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Integrated Circuit Systems, Inc.
ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
FEATURES
* Dual differential 3.3V LVPECL outputs * Selectable crystal oscillator interface or LVCMOS/LVTTL TEST_CLK * Output frequency range: 70MHz to 680MHz * Crystal input frequency range: 12MHz to 32MHz * VCO range: 560MHz to 680MHz * Parallel or serial interface for programming feedback and output dividers * Input P_DIV under parallel load control * RMS phase jitter at 156.25MHz (1.875MHz to 20MHz): 0.49ps (typical), P_DIV = /1 * 3.3V supply voltage * 0C to 70C ambient operating temperature * Lead-Free package fully RoHS compliant
GENERAL DESCRIPTION
The ICS843020-01 is a general purpose, dual output Crystal-to-3.3V Differential LVPECL High FreHiPerClockSTM quency Synthesizer and a member of the FemtoClocksTM family of High Performance Clock Solutions from ICS. The ICS843020-01 is based on ICS' 3rd generation VCO technology and is capable of sub1ps RMS Phase Jitter performance, making it ideal for use in 10 Gigabit Ethernet, 10 Gigabit Fibre Channel, SONET and Serial ATA applications.
ICS
The ICS843020-01 is a highly flexible programmable synthesizer capable of generating output frequencies over a range of 70MHz to 680MHz. The output frequency can be programmed in small step sizes as low as 250kHz when using a 16MHz crystal, /8 input divider, and output divider = /8.
BLOCK DIAGRAM
VCO_SEL XTAL_SEL TEST_CLK XTAL_IN OSC XTAL_OUT P_DIV /P 0 /8 Float /1 (default) 1 /4 1 0
PIN ASSIGNMENT
VCO_SEL nP_LOAD XTAL_IN
32 31 30 29 28 27 26 25 M5 M6 M7 M8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
TEST VCC FOUT1 nFOUT1 VCCO FOUT0 nFOUT0 VEE
M4
PLL
PHASE DETECTOR MR /M VCO 0 1 /N /1 /2 /4 /8
N0 N1 P_DIV FOUT0 nFOUT0 FOUT1 nFOUT1 VEE
ICS843020-01
M3
M2
M1
M0
24 23 22 21 20 19 18 17
XTAL_OUT TEST_CLK XTAL_SEL VCCA S_LOAD S_DATA S_CLOCK MR
S_LOAD S_DATA S_CLOCK nP_LOAD M0:M8 N0:N1
CONFIGURATION INTERFACE LOGIC
TEST
32-Lead LQFP 7mm x 7mm x 1.4mm package body Y Package Top View
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Integrated Circuit Systems, Inc.
ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
default state that will automatically occur during power-up. The TEST output is LOW when operating in the parallel input mode. The relation-ship between the VCO frequency, the crystal frequency and the M divider is defined as follows: fVCO = fxtal x M P The M value and the required values of M0 through M8 are shown in Table 3B to program the VCO Frequency Function Table. Valid M values for which the PLL will achieve lock for a 25MHz reference are defined as 23 M 27 (P = /1). The frequency out is defined as follows: FOUT = fVCO = fxtal x M N NxP Serial operation occurs when nP_LOAD is HIGH and S_LOAD is LOW. The shift register is loaded by sampling the S_DATA bits with the rising edge of S_CLOCK. The contents of the shift register are loaded into the M divider and N output divider when S_LOAD transitions from LOW-to-HIGH. The M divide and N output divide values are latched on the HIGH-toLOW transition of S_LOAD. If S_LOAD is held HIGH, data at the S_DATA input is passed directly to the M divider and N output divider on each rising edge of S_CLOCK. The serial mode can be used to program the M and N bits and test bits T1 and T0. The internal registers T0 and T1 determine the state of the TEST output as follows: T1 0 0 1 1 T0 0 1 0 1 TEST Output LOW S_Data, Shift Register Input Output of M divider CMOS Fout
FUNCTIONAL DESCRIPTION
NOTE: The functional description that follows describes operation using a 25MHz crystal. Valid PLL loop divider values for different crystal or input frequencies are defined in the Input Frequency Characteristics, Table 5, NOTE 1.
