

TSSetup Time 7 ns

THHold Time 7 ns

±5V Electrical Characteristics (Note 5)

Unless otherwise specified, typical conditions are: TA = 25°C, AV = +2, VS = ±5V, RL = 100Ω; Boldface limits apply at the tem-

perature extremes.

Symbol Parameter Conditions Min

(Note 8)

Typ

(Note 7)

Max

(Note 8)

Units

Frequency Domain Performance

SSBW −3 dB Bandwidth VOUT = 0.5 VPP 475

MHz

LSBW VOUT = 2 VPP, RL = 1 kΩ 550

VOUT = 2 VPP, RL = 150Ω 450

GF 0.1 dB Gain Flatness VOUT = 2 VPP, RL = 150Ω 100 MHz

DG Differential Gain RL = 150Ω, 3.58 MHz/ 4.43 MHz 0.04 %

DP Differential Phase RL = 150Ω, 3.58 MHz/ 4.43 MHz 0.04 deg

Time Domain Response

trRise Time 2V Step, 10% to 90% 1.4 ns

tfFall Time 2V Step, 10% to 90% 1.3 ns

OS Overshoot 2V Step 2 %

SR Slew Rate 6 VPP, 40% to 60% (Note 6) 1800 V/µs

tsSettling Time 2V Step, VOUT Within 0.5% 7 ns

Distortion And Noise Response

HD2 2nd Harmonic Distortion 2 VPP, 5 MHz −80 dBc

HD3 3rd Harmonic Distortion 2 VPP, 5 MHz −70 dBc

enInput Referred Voltage Noise >1 MHz 12 nV/

inInput Referred Noise Current >1 MHz 2 pA/

Switching Time 15 ns

XTLK Cross Talk All Hostile, f = 100 MHz −45 dBc

Channel to Channel, f = 100 MHz −52 dBc

ISOL Off Isolation f = 100 MHz −65 dBc

Static, DC Performance

AVGain LMH6583 1.986 2.00 2.014

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LMH6583

Symbol Parameter Conditions Min

(Note 8)

Typ

(Note 7)

Max

(Note 8)

Units

VOS Offset Voltage Input Referred ±2 ±17 mV

TCVOS Output Offset Voltage Average Drift (Note 10) 38 µV/°C

IBInput Bias Current Non-Inverting (Note 9) −5 −12 µA

TCIBInput Bias Current Average Drift Non-Inverting (Note 10) −12 nA/°C

VOOutput Voltage Range RL = 100Ω +3.3

−3.4

±3.6 V

VOOutput Voltage Range RL = ∞±3.7 ±3.9 V

PSRR Power Supply Rejection Ratio DC 42 45 dB

XTLK DC Crosstalk DC, Channel to Channel −58 −90 dB

ISOL DC Off Isloation DC −60 −90 dB

ICC Positive Supply Current RL = ∞ 110 130 mA

IEE Negative Supply Current RL = ∞ 104 124 mA

Tri State Supply Current RST Pin > 2.0V 22 30 mA

Miscellaneous Performance

RIN Input Resistance Non-Inverting 100 kΩ

CIN Input Capacitance Non-Inverting 1 pF

ROOutput Resistance Enabled Closed Loop, Enabled 300 mΩ

ROOutput Resistance Disabled Disabled, Resistance to Ground 1100 1300 1450 Ω

CMVR Input Common Mode Voltage

Range

±3.0 V

IOOutput Current Sourcing, VO = 0 V ±60 ±70 mA

Digital Control

VIH Input Voltage High 2.0 V

VIL Input Voltage Low 0.8 V

VOH Output Voltage High >2.4 V

VOL Output Voltage Low <0.4 V

TSSetup Time 5 ns

THHold Time 5 ns

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is

intended to be functional, but specific performance is not guaranteed. For guaranteed specifications, see the Electrical Characteristics tables.

Note 2: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC)

Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC).

Note 3: The maximum output current (IOUT) is determined by device power dissipation limitations.

Note 4: The maximum power dissipation is a function of TJ(MAX)and θJA. The maximum allowable power dissipation at any ambient temperature is

PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board.

