1. FAN324x Family of Smart Relay Drivers
Service Connect/Disconnect Switch
May, 2013

2. Meter Power Supply Simplified Diagram

3. Fairchild Solutions for Smart Meter

4. Outline Why use Smart Relay Drivers
What is a Service Connect/Disconnect Switch?
– Application Overview
Typical Circuit Implementations
Introducing FAN324x Family of Smart Relay Drivers
Features, Functionality
Block Diagram
Customization
Relay Drivers Portfolio

5. Why Use Smart Relay Drivers
The integrated solutions save space and cost as well as add timers
and protection functions to make the relay driving solutions safer and smarter in noisy environments
Accurate timer pulses regardless of input pulse variations and glitches
Accurate input filter time (factory adjustable) and XOR input protection
Accurate maximum output pulse width (factory adjustable)
Output can follow input width or give maximum limit (mode factory adjustable)
Protection functions for the switches
Internal thermal shutdown protection
Single-bias-voltage architecture allows isolated and non-isolated designs
Smaller overall PCB footprint
Lower overall cost
Applications
Smart Meters Service Connect/Disconnect
Solar Inverter Grid Connect
Energy Generation & Distribution
Building and Home Control

6. Key Application: Service Disconnect
Reasons for E-Service Connect/Disconnect Function
Remote connection/disconnection of customers from the electric grid:
Long term vacancy of the premises
Change in occupancy
Delayed or no payment of electric bills
Grid management in case of natural disasters/fire or maintenance/installations, etc.
Theft
Electricity theft prevention
Make disconnect relay to be difficult to reset (need stiff resistance in connect direction  New solenoid designs)
After power fail, has to complete disconnect from stored power.
Safety
Instances of meter-originated fires reported after smart meter installations into old meter sockets (reported in the press which raised public concern)
Probable cause is overheating due to corrosion in older sockets creating heat
Meter manufactures are investigating over-temperature detection and meter disconnect to reduce further heating until socket is repaired.
Power Saving
By using latching relays, there is no power loss from continuous driving current

7. Key Application: Service Disconnect
Application Overview
Typically, relays are used for controlling the connection to the grid (typical solutions are shown on the next slide):
The relay must be energized which is the function of the relay disconnect driver circuit – done by discrete solutions today.
The relay is operated infrequently. Total number of switching action during the life time of the E-Meter may be only a few hundred of times (The E-Meter may be tested during development up to 5,000 connect / disconnect cycles.)
The driver circuit must be tolerant of the noisy environment of the E-Meter, it is directly connected to the incoming feed from the grid and controlled by a microcontroller
The solution must be temper proof which impacts the relay construction and solenoid design and electrical requirements.

8. Key Application: Service Disconnect
Typical Implementations
Typical input voltage range: 12 V – 40 V
Typical current levels: up to 1.2 A
Typical pulse width range: 20 ms – 150 ms
Typical re-try interval range: 300 ms – 3 s

9. Key Application: Service Disconnect
Implementations
Solutions using our low-side drivers (FAN3227TMX) are already in production for 12-V relay systems. We are continuing to see application requirements for 24-V and higher relays.
Issues:
Noise filtering is inaccurate and uses lots of components.
Timings are not flexible, need to play with R-C time constants.
The driver’s DC current rating and maximum operating voltage limit the application space.

10. FAN324x Smart Dual-Coil Relay Drivers
A family of new ICs is now available (FAN324x family)
Single development for a family of drivers with integrated switches with wafer level trim capability to customize operating parameters for different customers (FAN3240, FAN3241)
These products can also be general relay drivers for dual-coil relays and therefore are not limited to E-Meters connect/disconnect applications.
The integrated solutions will save space and cost as well as add timers and protection functions to make the solution safer and smarter.
accurate timer pulses regardless of input pulse variations and glitches
protection functions for the switches
smaller overall PCB footprint
lower overall cost

11. FAN324x Smart Dual-Coil Relay Drivers
SOIC-8 Package
Part Number
Minimum Input Pulse
Maximum Output Pulse
Output Pulse Width
FAN3240TMX
15 ms
150 ms
Follows Input Width
FAN3241TMX
1 ms
30 ms
Always Maximum
FAN324xTMX
Factory adjustable
(0.12 ms – 20 ms)
(1 ms – 350 ms)
Factory adjustable between two modes

12. FAN324x Features & Functionality
8-V to 60-V operating range for use with 12-V, 24-V or 48-V relays
Strong DC current to break through welded contacts without using external switches
Accurate input-filter time (factory adjustable) and XOR input protection
Accurate maximum-output-pulse width (factory adjustable)
Output can follow input width or give maximum limit (mode factory adjustable)
Internal thermal-shutdown protection
Single-bias-voltage design for the chip allows isolated and non-isolated designs
Inputs compatible with 3.3-V or 5-V square-wave logic signals
Enable pin for operational flexibility
8-Lead SOIC Package
Rated from –40 ºC to +105 ºC Ambient
Applications
Smart E-Meters, Energy Generation & Distribution, Building and Home Control
Description
The FAN324x family is a dual high-current gate driver designed to drive a relay that connect and disconnect the power service in electronic meters. The driver provides strong dc current to drive polarized latching relays.
The filter/timer block provides protection from inadvertent noisy input signals by input pulse qualification and maximum output pulse width limit..

