MOTOROLA MPC949

SEMICONDUCTOR TECHNICAL DATA
The MPC949 is a low voltage CMOS, 15 output clock buffer. The 15
outputs can be configured into a standard fanout buffer or into 1X and
1/2X combinations. The device features a low voltage PECL input, in
addition to its LVCMOS/LVTTL inputs, to allow it to be incorporated into
larger clock trees which utilize low skew PECL devices (see the
MC100LVE111 data sheet) in the lower branches of the tree. The fifteen
outputs were designed and optimized to drive 50Ω series or parallel
terminated transmission lines. With output to output skews of 300ps the
MPC949 is an ideal clock distribution chip for synchronous systems
which need a tight level of skew from a large number of outputs. For a
similar product with a smaller fanout and package consult the MPC946
data sheet.
•
•
•
•
•
•
•
•
•
LOW VOLTAGE
1:15 PECL TO CMOS
CLOCK DRIVER
Clock Distribution for Pentium Systems with PCI
Low Voltage PECL Clock Input
2 Selectable LVCMOS/LVTTL Clock Inputs
350ps Maximum Output to Output Skew
Drives up to 30 Independent Clock Lines
Maximum Output Frequency of 150MHz
High Impedance Output Enable
FA SUFFIX
52–LEAD TQFP PACKAGE
CASE 848D–03
52–Lead TQFP Packaging
3.3V VCC Supply
With an output impedance of approximately 7Ω, in both the HIGH and
the LOW logic states, the output buffers of the MPC949 are ideal for
driving series terminated transmission lines. More specifically each of the
15 MPC949 outputs can drive two series terminated transmission lines.
With this capability, the MPC949 has an effective fanout of 1:30 in
applications using point–to–point distribution schemes.
The MPC949 has the capability of generating 1X and 1/2X signals from a 1X source. The design is fully static, the signals are
generated and retimed inside the chip to ensure minimal skew between the 1X and 1/2X signals. The device features selectability
to allow the user to select the ratio of 1X outputs to 1/2X outputs.
Two independent LVCMOS/LVTTL compatible clock inputs are available. Designers can take advantage of this feature to
provide redundant clock sources or the addition of a test clock into the system design. With the TCLK_Sel input pulled HIGH the
TCLK1 input is selected. The PCLK_Sel input will select the PECL input clock when driven HIGH.
All of the control inputs are LVCMOS/LVTTL compatible. The Dsel pins choose between 1X and 1/2X outputs. A LOW on the
Dsel pins will select the 1X output. The MR/OE input will reset the internal flip flops and tristate the outputs when it is forced HIGH.
The MPC949 is fully 3.3V compatible. The 52 lead TQFP package was chosen to optimize performance, board space and cost
of the device. The 52–lead TQFP has a 10x10mm body size with a 0.65mm pin spacing.
Pentium is a trademark of Intel Corporation.
