Texas Instruments | Applications of Logic and Translation in Video Doorbells | Application notes | Texas Instruments Applications of Logic and Translation in Video Doorbells Application notes

Texas Instruments Applications of Logic and Translation in Video Doorbells Application notes
Application Report
SCLA018 – March 2019
Optimizing Video Doorbell Designs with Common Logic
Use Cases
ABSTRACT
Logic and translation devices can be found in the majority of electronic systems. Video doorbells integrate
numerous subsystems together that often require additional signal interfacing, such as when the system
controller needs to operate at a different voltage than the wireless interface card, and translation must be
used for the data, or when more LEDs must be controlled than there are pins available on the system
controller. All of the use cases shown in the Block Diagram and Logic and Translation Use Cases sections
of this document are commonly seen in video doorbell designs.
Logic gates, voltage translators, and other logic devices are used for many purposes throughout modern
electronic systems. This document provides example solutions for common design challenges that can be
solved using logic and translation. Not all of the solutions here appear in every system, however all
solutions shown are commonly used and effective.
There are dozens of logic families available from Texas Instruments, and it can be difficult to select the
correct one for the application. Video doorbells are generally very small, and prefer low power solutions,
which makes it easier to identify an appropriate family for this application. See Recommended Logic and
Translation Families for video doorbells in this document for help finding the correct logic family for your
use case.
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Contents
Block Diagram ................................................................................................................
Optimize System Controller to Wireless Module Interface .............................................................
Logic and Translation Use Cases .........................................................................................
Recommended Logic and Translation Families for Video Doorbells..................................................
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3
4
9
List of Figures
1
Simplified Block Diagram for Video Doorbells ........................................................................... 2
2
SPI Translation for System Controller to WiFi Module Interface ...................................................... 3
3
Using Two Shift Registers to Control 16 LEDs with Three Signals (Data, Shift Clock, Output Register
Clock) ......................................................................................................................... 4
4
Using Logic as Indicator LED Driver Application Examples
5
6
...........................................................
.................................................................................................................................
Using Logic to Prevent Multiple Triggers of a CMOS Input Due to Switch Bounce ................................
5
5
6
7
Using an Unbuffered Inverter and Schmitt-trigger Inverter to Generate a Clock Signal From a Crystal
Oscillator ...................................................................................................................... 6
8
Using Voltage Translation with a SPI-communication Bus ............................................................. 7
9
Using Voltage Translation with GPIO Communications ................................................................ 7
10
Using Voltage Translation with an I2 Communication Bus
11
.............................................................
Using Voltage Translation with an SD Card Communication Bus .....................................................
8
8
List of Tables
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1
Block Diagram
(1)
1
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Block Diagram
8V-36V/110V-230V AC
Non-Isolated AC/DC
Power Supply
Energy Storage
Non-Isolated DC/DC
Power Supply
Chime
USB Supply
Protection
Crystal
Driver
USB
Point of Load
Clocking
Wireless
Interface
SPI
Input User
Interface
Ambient
Light Sensor
Debounce
PIR-Based
Motion Detection
IRIS,
IR Cut Filter,
Auto-Focus,
Zoom
x
Lens
Motor Driver
Memory
I2C
Digital Media
Processor
Image
Sensor
Image
Sensor
Interface
SD Card
Interface
SD
Open-Drain
Buffer
Signal Input/Output Protection
IR LED
Illumination
LED
Driver
Output
User
Interface
GPIO
Indicator
LEDs
I/O
Expansion
Environment
Sensing
Two-Way Audio
Communication
Self-Diagnostics
And
Monitoring
%
Figure 1. Simplified Block Diagram for Video Doorbells
For a more complete view, see the interactive online End Equipment Reference Diagram.
(1)
2
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Optimize System Controller to Wireless Module Interface
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2
Optimize System Controller to Wireless Module Interface
It is often desirable to have the system controller for a battery powered device such as a video doorbell to
be as low voltage as possible. Reducing supply voltage reduces power consumption significantly, however
this reduction in voltage also limits the peripherals that can be operated. It is very common for wireless
interface modules to need at least 1.8 V supply and signal levels, sometimes requiring as much as 5 V for
the supply.