Note 5: Electrical Table values apply only for factory testing conditions at the temperature indicated. No guarantee of parametric performance is indicated in the

electrical tables under conditions different than those tested.

Note 6: Slew Rate is the average of the rising and falling edges.

Note 7: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will

also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material.

Note 8: Room Temperature limits are 100% production tested at 25°C. Device self heating results in TJ ≥ TA, however, test time is insufficient for TJto reach

steady state conditions. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods.

Note 9: Negative input current implies current flowing out of the device.

Note 10: Drift determined by dividing the change in parameter at temperature extremes by the total temperature change.

Note 11: This parameter is guaranteed by design and/or characterization and is not tested in production.

Ordering Information

Package Part Number Package Marking Transport Media NSC Drawing

64-Pin QFP LMH6583YA LMH6583YA 160 Units/Tray VXE64A

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LMH6583

Typical Performance Characteristics

2 VPP Frequency Response

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2 VPP Frequency Response

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Large Signal Bandwidth

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Large Signal Bandwidth

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Small Signal Bandwidth

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Small Signal Bandwidth

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LMH6583

Frequency Response 1 kΩ Load

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Group Delay

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2 VPP Pulse Response

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2 VPP Pulse Response

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4 VPP Pulse Response

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4 VPP Pulse Response Broadcast

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LMH6583

4 VPP Pulse Response

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6 VPP Pulse Response

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2 VPP Off Isolation

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2 VPP Crosstalk

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2 VPP All Hostile Crosstalk

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Second Order Distortion (HD2) vs. Frequency

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LMH6583

Third Order Distortion (HD3) vs. Frequency

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Second Order Distortion vs. Frequency

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Third Order Distortion vs. Frequency

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No Load Output Swing

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Positive Swing over Temperature

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Negative Swing Over Temperature

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LMH6583

No Load Output Swing

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Positive Swing over Temperature

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Negative Swing over Temperature

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Enabled Output Impedance

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Disabled Output Impedance

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Switching Time

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LMH6583

Application Information

INTRODUCTION

The LMH6583 is a high speed, fully buffered, non blocking,

analog crosspoint switch. Having fully buffered inputs allows

the LMH6583 to accept signals from low or high impedance

sources without the worry of loading the signal source. The

fully buffered outputs will drive 75Ω or 50Ω back terminated

transmission lines with no external components other than the

termination resistor. When disabled, the outputs are in a high

impedance state. The LMH6583 can have any input connect-

ed to any (or all) output(s). Conversely, a given output can

have only one associated input.

INPUT AND OUTPUT EXPANSION

The LMH6583 has high impedance inactive states for both

inputs and outputs allowing maximum flexibility for Crosspoint

expansion. In addition the LMH6583 employs diagonal sym-

metry in pin assignments. The diagonal symmetry makes it

easy to use direct pin to pin vias when the parts are mounted

on opposite sides of a board. As an example two LMH6583

chips can be combined on one board to form either an 16 x

16 crosspoint or a 32 x 8 crosspoint. To make a 16 x 16 cross-

point all 16 input pins would be tied together (Input 0 on side

1 to input 15 on side 2 and so on) while the 8 output pins on

each chip would be left separate. To make the 32 x 8 cross-

point, the 8 outputs would be tied together while all 32 inputs

would remain independent. In the 32 x 8 configuration it is

important not to have 2 connected outputs active at the same

time. With the 16 x 16 configuration, on the other hand, having

two connected inputs active is a valid state. Crosspoint ex-

pansion as detailed above has the advantage that the signal

path has only one crosspoint in it at a time. Expansion meth-

ods that have cascaded stages will suffer bandwidth loss far

greater than the small loading effect of parallel expansion.

Output expansion is very straight forward. Connecting the in-

puts of two crosspoint switches has a very minor impact on

performance. Input expansion requires more planning. As

show in Figure 1 and Figure 2 there are two ways to connect

the outputs of the crosspoint switches. In Figure 2 the cross-

point switch outputs are connected directly together and

share one termination resistor. This is the easiest configura-

tion to implement and has only one drawback. Because the

disabled output of the unused crosspoint (only one output can

be active at a time) has a small amount of capacitance the

frequency response of the active crosspoint will show peak-

ing. This is illustrated in Figure 4 and Figure 5. In most cases

this small amount of peaking is not a problem.

