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IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
PROGRAMMABLE CLOCK GENERATOR
IDT5V925
* * * * * * *
FEATURES:
DESCRIPTION:
* * * *
3V to 3.6V operating voltage 3.125 MHz to 160MHz output frequency range 4 programmable frequency outputs Input from fundamental crystal oscillator or external source Balanced Drive Outputs 12mA PLL disable mode for low frequency testing Select inputs (S[1:0]) for divide selection (multiply ratio of 2, 3, 4, 5, 6, 7, and 8) 5V tolerant inputs Low output skew/jitter External PLL feedback, internal loop filter Available in 16-pin QSOP package
APPLICATIONS:
* * * * * Ethernet/fast ethernet Router Network switches SAN Instrumentation
The IDT5V925 is a high-performance, low skew, low jitter phase-locked loop (PLL) clock driver. It provides precise phase and frequency alignment of its clock outputs to an externally applied clock input or internal crystal oscillator. The IDT5V925 has been specially designed to interface with Gigabit Ethernet and Fast Ethernet applications by providing a 125MHz clock from 25MHz input. It can also be programmed to provide output frequencies ranging from 3.125MHz to 160MHz with input frequencies ranging from 3.125MHz to 80MHz. The IDT5V925 includes an internal RC filter that provides excellent jitter characteristics and eliminates the need for external components. When using the optional crystal input, the chip accepts a 10-30MHz fundamental mode crystal with a maximum equivalent series resistance of 50. The onchip crystal oscillator includes the feedback resistor and crystal capacitors (nominal load capacitance is 15pF).
FUNCTIONAL BLOCK DIAGRAM
S0 S1
SE LEC T M OD E FB C LKIN PH ASE DETEC TO R LOO P FILTER VC O 0
1
VC O DIVIDE 1/N
Q /N
X2
X1 OPTION AL C RYSTAL XTAL OSC
Q0
Q1
Q2
OE
The IDT logo is a registered trademark of Integrated Device Technology, Inc.
INDUSTRIAL TEMPERATURE RANGE
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c 2002 Integrated Device Technology, Inc.
SEPTEMBER 2002
DSC-5943/1
IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS(1)
Symbol VTERM Description Supply Voltage to Ground DC Output Voltage VOUT DC Input Voltage VIN TA = 85C TSTG Maximum Power Dissipation Storage Temperature Max -0.5 to +7 -0.5 to VCC +0.5 -0.5 to +7 .55 -65 to +150 Unit V V V W C
S1 S0 GNDQ VDDQ X1 X2 CLKIN FB
1 2 3 4 5 6 7 8
QSOP TOP VIEW
1 6 1 5 1 4 1 3 1 2 1 1 1 0 9
VDD GND Q2 Q1 Q0 Q/N GND OE
NOTE: 1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
PIN DESCRIPTION
Pin Names CLKIN X1 (1) I/O I I O I Description Input clock Crystal oscillator input. Connected to GND if oscillator not required. Crystal oscillator output. Leave unconnected for clock input. PLL feedback input which should be connected to Q/N output pin only. PLL locks onto positive edge of FB signal. Three level divider/mode select pins. Float to MID. Output at N*CLKIN frequency Programmable divide-by-N clock output Tri-state output enable. When asserted HIGH, clock outputs are high impedance. Power supply for output buffers Ground supply for output buffers Power supply for PLL Ground supply for PLL
CRYSTAL SPECIFICATION
The crystal oscillators should be fundamental mode quartz crystals: overtone crystals are not suitable. Crystal frequency should be specified for parallel resonance with 50 maximum equivalent series resonance.
X2 (1) FB
S[1:0] Q[2:0] Q/N OE VDD GND VDDQ GNDQ
I O O I PWR PWR PWR PWR
FUNCTION TABLE
Output Used for Feedback Q/N Allowable CLKIN Range (MHz)(1,2) Minimum 25/N Maximum 160/N
NOTE: 1. For best accuracy, use parallel resonant crystal specified for a load capacitance of 15pF.
Output Frequency Relationships Q/N CLKIN Q[2:0] CLKIN x N
NOTES: 1. Operation in the specified CLKIN frequency range guarantees that the VCO will operate in the optimal range of 25MHz to 160MHz. Operation with CLKIN outside specified frequency ranges may result in invalid or out-of-lock outputs. 2. Q[2:0] is not allowed to be used as feedback.
