APPLICATION INFORMATION (cont.)
Synchronizing The Oscillator
UC1875/6/7/8
UC2875/6/7/8
UC3875/6/7/8
The CLOCKSYNC pin of the oscillator may be used to synchronize multiple UC1875 devices simply by connecting
the CLOCKSYNC of each UC1875 to the others:
1875/6/7/8s only
UDG-95080
All ICs will sync to chip with the fastest local oscillator.
R1 & RN
may
be needed to keep sync pulse narrow due to capacitance on line.
R1 & RN
may
also be needed to properly terminate R
SYNC
line.
Syncing to external TTL/CMOS
UDG-95081
ICs will sync to fastest chip or TTL clock if it is higher frequency.
R & RN
may
be needed for same reasons as above
Although each UC1875/6/7/8 has a local oscillator fre-
quency, the group of devices will synchronize to the
fastest oscillator driving the CLOCKSYNC pin. This ar-
rangement allows the synchronizing connection be-
tween ICs to be broken without any local loss of
functionality.
Synchronizing the device to an external clock signal
may be accomplished with a minimum of external cir-
cuitry, as shown in the previous figure.
Capacitive loading on the CLOCKSYNC pin will in-
crease the clock pulse width, and may adversely effect
system performance. Therefore, a resistor to ground
from the CLOCKSYNC pin is optional, but may be re-
quired to offset capacitive loading on this pin. These re-
sistors are shown in the oscillator schematics as R1,
RN.
8
TI [ TEXAS INSTRUMENTS ]