As illustrated in Figure 1 each crosspoint output can be given

its own termination resistor. This results in a frequency re-

sponse nearly identical to the non expansion case. There is

one drawback for the gain of 2 crosspoint, and that is gain

error. With a 75Ω termination resistor the 1250Ω resistance

of the disabled crosspoint output will cause a gain error. In

order to counter act this the termination resistors of both

crosspoints should be adjusted to approximately 71Ω. This

will provide very good matching, but the gain accuracy of the

system will now be dependent on the process variations of

the crosspoint resistors which have a variability of approxi-

mately ±20%.

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FIGURE 1. Output Expansion

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FIGURE 2. Input Expansion with Shared Termination

Resistors

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LMH6583

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FIGURE 3. Input Expansion with Separate Termination

Resistors

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FIGURE 4. Input Expansion Frequency Response

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FIGURE 5. Input Expansion Frequency Response

DRIVING CAPACITIVE LOADS

Capacitive output loading applications will benefit from the

use of a series output resistor ROUT. Capacitive loads of

5 pF to 120 pF are the most critical, causing ringing, frequency

response peaking and possible oscillation. The chart “Sug-

gested ROUT vs. Cap Load” gives a recommended value for

selecting a series output resistor for mitigating capacitive

loads. The values suggested in the charts are selected for 0.5

dB or less of peaking in the frequency response. This gives a

good compromise between settling time and bandwidth. For

applications where maximum frequency response is needed

and some peaking is tolerable, the value of ROUT can be re-

duced slightly from the recommended values. When driving

transmission lines the 50Ω or 75Ω matching resistor makes

the series output resistor unnecessary.

USING OUTPUT BUFFERING TO ENHANCE BANDWIDTH

AND INCREASE RELIABILITY

The LMH6583 crosspoint switch can offer enhanced band-

width and reliability with the use of external buffers on the

outputs. The bandwidth is increased by unloading the outputs

and driving a higher impedance. The 1 kΩ load resistor was

chosen to provide the best performance on our evaluation

board. See the Frequency Response 1 kΩ Load curve in the

Typical Performance section for an example of bandwidth

achieved with less loading on the outputs. For this technique

to provide maximum benefit a very high speed amplifier such

as the LMH6703 should be used, as shown in Figure 6 .

Besides offering enhanced bandwidth performance using an

external buffer provides for greater system reliability. The first

advantage is to reduce thermal loading on the crosspoint

switch. This reduced die temperature will increase the life of

the crosspoint. The second advantage is enhanced ESD re-

liability. It is very difficult to build high speed devices that can

withstand all possible ESD events. With external buffers the

crosspoint switch is isolated from ESD events on the external

system connectors.

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LMH6583

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FIGURE 6. Buffered Output

In the example in Figure 6the resistor RL is required to provide

a load for the crosspoint output buffer. Without RLexcessive

frequency response peaking is likely and settling times of

transient signals will be poor. As the value of RL is reduced

the bandwidth will also go down. The amplifier shown in the

example is an LMH6703 this amplifier offers high speed and

flat bandwidth. Another suitable amplifiers is the LMH6702.

The LMH6702 is a faster amplifier that can be used to gen-

erate high frequency peaking in order to equalize longer cable

lengths. If board space is at a premium the LMH6739 or the

LMH6734 are triple selectable gain buffers which require no

external resistors.

CROSSTALK

When designing a large system such as a video router

crosstalk can be a very serious problem. Extensive testing in

our lab has shown that most crosstalk is related to board lay-

out rather than occurring in the crosspoint switch. There are

many ways to reduce board related crosstalk. Using con-

trolled impedance lines is an important step. Using well de-

coupled power and ground planes will help as well. When

crosstalk does occur within the crosspoint switch itself it is

often due to signals coupling into the power supply pins. Using

appropriate supply bypassing will help to reduce this mode of

coupling. Another suggestion is to place as much grounded

copper as possible between input and output signal traces.