10/96
 Motorola, Inc. 1996
1
REV 1
MPC949
NC
0
4
1
Qc0:3
Dselc
0
6
1
Qd0:5
Dseld
NC
Qd5
GNDd
GNDc
Qc3
VCCc
Qc2
GNDb
23
GNDd
Qb1
44
22
Qd3
VCCb
45
21
VCCd
Qb0
46
20
Qd2
GNDb
47
19
GNDd
GNDa
48
18
Qd1
Qa1
49
17
VCCd
VCCa
50
16
Qd0
Qa0
51
15
GNDd
GNDa
52
14
NC
FUNCTION TABLE
MOTOROLA
GNDc
Qd4
43
MR/OE
TCLK_Sel
PCLK_Sel
Dseln
MR/OE
Qc1
24
MPC949
1
2
3
4
5
6
7
8
9 10 11 12 13
GNDI
Dselb
42
Dseld
1
Qb0:2
VCCd
Qb2
Dselc
3
25
Dselb
0
41
Dsela
Dsela
NC
VCCb
PCLK
PCLK_Sel
1
Qa0:1
PCLK
2
TCLK1
0
39 38 37 36 35 34 33 32 31 30 29 28 27
26
40
TCLK0
÷2
R
1
PCLK
PCLK
PCLK_Sel
Input
VCCc
÷1
0
VCCI
1
TCLK_Sel
TCLK1 (LVTTL)
MR/OE
0
NC
TCLK_Sel
TCLK0 (LVTTL)
Qc0
Figure 2. 52–Lead Pinout (Top View)
GNDc
Figure 1. Logic Diagram
PIN DESCRIPTION
0
1
Pin Name
TCLK0
TCLKn
÷1
Enabled
TCLK1
PCLK
÷2
Hi–Z
TCLK_Sel
(Int Pulldown)
Select pin to choose TCKL0 or TCLK1
TCLK0:1
(Int Pullup)
LVCMOS/LVTTL clock inputs
PCLK
(Int Pulldown)
True PECL clock input
PCLK
(Int Pullup)
Compliment PECL clock input
Dseln
(Int Pulldown)
1x or 1/2x input divide select pins
MR/OE
(Int Pulldown)
Internal reset and output tristate control pin
PCLK_Sel
(Int Pulldown)
Select Pin to choose TCLK or PCLK
2
Function
TIMING SOLUTIONS
BR1333 — Rev 6
MPC949
ABSOLUTE MAXIMUM RATINGS*
Symbol
Parameter
Min
Max
Unit
VCC
Supply Voltage
–0.3
4.6
V
VI
Input Voltage
–0.3
VDD + 0.3
V
IIN
Input Current
TBD
TBD
mA
TStor
Storage Temperature Range
–40
125
°C
* Absolute maximum continuous ratings are those values beyond which damage to the device may occur. Exposure to these conditions or conditions beyond those
indicated may adversely affect device reliability. Functional operation under absolute–maximum–rated conditions is not implied.
DC CHARACTERISTICS (TA = 0° to 70°C, VCC = 3.3V ±5%)
Symbol
Characteristic
Min
Typ
2.0
Max
Unit
3.60
V
0.8
V
Condition
VIH
Input HIGH Voltage
(Except PECL_CLK)
VIL
Input LOW Voltage
(Except PECL_CLK)
VPP
Peak–to–Peak Input Voltage
PECL_CLK
300
1000
mV
VCMR
Common Mode Range
PECL_CLK
VCC – 2.0
VCC – 0.6
V
Note 1.
VOH
Output HIGH Voltage
V
IOH = –20mA (Note 2.)
VOL
Output LOW Voltage
IIN
Input Current
CIN
Input Capacitance
Cpd
Power Dissipation Capacitance
2.5
0.4
V
IOL = 20mA (Note 2.)
±120
µA
Note 3.
4
pF
25
pF
Per Output
ICC
Maximum Quiescent Supply Current
70
85
mA
1. VCMR is the difference from the most positive side of the differential input signal. Normal operation is obtained when the “HIGH” input is within
the VCMR range and the input swing lies within the VPP specification.
2. The MPC949 outputs can drive series or parallel terminated 50Ω (or 50Ω to VCC/2) transmission lines on the incident edge (see Applications
Info section).
3. Inputs have pull–up/pull–down resistors which affect input current.
AC CHARACTERISTICS (TA = 0° to 70°C, VCC = 3.3V ±5%)
Symbol
Characteristic
Min
Typ
Fmax
Maximum Input Frequency
tPLH
Propagation Delay
PECL_CLK to Q
TTL_CLK to Q
4.0
4.2
6.5
7.5
tPHL
Propagation Delay
PECL_CLK to Q
TTL_CLK to Q
3.8
4.0
tsk(o)
Output–to–Output Skew
tsk(pr)
Part–to–Part Skew
tPZL,tPZH
tPLZ,tPHZ
Max
150
Unit
Condition
MHz
Note 4.
9.0
10.6
ns
Note 4.
