Texas Instruments | Voltage and Processor Monitoring Solutions in Factory Automation and Control App | Application notes | Texas Instruments Voltage and Processor Monitoring Solutions in Factory Automation and Control App Application notes

Texas Instruments Voltage and Processor Monitoring Solutions in Factory Automation and Control App Application notes
Application Report
SNVA879 – May 2019
Voltage and Processor Monitoring Solutions in Factory
Automation and Control Applications
Michael DeSando
ABSTRACT
This document covers recommendations for voltage and processor monitoring in factory automation and
control applications. These recommendations can be applied to industrial applications that use the
common voltage rails mentioned in this document.
1
2
3
4
5
6
Contents
Introduction ................................................................................................................... 2
Voltage Monitoring ........................................................................................................... 3
Processor Monitoring ........................................................................................................ 7
Safety Related System Monitoring ........................................................................................ 8
Summary of Devices ........................................................................................................ 9
References .................................................................................................................. 10
List of Figures
1
Typical Monitoring Required in Factory Automation and Control Applications ...................................... 2
2
TPS3701 Undervoltage and Overvoltage Monitoring Solution
3
TPS3701 Example Layout .................................................................................................. 3
4
Two TL431LI + Dual Comparator Undervoltage and Overvoltage Monitoring Solution ............................ 4
5
Two TL431LI + Dual Comparator Example Layout
6
........................................................
.....................................................................
Window Watchdog (left) vs Standard Watchdog (right) ................................................................
3
4
7
List of Tables
1
Comparison Between Discrete vs Integrated for Undervoltage and Overvoltage Monitoring Solution ........... 4
2
Comparison of Device Recommendations ............................................................................... 9
3
Alternative Device Recommendations ................................................................................... 10
Trademarks
All trademarks are the property of their respective owners.
SNVA879 – May 2019
Submit Documentation Feedback
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
1
Introduction
1
www.ti.com
Introduction
In every factory automation application, and most industrial applications, there are multiple power rails that
power various subsystems within the application. Figure 1 shows some of the common subsystems in
nearly all factor automation applications and in many industrial applications that require voltage and
processor monitoring. At the front end, the AC power coming from the grid is converted to a DC voltage of
12V or 24V. This main supply rail is then converted to the various lower voltage rails required by the rest
of the system. The number of rails and the rail voltages differ from application to application but the need
to monitor these voltage rails to make sure they are in the correct range never changes. Almost every
microcontroller (MCU), microprocessor (MPU), field programmable gate array (FPGA), or application
specific integrated circuit (ASIC) requires very tight tolerance on the power supply otherwise the device
will not function properly thus requiring a voltage monitoring solution to shut the system down if the power
supply is out of range. In large industrial machines, a faulty voltage rail can lead to system failure resulting
in damage or injury. Even once the voltage rail is within range, there is a change that software or faulty
code can cause the MCU, MPU, or FPGA to latch up and stop working as expected. There is no reason to
risk operating such applications in faulty conditions so monitoring the voltage rails and processors are
always recommended and even required in safety critical applications. At the bare minimum, the main
supply voltage rail along with the core rails for the MCUs, MPUs, and FPGAs need to be monitored.
Common Factory Automation & Control Block Diagram
UV + OV Monitor: 5V 3.3V 1.8V ~ 0.6V
UV + OV Monitor: 24V
Watchdog
Figure 1. Typical Monitoring Required in Factory Automation and Control Applications
If the application must meet safety requirements, every core voltage needs undervoltage and overvoltage
monitoring. In addition to voltage monitoring, processor activity must also be monitored using an external
watchdog. The highest safety ratings require monitoring every voltage rail for both undervoltage and
overvoltage in addition to using independent window watchdogs for every MCU, MPU, and FPGA in the
system. With so many different voltage rails often found in industrial applications, the monitoring solutions
can become confusing and overwhelming. This document serves to provide the recommended monitoring
solutions for various subsystems commonly found in industrial applications.
2
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
SNVA879 – May 2019
Submit Documentation Feedback
Voltage Monitoring
www.ti.com
2
Voltage Monitoring
Voltage monitoring is accomplished with a voltage supervisor also called a reset IC. When the voltage
supervisor does not have a reset delay when returning from a fault condition, the device is called a voltage
detector. In some cases, specifically when monitoring high voltage rails, a shunt voltage reference can be
used as a lower cost solution with less features and flexibility compared to voltage supervisors.