Controller
Peripheral
SCK
SCK
MOSI
MOSI
MISO
MISO
SS
SS
Figure 2. SPI Translation for System Controller to WiFi Module Interface
Serial Peripheral Interface (SPI) provides up to 10 Mbps of data transfer and is typically used for this type
of communication. There are two common solutions used for translating the voltage of this interface using
either the TXB0104 or the SN74AVC4T774 voltage translators.
TXB0104
• Auto-bidirectional: No direction configuration required
• Works for 1.2-V to 5-V translation
• 20 Mbps per channel at 1.2-V operation
SN74AVC4T774
• 100 Mbps at 1.2-V operation
• Requires direction configuration; typically hard-configured to unidirectional translation
• 3.6-V maximum operating voltage
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Logic and Translation Use Cases
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Logic and Translation Use Cases
3.1
Logic Use Cases
3.1.1
Increase Number of Controller Outputs
System
Controller
Figure 3. Using Two Shift Registers to Control 16 LEDs with Three Signals (Data, Shift Clock, Output
Register Clock)
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•
•
4
As few as two outputs can be turned into 8 outputs with one serial-in parallel-out shift register.
Shift registers can be daisy chained for producing large numbers of outputs.
Low current (< 8 mA) LEDs can be driven directly.
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Logic and Translation Use Cases
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3.1.2
Drive Indicator LEDs
Figure 4. Using Logic as Indicator LED Driver Application Examples
•
•
•
•
3.1.3
Add system indicators without controller interaction required.
Most logic gates can drive low current indicator LEDs (1mA to 25 mA).
Logic functions add configurability.
Disable indicator LEDs as desired.
Open-Drain Buffer
5V
5-V
Gate
Driver
2-V
Input
Figure 5.
•
•
•
•
Control input thresholds with device supply voltage.
Control output voltage with pullup supply voltage.
Provides high-impedance output for discharge-only applications.
See TI's Translate Unidirectional Signals Using Open-Drain Outputs video for more information about
this use case.
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Logic and Translation Use Cases
3.1.4
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Debounce Switches and Buttons
CMOS
Device
Figure 6. Using Logic to Prevent Multiple Triggers of a CMOS Input Due to Switch Bounce
•
•
•
•
•
•
3.1.5
Prevents multiple triggers of CMOS inputs due to switch bounce
Works when the system controller is asleep
Works without a system controller
Reduces controller code complexity, no software debounce required
See TI's Debounce a Switch video for more information about this use case.
Visit TI's Online parametric search tool to find the correct Schmitt-trigger buffer.
Generate a Clock Signal from a Crystal Oscillator
Clocked Device
U
CLK
Figure 7. Using an Unbuffered Inverter and Schmitt-trigger Inverter to Generate a Clock Signal From a
Crystal Oscillator
•
•
•
•
•
•
6
Drive crystal oscillators directly.
Can be disabled with added logic
Allows for selectable system clocks with multiple crystals
Outputs a clean and reliable square wave
See Use of the CMOS Unbuffered Inverter in Oscillator Circuits Application Report for more information
about this use case.
Visit TI's Online parametric search tool to find the correct inverter.
Optimizing Video Doorbell Designs with Common Logic Use Cases
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Logic and Translation Use Cases
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3.2
Voltage Translation Use Cases
3.2.1
SPI Communication
Controller
Peripheral
SCK
SCK
MOSI
MOSI
MISO
MISO
SS
SS
Figure 8. Using Voltage Translation with a SPI-communication Bus
•
•
•
•
•
3.2.2
Enable communication when devices have mismatched logic voltage levels.
Prevent damage to devices that cannot support higher voltage inputs.
Improve data rates over discrete translation solutions.
Provides protection from disconnected peripherals
Visit TI's Online parametric search tool to find the correct voltage level translator.
GPIO Communication
Lower-voltage
Peripherals
Controller
Higher-voltage
Peripherals
Peripheral
A1
AutoBidirectional
Peripheral
B1
Peripheral
A2
Input
Peripheral
B2
Peripheral
A3
Output
Peripheral
B3
Peripheral
A4
Input / Output
Peripheral
B4
Direction
Select
Figure 9. Using Voltage Translation with GPIO Communications
•
•
•
•
•
Enable communication when devices have mismatched logic voltage levels.
Prevent damage to devices that cannot support higher voltage inputs.
Improve data rates over discrete translation solutions.
Provides protection from disconnected peripherals
Visit TI's Online parametric search tool to find the correct voltage level translator.