6.2
7.2
8.6
10.5
ns
Note 4.
300
350
ps
Note 4.
1.5
2.0
2.75
4.0
ns
Note 5.
Output Enable Time
3
11
ns
Note 4.
Output Disable Time
3
11
ns
Note 4.
1.0
ns
0.8V to 2.0V
PECL_CLK to Q
TTL_CLK to Q
tr, tf
Output Rise/Fall Time
4. Driving 50Ω transmission lines terminated to VCC/2.
5. Part–to–part skew at a given temperature and voltage.
0.10
TIMING SOLUTIONS
BR1333 — Rev 6
3
MOTOROLA
MPC949
APPLICATIONS INFORMATION
line impedances. The voltage wave launched down the two
lines will equal:
Driving Transmission Lines
The MPC949 clock driver was designed to drive high
speed signals in a terminated transmission line environment.
To provide the optimum flexibility to the user, the output
drivers were designed to exhibit the lowest impedance
possible. With an output impedance of less than 10Ω the
drivers can drive either parallel or series terminated
transmission lines. For more information on transmission
lines the reader is referred to application note AN1091 in the
Timing Solutions brochure (BR1333/D).
VL = VS ( Zo / Rs + Ro +Zo) = 3.0 (25/53.5) = 1.40V
At the load end the voltage will double, due to the near
unity reflection coefficient, to 2.8V. It will then increment
towards the quiescent 3.0V in steps separated by one round
trip delay (in this case 4.0ns).
3.0
In most high performance clock networks point–to–point
distribution of signals is the method of choice. In a
point–to–point scheme either series terminated or parallel
terminated transmission lines can be used. The parallel
technique terminates the signal at the end of the line with a
50Ω resistance to VCC/2. This technique draws a fairly high
level of DC current and thus only a single terminated line can
be driven by each output of the MPC949 clock driver. For the
series terminated case however there is no DC current draw,
thus the outputs can drive multiple series terminated lines.
Figure 3 illustrates an output driving a single series
terminated line vs two series terminated lines in parallel.
When taken to its extreme the fanout of the MPC949 clock
driver is effectively doubled due to its capability to drive
multiple lines.
VOLTAGE (V)
2.5
OutA
tD = 3.8956
2.0
In
1.5
1.0
0.5
0
2
MPC949
OUTPUT
BUFFER
IN
7Ω
MPC949
OUTPUT
BUFFER
IN
OutB
tD = 3.9386
4
6
8
TIME (nS)
10
12
14
Figure 4. Single versus Dual Waveforms
RS = 43Ω
ZO = 50Ω
Since this step is well above the threshold region it will not
cause any false clock triggering, however designers may be
uncomfortable with unwanted reflections on the line. To
better match the impedances when driving multiple lines the
situation in Figure 5 should be used. In this case the series
terminating resistors are reduced such that when the parallel
combination is added to the output buffer impedance the line
impedance is perfectly matched.
OutA
RS = 43Ω
ZO = 50Ω
OutB0
7Ω
RS = 43Ω
ZO = 50Ω
MPC949
OUTPUT
BUFFER
OutB1
ZO = 50Ω
RS = 36Ω
ZO = 50Ω
7Ω
Figure 3. Single versus Dual Transmission Lines
The waveform plots of Figure 4 show the simulation
results of an output driving a single line vs two lines. In both
cases the drive capability of the MPC949 output buffers is
more than sufficient to drive 50Ω transmission lines on the
incident edge. Note from the delay measurements in the
simulations a delta of only 43ps exists between the two
differently loaded outputs. This suggests that the dual line
driving need not be used exclusively to maintain the tight
output–to–output skew of the MPC949. The output waveform
in Figure 4 shows a step in the waveform, this step is caused
by the impedance mismatch seen looking into the driver. The
parallel combination of the 43Ω series resistor plus the output
impedance does not match the parallel combination of the
MOTOROLA
RS = 36Ω
7Ω + 36Ω k 36Ω = 50Ω k 50Ω
25Ω = 25Ω
Figure 5. Optimized Dual Line Termination
SPICE level output buffer models are available for
engineers who want to simulate their specific interconnect
schemes. In addition IV characteristics are in the process of
being generated to support the other board level simulators in
general use.