2.1
24-V Rail Monitor
There are two recommended solutions for monitoring the 24-V rail common in many industrial
applications. The first recommendation consists of a single wide Vin voltage detector that is highly
adjustable and very accurate providing as shown in Figure 2. The second solutions uses multiple devices
working together to create a monitoring solution that is less adjustable, less accurate, larger footprint, but
can be lower cost as shown in Figure 4.
• TPS3701: wide Vin voltage detector can monitor voltages up to 36 V and provides 0.25% typical
monitoring accuracy. The size of the 6-pin SOT package is 2.9 mm x 1.6 mm and only requires three
external resistors to set the fault threshold and at least one external pull-up resistor for the open-drain
output as shown in Figure 3. The TPS3701 provides both undervoltage and overvoltage monitoring in
a convenient single device solution.
• Two TL431LI + Two Comparators: This solutions uses four lower cost components to create an
undervoltage and overvoltage monitoring solution. The solution requires at least four external resistors
to set the fault threshold of the two TL431LI devices in addition to two pull-up resistors for each. An
additional two external resistors for each comparator is required if level shifting is needed. Although
this solution can be lower cost, often times the size of the devices plus the external components make
it a large footprint solution as shown in Figure 5. The monitoring accuracy depends on the grade of
TL431LI in addition to the grade of the resistors used. This solution provides typical monitoring
accuracy between 3% to 6% and does not provide accurate hysteresis.
VCC
TPS3701
INA
OUTA
INB
OUTB
OV or UV Fault
Figure 2. TPS3701 Undervoltage and Overvoltage Monitoring Solution
Figure 3. TPS3701 Example Layout
SNVA879 – May 2019
Submit Documentation Feedback
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
3
Voltage Monitoring
www.ti.com
VCC
VCC
VCC
+
±
VCC
OV or UV Fault
VCC
VCC
+
±
Figure 4. Two TL431LI + Dual Comparator Undervoltage and Overvoltage Monitoring Solution
Figure 5. Two TL431LI + Dual Comparator Example Layout
Table 1 shows a comparison between the undervoltage and overvoltage solution using discrete
components vs an voltage supervisor IC.
Table 1. Comparison Between Discrete vs Integrated for Undervoltage and Overvoltage Monitoring
Solution
2x TL431LI + LM2903 Dual Comparator
4
TPS3701
Number of Components
12
5
Approximate Footprint Area
0.620 in2
0.36 in2
Max Input Voltage
36 V
36 V
Max Approximate Supply
Current
~2 mA (TL431LI typical) + ~2 mA (TL431LI typical) + 2.5 mA
(LM2903 max) = 4.5 mA
11 µA (TPS3701 max)
Typical Voltage Monitoring
Accuracy
3% to 6%
0.25%
Approximate Cost (1k units)
2x $0.07 + $0.08 + 9x $0.02 = $0.40
$0.89 + 4x $0.02 = $0.97
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
SNVA879 – May 2019
Submit Documentation Feedback
Voltage Monitoring
www.ti.com
2.2
12-V Rail Monitor
In some factory automation and control applications, the 24-V rail is regulated down to 12 V for powering
lower voltage regulators or drive circuitry such as LED drivers found in CNC machines. Sometimes a
window voltage monitoring device is required whereas sometimes just a undervoltage monitoring device
can be used. The requirements of the application will determine the recommendation to choose.
• TPS3700: window voltage detector monitors up to 18 V and provides 0.25% typical monitoring
accuracy. This device is offered in the 6-pin SOT and 6-pin WSON packages previously described and
requires three external resistors to set the fault threshold and at least one pull-up resistor for the opendrain output. Use this device when monitoring higher than 5 V but less than 18 V and undervoltage
and overvoltage monitoring are required.
• TPS3710: voltage detector monitors voltages up to 18 V and provides 0.25% typical monitoring
accuracy. This device is offered in the 6-pin SOT and 6-pin WSON packages previously described and
requires two external resistors to set the fault threshold and at least one pull-up resistor for the opendrain output. Use this device when monitoring higher than 5 V but less than 18 V and only
undervoltage monitoring is required.
2.3
5-V and 3.3-V Undervoltage and Overvoltage Rail Monitor
The 24-V rail is typically regulated down to lower common rail voltages of 5 V or 3.3 V for various
subsystems in the application. In CPU subsystems, the 5-V and 3.3-V rails are used for the MCU, MPU, or
FPGA making these rails critical for the success of the application. In this case, the 5-V rail and 3.3-V rails
must be monitored for undervoltage and overvoltage because of how critical these rails are for the rest of
the system as any voltage fault on these rails could be catastrophic for the system. There are two
recommended monitoring solutions for these critical rails.
