analog_switches.pdf

8/12/2019 analog_switches.pdf

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Introduction

Purpose:

To introduce NXPs high performance analog switch offering.

Objectives

Review analog switches configurations & critical electrical parameters.

Review NXP portfolio & nomenclature.

Review package offering & trends.

Review of 3 simple application examples.

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The purpose of this module is to introduce you to NXPs analog switchoffering.

It will first cover analog switch basics: what are the different types ofswitches out there, what are the critical parameters and what they mean

for a particular application.

In a second time, we will go over the NXP analog switch portfolio and

nomenclature.

Then we will look at the latest packaging trends in leadless packages.

We will conclude with 3 simple applications examples using low ohmic

analog switches.

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The T (translator/level shifter) functionincluded in many switches

3.6 V

ASIC

1.8 V 3.6 V

1T34

ASIC NX3L1G315774AUP1T34

The T feature: Reduces part count Saves space Lowers cost Simplifies overall design

ASIC

ASIC

1.8 V 3.6 V

T

NX3L1T3157

In some applications, analog switches are at the interface between a lowvoltage ASIC and a higher supply voltage component. In order for the

switch to be activated properly, a voltage translator (or level shifter) istypically used on the select pin to insure the minimum activation threshold

is met.

NXP analog switches offer a complete family of devices that integrate thetranslator function, thus saving part count, PCB space, and lowering

overall system cost.


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6

SPDTSPST

(NO)

SPST

(NC)

SPST 2x

(NC)

SPST 2x(NO)

NX3L1G66

NX3L2G66

NX3L1G384

NX3L2G384

NX3L1G3157

NX3L4684NX3L2267

NX3L4357

DPDT DPDT2x

NX3L2467

NX3L1G53

SPDT

Enable

NX3L1T66 NX3L1T384 NX3L1T3157NX3L1T53

NX3L2T66 NX3L2T384

SPDT

2x

SP3T

Enable

NX3L2467

NX3 Family Switches by Function

The T in the part number distinguishes analog switches with theintegrated translator function. Some part numbers are highlighted in this

slide for the low ohmic NX3 family of switches. The G parts do notinclude the translator function.


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Critical Parameters what they mean

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Switch configuration (SPST, SPDT, DPDT) pick the right configurationand control pin option for the application.

Supply voltage (VCC) is the biasing voltage required to power the switch.Lower VCC means less head room to pass a signal. Some applications likeaudio, may require negative voltage capability to maintain signal integrity.

ON resistance (RON) is the resistance from input to output when the switch isclosed. The lower the RON, the less the signal passing through the switch willbe attenuated. RON will vary with voltage, temperature, and load current. Ameasure of this variation is delta RON (RON). Selecting a low RON device willminimize signal distortion.

Bandwidth (f-3dB) is the frequency at which the signal is attenuated by -3 dBfrom its dc level. It represents the upper cutoff frequency of the switch. The

higher the bandwidth, the higher the data rate it can support and the larger theamount of information it can handle.

Particular attention should be given to the following parameters whenselecting a switch.

Switch configuration this is the first step in selecting a switch. Choosethe right configuration (SPST, SPDT, DPDT) for the application. Insure

to use the correct control pin option to toggle switches independently or all

together.

Supply voltage (VCC). is the biasing voltage required to power up the

switch. A lower VCC means there is less head room to pass a signal.Some applications like audio, may require negative voltage capability to

maintain signal integrity as some audio signals have a negative

component.

ON Resistance (RON) is the resistance from input to output when theswitch is closed. The lower the line resistance, the less the signal passingthrough the switch will be attenuated. RON will vary with voltage,

temperature, and load current. A measure of this variation is delta RON .

Selecting a low RON device will minimize signal distortion.

Bandwidth (f-3dB) is the frequency at which the signal is attenuated by -3dB from its DC level. In other words, it represents the upper cutoff

frequency of the switch. It is directly related to data rate. The higher the

bandwidth, the higher the data rate it can support and the larger the

amount of information it can handle. This is particularly important when

dealing with fast signal applications like video or USB. A good rule ofthumb is to select a switch with 3 times the bandwidth of the signal

frequency to maintain good signal integrity.

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Critical Parameters what they mean (continued)

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ON state capacitance (CS(ON)) is the equivalent capacitance of the switchwhile closed. This capacitive loading of the line will affect overall bandwidth and

drive current. A lower CS(ON) helps minimize negative effects to the signal.

