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Freescale Semiconductor, Inc.
SEMICONDUCTOR TECHNICAL DATA
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Low Voltage PLL Clock Driver
The MPC958 is a 3.3V compatible, PLL based clock driver device targeted for high performance clock tree designs. With output frequencies of up to 200MHz and output skews of 200ps the MPC958 is ideal for the most demanding clock tree designs. The devices employ a fully differential PLL design to minimize cycle-to-cycle and phase jitter.
MPC958
* Fully Integrated PLL * Output Frequency up to 200MHz
LOW VOLTAGE PLL CLOCK DRIVER
Freescale Semiconductor, Inc...
* Outputs Disable in High Impedance * LQFP Packaging * 100ps Cycle-to-Cycle Jitter
The MPC958 has a differential LVPECL reference input along with an external feedback input. These features make the MPC958 ideal for use as a zero delay, low skew fanout buffer. The device performance has been tuned and optimized for zero delay performance. The MR/OE input pin will tristate the output buffers when driven "high". The MPC958 is fully 3.3V compatible and requires no external loop filter components. All control inputs accept LVCMOS or LVTTL compatible levels while the outputs provide LVCMOS levels with the ability to drive terminated 50 transmission lines. For series terminated 50 lines, each of the MPC958 outputs can drive two traces giving the device an effective fanout of 1:22. The device is packaged in a 7x7mm 32-lead LQFP package to provide the optimum combination of board density and performance.
FA SUFFIX 32-LEAD LQFP PACKAGE CASE 873A-02
QFB
(Int pull up)
PECL_CLK (Int pull down) PECL_CLK FB_CLK VCO_SEL BYPASS MR/OE PLL_EN
(Int pull up)
0 Phase Detector LPF VCO 200-400MHz 1 /2 0 1 /2
0 1
9
Q0:8
Q9
(Int pull up) (Int pull up) (Int pull down) (Int pull up)
Figure 1. Logic Diagram
06/00
(c) Motorola, Inc. 2000
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MPC958
GNDO GNDO VCCO VCCO
Q2
Q3
Q4
Q5
FUNCTION TABLES
24 GNDO Q1 VCCO Q0 GNDO QFB 25 26 27 28 23 22 21 20 19 18 17 16 15 14 13 Q6 VCCO Q7 GNDO Q8 VCCO Q9 GNDO BYPASS 1 0 MR/OE 1 0 VCO_SEL 1 0 PLL_EN 1 0 Function PLL Enabled PLL Bypass Function Outputs Disabled Outputs Enabled Function /2 /1 Function Select VCO Select PECL_CLK
MPC958
29 30 31 32 1 2 3 4 5 6 7 8 12 11 10 9
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VCCO VCO_SEL
PECL_CLK
PECL_CLK
FB_CLK
PLLEN
VCCA
MR/OE
Figure 2. 32-Lead Pinout (Top View)
ABSOLUTE MAXIMUM RATINGS*
Symbol VCC VI IIN TStor Supply Voltage Input Voltage Input Current Storage Temperature Range -40 Parameter Min -0.3 -0.3 Max 4.6 VCC + 0.3 20 125 Unit V V mA 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.
THERMAL CHARACTERISTICS Proper thermal management is critical for reliable system operation. This is especially true for high fanout and high drive capability products. Generic thermal information is available for the Motorola Clock Driver products. The means of calculating die power, the corresponding die temperature and the relationship to longterm reliability is addressed in the Motorola application note AN1545.
BYPASS
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GNDI
TIMING SOLUTIONS
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MPC958
DC CHARACTERISTICS (TA = 0 to 70C, VCC = 3.3V 5%)
Symbol VIH VIL VPP VCMR VOH VOL IIN CIN Cpd Characteristic Input HIGH Voltage LVCMOS Inputs Input LOW Voltage LVCMOS Inputs Peak-to-Peak Input Voltage PECL_CLK Common Mode Range Output HIGH Voltage Output LOW Voltage Input Current Input Capacitance Power Dissipation Capacitance Maximum Quiescent Supply Current 25 75 PECL_CLK 300 1.0 2.4 0.5 120 4 Min 2.0 Typ Max 3.6 0.8 1000 3.0 Unit V V mV V V V A pF pF mA Per Output All VCC Pins Note 1. IOH = -20mA, Note 2. IOL = 20mA, Note 2. Condition
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ICC
ICCPLL Maximum PLL Supply Current 15 20 mA VCCA Pin Only 1. VCMR is the center of the differential input signal. Normal operation is obtained when the input crosspoint is within the VCMR range and the input swing lies within the VPP specification. 2. The MPC958 outputs can drive series or parallel terminated 50 (or 50 to VCC/2) transmission lines on the incident edge (see Applications Info section).