Care must be taken, though, not to influence the signal trace

impedances by placing shielding copper too closely. One oth-

er caveat to consider is that as shielding materials come

closer to the signal trace the trace needs to be smaller to keep

the impedance from falling too low. Using thin signal traces

will result in unacceptable losses due to trace resistance. This

effect becomes even more pronounced at higher frequencies

due to the skin effect. The skin effect reduces the effective

thickness of the trace as frequency increases. Resistive loss-

es make crosstalk worse because as the desired signal is

attenuated with higher frequencies crosstalk increases at

higher frequencies.

DIGITAL CONTROL

Block Diagram

20150411

FIGURE 7.

The LMH6583 has internal control registers that store the

programming states of the crosspoint switch. The logic is two

staged to allow for maximum programming flexibility. The first

stage of the control logic is tied directly to the crosspoint

switching matrix. This logic consists of one register for each

output that stores the on/off state and the address of which

input to connect to. These registers are not directly accessible

by the user. The second level of logic is another bank of reg-

isters identical to the first, but set up as shift registers. These

registers are accessed by the user via the serial input bus. As

described further below, there are two modes for programing

the LMH6582, Serial Mode and Addressed Mode.

The LMH6583 is programmed via a serial input bus with the

support of 4 other digital control pins. The Serial bus consists

of a clock pin (CLK), a serial data in pin (DIN), and a serial

data out pin (DOUT). The serial bus is gated by a chip select

pin (CS). The chip select pin is active low. While the chip se-

lect pin is high all data on the serial input pin and clock pins

is ignored. When the chip select pin is brought low the internal

logic is set to begin receiving data by the first positive transi-

tion (0 to 1) of the clock signal. The chip select pin must be

brought low at least 5 ns before the first rising edge of the

clock signal. The first data bit is clocked in on the next nega-

tive transition (1 to 0) of the clock signal. All input data is read

from the bus on the negative edge of the clock signal. Once

the last valid data has been clocked in, the chip select pin

must go high then the clock signal must make at least one

more low to high transition. Otherwise invalid data will be

clocked into the chip. The data clocked into the chip is not

transferred to the crosspoint matrix until the CFG pin is pulsed

high. This is the case regardless of the state of the Mode pin.

The CFG pin is not dependent on the state of the Chip select

pin. If no new data is clocked into the chip subsequent pulses

on the CFG pin will have no effect on device operation.

The programming format of the incoming serial data is se-

lected by the MODE pin. When the mode pin is HIGH the

crosspoint can be programmed one output at a time by en-

tering a string of data that contains the address of the output

that is going to be changed (Addressed Mode). When the

mode pin is LOW the crosspoint is in Serial Mode. In this

mode the crosspoint accepts a 40 bit array of data that pro-

grams all of the outputs. In both modes the data fed into the

chip does not change the chip operation until the Configure

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LMH6583

pin is pulsed high. The configure and mode pins are inde-

pendent of the chip select pin.

THREE WIRE VS. FOUR WIRE CONTROl

There are two ways to connect the serial data pins. The first

way is to control all 4 pins separately, and the second option

is to connect the CFG and the CS pins together for a 3 wire

interface. The benefit of the 4 wire interface is that the chip

can be configured independently of the CS pin. This would be

an advantage in a system with multiple crosspoint chips

where all of them could be programmed ahead of time and

then configured simultaneously. The 4 wire solution is also

helpful in a system that has a free running clock on the CLK

pin. In this case, the CS pin needs to be brought high after the

last valid data bit to prevent invalid data from being clocked

into the chip.

The three wire option provides the advantage of one less pin

to control at the expense of having less flexibility with the

configure pin. One way around this loss of flexibility would be

If the clock signal is generated by an FPGA or microcontroller

where the clock signal can be stopped after the data is

clocked in. In this case the Chip select function is provided by

the presence or absence of the clock signal.