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Logic and Translation Use Cases
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I2C Communication
3.2.3
Controller
Peripheral 1
SDA
SDA
SCL
SCL
Peripheral 2
SDA
SCL
Figure 10. Using Voltage Translation with an I2 Communication Bus
•
•
•
•
3.2.4
Enable communication when devices have mismatched logic voltage levels.
Prevent damage to devices that cannot support higher voltage inputs.
Improve data rates over discrete translation solutions.
Visit TI's Online parametric search tool to find the correct voltage level translator.
SD Card Communication
Controller
SD Card
CLK
CLK
CMD
CMD
Data0
DAT0
Data1
DAT1
Data2
DAT2
Data3
DAT3
Figure 11. Using Voltage Translation with an SD Card Communication Bus
•
•
•
•
•
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Enable communication when devices have mismatched logic voltage levels.
Prevent damage to devices that cannot support higher voltage inputs.
Improve data rates over discrete translation solutions.
Protect controller while SD Card is not connected.
Visit TI's Online parametric search tool to find the correct voltage level translator.
Optimizing Video Doorbell Designs with Common Logic Use Cases
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Recommended Logic and Translation Families for Video Doorbells
4
Recommended Logic and Translation Families for Video Doorbells
4.1
AUP: Advanced Ultra-low-Power CMOS Logic and Translation
Key Features: SN74AUPxGxxxx
• Low static-power and dynamic-power consumption
• Wide VCC operating range: 0.8 V to 3.6 V
• Input hysteresis allows for slow input transition rate.
• Best in class for speed-power optimization
• Ioff spec for partial power down support
• Packaging Options: DSBGA, SC70, SM8, SON, SOT-23, SOT, UQFN, US8, X2SON
Key Features: SN74AUPxTxxxx
• Low static-power and dynamic-power consumption
• 1.65-V to 3.6-V translation range
• Best in class for speed-power optimization
• Ioff spec for partial power down support
Visit TI's Online parametric search tool to find the correct AUP family logic and voltage level translation
devices.
4.2
AXC: Advanced Extremely low-voltage CMOS Translation
Key Features
• Up and down translation across 0.65 V to 3.6 V
• Designed with glitch suppression circuitry to improve power sequencing performance
• Maximum Quiescent Current (ICCA + ICCB) of 6 µA (85°C Maximum) and 14 µA (125°C Maximum)
• Up to 500-Mbps support when translating from 1.8 V to 3.3 V
• VCC Isolation Feature: If either VCC input is below 100 mV, all I/Os outputs are disabled and become
high impedance.
• Ioff supports partial-power-down mode operation.
• Operating Temperature: –40°C to + 125°C
• Packaging Options: DSBGA, SC70, SM8, SON, SOT-23, SOT, UQFN, US8, X2SON
Visit TI's Online parametric search tool to find the correct AXC family voltage level translation devices.
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Recommended Logic and Translation Families for Video Doorbells
4.3
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LVC: Low-Voltage CMOS Logic and Translation
Key Features: SN74LVCxxxx
• Huge portfolio of logic functions
• LVC: 4+ channels per package
• Over-voltage tolerant inputs allow unidirectional down-translation with any function.
• High-drive outputs (up to 32 mA)
• Up to 250-Mbps operation
• Ioff supports partial-power-down mode operation.
• Packaging Options: SOIC, TSSOP, VQFN, SOP, SSOP
Key Features: SN74LVCxGxxxx
• Put 1, 2, or 3 channels of any logic function exactly where you need them.
• Configurable gates available ('57, '58, '97, '98, '99 functions)
• Over-voltage tolerant inputs allow unidirectional down-translation with any gate or buffer.
• High-drive outputs (up to 32 mA)
• Up to 250 Mbps operation
• Ioff supports partial-power-down mode operation.
• Packaging Options: SOT-23, SC70, X2SON, SOT-5X3, SON, DSBGA
Key Features: SN74LVCxTxxxx
• LVCxT: Up and down translation across 1.65 V to 5.5 V
• 1, 2, 8, or 16 channels per device
• High-drive outputs (up to 32 mA)
• Up to 250 Mbps operation
• Ioff supports partial-power-down mode operation.
Visit TI's Online parametric search tool to find the correct LVC family logic and voltage level translation
devices.
10
Optimizing Video Doorbell Designs with Common Logic Use Cases
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