• TPS3850: window voltage supervisor monitors up to 5 V for both undervoltage and overvoltage and
provides 0.8% typical monitoring accuracy. The size of the 10-pin VSON package is 3 mm x 3 mm and
only requires at least one external pull-up resistor for the open-drain output. The key value add for this
device is the built-in window watchdog that monitors processor activity for both early and late timing
faults. Window watchdogs are a system requirement to meet the higher safety ratings when the
application uses MCUs, MPUs, and FPGAs to improve reliability by preventing a faulty software issue
from causing system failure.
• TPS3703-Q1: window voltage supervisor monitors voltages up to 5.5 V and provides 0.25% typical
monitoring accuracy. The size of the 6-pin WSON package is 1.5 mm x 1.5 mm and only requires at
least one external pull-up resistor for the open-drain output. The TPS3703-Q1 provides both
undervoltage and overvoltage monitoring in a convenient single device solution in addition to
programmable delay for sequencing purposes or return from fault deglitching and manual reset for
disabling the device via an external signal. When the TPS3703-Q1 is being used to monitor a MCU,
MPU, or FPGA in a safety-critical application, an additional standalone window watchdog must also be
used to monitor the processor activity to meet the safety standards that require the highest reliability.
SNVA879 – May 2019
Submit Documentation Feedback
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
5
Voltage Monitoring
2.4
www.ti.com
Monitoring Multiple Voltage Rails Between 5 V and 0.4 V
The 5-V and 3.3-V rails may also be used for other devices other than the processors and are further
regulated down to various low voltage rails used throughout the subsystems for MCU, MPU, FPGA, or
PMIC core rails, DDR, SD cards, USB power, etc. The voltage monitoring requirement for these various
rails will differ from system to system so the recommended monitoring solutions must be evaluated on a
case by case basis. There can be duplicate rails or any number of voltage rails that need monitoring
depending on the system requirements and complexity of the system. The voltage monitoring solution for
these rails can use any combination of the below recommendations to cover nearly all power tree
situations.
2.4.1
Single Channel Voltage Monitoring
These devices monitoring one voltage rail with a sense input that can be fixed for a common voltage rail
or can be adjustable with an external resistor divider for voltage monitor flexibility.
• TPS3703-Q1: window voltage supervisor is described above and is the top recommendation for
monitoring undervoltage and overvoltage for 5-V rails and lower.
• TPS3808: voltage supervisor monitors many of the common voltage rails using the fixed voltage
variants and voltages down to 0.405 V using the adjustable variant. TPS3808 provides programmable
reset delay along with manual reset and requires a pull-up resistor for the open-drain output.
• TPS3620: back-up battery voltage supervisor monitors a voltage and switches over to an external
battery when the main power fails.
2.4.2
2.4.3
Dual Channel Voltage Monitoring
• TPS3779: dual voltage detector monitors two independent channels down to 1.074 V for undervoltage
faults and provides 1% typical monitoring accuracy. The independent sense inputs correspond to two
independent active-low Reset push-pull outputs so no pull-up resistors are required.
• TPS3110: voltage supervisor monitors undervoltage faults down to 0.86 V and includes a built-in
standard watchdog. This device provides 0.75% typical monitoring accuracy and includes a manual
reset.
Triple Channel Voltage Monitoring
TPS3307: triple channel voltage supervisor monitors three independent channels down to 1.25 V at
2.4% monitor accuracy and provides a single common push-pull output so no pull-up resistor is
required.
• TPS3306: triple channel voltage supervisor monitors three independent channels down to 1.25 V at
2.4% monitor accuracy and provides two open-drain outputs that each require a pull-up resistor. This
device also includes a built-in standard watchdog.
•
2.4.4
Quad Channel Voltage Monitoring
TPS386956: quad channel device monitors four independent channels, one for 3.3-V rail monitoring,
and the other three channels are adjustable down to 0.4 V at 0.25% monitoring accuracy. This
provides a single open-drain output so a pull-up resistor is required and also includes a manual reset.
• TPS386000: quad channel device monitors four independent channels down to 0.4 V at 0.25%
accuracy and provides four corresponding independent open-drain outputs each requiring a pull-up
resistor unless tied to together. This device also includes a built-in standard watchdog, a manual reset,
and an additional monitoring pin that is used for overvoltage monitoring for the fourth sense pin.