SERIAL PROGRAMMING MODE

Serial programming mode is the mode selected by bringing

the MODE pin low. In this mode a stream of 40 bits programs

all 8 outputs of the crosspoint. The data is fed to the chip as

shown in the Serial Mode Data Frame tables below (4 tables

are required to show the entire data frame). The table is ar-

ranged such that the first bit clocked into the crosspoint

select pin is left low after the valid data is shifted into the chip

and if the clock signal keeps running then additional data will

be shifted into the register, and the desired data will be shifted

out.

Also illustrated is the timing relationships for the digital pins

in the Timing Diagram for Serial Mode shown below. It is im-

portant to note that all the pin timing relationships are impor-

tant, not just the data and clock pins. One example is that the

Chip Select pin (CS) must transition low before the first rising

edge of the clock signal. This allows the internal timing circuits

to synchronize to allow data to be accepted on the next falling

edge. After the final data bit has been clocked in, the chip

select pin must go high, then the clock signal must make at

least one more low to high transition. As shown in the timing

diagram, the chip select pin state should always occur while

the clock signal is low. The configure (CFG) pin timing is not

so critical, but it does need to be kept low until all data has

been shifted into the crosspoint registers.

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Timing Diagram for Serial Mode

Serial Mode Data Frame (First 2 Words)

Output 0 Output 1

Input Address On = 0 Input Address On = 0

LSB MSB Off = 1 LSB MSB Off = 1

0123456789

Off = TRI-STATE®, Bit 0 is first bit clocked into device.

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LMH6583

Serial Mode Data Frame (Continued)

Output 2 Output 3

Input Address On = 0 Input Address On = 0

LSB MSB Off = 1 LSB MSB Off = 1

10 11 12 13 14 15 16 17 18 19

Serial Mode Data Frame (Continued)

Output 4 Output 5

Input Address On = 0 Input Address On = 0

LSB MSB Off = 1 LSB MSB Off = 1

20 21 22 23 24 25 26 27 28 29

Serial Mode Data Frame (Last 2 Words)

Output 6 Output 7

Input Address On = 0 Input Address On = 0

LSB MSB Off = 1 LSB MSB Off = 1

30 31 32 33 34 35 36 37 38 39

Bit 39 is last bit clocked into device.

ADDRESSED PROGRAMMING MODE

Addressed programming mode makes it possible to change

only one output register at a time. To utilize this mode the

mode pin must be High. All other pins function the same as

in serial programming mode except that the word clocked in

is 8 bits and is directed only at the output specified. In ad-

dressed mode the data format is shown below in the table

titled Addressed Mode Word Format.

Also illustrated is the timing relationships for the digital pins

in the Timing Diagram for Addressed Mode shown below. It

is important to note that all the pin timing relationships are

important, not just the data and clock pins. One example is

that the Chip Select pin (CS) must transition low before the

first rising edge of the clock signal. This allows the internal

timing circuits to synchronize to allow data to be accepted on

the next falling edge. After the final data bit has been clocked

in, the chip select pin must go high, then the clock signal must

make at least one more low to high transition. As shown in the

timing diagram, the chip select pin state should always occur

while the clock signal is low. The configure (CFG) pin timing

is not so critical, but it does need to be kept low until all data

has been shifted into the crosspoint registers.

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LMH6583

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Timing Diagram for Addressed Mode

Addressed Mode Word Format

Output Address Input Address TRI-STATE

LSB MSB LSB MSB 1 = TRI-STATE

0 = On

01234567

Bit 0 is first bit clocked into device.

DAISY CHAIN OPTION IN SERIAL MODE

The LMH6583 supports daisy chaining of the serial data

stream between multiple chips. This feature is available only

in the Serial programming mode. To use this feature serial

data is clocked into the first chip DIN pin, and the next chip

DIN pin is connected to the DOUT pin of the first chip. Both

chips may share a chip select signal, or the second chip can

be enabled separately. When the chip select pin goes low on

both chips a double length word is clocked into the first chip.