13. FAN324x Block Diagram and Operation
5VB: output of the on-board linear regulator (5V).
Facilitates isolated designs
Provides well defined constant internal bias to drive the output transistors (to achieve and guarantee RDSON)
EN: dual purpose pin for receiving an ENABLE signal from a logic level source or provide UVLO function for the logic supply (3.3V or 5V).
INPUT (IN1, IN2): compatible with 3.3V or 5V square wave logic signals (fast rise and fall time desired).
VS: bias voltage for the chip. Must be the same as the bias voltage powering the relay.
OUTPUT (OUT1, OUT2):
Open drain architecture, pulls low to drive the relay (inverting output)
Voltage rating is 80V abs. maximum, 60V maximum operating voltage
less than 1Ω output impedance for high DC current capability
GND: system ground potential.
ENBL
IN1
IN2
OUT1
OUT2 1

14. Dual-Coil Relay Drive Requirements
Conditiona
Issue
FAN324x Solution
Two switches must not be on at the same time.
Excessive currents to be drawn from the supply rail, resulting in improper operation and relay damage.
XOR Protection
The pulse must be longer than the minimum duration specified in the relay specification.
The relay contact can take a relatively long time for the relay contact to travel between its stationary ON and OFF positions
Set qualification time tQUAL:
FAN3240 = 15 ms
FAN3241 = 1 ms
The maximum drive pulse width needs to be limited.
Potential saturation of the relay winding leading to over-heating of the coils and drive electronics.
Set maximum pulse width tMAX:
FAN3240 = 150 ms
FAN3241 = 30 ms
Flexible output behavior to either follow input width or give maximum limit (for valid input pulses)
Always tMAX option relieves the micro-controller to do other monitoring functions.
FAN3240 = Follows Input Width
FAN3241 = Always tMAX
The relay has defines the minimum and maximum operating voltages for reliable operation of the contact(s).
Improper relay operation.
The driver UVLO function monitors the relay bias voltage for sufficient voltage level.
Isolated power supply designs
Sometimes isolation is required in cases where there is wired communications or a number of circuits on different input phases controlled from a common point.
Single-bias-voltage architecture
Integration of drive control, accurate timer pulses regardless of input variations, and thermal shutdown protection for the internal switches
Smaller overall PCB footprint and
Lower overall cost
Integrated solutions of FAN324x smart dual-coil relay drivers.

15. Smart Dual-Coil Relay Drive Operation
Input Qualification
Top input pulse is shorter than tQUAL,the set qualification time of FAN3240. It is ignored.
Maximum Output Pulse Width
The driver limits the output to the tMAX of FAN3240 in a condition where the input pin gets stuck high.
Noise on the Inactive Input
While one of the inputs receives a valid, qualified input, noise in the other input is ignored.
XOR Protection
Prohibits output pulses when two qualified input signals are received at the same time.

16. Minimum Input Pulse Width (TQUAL) Maximum Output Pulse Width (TMAX)
FAN324x Customization
Customization (and Trim):
Timing Parameters and the Operating Mode are programmed at the factory to provide flexibility for different relay types and customer requirements.
TQUAL can be adjusted between 128 µs and 20 ms
TMAX is adjustis from 1 ms to 350 ms
The Operating Mode can set for the output to either follow the input pulse width or to provide the maximum pulse width limit
The FAN3240 and FAN3241 are already set with two pre-defined configurations.
Contact Fairchild sales representatives for additional configurations.
Part Number
Minimum Input Pulse Width (TQUAL)
Maximum Output Pulse Width (TMAX)
Operating Mode
FAN3240TMX
15 ms
150 ms
Follow input up to TMAX
FAN3241TMX
1 ms
30 ms
Fixed (= TMAX)
FAN324xTMX
Factory adjustable
(0.12 ms – 20 ms)
(1 ms – 350 ms)
Factory adjustable between two modes

17. Factory adj. between two modes
Relay Drivers
Simple Selection Chart
Product
Availa-ble
Gate Drive
Max. Op. Voltage
12 V
Relay
24 V Relay
48 V Relay
Relay Config.
Motor Drive
Min. Input Pulse
Max. Output Pulse
XOR Logic Prot.
Output Behavior
FAN3240TMX
Q4’2012
> 10 A
60 V 
Dual-Coil --
15 ms
150 ms
Follows Input
FAN3241TMX
1 ms
30 ms
Max. Pulse Width Always
FAN324xTMX (New options)
2013
Factory adjust
(0.12 – 20 ms)
(1 – 350 ms)
Factory adj. between two modes
FAN3227TMX Y
2 A
18 V
Dual or Single Coil
FAN3224TMX
4 A
Note: These products can also be general relay drivers and are not limited to E-Meters.

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