Input voltage range (VI) is the maximum voltage that can be applied at thecontrol pin, that is between the control pin to ground.

Switch voltage (VSW) is the maximum voltage that can be applied at an inputpin with respect to ground.

Enable / disable time (ten/ tdis) is the take it takes for the switch to changestate from the time the select pin has been triggered.

Select/control pin threshold levels (TTL vs. CMOS) - Switches can betriggered at different threshold levels. TTL trigger levels are typically at 0.7

and1.4V. CMOS levels are at 30 and 70% of the supply voltage. Package size - multiple packages and pin configurations available. Select the

proper package option to ease PCB layout.

ON state capacitance (CS(ON)) is the equivalent capacitance of theswitch while closed. The capacitance will induce capacitive loading on

the line and affect overall bandwidth and drive current. A lower CS(ON) istypically desired to minimize negative effects to the signal.

Input voltage range (VI) is the maximum voltage that can be applied at

the control pin, that is between the control pin to ground. In somesituation, an external component may be required to level shift the input

to the right voltage level if the switch cannot meet the proper input level

for the application.

Switch voltage (VSW) is the maximum voltage that can be applied at the

input pin with respect to ground.

Enable / disable time (ten/ tdis) is the time it takes for the switch tochange state from the time the select pin has been triggered.

Select or control pin threshold level (TTL vs. CMOS). Switches can betriggered at different threshold levels. As an approximation, TTL

threshold levels are at 0.7 and 1.4V. CMOS levels are typically at 30%

and 70% of the supply voltage. One has to be careful to select the rightswitch to guarantee the select signal used can correctly trigger the

switch.

Package selection is important. There are multiple package and pin

configurations available. Be sure to select the proper package option to

ease the layout of the PCB.

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NX3 Offering Summary Table

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No / NC = switch is normally opened or normally closed

NXP has already introduced over 47 part numbers in the low ohmic NX3analog switch family. These switches target applications where low ON

resistance is critical. They exhibit a resistance of less than 1 Ohm for theL series, and less than 0.5 Ohm for the V series. They also offer -90

dB isolation and crosstalk for superior signal integrity, and a low current

consumption for higher power savings. They are available in the Picogate

and the tiny leadless MicroPak packages, 0.35 mm pitch GF and GS, andthe newest 0.3 mm pitch GN package. The table in this slide summarizes

the critical parameters for each switch type of this family. This first portion

is for single switches in SPDT and SPST configurations.

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This is the continuation of the selection table showing the multipleswitches in SPST, SPDT, DPDT, SP3T configurations.

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NX3Lxxx Switches Nomenclature

This table summarizes the nomenclature for the NX3 family of switches,easing the selection process. The first 2 letters indicate the switch family.

The 3rd

digit represent the supply voltage capability of the device. A NX3device for example is rated for 3V. A NX5 device will be rated for 5V

applications. The on resistance, the 4th digit, is denoted by an C, L, or V.

A C for greater than 1 ohm resistance, L for less than 1 ohm, and V for

less than 0.5 ohm. The 5th character represent the number of switchesintegrated in the device. The next letter indicate if the translation function

is integrated on the select pin. A T meaning it is integrated, a G meaning

there is not translation on the select pin. The next 4 digits indicate the

function type. If the devices integrates a special function, such as shunt

resistors, negative swing or an enable pin, it will be indicated in this

section. Finally the last 2 letters indicate the package type. So anNX3L1G3157GW is a Single SPDT analog switch with 3 volt VCCcapability, 1 ohm or lower RON, in a SOT886 package.

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5 pins 6 pins 8 pins 10 pins 16 pins 20 pins

0.65mm

pitch

0.5mm

pitch

0.4mm

pitch

0.35mm

pitch

0.3mm

pitch

GF (SOT891)

1.0 x 1.0 x 0.5

GS (SOT1202)

1.0 x 1.0 x 0.35

GN (SOT1115)1.0 x 0.90 x 0.35

GN (SOT1116)

1.0 x 1.20 x 0.35

GS (SOT1203)1.0 x 1.35 x 0.35

GW (SOT353)2.0 x 2.0 x 1.0

GW (SOT363)2.0 x 2.0 x 1.0

GD (SOT996)

2.0 x 3.0 x 0.5

HR (SOT1039)3.0 x 3.0 x 0.5

TK (SOT650)3.0 x 3.0 x 0.85

BX (SOT1045)