The ICS843020-01 features a fully integrated PLL and therefore requires no external components for setting the loop bandwidth. A fundamental crystal is used as the input to the onchip oscillator. The output of the oscillator is fed into the phase detector. A 25MHz crystal provides a 25MHz phase detector reference frequency. The VCO of the PLL operates over a range of 560MHz to 680MHz. The output of the M divider is also applied to the phase detector. The phase detector and the M divider force the VCO output frequency to be M times the reference frequency by adjusting the VCO control voltage. Note that for some values of M (either too high or too low), the PLL will not achieve lock. The output of the VCO is scaled by a divider prior to being sent to each of the LVPECL output buffers. The divider provides a 50% output duty cycle. The ICS843020-01 supports either serial or parallel programming modes to program the M feedback divider and N output divider. The input divider P can only be changed using the P_DIV pin. It cannot be changed from the default /1 setting using the serial interface. Figure 1 shows the timing diagram for each mode. In parallel mode, the nP_LOAD input is initially LOW. The data on inputs M0 through M8 and N0 and N1 is passed directly to the M divider and N output divider. On the LOW-to-HIGH transition of the nP_LOAD input, the data is latched and the M divider remains loaded until the next LOW transition on nP_LOAD or until a serial event occurs. As a result, the M and N bits can be hardwired to set the M divider and N output divider to a specific
SERIAL LOADING
S_CLOCK
S_DATA
T1
T0
*NULL
N1
N0
M8
M7
M6
M5
M4
M3
M2
M1
M0
t
S_LOAD
S
t
H
nP_LOAD
t
S
PARALLEL LOADING
M0:M8, N0:N1, P_DIV
M, N, P
nP_LOAD
t
S
t
H
Time
FIGURE 1. PARALLEL & SERIAL LOAD OPERATIONS
*NOTE: The NULL timing slot must be observed.
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
Type Input Input Input Input Power Output Power Output Power Output Pullup M divider inputs. Data latched on LOW-to-HIGH transition of Pulldown nP_LOAD input. LVCMOS / LVTTL interface levels. Pulldown Determines output divider value as defined in Table 3C, Function Table. LVCMOS / LVTTL interface levels. Description
TABLE 1. PIN DESCRIPTIONS
Number 1 2, 3, 4, 28, 29, 30, 31, 32 5, 6 7 8 , 16 9 10 11, 12 13 14, 15 Name M5 M6, M7, M8, M0, M1, M2, M3, M4 N0, N1 P_DIV VEE TEST VCC FOUT1, nFOUT1 VCCO FOUT0, nFOUT0
Pullup/ Input divide select. 0 = /8, Float = /1 (default), 1 = /4. Pulldown Negative supply pins. Test output which is ACTIVE in the serial mode of operation. Output driven LOW in parallel mode. LVCMOS/LVTTL interface levels. Core supply pin. Differential output for the synthesizer. LVPECL interface levels. Output supply pin. Differential output for the synthesizer. LVPECL interface levels. Active High Master Reset. When logic HIGH, forces the internal dividers are reset causing the true outputs FOUTx to go low and the inver ted outputs nFOUTx to go high. When logic LOW, the internal dividers and the outputs are enabled. Asser tion of MR does not affect loaded M, N, and T values. LVCMOS / LVTTL interface levels. Clocks in serial data present at S_DATA input into the shift register on the rising edge of S_CLOCK. LVCMOS/LVTTL interface levels. Shift register serial input. Data sampled on the rising edge of S_CLOCK. LVCMOS/LVTTL interface levels. Controls transition of data from shift register into the dividers. LVCMOS / LVTTL interface levels. Analog supply pin. Selects between cr ystal or test inputs as the PLL reference source. Selects XTAL inputs when HIGH. Selects TEST_CLK when LOW. LVCMOS / LVTTL interface levels. Test clock input. LVCMOS / LVTTL interface levels. Crystal oscillator interface. XTAL_IN is the input. XTAL_OUT is the output. Parallel load input. Determines when data present at M8:M0 is loaded into M divider, and when data present at N1:N0 sets the N output divider value. LVCMOS / LVTTL interface levels. Determines whether synthesizer is in PLL or bypass mode. LVCMOS / LVTTL interface levels.
