Functional Blocks: Difference between revisions
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* Integrated or external battery backup | * Integrated or external battery backup | ||
** 12V sealed lead-acid | ** 12V sealed lead-acid | ||
** Connection point for monitoring DC/Battery voltage | |||
===Power Input Protection=== | ===Power Input Protection=== | ||
| Line 15: | Line 16: | ||
*** Quick rise time | *** Quick rise time | ||
* LC or capacitor filtering | * LC or capacitor filtering | ||
** Good for fast pulses, general ESD filtering | ** Good for fast pulses, general ESD filtering and immunity | ||
=== Internal Power Supply === | === Internal Power Supply === | ||
| Line 35: | Line 36: | ||
** Omron G5LE-14 DC12 (10A, square) | ** Omron G5LE-14 DC12 (10A, square) | ||
* No ground plane on output traces | * No ground plane on output traces | ||
* | * Trace separation for 250V+ voltage rating | ||
=== Logic input protection === | === Logic input protection === | ||
| Line 47: | Line 48: | ||
***May cause problems with data signals | ***May cause problems with data signals | ||
*ESD Suppression chips | *ESD Suppression chips | ||
*Op-Amp on inputs | |||
**Provides impedence matching and logic buffering | |||
**Good choice for high-impedence and other non-standard devices | |||
=== Logic pull-up === | |||
* Internal pull-up resistor (software addressable) | |||
**Provides ~50K impedence | |||
**Some logic pins may not have pull-ups avialable | |||
**Weak compared to external resistor/state easily changed | |||
* External 10K resistor | |||
**Robust, simple | |||
**Not as flexible as internal pull-ups | |||
**Can be configurable via jumper | |||
=== RS-485 Circuit === | === RS-485 Circuit === | ||
| Line 63: | Line 77: | ||
** NXP | ** NXP | ||
***PCF8563 | ***PCF8563 | ||
*Crystal | |||
** [http://www.maxim-ic.com/app-notes/index.mvp/id/58 Maxim Crystal Selection Notes] | |||
=== External Power Rails === | === External Power Rails === | ||
* Overvoltage protection | * Overvoltage protection | ||
** MOVs | |||
**TVS diodes | |||
*Overcurrent protection | *Overcurrent protection | ||
**High-side switching ICs with built-in protection | |||
**Polyfuses | |||
* ESD Protection | * ESD Protection | ||
**TVS diodes | **TVS diodes | ||
**Decoupling caps | **Decoupling caps | ||
=== Terminals === | === Terminals === | ||
*3.5mm screw terminals | *3.5mm screw terminals | ||
**Pluggable | **Pluggable, straight | ||
***Phoenix 8-position header, part #1945151 | |||
***Phoenix 2-position pluggable terminal, part #1984015 | |||
***Phoenix 3-position pluggable terminal, part #1984028 | |||
***Phoenix 4-position pluggable terminal, part #1984057 | |||
***Phoenix 6-position pluggable terminal, part #1984073 | |||
**Pluggable, right-angle | |||
**Non-Pluggable | **Non-Pluggable | ||
===Circuit Board=== | |||
*PCB Specs | |||
**FR4 PCB material | |||
**0.62" substrate thickness | |||
**1oz Copper | |||
**HASL finish or Gold | |||
**Double-sided with PTH and vias | |||
**Solder Mask both sides | |||
**Silk-screened legend on both sides | |||
*Grounding | |||
**Continuous ground plane or mesh on bottom layer | |||
**Optional double ground or power plane on top layer | |||
**Exposed ground plane at case screw holes | |||
**Separate ground for differential signals as needed | |||
Latest revision as of 14:04, 20 November 2011
External Power Supply
- 3-5A Switching PS
- Integrated or external battery backup
- 12V sealed lead-acid
- Connection point for monitoring DC/Battery voltage
Power Input Protection
- In-line or crowbar diode
- 6A Silicon rectifier type
- 30V MOV (10mm)
- Good for slow transients
- High energy capability
- Non-polarized
- TVS Diode
- Good for fast-moving transients
- Quick rise time
- LC or capacitor filtering
- Good for fast pulses, general ESD filtering and immunity
Internal Power Supply
- MC34063 Switching Power Supply
- Adaptable for 5V or 3.3V
- Cheap
Output Drivers and Protection
- Integrated Driver Chip
- ULN2004 or ULN2803 for 7-8 outputs
- Includes flyback diodes
- Suitable for relays or external
- Current-limit external (LED/buzzer) outputs
- SMT Resistors
Relays
- Form C relays for external switching
- Omron G5SB-1 DC12 (5A, rectangular)
- Omron G5LE-14 DC12 (10A, square)
- No ground plane on output traces
- Trace separation for 250V+ voltage rating
Logic input protection
- Current-limiting resistor
- MELF or other type with pulse-handling capability
- Pulse clamping
- TVS Diode
- Zener diode
- 0.22uF decoupling capacitor
- Provides ESD protection
- May cause problems with data signals
- ESD Suppression chips
- Op-Amp on inputs
- Provides impedence matching and logic buffering
- Good choice for high-impedence and other non-standard devices
Logic pull-up
- Internal pull-up resistor (software addressable)
- Provides ~50K impedence
- Some logic pins may not have pull-ups avialable
- Weak compared to external resistor/state easily changed
- External 10K resistor
- Robust, simple
- Not as flexible as internal pull-ups
- Can be configurable via jumper
RS-485 Circuit
- Integrated driver chips
- Dallas/Maxim
- MAX-485
- Texas Instruments
- SN65HVD485EDR
- Dallas/Maxim
Real-time Clock
- Dedicated chip with battery backup
- Dallas/Maxim
- DS-1307 (+/-20ppm, I2C)
- DS3231 (+/-2ppm, I2C)
- DS1302 (SPI, supercap backup)
- NXP
- PCF8563
- Dallas/Maxim
- Crystal
External Power Rails
- Overvoltage protection
- MOVs
- TVS diodes
- Overcurrent protection
- High-side switching ICs with built-in protection
- Polyfuses
- ESD Protection
- TVS diodes
- Decoupling caps
Terminals
- 3.5mm screw terminals
- Pluggable, straight
- Phoenix 8-position header, part #1945151
- Phoenix 2-position pluggable terminal, part #1984015
- Phoenix 3-position pluggable terminal, part #1984028
- Phoenix 4-position pluggable terminal, part #1984057
- Phoenix 6-position pluggable terminal, part #1984073
- Pluggable, right-angle
- Non-Pluggable
- Pluggable, straight
Circuit Board
- PCB Specs
- FR4 PCB material
- 0.62" substrate thickness
- 1oz Copper
- HASL finish or Gold
- Double-sided with PTH and vias
- Solder Mask both sides
- Silk-screened legend on both sides
- Grounding
- Continuous ground plane or mesh on bottom layer
- Optional double ground or power plane on top layer
- Exposed ground plane at case screw holes
- Separate ground for differential signals as needed