2.5 x 4.5 x 0.5

GF(SOT1081)1.7 x 1.0 x 0.4

GM (SOT1049)

2.0 x 1.55 x 0.5

GU (SOT1161)1.8 x 2.6 x 0.5

GU (SOT1160)1.4 x 1.8 x 0.5

GF (SOT1089)1.0 x 1.35 x 0.5

NXP Common Switch Packages

GM - SOT8861.0 x 1.6 x 0.5

Dimensions: Width x Length x Height

NXP carries one of the most extensive array of leadless packages on themarket and offers the lowest 0.3 mm pitch package solution currently

available for switches. Most switches are offered in 5, 6, 8, 10, 16, and 20pin packages, with pitch ranging from 0.65 mm, all the way down to 0.3

mm. Most leaded and WCSP packages can be replaced by a leadless

package. There are multiple advantages in going to a leadless solution as

we will see in the next slide.

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Same die used as in larger packages, all functions available.

Operating temp range 40oC to 125oC.

Automotive qualified; JEDEC-STD-20C and Q100.

Pad spacing: 0.5, 0.4, 0.35 and 0.30 mm.

Lowest profile height (down to 0.35mm) packages.

Stronger contact with PCB compared to WCSP packages.

Drop-in replacement for most leaded/WCSP packages.

Pb-free, RoHS and Dark Green compliant.

Eliminated risk of whisker growth (NiPdAu).

Unlimited out of bag floor life at 30C/85% RH

Benefits of Leadless Packages

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Going to a leadless package allows to fit a larger die inside the samefootprint as a leaded package, therefore better performance can be

achieved for the same footprint. As an alternative, a smaller solution canalso be provided with the same electrical characteristics.

NXP leadless packages are characterized over an extended temperature

range of -40 to 125 degrees celcius, typical devices only go up to 85degree celcius. This make them suitable for high stress environment such

as automotive and military applications. Reliability is also superior to

WCSP and leaded packages, offering better adhesion to the PCB andbeing more impervious to chipping around the edges, these packages

yield far less failures during assembly and the overall life of the end

product. The leads are coated with Nickel Paladium Gold to prevent

oxidation. This allows an unlimited life time storage while out of the bagand negligible loss of inventory. All leadless packages are Pb-free, RoHS

and Dark Green compliant.


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Application Example #2

This is another audio application. Here the baseband has two differentaudio sources. One from the handset itself, the other from a bluetooth

headset. The switch allows to route the audio signals to the internalspeaker and microphone, or to those of the headset. Again, this type of

setup allows part savings and PCB space savings.

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Test mode implementationprior to product release

By using two SPDT switches,

GPIO1 and 2 can be extended totest an external circuit, whenrequired, without modifying the

design.

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Application Example #3

This last application example shows an NX3L1T3157 analog switch usedto route data signals. It is common for electronic devices to require testing

at the assembly site to ensure proper functioning. This is done byconnecting externally through GPIO ports to activate a test routine. Prior

to the product being released to the market, the test ports need to be

disabled to insure that no wrong user operation could damage the device.

A simple way to do this is through the use of analog switches. While inproduction, the switch allows connection from the GPIO connectors to the

internal test circuit. The switches are then toggled to prevent access,

while allowing reuse of the GPIOs for everydays use without risk to the

device.

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Brochure Sample kit

17http://ics.nxp.com/products/switches/

For further information on NXP analog switches, please visit our dedicatedwebsite at http://ics.nxp.com/products/switches/

You can also download data sheets and order brochures and sample kitsonline.

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Summary

While selecting analog switches, it is important to pay attention to the

key parameters (Configuration, RON, VCC, f-3dB, CS(ON), VI, package) tomeet the application requirements.

NXP provides high performance analog switches in all commonconfigurations tailored to answer specific application needs and easedesign effort.

The NX3 family of switches offers very low on resistance and is

available in a wide variety of leadless packages to meet todays

stringent board space constraints and reliability requirements.

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In Summary, while selecting analog switches, it is important to payattention to the key parameters such as, switch configuration, on

resistance, supply voltage, bandwidth, on resistance, input voltage andpackage. This will insure the switch meets the applications requirements.

NXP provides high performance analog switches in all commonconfigurations tailored to answer specific application needs and easedesign effort.

The NX3 family of switches is offers very low on resistance and is

available in a wide variety of leadless packages to meet todays stringent

board space constraints and reliability requirements.

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