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IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
DIVIDE SELECTION TABLE (1)
S1 L L L M M M H H H S0 L M H L M H L M H 2 3 4 5(3) 6 7 8 16 Divide-by-N Value FACTORY TEST (2) PLL PLL PLL PLL PLL PLL PLL TEST(4) Mode
NOTES: 1. H = HIGH M = MEDIUM L = LOW 2. Factory Test Mode: operation not specified, 3. Ethernet mode (use a 25MHz input frequency and Q/N as feedback). 4. Test mode for low frequency testing. In this mode, CLKIN bypasses the VCO (VCO powered down). Frequency must be > 1MHz due to dynamic circuits in the frequency dividers. Q[2:0] outputs are divided by 2 in test mode.
OPERATING CONDITIONS
Symbol VDD/VDDQ TA CL CIN Description Power Supply Voltage Operating Temperature Output Load Capacitance Input Capacitance, CLKIN, FB, OE, F = 1MHz, VIN = 0V, TA = 25C Min. 3 -40 -- -- Typ. 3.3 +25 -- 5 Max. 3.6 +85 15 7 Unit V C pF pF
DC ELECTRICAL CHARACTERISTICS OVER OPERATING RANGE
Following Conditions Apply Unless Otherwise Specified: Industrial: TA = -40C to +85C, VCC = 3.3V 0.3V
Symbol VIL VIH VIHH(1) VIMM(1) VILL(1) IIN Parameter Input LOW Voltage Input HIGH Voltage Input HIGH Voltage Input MID Voltage Input LOW Voltage Input Leakage Current (CLKIN, FB Inputs only) 3-Level Input DC Current, S[1:0] Input HIGH Current Output LOW Voltage Output HIGH Voltage Test Conditions Min. -- 2 VDD - 0.6 VDD/2 - 0.3 -- -5 -- - 50 - 200 -5 -- 2.4 Typ.(7) -- -- -- -- -- -- -- -- -- 0.07 0.15 2.8 Max 0.8 -- -- VDD/2 + 0.3 0.6 +5 +200 +50 -- +5 0.55 -- Unit V V V V V A
3-level input only 3-level input only 3-level input only VIN = VDD or GND, VDD = Max VIN = VDD VIN = VDD/2 VIN = GND VIN = VDD IOL = 12mA IOH = -12mA HIGH Level MID Level LOW Level
I3 IIH VOL VOH
A A V V
NOTE: 1. These inputs are normally wired to VCC, GND, or unconnected. If the inputs are switched in real time, the function and timing of the outputs may glitch, and the PLL may require an additional lock time before all the datasheet limits are achieved.
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IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
POWER SUPPLY CHARACTERISTICS
Symbol IDDQ Parameter Quiescent Supply Current Test Conditions (1) VDD = Max. CLKIN = FB = X1 = GND S[1:0] = HH OE = H All outputs unloaded IDD IDD Supply Current per Input Dynamic Supply Current VDD = Max., VIN = 3V VDD = 3.6V S[1:0] =LM OE = GND FOUT = 60MHz All outputs unloaded
NOTE: 1. For conditions shown as Min. or Max., use the appropriate values specified under DC Electrical Characteristics.
Min. --
Typ. 0.7
Max 2
Unit mA
-- --
1 77
30 130
A mA
AC ELECTRICAL CHARACTERISTICS OVER OPERATING RANGE
Following Conditions Apply Unless Otherwise Specified: Industrial: TA = -40C to +85C, VCC = 3.3V 0.3V
Symbol tR, tF dT tPD tSK tJ fOUT Parameter Rise Time, Fall Time (1) Output/Duty Cycle (1) CLKIN to FB
(1)
Test Conditions 0.8V to 2V VT = VDD/2 VT = VDD/2 VT = VDD/2; Q[2:0] VT = VDD/2; Q/N - Q[2:0]
Min. -- 45 - 300 -- -- -- 25
Typ. 0.7 -- -- -- -- -- --
Max. 1.5 55 300 100 300 200 160
Unit ns % ps ps ps MHz
Output to Output Skew (1) Cycle - Cycle Jitter (1) Output Frequency
NOTE: 1. This parameter is guaranteed by design but not tested.
INPUT TIMING REQUIREMENTS
Symbol tR, tF DH fOSC fIN Description Maximum Input Rise and Fall Time, 0.8V to 2V Input Duty Cycle (1) XTAL Oscillator Frequency Input Frequency
(1)
Min. -- 25 -- 25/N
Max. 2 75 30 160/N
Unit ns % MHz MHz
NOTE: 1. This parameter is guaranteed by design but not tested.