17
MR
Input
Pulldown
18 19 20 21 22 23 24, 25 26 27
S_CLOCK S_DATA S_LOAD VCCA XTAL_SEL TEST_CLK XTAL_OUT, XTAL_IN nP_LOAD VCO_SEL
Input Input Input Power Input Input Input Input Input
Pulldown Pulldown Pulldown
Pullup Pulldown
Pulldown Pullup
NOTE: Pullup and Pulldown refer to internal input resistors. See Table 2, Pin Characteristics, for typical values.
TABLE 2. PIN CHARACTERISTICS
Symbol CIN RPULLUP RPULLDOWN Parameter Input Capacitance Input Pullup Resistor Input Pulldown Resistor Test Conditions Minimum Typical 4 51 51 Maximum Units pF k k
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
TABLE 3A. PARALLEL
AND
SERIAL MODE FUNCTION TABLE
Inputs Conditions S_DATA X X X Data Data Data X Data Reset. Forces outputs LOW. Data on M and N inputs passed directly to the M divider and N output divider. TEST output forced LOW. Data is latched into input registers and remains loaded until next LOW transition or until a serial event occurs. Serial input mode. Shift register is loaded with data on S_DATA on each rising edge of S_CLOCK. Contents of the shift register are passed to the M divider and N output divider. M divider and N output divider values are latched. Parallel or serial input do not affect shift registers. S_DATA passed directly to M divider as it is clocked. X X L L L H X X X L L X
MR H L L L L L L L
nP_LOAD X L H H H H H
M X Data Data X X X X X
N X Data Data X X X X X
S_LOAD S_CLOCK
NOTE: L = LOW H = HIGH X = Don't care = Rising edge transition = Falling edge transition
TABLE 3B. PROGRAMMABLE VCO FREQUENCY FUNCTION TABLE
VCO Frequency (MHz) 575 * 600 * M Divide 23 * 24 * 256 M8 0 * 0 * 128 M7 0 * 0 * 64 M6 0 * 0 *
WITH
P = /1 (P_DIV = FLOAT)
32 M5 0 * 0 * 16 M4 1 * 1 * 8 M3 0 * 1 * 4 M2 1 * 0 * 2 M1 1 * 0 * 1 M0 1 * 0 * 1
675 27 0 0 0 0 1 1 0 1 NOTE 1: These M divide values and the resulting frequencies correspond to crystal or TEST_CLK input frequency of 25MHz.
TABLE 3C. PROGRAMMABLE VCO FREQUENCY FUNCTION TABLE
VCO Frequency (MHz) 575 * 600 * M Divide 92 * 96 * 256 M8 0 * 0 * 128 M7 0 * 0 * 64 M6 1 * 1 *
WITH
P = /4 (P_DIV = 1)
32 M5 0 * 1 * 16 M4 1 * 0 * 8 M3 1 * 0 * 4 M2 1 * 0 * 2 M1 0 * 0 * 1 M0 0 * 0 * 0
675 108 0 0 1 1 0 1 1 0 NOTE 1: These M divide values and the resulting frequencies correspond to crystal or TEST_CLK input frequency of 25MHz.
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
WITH
TABLE 3D. PROGRAMMABLE VCO FREQUENCY FUNCTION TABLE
VCO Frequency (MHz) 575 * 600 * M Divide 184 * 192 * 256 M8 0 * 0 * 128 M7 1 * 1 * 64 M6 0 * 1 *
P = /8 (P_DIV = 0)
32 M5 1 * 0 * 16 M4 1 * 0 * 8 M3 1 * 0 * 4 M2 0 * 0 * 2 M1 0 * 0 * 1 M0 0 * 0 * 0
675 216 0 1 1 0 0 1 1 1 NOTE 1: These M divide values and the resulting frequencies correspond to crystal or TEST_CLK input frequency of 25MHz.