•
6
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
SNVA879 – May 2019
Submit Documentation Feedback
Processor Monitoring
www.ti.com
3
Processor Monitoring
Monitoring MCUs, MPUs, and FPGAs are accomplished with watchdogs. Watchdogs are devices that
monitor a processor and create a fault signal if the processor stops working correctly. The watchdog is
configured to expect a signal from the processor every so often and if the signal doesn't arrive at the
correct time, the watchdog triggers a fault. Some watchdogs include a voltage supervisor that monitors
voltage in addition to the watchdog that monitors the processor in a single device. If the device is just a
watchdog, this is called a standalone watchdog. Watchdogs are categorized into two categories: standard
and window. As Figure 6 shows, standard watchdogs require a pulse before a certain time period
otherwise a fault occurs. Standard watchdogs trigger a fault when the processor sends a pulse too late or
not at all. Window watchdogs require a pulse within a certain time window otherwise a fault occurs.
Window watchdogs trigger a fault when the processor sends a pulse too early, too late, or not at all.
Early Fault
WDI
WDO
Correct Operation
Correct Operation
WDI
WDI
WDO
WDO
Late Fault
WDI
WDI
WDO
Late Fault
WDO
Figure 6. Window Watchdog (left) vs Standard Watchdog (right)
3.1
Watchdog Solutions
A standard watchdog is the minimum recommended monitoring solution for any processor in the
application. If the application intends to meet higher safety ratings, a window watchdog is required for
every processor in the application. The higher safety ratings require a window watchdog in addition to
monitoring the processor core rails for undervoltage and overvoltage. In this case, an voltage supervisor +
watchdog device may be used and/or multiple monitoring devices working together. Monitoring devices in
any application serve to add protection, reliability, redundancy, and robustness. Below are some of the top
watchdog recommendations.
3.1.1
Standalone Window Watchdog
Standalone watchdogs only monitor processor activity and do not include any voltage monitoring
capability.
• TPS3430: standalone window watchdog with fully programmable watchdog timeout, watchdog reset
delay, and disable.
3.1.2
Window Watchdog + Single Channel Voltage Monitor
• TPS3850: a fully programmable window watchdog in addition to a single channel undervoltage and
overvoltage voltage supervisor.
• TPS3813: a fully programmable window watchdog in addition to a single channel undervoltage only
voltage supervisor.
SNVA879 – May 2019
Submit Documentation Feedback
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
7
Safety Related System Monitoring
3.1.3
•
•
www.ti.com
Standard Watchdog + Single Channel Voltage Monitor
TPS3823: a fixed voltage supervisor for common rails and includes a built-in fixed standard watchdog.
TPS3123: a fixed voltage supervisor for common low voltage rails and includes a built-in fixed
standard watchdog.
3.1.4
Standard Watchdog + Multi-channel Voltage Monitor
• TPS3110: a dual voltage supervisor with adjustable rails and includes a built-in fixed standard
watchdog.
• TPS3306: a triple voltage supervisor (two sense inputs and one power-fail input) and includes a built-in
fixed standard watchdog.
• TPS386000: a quad voltage supervisor and includes a built-in fixed standard watchdog.
4
Safety Related System Monitoring
Some factory automation and control applications must meet certain safety ratings with the main three
safety levels being safety integrity level (SIL), category level (CAT), performance level (PL). The risk level
of the particular application failing determines the safety rating required. This section does not provide
specific safety rating requirements as the safety ratings require a case by case analysis but will provide
general recommendations to increase the safety rating of the system.
4.1
Minimum Safety Recommendation
At
•
•
•
4.2
a bare minimum, these following recommendations must be met:
All main voltage rails should be monitored: 24 V, 5 V, 3.3 V.
All MCU, MPU, and FPGA core rails should be monitored.
Every MCU, MPU, and FPGA should be monitored with a watchdog unless the device has a built in
watchdog being used or if the device has no impact on the system functionality.
Medium Safety Recommendation
To meet the next level of safety ratings often required in applications designed to meet basic safety
compliance, the following recommendations should be met:
• All main voltage rails should be monitored for undervoltage and overvoltage: 24 V, 5 V, 3.3 V.
• All MCU, MPU, and FPGA core rails should be monitored for undervoltage and overvoltage.
• Every MCU, MPU, and FPGA should be monitored with a window watchdog regardless if the device
has a built in watchdog being used.
4.3
Maximum Safety Recommendation
To meet the highest level of safety ratings required by the most safety critical applications, the following
recommendations must be met:
• All main voltage rails must be monitored for undervoltage and overvoltage: 24 V, 5 V, 3.3 V. These
applications require additional fail-safe analysis and circuitry which may include redundant voltage
monitoring using two independent devices per voltage rail.
• All MCU, MPU, and FPGA core rails must be monitored for undervoltage and overvoltage. Similar to
the main voltage rails, these rails may require redundant voltage monitoring using independent devices
such that if any one device fails, the entire system doesn't fail as a result.