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IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
TEST LOADS AND WAVEFORMS
3V
V CC
2V VTH = V C C /2
150
0.8 0V
OUTPUT
1ns
1ns
Input Test Waveform
15pF 150
VCC 2V
AC Test Load
VTH = V C C /2 0.8 0V
tR
tF
Output Waveform HOW TO USE THE 5V925 The 5V925 is a general-purpose phase-locked loop (PLL) that can be used as a zero delay buffer or a clock multiplier. It generates three outputs at the VCO frequency and one output at the VCO frequency divided by n, where n is determined by the Mode/Frequency Select input pins S0 and S1. The PLL will adjust the VCO frequency (within the limits of the Function Table) to ensure that the input frequency equals the Q/N frequency. The 5V925 can accept two types of input signal. The first is a reference clock generated by another device on the board which needs to be reproduced with a minimal delay between the incoming clock and output. The second is an external crystal. When used in the first mode, the crystal input (X1) should be tied to ground and the crystal output (X2) should be left unconnected. By connecting Q/N to FB (see Figure 1), the 5V925 not only becomes a zero delay buffer, but also a clock multiplier. With proper selection of S0 and S1, the Q0-Q2 outputs will generate two, three, up to eight times the input clock frequency. Make sure that the input and output frequency specifications are not violated (refer to Function Table). There are some applications where higher fan-out is required. These kinds of applications could be addressed by using the 5V925 in conjunction with a clock buffer such as the 49FCT3805. Figure 2 shows how higher fan-out with different clock rates can be generated.
FB Q /N CLKIN X2 X1 5V925 Q0 Q1 Q2
FB Q/N C LKIN 5V925 X2 X1 Q[2:0]
INA
5 C O PIES OF Q /N
49FC T3805 5 C O PIES OF Q
INB
S0
S1
S0
S1
Figure 1 5
Figure 2
IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
By connecting one of the 49FCT3505 outputs to the FB input of the 5V925 , the propagation delay from CLKIN to the output of the 49FCT3505 will be nearly zero. To ensure PLL stability, only one 49FCT3505 should be included between Q/N and FB.
The second way to drive the input of the 5V925 is via an external crystal. When connecting an external crystal to pins 5 and 6, the X2 pin must be shorted to the CLKIN (pin 7) as shown in Figure 3. For best accuracy, a parallel resonant crystal with a crystal load capacitance rating of 15pF should be used. To reduce the parasitic between the external crystal and the 5V925 , it is recommended to connect the crystal as close as possible to the X1 and X2 pins.
FB CLKIN X2
5V925
Q /N Q0
XTAL OSC
Q1 Q2
X1
S0
S1
Figure 3
One of the questions often asked is what is the accuracy of our clock generators? In applications where clock synthesizers are used, the terms frequency accuracy and frequency error are used interchangeably. Here, frequency accuracy (or error) is based on two factors. One is the input frequency and the other is the multiplication factor. Clock multipliers (or synthesizers) are governed by the equation: Output Frequency = (M)* Input Frequency N where "M" is the feedback divide and "N" is the reference divide. If the ratio of M/N is not an integer, then the output frequency will not be an exact multiple of the input. On the other hand, if the ratio were a whole number, the output clock would be an exact multiple of the input. In the case of 5V925, since the reference divide ("N") is "1", the equation is a strong function of the feedback divide ("M"). In addition, since the feedback is an integer, the
output frequency error (or accuracy) is merely a function of how accurate the input is. For instance, 5V925 could accept two forms of input, one from a crystal oscillator (see Figure 1) and the other from a crystal (see Figure 3). By using a 20MHz clock with a multiplication factor of 5 (with an accuracy of 30 parts per million), one can easily have three copies of 100MHz of clock with 30PPM of accuracy. Frequency accuracy is defined by the following equation: Accuracy = (Measured Freq. - Nominal Freq.) Nominal Frequency where measured frequency is the average frequency over certain number of cycles (typically 10,000) and the nominal frequency is the desired frequency.
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IDT5V925 PROGRAMMABLE CLOCK GENERATOR
INDUSTRIAL TEMPERATURE RANGE
ORDERING INFORMATION
IDT XXXX Device Type X Package X Process
I Q 5V925
-40C to +85C (Industrial) Quarter Size Outline Package (150 mil.) Programmable Clock Generator
CORPORATE HEADQUARTERS 2975 Stender Way Santa Clara, CA 95054
for SALES: 800-345-7015 or 408-727-6116 fax: 408-492-8674 www.idt.com
for Tech Support: logichelp@idt.com (408) 654-6459
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