TABLE 3E. PROGRAMMABLE OUTPUT DIVIDER FUNCTION TABLE
Inputs N1 0 0 1 1 N0 0 1 0 1 N Divider Value 1 2 4 8 Output Frequency (MHz) Minimum 560 280 140 70 Maximum 680 340 17 0 85
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
4.6V -0.5V to VCC + 0.5 V -0.5V to VDDO + 0.5V 50mA 100mA 47.9C/W (0 lfpm) -65C to 150C NOTE: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These ratings are stress specifications only. Functional operation of product at these conditions or any conditions beyond those listed in the DC Characteristics or AC Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods may affect product reliability.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC Inputs, VI Outputs, VO (LVCMOS) Outputs, IO (LVPECL) Continuous Current Surge Current Package Thermal Impedance, JA Storage Temperature, TSTG
TABLE 4A. POWER SUPPLY DC CHARACTERISTICS, VCC = VCCA = VCCO = 3.3V5%, TA = 0C TO 70C
Symbol VCC VCCA VCCO IEE ICCA ICCO Parameter Core Supply Voltage Analog Supply Voltage Output Supply Voltage Power Supply Current Analog Supply Current Output Supply Current Test Conditions Minimum 3.135 3.135 3.135 Typical 3.3 3.3 3.3 Maximum 3.465 3.465 3.465 180 13 14 Units V V V mA mA mA
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
Test Conditions Minimum 2 VCC - 0.4 -0.3 0.8 VCC + 0.4 VCC/2 - 0.1 VCC = VIN = 3.465V VCC = VIN = 3.465V VCC = 3.465V, VIN = 0V VCC = 3.465V, VIN = 0V -5 VCC/2 + 0.1 150 5 Typical Maximum VCC + 0.3 Units V V V V V A A A
TABLE 4B. LVCMOS / LVTTL DC CHARACTERISTICS, VCC = VCCA = VCCO = 3.3V5%, TA = 0C TO 70C
Symbol Parameter Input High Voltage VCO_SEL, XTAL_SEL, MR, S_LOAD, nP_LOAD, S_DATA, S_CLOCK, TEST_CLK, M0:M8, N0:N1 P_DIV VCO_SEL, XTAL_SEL, MR, S_LOAD, nP_LOAD, S_DATA, S_CLOCK, TEST_CLK, M0:M8, N0:N1 P_DIV P_DIV M0-M4, M6-M8, N0, N1, MR, S_CLOCK, TEST_CLK, P_DIV S_DATA, S_LOAD, nP_LOAD M5, XTAL_SEL, VCO_SEL M0-M4, M6-M8, N0, N1, MR, S_CLOCK, TEST_CLK, S_DATA, S_LOAD, nP_LOAD M5, P_DIV, XTAL_SEL, VCO_SEL, TEST; NOTE 1 TEST; NOTE 1
VIH
VIL
Input Low Voltage Input Mid Voltage Input High Current
VIM
IIH
IIL
Input Low Current
-150 2.6 0.5
A V V
VOH VOL
Output High Voltage Output Low Voltage
NOTE 1: Outputs terminated with 50 to VCCO/2.
TABLE 4C. LVPECL DC CHARACTERISTICS, VCC = VCCA = VCCO = 3.3V5%, TA = 0C TO 70C
Symbol VOH VOL Parameter Output High Voltage; NOTE 1 Output Low Voltage; NOTE 1 Test Conditions Minimum VCCO - 1.4 VCCO - 2.0 Typical Maximum VCCO - 0.9 VCCO - 1.7 1.0 Units V V V
VSWING Peak-to-Peak Output Voltage Swing 0.6 NOTE 1: Outputs terminated with 50 to VCCO - 2V. See "Parameter Measurement Information" section, "3.3V Output Load Test Circuit".