PLL INPUT REFERENCE CHARACTERISTICS (TA = 0 to 70C)
Symbol fref Characteristic Reference Input Frequency Min Note 3. Max Note 3. Unit MHz % Condition
frefDC Reference Input Duty Cycle 25 75 3. Maximum and minimum input reference is limited by the VCO lock range and the feedback divider.
AC CHARACTERISTICS (TA = 0C to 70C, VCC = 3.3V 5%)
Symbol tr, tf tpw tsk(O) fVCO fmax Characteristic Output Rise/Fall Time Output Duty Cycle PLL Mode Min 0.10 tcycle/2 - 400 Typ Max 1.0 tcycle/2 + 400 200 200 PLL Mode PLL Mode Bypass Mode 50 100 -70 3.0 400 100 200 200 130 7.0 7 6 100 10 Unit ns ps ps MHz MHz VCO_SEL = `1' VCO_SEL = `0' Note 4. PLL Bypassed Condition 0.8 to 2.0V Note 4. Note 4. Note 4.
Output-to-Output Skews (Relative to QFB) PLL VCO Lock Range Maximum Output Frequency (Note 4.)
tpd(lock) tpd(bypass) tPLZ,HZ tPZL tjitter
Input to Ext_FB Delay (with PLL Locked @ 100MHz) Input to Q Delay Output Disable Time Output Enable Time Cycle-to-Cycle Jitter (Peak-to-Peak)
ps ns ns ns ps ms
Note 4.
tlock Maximum PLL Lock Time 4. Termination of 50W to VCC/2.
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Freescale Semiconductor, Inc.
MPC958
Power Supply Filtering The MPC958 is a mixed analog/digital product and as such it exhibits some sensitivities that would not necessarily be seen on a fully digital product. Analog circuitry is naturally susceptible to random noise, especially if this noise is seen on the power supply pins. The MPC958 provides a separate power supply for the phase-locked loop (VCCA) of the device. The purpose of this design technique is to try and isolate the high switching noise digital outputs from the relatively sensitive internal analog phase-locked loop. In a controlled environment such as an evaluation board this level of isolation is sufficient. However, in a digital system environment where it is more difficult to minimize noise on the power supplies a second level of isolation may be required. The simplest form of isolation is a power supply filter on the VCCA pin for the MPC958. Figure 3 illustrates a typical power supply filter scheme. The MPC958 is most susceptible to noise with spectral content in the 1KHz to 1MHz range. Therefore the filter should be designed to target this range. The key parameter that needs to be met in the final filter design is the DC voltage drop that will be seen between the VCC supply and the VCCA pin of the MPC958. From the data sheet the IVCCA current (the current sourced through the VCCA pin) is typically 15mA (20mA maximum), assuming that a minimum of 3.0V must be maintained on the VCCA pin very little DC voltage drop can be tolerated when a 3.3V VCC supply is used. The resistor shown in Figure 3 must have a resistance of 10-15 to meet the voltage drop criteria. The RC filter pictured will provide a broadband filter with approximately 100:1 attenuation for noise whose spectral content is above 20KHz. As the noise frequency crosses the series resonant point of an individual capacitor it's overall impedance begins to look inductive and thus increases with increasing frequency. The parallel capacitor combination shown ensures that a low impedance path to ground exists for frequencies well above the bandwidth of the PLL. It is recommended that the user start with an 8-10 resistor to avoid potential VCC drop problems and only move to the higher value resistors when a higher level of attenuation is shown to be needed. be applications in which overall performance is being degraded due to system power supply noise. The power supply filter schemes discussed in this section should be adequate to eliminate power supply noise related problems in most designs. Driving Transmission Lines The MPC958 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 approximately 20 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). 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 50 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 MPC958 clock driver. For the series terminated case however there is no DC current draw, thus the outputs can drive multiple series terminated lines. Figure 4 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 MPC958 clock driver is effectively doubled due to its capability to drive multiple lines.
