GAC BACLPLANE

This backplane integrates the GAC's 4IP cards, 8IP cards, Buffer cards, Clock cards and the Control PC. Totaly there are fifteen cards connected to the Backplane, viz :

4IPCARD	8 Nos.
8IPCARD	3 Nos.
BUFFER CARD	3 Nos.
CLOCK CARD	1 Nos.

There is a provision to put a Controller card, or connect directly to a Control PC. At present it is directly connected to the Control PC through a cable, hence no Controller card is used.
The power for all these cards are distributed through the backplane. Hence there is a separate power ( VCC & VEE ) entry point for every card and separate FUSE for each of these points. The GROUND and VCC lines enter 2 common BUS BARS and then get distributed to these power entry points. These entry points are located behind each of these cards. The GROUND plane is common to all the boards. The VCC plane is a split type and is separate for each of these points. The +5V indicator LEDs are powered from these VCC planes. If the FUSE of any card blows, the ( Red colour ) LED indicator will go off. The cards ( 4IP, Clock & Buffer cards ) which takes VEE supply, the connections are made on the outer layers ( comp & sold ). The VEE supply lines also have a fuse and LED ( Yellow colour ) indicators.
This Backplane is a 4 layer PCB. The inner two layers are Power planes ( GND & split VCC ), the outer two layers are used for signal routing. The signals from FFT system enters the 50 pin berg connectors behind the 4IP cards. Signals from 4IPs to 8IPs goes through the backplane tracks. The signals from 8IPs to Buffer cards are made using specially made cables. Critical signal connections are mede by wire wrapping. High speed signals like CLK, INIT etc. are daisy chained and terminations are provided at the last point.

GOBACK TO GAC SUBSYSTEM
GOTO DIGITAL BACKEND