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
Test Conditions Minimum Typical Maximum Units
TABLE 5. INPUT FREQUENCY CHARACTERISTICS, VCC = VCCA = VCCO = 3.3V5%, TA = 0C TO 70C
Symbol Parameter
TEST_CLK; NOTE 1 12 32 MHz XTAL_IN, XTAL_OUT; Input Frequency 12 32 MHz fIN NOTE 1 S_CLOCK 32 MHz e set for the VCO to operate within the NOTE 1: For the input crystal and TEST_CLK frequency range, the M value must b 560MHz to 680MHz range. Using the minimum input frequency of 12MHz, valid values of M are 47 M 57, with input divider P = /1 (P_DIV = Float). Using the maximum frequency of 32MHz, valid values of M are 18 M 21.
TABLE 6. CRYSTAL CHARACTERISTICS
Parameter Mode of Oscillation Frequency Equivalent Series Resistance (ESR) Shunt Capacitance Drive Level 12 Test Conditions Minimum Typical Maximum 32 50 7 1 Units MHz pF mW
Fundamental
TABLE 7. AC CHARACTERISTICS, VCC = VCCA = VCCO = 3.3V5%, TA = 0C TO 70C
Symbol Parameter FOUT Output Frequency RMS Phase Jitter, (Random); NOTE 1, 4 Output Skew; NOTE 2, 3 Output Rise/Fall Time M, N to nP_LOAD tS Setup Time S_DATA to S_CLOCK S_CLOCK to S_LOAD M, N to nP_LOAD tH odc Hold Time S_DATA to S_CLOCK S_CLOCK to S_LOAD Output Duty Cycle Test Conditions 156.25MHz (1.875MHz to 20MHz) 20% to 80% 175 5 5 5 5 5 5 47 53 1 Minimum 70 0.49 10 800 Typical Maximum 680 Units MHz ps ps ps ns ns ns ns ns ns % ms
tjit(O) tsk(o)
tR / tF
PLL Lock Time tLOCK See Parameter Measurement Information section. NOTE 1: Please refer to the Phase Noise Plot. NOTE 2: Defined as skew between outputs at the same supply voltage and with equal load conditions. Measured at the output differential cross points. NOTE 3: This parameter is defined in accordance with JEDEC Standard 65. NOTE 4: Tested with P_DIV = VCC/2.
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
TYPICAL PHASE NOISE AT 156.25MHZ
-10 -20 -30 -40 -50
Filter 156.25MHz
RMS Phase Jitter (Random) 1.875MHz to 20MHz = 0.49ps (typical)
0
NOISE POWER dBc Hz
-60 -70 -80 -90 -100 -110 -120 -130 -140
Raw Phase Noise Data
100 1k 10k
-150 -160 -170 -180 -190
Phase Noise Result by adding a Filter to raw data
100k
1M
10M
100M
OFFSET FREQUENCY (HZ)
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
PARAMETER MEASUREMENT INFORMATION
2V
V CC , VCCA, VCCO
Qx
SCOPE
nFOUTx FOUTx nFOUTy FOUTy
LVPECL
nQx
VEE
tsk(o)
-1.3V 0.165V
3.3V OUTPUT LOAD AC TEST CIRCUIT
OUTPUT SKEW
Phase Noise Plot
Noise Power
nFOUTx FOUTx
Pulse Width t
Phase Noise Mask
PERIOD
odc =
f1 Offset Frequency f2
t PW t PERIOD
RMS Jitter = Area Under the Masked Phase Noise Plot
PHASE JITTER
OUTPUT DUTY CYCLE/PULSE WIDTH/PERIOD
80% Clock Outputs
80% VSW I N G
20% tR tF
20%
OUTPUT RISE/FALL TIME
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER APPLICATION INFORMATION
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins are vulnerable to random noise. The ICS843020-01 provides separate power supplies to isolate any high switching noise from the outputs to the internal PLL. VCC, VCCA, and VCCO should be individually connected to the power supply plane through vias, and bypass capacitors should be used for each pin. To achieve optimum jitter performance, power supply isolation is required. Figure 2 illustrates how a 10 resistor along with a 10F and a .01F bypass capacitor should be connected to each VCCA pin.