4
TIMING SOLUTIONS
BR1333 — Rev 6
MPC949
OUTLINE DIMENSIONS
FA SUFFIX
TQFP PACKAGE
CASE 848D–03
ISSUE C
4X
–X–
X=L, M, N
4X TIPS
0.20 (0.008) H L–M N
0.20 (0.008) T L–M N
CL
52
AB
40
1
G
39
AB
3X VIEW
Y
–L–
VIEW Y
–M–
B
V
B1
13
ÇÇÇÇ
ÉÉÉÉ
ÉÉÉÉ
ÇÇÇÇ
V1
J
27
14
26
0.13 (0.005)
–N–
A1
BASE METAL
F
PLATING
M
D
T L–M
U
S
N
S
SECTION AB–AB
ROTATED 90_ CLOCKWISE
S1
A
S
4X
C
θ2
0.10 (0.004) T
–H–
–T–
SEATING
PLANE
4X
θ3
VIEW AA
0.05 (0.002)
S
W
θ1
2XR
R1
0.25 (0.010)
C2
θ
GAGE PLANE
K
C1
E
Z
VIEW AA
TIMING SOLUTIONS
BR1333 — Rev 6
5
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DATUM PLANE –H– IS LOCATED AT BOTTOM OF
LEAD AND IS COINCIDENT WITH THE LEAD
WHERE THE LEAD EXITS THE PLASTIC BODY AT
THE BOTTOM OF THE PARTING LINE.
4. DATUMS –L–, –M– AND –N– TO BE DETERMINED
AT DATUM PLANE –H–.
5. DIMENSIONS S AND V TO BE DETERMINED AT
SEATING PLANE –T–.
6. DIMENSIONS A AND B DO NOT INCLUDE MOLD
PROTRUSION. ALLOWABLE PROTRUSION IS
0.25 (0.010) PER SIDE. DIMENSIONS A AND B DO
INCLUDE MOLD MISMATCH AND ARE
DETERMINED AT DATUM PLANE -H-.
7. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. DAMBAR PROTRUSION SHALL
NOT CAUSE THE LEAD WIDTH TO EXCEED 0.46
(0.018). MINIMUM SPACE BETWEEN
PROTRUSION AND ADJACENT LEAD OR
PROTRUSION 0.07 (0.003).
DIM
A
A1
B
B1
C
C1
C2
D
E
F
G
J
K
R1
S
S1
U
V
V1
W
Z
θ
θ1
θ2
θ3
MILLIMETERS
MIN
MAX
10.00 BSC
5.00 BSC
10.00 BSC
5.00 BSC
–––
1.70
0.05
0.20
1.30
1.50
0.20
0.40
0.45
0.75
0.22
0.35
0.65 BSC
0.07
0.20
0.50 REF
0.08
0.20
12.00 BSC
6.00 BSC
0.09
0.16
12.00 BSC
6.00 BSC
0.20 REF
1.00 REF
0_
7_
–––
0_
12 _ REF
5_
13 _
INCHES
MIN
MAX
0.394 BSC
0.197 BSC
0.394 BSC
0.197 BSC
–––
0.067
0.002
0.008
0.051
0.059
0.008
0.016
0.018
0.030
0.009
0.014
0.026 BSC
0.003
0.008
0.020 REF
0.003
0.008
0.472 BSC
0.236 BSC
0.004
0.006
0.472 BSC
0.236 BSC
0.008 REF
0.039 REF
0_
7_
–––
0_
12 _ REF
5_
13 _
MOTOROLA
MPC949
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MOTOROLA
◊
6
MPC949/D
TIMING SOLUTIONS
BR1333 — Rev 6