• Every MCU, MPU, and FPGA must be monitored with a window watchdog in addition to the device's
built in watchdog or an additional redundant watchdog device.
To reach the highest safety ratings, there must be redundancy in monitoring on every main voltage rail
and processor and care must be taken to assure one failure doesn't result in the entire system failing. If a
failure does occur, the failure must result in a safe fault mode that does not cause further damage or injury
and remains in the fail-safe mode until user intervention.
8
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
SNVA879 – May 2019
Submit Documentation Feedback
Summary of Devices
www.ti.com
5
Summary of Devices
Table 2 shows a comparison of every device mentioned in this document.
Table 2. Comparison of Device Recommendations
Number of
Voltage
Monitor Inputs
Voltage Monitor
Minimum
Voltage Monitor
Maximum
Voltage
Monitor Type
Watchdog
Type
TPS3808 (1)
1
0.405 V
6.5 V
undervoltage
none
manual reset,
programmable reset
delay
TPS3620
2
1.15 V
5V
undervoltage
none
battery backup switch
over
TPS3710
1
0.4 V
18 V
undervoltage
none
wide Vin
TPS3700
2
0.4 V
18 V
undervoltage +
overvoltage
none
wide Vin, window
monitor
TPS3701
2
0.4 V
36 V
undervoltage +
overvoltage
none
wide Vin, window
monitor
TPS3703Q1
1
0.9 V
5.5 V
undervoltage +
overvoltage
none
window monitor, manual
reset, programmable
reset delay, latch
capability
TPS3779
2
1.2 V
6.5 V
undervoltage
none
dual voltage monitor
TPS3110
2
0.9 V
3.6 V
undervoltage
standard
dual low voltage monitor
with standard watchdog
TPS3306
3
1.25 V
6V
undervoltage
standard
triple voltage monitor
with standard watchdog
TPS3307
3
1.25 V
6V
undervoltage
none
triple voltage monitor
TPS386956
4
0.4 V
6V
undervoltage
none
quad voltage monitor,
manual reset
standard
Features
quad voltage monitor
with standard watchdog,
manual reset,
programmable reset
delay
TPS386000
4
0.4 V
6V
undervoltage +
single
overvoltage
TPS3430
0
none
none
none
window
standalone
TPS3123
1
1.2 V
3V
undervoltage
standard
low voltage monitor with
standard watchdog
TPS3823
1
2.5 V
5V
undervoltage
standard
voltage monitor with
standard watchdog
TPS3813
1
2.5 V
5V
undervoltage
window
voltage monitor with
window watchdog
TPS3850
1
0.4 V
6.5 V
undervoltage +
overvoltage
window
window voltage monitor
with window watchdog
(1)
programmable window
watchdog
If monitoring above 1.15 V, use TPS3890 for lower Iq, better voltage monitoring accuracy, and smaller package size.
SNVA879 – May 2019
Submit Documentation Feedback
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
9
References
6
www.ti.com
References
There are other references that relate to voltage and processor monitoring that may be useful. Please see
the references below for more content and information.
• Importance of monitoring the core voltage rails of MCUs, MPUs, and FPGAs: Oh yes! My FPGA
application is safe
NOTE: This document references TPS3702 but please consider the newer device TPS3703-Q1 as
this device has more features and better performance!
•
•
Importance of processor monitoring using a watchdog: What is a watchdog timer and why is it
important?
Voltage Supervisors (Reset ICs): Frequently Asked Questions (FAQs)
Table 3. Alternative Device Recommendations
10
Device
Description
TPS3840
Nano-Iq, 1% Voltage Monitoring Accuracy, Programmable time delay, SOT package type,
Active-low / high, Open-drain / Push-pull
TPS3831
150uA Nano-Iq, X2SON (1mm x 1mm) small footprint size
TPS389x
1% Voltage Monitoring Accuracy, Programmable time delay, Active-low / high, Open-drain /
Push-pull, USON (1.45mm x 1mm) small footprint size
Voltage and Processor Monitoring Solutions in Factory Automation and
Control Applications
Copyright © 2019, Texas Instruments Incorporated
SNVA879 – May 2019
Submit Documentation Feedback
IMPORTANT NOTICE AND DISCLAIMER
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE
DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY
IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD
PARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable
standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you
permission to use these resources only for development of an application that uses the TI products described in the resource. Other
reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third
party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims,
damages, costs, losses, and liabilities arising out of your use of these resources.
TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either on
ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable
warranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2019, Texas Instruments Incorporated
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Related manuals

Download PDF

advertising