3.3V VCC .01F V CCA .01F 10F 10
FIGURE 2. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
A crystal can be characterized for either series or parallel mode operation. The ICS843020-01 has a built-in crystal oscillator circuit. This interface can accept either a series or parallel crystal without additional components and generate frequencies with accuracy suitable for most applications. Additional accuracy can be achieved by adding two small capacitors C1 and C2 as shown in Figure 3.
XTAL_OUT C1 18p X1 18pF Parallel Crystal XTAL_IN C2 22p
Figure 3. CRYSTAL INPUt INTERFACE
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
drive 50 transmission lines. Matched impedance techniques should be used to maximize operating frequency and minimize signal distortion. Figures 4A and 4B show two different layouts which are recommended only as guidelines. Other suitable clock layouts may exist and it would be recommended that the board designers simulate to guarantee compatibility across all printed circuit and clock component process variations.
TERMINATION
FOR
LVPECL OUTPUTS
The clock layout topology shown below is a typical termination for LVPECL outputs. The two different layouts mentioned are recommended only as guidelines. FOUT and nFOUT are low impedance follower outputs that generate ECL/LVPECL compatible outputs. Therefore, terminating resistors (DC current path to ground) or current sources must be used for functionality. These outputs are designed to
3.3V
Zo = 50
125
FOUT FIN
125
Zo = 50
Zo = 50 50 1 Z ((VOH + VOL) / (VCC - 2)) - 2 o 50 VCC - 2V RTT
FOUT
FIN
Zo = 50 84 84
RTT =
FIGURE 4A. LVPECL OUTPUT TERMINATION
FIGURE 4B. LVPECL OUTPUT TERMINATION
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
line. The layout in the actual system will depend on the selected component types, the density of the components, the density of the traces, and the stack up of the P.C. board.
LAYOUT GUIDELINE
The schematic of the ICS843020-01 layout example used in this layout guideline is shown in Figure 5A. The ICS84302001 recommended PCB board layout for this example is shown in Figure 5B. This layout example is used as a general guide-
C1 X1 32 31 30 29 28 27 26 25
C2
U1 VCC R5 1K 1 2 3 4 5 6 7 8
M4 M3 M2 M1 M0 VCO_SEL nP_LOAD XTAL_I
VCC 24 23 22 21 20 19 18 17 R7 10 VCCA S_LOAD S_DATA S_CLOCK C11 0.01u C16 10u
'1' Float '0'
R6 1K
9 10 11 12 VCC 13 FOUT 14 FOUTN 15 16
ICS843020-01
TEST VCC FOUT1 nFOUT1 VCCO FOUT0 nFOUT0 VEE
M5 M6 M7 M8 N0 N1 P_DIV VEE
XTAL_O T_CLK nXTAL_SEL VCCA S_LOAD S_DATA S_CLOCK MR
REF_IN XTAL_SEL
VCC
Logic Input Pin Examples
VCC
VCC
R1 133 Zo = 50 Ohm TL1
R3 133
Set Logic Input to '1'
RU1 1K
VCC
Set Logic Input to '0'
RU2 Not Install
C14 0.1u C15 0.1u + Zo = 50 Ohm TL2 R2 82.5 R4 82.5 -
To Logic Input pins
RD1 Not Install RD2 1K
To Logic Input pins
FIGURE 5A. SCHEMATIC OF RECOMMENDED LAYOUT
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
* The differential 50 output traces should have the same length. * Avoid sharp angles on the clock trace. Sharp angle turns cause the characteristic impedance to change on the transmission lines. * Keep the clock traces on the same layer. Whenever possible, avoid placing vias on the clock traces. Placement of vias on the traces can affect the trace characteristic impedance and hence degrade signal integrity. * To prevent cross talk, avoid routing other signal traces in parallel with the clock traces. If running parallel traces is unavoidable, allow a separation of at least three trace widths between the differential clock trace and the other signal trace. * Make sure no other signal traces are routed between the clock trace pair. * The matching termination resistors should be located as close to the receiver input pins as possible.
The following component footprints are used in this layout example: All the resistors and capacitors are size 0603.