As the first word is clocking into the first chip the second chip

is receiving the data that was originally in the shift register of

the first chip (invalid data). When a full 40 bits have been

clocked into the first chip the next clock cycle begins moving

the first frame of the new configuration data into the second

chip. With a full 80 clock cycles both chips have valid data and

the chip select pin of both chips should be brought high to

prevent the data from overshooting. A configure pulse will ac-

tivate the new configuration on both chips simultaneously, or

each chip can be configured separately. The mode, chip se-

lect, configure and clock pins of both chips can be tied to-

gether and driven from the same sources.

SPECIAL CONTROL PINS

The LMH6583 has two special control pins that function in-

dependent of the serial control bus. One of these pins is the

reset (RST) pin. The RST pin is active high meaning that a

logic 1 level the chip is configured with all outputs disabled

and in a high impedance state. The RST pin programs all the

registers with input address 0 and all the outputs are turned

off. In this configuration the device draws only 20 mA. The

reset pin can used as a shutdown function to reduce power

consumption. The other special control pin is the broadcast

(BCST) pin. The BCST pin is also active high and sets all the

outputs to the on state connected to input 0. Both of these

pins are level sensitive and require no clock signal. The two

special control pins overwrite the contents of the configuration

THERMAL MANAGEMENT

The LMH6583 is packaged in a thermally enhanced Quad Flat

Pack package. Even so, it is a high performance device that

produces a significant amount of heat. With a ±5V supply, the

LMH6583 will dissipate approximately 1.1W of idling power

with all outputs enabled. Idling power is calculated based on

the typical supply current of 110 mA and a 10V supply voltage.

This power dissipation will vary within the range of 800 mW

to 1.4W due to process variations. In addition, each equiva-

lent video load (150Ω) connected to the outputs should be

budgeted 30 mW of power. For a typical application with one

video load for each output this would be a total power of 1.14

W. With a typical θJA of 27°C/W this will result in the silicon

being 31°C over the ambient temperature. A more aggressive

application would be two video loads per output which would

15 www.national.com

LMH6583

result in 1.38 W of power dissipation. This would result in a

37°C temperature rise. For heavier loading, the QFP package

thermal performance can be significantly enhanced with an

external heat sink and by providing for moving air ventilation.

Also, be sure to calculate the increase in ambient temperature

from all devices operating in the system case. Because of the

high power output of this device, thermal management should

be considered very early in the design process. Generous

passive venting and vertical board orientation may avoid the

need for fan cooling or heat sinks. Also, the LMH6583 can be

operated with a ±3.3V power supply. This will cut power dis-

sipation substantially while only reducing bandwidth by about

10% (2 VPP output). The LMH6583 is fully characterized and

factory tested at the ±3.3V power supply condition for appli-

cations where reduced power is desired.

If a heat sink is desired AAVD/Thermalloy part #

375324B00035G is the proper size for the LMH6583 pack-

age. This heat sink comes with adhesive tape for ease in

assembly. With natural convection the heat sink will reduce

the θJA from 27°C/W to approximately 21°C/W. Using a fan

will increase the effectiveness of the heat sink considerably.

When doing thermal design it is important to note that every-

thing from board layout to case material will impact the actual

θJA of the device. The θJA specified in the datasheet is for a

typical board layout.

20150453

FIGURE 8. Maximum Dissipation vs. Ambient

Temperature

PRINTED CIRCUIT LAYOUT

Generally, a good high frequency layout will keep power sup-

ply and ground traces away from the input and output pins.

Parasitic capacitances on these nodes to ground will cause

frequency response peaking and possible circuit oscillations

(see Application Note OA-15 for more information). If digital

control lines must cross analog signal lines (particularly in-

puts) it is best if they cross perpendicularly. National Semi-

conductor suggests the following evaluation boards as a

guide for high frequency layout and as an aid in device testing

and characterization:

Device Package Evaluation Board

Part Number

LMH6583 64-Pin TQFP LMH730156

www.national.com 16

LMH6583

Physical Dimensions inches (millimeters) unless otherwise noted

64-Pin Exposed Pad QFP

NS Package Number VXE64A

17 www.national.com

LMH6583

Notes

LMH6583 16x8 550 MHz Analog Crosspoint Switch, Gain of 2

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