© Semiconductor Components Industries, LLC, 2006
November, 2006 − Rev. 8
1 Publication Order Number:
MC10H642/D
MC10H642, MC100H642
68030/040 PECL to TTL
Clock Driver
Description
The MC10H/100H642 generates the necessary clocks for the
68030, 68040 and similar microprocessors. It is guaranteed to meet the
clock specifications required by the 68030 and 68040 in terms of
part−to−part skew, within−part skew and also duty cycle skew.
The user has a choice of using either TTL or PECL (ECL referenced
to +5.0 V) for the input clock. TTL clocks are typically used in present
MPU systems. However, as clock speeds increase to 50 MHz and
beyond, the inherent superiority of ECL (particularly differential
ECL) as a means of clock signal distribution becomes increasingly
evident. The H642 also uses differential PECL internally to achieve its
superior skew characteristic.
The H642 includes divide−by−two and divide−by−four stages, both
to achieve the necessary duty cycle skew and to generate MPU clocks
as required. A typical 50 MHz processor application would use an
input clock running at 100 MHz, thus obtaining output clocks at
50 MHz and 25 MHz (see Logic Diagram).
The 10H version is compatible with MECL 10H™ ECL logic levels,
while the 100H version is compatible with 100K levels (referenced to
+5.0 V).
Features
• Generates Clocks for 68030/040
• Meets 030/040 Skew Requirements
• TTL or PECL Input Clock
• Extra TTL and PECL Power/Ground Pins
• Asynchronous Reset
• Single +5.0 V Supply
• Pb−Free Packages are Available*
Function
Reset(R): LOW on RESET forces all Q outputs LOW.
Select(SEL): LOW selects the ECL input source (DE/DE). HIGH
selects the TTL input source (DT).
The H642 also contains circuitry to force a stable input state of the
ECL differential input pair, should both sides be left open. In this Case,
the DE side of the input is pulled LOW, and DE goes HIGH.
Power Up: The device is designed to have positive edges of the ÷2
and ÷4 outputs synchronized at Power Up.
*For additional information on our Pb−Free strategy and soldering details, please
download the ON Semiconductor Soldering and Mounting Techniques
Reference Manual, SOLDERRM/D.
MARKING DIAGRAM*
xxx = 10 or 100
A = Assembly Location
WL = Wafer Lot
YY = Year
WW = Work Week
G= Pb−Free Package
PLCC−28
FN SUFFIX
CASE 776
MCxxxH642G
AWLYYWW
1
http://onsemi.com
*For additional marking information, refer to
Application Note AND8002/D.
See detailed ordering and shipping information in the package
dimensions section on page 8 of this data sheet.
ORDERING INFORMATION