POWER AND GROUNDING
Place the decoupling capacitors C14 and C15, as close as possible to the power pins. If space allows, placement of the decoupling capacitor on the component side is preferred. This can reduce unwanted inductance between the decoupling capacitor and the power pin caused by the via. Maximize the power and ground pad sizes and number of vias capacitors. This can reduce the inductance between the power and ground planes and the component power and ground pins. The RC filter consisting of R7, C11, and C16 should be placed as close to the VCCA pin as possible.
CLOCK TRACES AND TERMINATION
Poor signal integrity can degrade the system performance or cause system failure. In synchronous high-speed digital systems, the clock signal is less tolerant to poor signal integrity than other signals. Any ringing on the rising or falling edge or excessive ring back can cause system failure. The shape of the trace and the trace delay might be restricted by the available space on the board and the component location. While routing the traces, the clock signal traces should be routed first and should be locked prior to routing other signal traces.
CRYSTAL
The crystal X1 should be located as close as possible to the pins 25 (XTAL_IN) and 24 (XTAL_OUT). The trace length between the X1 and U1 should be kept to a minimum to avoid unwanted parasitic inductance and capacitance. Other signal traces should not be routed near the crystal traces.
X1
C1 C2
GND VCC VIA
U1
PIN 1
C11 C16 VCCA R7
Close to the input pins of the receiver
C14
TL1N
C15
TL1
R1
R2
TL1N
TL1 TL1, TL21N are 50 Ohm traces and equal length
R3
R4
FIGURE 5B. PCB BOARD LAYOUT FOR ICS843020-01
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FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER POWER CONSIDERATIONS
This section provides information on power dissipation and junction temperature for the ICS843020-01. Equations and example calculations are also provided.
1. Power Dissipation. The total power dissipation for the ICS843020-01 is the sum of the core power plus the power dissipated in the load(s). The following is the power dissipation for VCC = 3.3V + 5% = 3.465V, which gives worst case results. NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
* *
Power (core)MAX = VCC_MAX * IEE_MAX = 3.465V * 180mA = 623.7mW Power (outputs)MAX = 30mW/Loaded Output pair If all outputs are loaded, the total power is 2 * 30mW = 60mW
Total Power_MAX (3.465V, with all outputs switching) = 623.7mW + 60mW = 683.7mW
2. Junction Temperature. Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of the device. The maximum recommended junction temperature for HiPerClockSTM devices is 125C.
The equation for Tj is as follows: Tj = JA * Pd_total + TA Tj = Junction Temperature JA = Junction-to-Ambient Thermal Resistance Pd_total = Total Device Power Dissipation (example calculation is in section 1 above) TA = Ambient Temperature In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance JA must be used. Assuming a moderate air flow of 200 linear feet per minute and a multi-layer board, the appropriate value is 42.1C/W per Table 8 below. Therefore, Tj for an ambient temperature of 70C with all outputs switching is: 70C + 0.684W * 42.1C/W = 98.8C. This is well below the limit of 125C. This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow, and the type of board (single layer or multi-layer).
TABLE 8. THERMAL RESISTANCE JA
FOR
32-PIN LQFP, FORCED CONVECTION
JA by Velocity (Linear Feet per Minute)
0
Single-Layer PCB, JEDEC Standard Test Boards Multi-Layer PCB, JEDEC Standard Test Boards 67.8C/W 47.9C/W
200
55.9C/W 42.1C/W
500
50.1C/W 39.4C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
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3. Calculations and Equations.
ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
The purpose of this section is to derive the power dissipated into the load. LVPECL output driver circuit and termination are shown in Figure 6.
VCCO
Q1
VOUT RL 50 VCCO - 2V
FIGURE 6. LVPECL DRIVER CIRCUIT
AND
TERMINATION
To calculate worst case power dissipation into the load, use the following equations which assume a 50 load, and a termination voltage of V - 2V.