MPC958 OUTPUT BUFFER IN
14
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RS = 36
ZO = 50 OutA
MPC958 OUTPUT BUFFER IN
14
RS = 36
ZO = 50 OutB0
3.3V ZO = 50
RS=5-15 VCCA 22F MPC958 VCC 0.01F 0.01F
RS = 36
OutB1
Figure 4. Single versus Dual Transmission Lines The waveform plots of Figure 5 show the simulation results of an output driving a single line vs two lines. In both cases the drive capability of the MPC958 output buffers is more than sufficient to drive 50 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 MPC958. The output waveform in Figure 5 shows a step in the waveform, this step is caused
Figure 3. Power Supply Filter Although the MPC958 has several design features to minimize the susceptibility to power supply noise (isolated power and grounds and fully differential PLL) there still may
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TIMING SOLUTIONS
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MPC958
by the impedance mismatch seen looking into the driver. The parallel combination of the 43 series resistor plus the output impedance does not match the parallel combination of the line impedances. The voltage wave launched down the two lines will equal: VL = VS ( Zo / (Rs + Ro +Zo)) Zo = 50 || 50 Rs = 36 || 36 Ro = 14 VL = 3.0 (25 / (18 + 14 + 25) = 3.0 (25 / 57) = 1.31V At the load end the voltage will double, due to the near unity reflection coefficient, to 2.62V. It will then increment towards the quiescent 3.0V in steps separated by one round trip delay (in this case 4.0ns). 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 6 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.
MPC958 OUTPUT BUFFER
14
RS = 22
ZO = 50
RS = 22
ZO = 50
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3.0 OutA tD = 3.8956 OutB tD = 3.9386
2.5
14 + 22 k 22 = 50 k 50 25 = 25 Figure 6. Optimized Dual Line Termination
VOLTAGE (V)
2.0 In 1.5
1.0
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.
0.5
0 2 4 6 8 TIME (nS) 10 12 14
Figure 5. Single versus Dual Waveforms
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MOTOROLA
Freescale Semiconductor, Inc.
MPC958
OUTLINE DIMENSIONS
FA SUFFIX LQFP PACKAGE CASE 873A-02 ISSUE A
A A1
32 25 4X
0.20 (0.008) AB T-U Z
1
-T- B
-U- V P AE
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B1
8
DETAIL Y
17
V1 AE DETAIL Y
9
-Z- 9 S1 S
4X
0.20 (0.008) AC T-U Z
G -AB-
SEATING PLANE
DETAIL AD
-AC-
BASE METAL
F
8X
M_ R
CE
SECTION AE-AE
X DETAIL AD
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GAUGE PLANE
0.250 (0.010)
H
W
K
Q_
EE EE EE EE
N
D
0.20 (0.008)
M
AC T-U Z
0.10 (0.004) AC
NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DATUM PLANE -AB- 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 -T-, -U-, AND -Z- TO BE DETERMINED AT DATUM PLANE -AB-. 5. DIMENSIONS S AND V TO BE DETERMINED AT SEATING PLANE -AC-. 6. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. ALLOWABLE PROTRUSION IS 0.250 (0.010) PER SIDE. DIMENSIONS A AND B DO INCLUDE MOLD MISMATCH AND ARE DETERMINED AT DATUM PLANE -AB-. 7. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. DAMBAR PROTRUSION SHALL NOT CAUSE THE D DIMENSION TO EXCEED 0.520 (0.020). 8. MINIMUM SOLDER PLATE THICKNESS SHALL BE 0.0076 (0.0003). 9. EXACT SHAPE OF EACH CORNER MAY VARY FROM DEPICTION. MILLIMETERS MIN MAX 7.000 BSC 3.500 BSC 7.000 BSC 3.500 BSC 1.400 1.600 0.300 0.450 1.350 1.450 0.300 0.400 0.800 BSC 0.050 0.150 0.090 0.200 0.500 0.700 12_ REF 0.090 0.160 0.400 BSC 1_ 5_ 0.150 0.250 9.000 BSC 4.500 BSC 9.000 BSC 4.500 BSC 0.200 REF 1.000 REF INCHES MIN MAX 0.276 BSC 0.138 BSC 0.276 BSC 0.138 BSC 0.055 0.063 0.012 0.018 0.053 0.057 0.012 0.016 0.031 BSC 0.002 0.006 0.004 0.008 0.020 0.028 12_ REF 0.004 0.006 0.016 BSC 1_ 5_ 0.006 0.010 0.354 BSC 0.177 BSC 0.354 BSC 0.177 BSC 0.008 REF 0.039 REF
J
DIM A A1 B B1 C D E F G H J K M N P Q R S S1 V V1 W X
TIMING SOLUTIONS
-T-, -U-, -Z-
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MPC958
NOTES
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MOTOROLA
Freescale Semiconductor, Inc.
MPC958
Freescale Semiconductor, Inc...
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