MC10H646 Datasheet, PDF (1/6 Pages) ON Semiconductor – PENTIUM MICROPROCESSOR PECL/TTL-TTL CLOCK DRIVER

MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
PECL/TTL-TTL 1:8 Clock
Distribution Chip
MC10H646
MC100H646
The MC10H/100H646 is a single supply, low skew translating 1:8 clock
driver. Devices in the Motorola H600 translator series utilize the 28–lead
PLCC for optimal power pinning, signal flow through and electrical
performance. The single supply H646 is similar to the H643, which is a
dual supply 1:8 version of the same function.
• PECL/TTL–TTL Version of Popular ECLinPS™ E111
• Low Skew
• Guaranteed Skew Spec
• Tri–State Enable
• Differential Internal Design
• VBB Output
• Single Supply
• Extra TTL and ECL Power/Ground Pins
• Matched High and Low Output Impedance
• Meets Specifications Required to Drive the Pentium™ Microprocessor
PENTIUM
MICROPROCESSOR
PECL/TTL–TTL
CLOCK DRIVER
The H646 was designed specifically to drive series terminated
transmission lines. Special techniques were used to match the HIGH and
LOW output impedances to about 7ohms. This simplifies the choice of the
termination resistor for series terminated applications. To match the HIGH
and LOW output impedances, it was necessary to remove the standard
IOS limiting resistor. As a result, the user should take care in preventing an
output short to ground as the part will be permanently damaged.
FN SUFFIX
PLASTIC PACKAGE
CASE 776–02
The H646 device meets all of the requirements for driving the 60 and 66MHz Pentium Microprocessor. The device has no PLL
components, which greatly simplifies its implementation into a digital design. The eight copies of the clock allows for
point–to–point clock distribution to simplify board layout and optimize signal integrity.
The H646 provides differential PECL inputs for picking up LOW skew PECL clocks from the backplane and distributing it to
TTL loads on a daughter board. When used in conjunction with the MC10/100E111, very low skew, very wide clock trees can be
designed. In addition, a TTL level clock input is provided for flexibility. Note that only one of the inputs can be used on a single
chip. For correct operation, the unused input pins should be left open.
The Output Enable pin forces the outputs into a high impedance state when a logic 0 is applied.
The output buffers of the H646 can drive two series terminated, 50Ω transmission lines each. This capability allows the H646
to drive up to 16 different point–to–point clock loads. Refer to the Applications section for a more detailed discussion in this area.
The 10H version is compatible with MECL 10H™ ECL logic levels. The 100H version is compatible with 100K levels.
MECL 10H and ECLinPS are trademarks of Motorola, Inc. Pentium is a trademark of Intel Corporation.
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© Motorola, Inc. 1996
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