CCO
*
For logic high, VOUT = V (V
CCO_MAX
OH_MAX
=V
CCO_MAX
- 0.9V
-V
OH_MAX
) = 0.9V =V - 1.7V
*
For logic low, VOUT = V (V
CCO_MAX
OL_MAX
CCO_MAX
-V
OL_MAX
) = 1.7V
Pd_H is power dissipation when the output drives high. Pd_L is the power dissipation when the output drives low. Pd_H = [(V - (V - 2V))/R ] * (V
L
OH_MAX
CCO_MAX
CCO_MAX
-V
OH_MAX
) = [(2V - (V
CCO_MAX
-V
OH_MAX
))/R ] * (V
L
CCO_MAX
-V
OH_MAX
)=
[(2V - 0.9V)/50) * 0.9V = 19.8mW
Pd_L = [(V
OL_MAX
- (V
CCO_MAX
- 2V))/R ] * (V
L
CCO_MAX
-V
OL_MAX
) = [(2V - (V
CCO_MAX
-V
OL_MAX
))/R ] * (V
L
CCO_MAX
-V
OL_MAX
)=
[(2V - 1.7V)/50) * 1.7V = 10.2mW Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW
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ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER RELIABILITY INFORMATION
TABLE 9. JAVS. AIR FLOW TABLE FOR 32 LEAD LQFP
JA by Velocity (Linear Feet per Minute)
0
Single-Layer PCB, JEDEC Standard Test Boards Multi-Layer PCB, JEDEC Standard Test Boards 67.8C/W 47.9C/W
200
55.9C/W 42.1C/W
500
50.1C/W 39.4C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
TRANSISTOR COUNT
The transistor count for ICS843020-01 is: 5371
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ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
PACKAGE OUTLINE - Y SUFFIX FOR 32 LEAD LQFP
TABLE 10. PACKAGE DIMENSIONS
JEDEC VARIATION ALL DIMENSIONS IN MILLIMETERS BBA SYMBOL N A A1 A2 b c D D1 D2 E E1 E2 e L ccc 0.45 0 --0.05 1.35 0.30 0.09 MINIMUM NOMINAL 32 --1.40 0.37 -9.00 BASIC 7.00 BASIC 5.60 Ref. 9.00 BASIC 7.00 BASIC 5.60 Ref. 0.80 BASIC 0.60 --0.75 7 0.10 1.60 0.15 1.45 0.45 0.20 MAXIMUM
Reference Document: JEDEC Publication 95, MS-026
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ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
Marking ICS843020A01 ICS843020A01 TBD TB D Package 32 Lead LQFP 32 Lead LQFP 32 Lead "Lead-Free" LQFP 32 Lead "Lead-Free" LQFP Shipping Packaging tray 1000 tape & reel tray 1000 tape & reel Temperature 0C to 70C 0C to 70C 0C to 70C 0C to 70C
TABLE 11. ORDERING INFORMATION
Part/Order Number ICS843020AY-01 ICS843020AY-01T ICS843020AY-01LF ICS843020AY-01LFT
NOTE: Par ts that are ordered with an "LF" suffix to the par t number are the Pb-Free configuration and are RoHS compliant.
The aforementioned trademarks, HiPerClockSTM and FemtoClocksTM are a trademark of Integrated Circuit Systems, Inc. or its subsidiaries in the United States and/or other countries. While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems, Incorporated (ICS) assumes no responsibility for either its use or for infringement of any patents or other rights of third parties, which would result from its use. No other circuits, patents, or licenses are implied. This product is intended for use in normal commercial applications. Any other applications such as those requiring extended temperature range, high reliability, or other extraordinary environmental requirements are not recommended without additional processing by ICS. ICS reserves the right to change any circuitry or specifications without notice. ICS does not authorize or warrant any ICS product for use in life support devices or critical medical instruments. 843020AY-01
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ICS843020-01
FEMTOCLOCKSTM 680MHZ, CRYSTAL-TO3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
REVISION HISTORY SHEET Description of Change Features section - changed Cr ystal frequency range bullet from 14MHz to 12MHz. Input Frequency Characteristics Table - changed 14MHz to 12MHz, and changed M values to correspond with the 12MHz change. Cr ystal Characteristics Table - Change Frequency min. from 14MHz to 12MHz. Date
Rev
Table
Page 1 8 8
B
T5 T6
4/14/05
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