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ICS726
12 TO 36 MHZ SOT-23 VCXO
Description
Used in conjunction with an external pullable quartz crystal, this monolithic integrated circuit replaces more costly hybrid (canned) VCXO devices. The ICS726 is designed primarily for data and clock recovery applications such as ADSL modems, set-top box receivers, and telecom systems. The frequency of the on-chip VCXO is adjusted by an external control voltage to the VIN pin. Since VIN is a high impedance input, it can be driven directly from an PWM RC integrator circuit. Frequency output increases with VIN voltage input. The usable range of VIN is 0 to 3.3 V.
Features
* Uses an inexpensive 12 to 36 MHz external crystal * Output frequency range of 12 to 36 MHz * On-chip VCXO with guaranteed pull range of 115
ppm minimum
* VCXO tuning voltage 0 to 3.3 V * Packaged in 6-pin TSOT-23-6 * Available in Pb (lead) free package
Block Diagram
VDD
VIN X1 12-36MHz Pullable Crystal X2 Voltage Controlled Crystal Oscillator
12-36MHz
GND
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ICS726 12 TO 36 MHZ SOT-23 VCXO
Pin Assignment
X2 GND CLK 1 2 3 6 5 4 X1 VI N VDD
T S OT - 2 3 - 6
Pin Descriptions
Pin Number
1 2 3 4 5 6
Pin Name
X2 GND CLK VDD VIN XI
Pin Type
Input Power Output Power Input Input Connect to ground.
Pin Description
Crystal connection. Connect to the external pullable crystal. VCXO CMOS level clock output at the frequency of the crystal. Connect to +3.3 V (0.01uf decoupling capacitor recommended). Voltage input to VCXO -- 0 to 3.3 V analog input which controls the oscillation frequency of the VCXO. Crystal connection. Connect to the external pullable crystal.
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External Component Selection
The ICS726 requires a minimum number of external components for proper operation.
Required Crystal Parameters:
Nominal Frequency as required MHz Initial Accuracy at 25C -20 min/+20 max ppm Temperature Stability -30 min/+30 max ppm Aging, 1st year -5 min/+5 max ppm Aging, 10 years -20 min/+20 max ppm Operating Temp. Range, C 0 min/+25 typ/+70 max or Operating Temp. Range, C -40 min/+25 typ/+85 max Load Capacitance 10 pf Shunt Capacitance, C0 7 pF Max C0/C1 Ratio 270 Max Equivalent Series Resistance 35 Max The third overtone mode of the crystal and all spurs must be >100 ppm distant from the 3x fundamental resonance measured with a physical load of 10 pF. The external crystal must be connected as close to the chip as possible and should be on the same side of the PCB as the ICS726. There should be no vias between the crystal pins and the X1 and X2 device pins. There should be no signal traces underneath or close to the crystal. See application note MAN05.
Decoupling Capacitor
A decoupling capacitor of 0.01F must be connected between VDD (pin 4) and GND (pin 2), as close to these pins as possible. For optimum device performance, the decoupling capacitor should be mounted on the component side of the PCB. Avoid the use of vias in the decoupling circuit.
Series Termination Resistor
When the PCB trace between the clock output (CLK, pin 3) and the load is over 1 inch, series termination should be used. To series terminate a 50 trace (a commonly used trace impedance) place a 33 resistor in series with the clock line, as close to the clock output pin as possible. The nominal impedance of the clock output is 20.
Quartz Crystal
The ICS726 VCXO function consists of the external crystal and the integrated VCXO oscillator circuit. To assure the best system performance (frequency pull range) and reliability, a crystal device with the recommended parameters (shown below) must be used, and the layout guidelines discussed in the following section shown must be followed. The frequency of oscillation of a quartz crystal is determined by its "cut" and by the load capacitors connected to it. The ICS726 incorporates on-chip variable load capacitors that "pull" (change) the frequency of the crystal. The crystal specified for use with the ICS726 is designed to have zero frequency error when the total of on-chip + stray capacitance is 14 pF.
Crystal Tuning Load Capacitors
The crystal traces should include pads for small fixed capacitors, one between X1 and ground, and another between X2 and ground. The need for these capacitors is determined at system prototype evaluation, and is influenced by the particular crystal used (manufacture and frequency) and by PCB layout. The typical required capacitor value is 1 to 4 pF. The procedure for determining the value of these capacitors can be found in application note MAN05.
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ICS726 12 TO 36 MHZ SOT-23 VCXO
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS726. These ratings, which are standard values for ICS commercially rated parts, are stress ratings only. Functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods can affect product reliability. Electrical parameters are guaranteed only over the recommended operating temperature range.
Item
Supply Voltage, VDD All Inputs and Outputs Ambient Operating Temperature Storage Temperature Soldering Temperature 7V
Rating
-0.5 V to VDD+0.5 V 0 to +70C -65 to +150C 260C
Recommended Operating Conditions
Parameter
Ambient Operating Temperature Power Supply Voltage (measured in respect to GND) Reference crystal parameters
Min.
0 +3.15
Typ.
Max.
+70 +3.45
Units
C V
Refer to page 3
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DC Electrical Characteristics
VDD=3.3 V 5% , Ambient temperature 0 to +70C, unless stated otherwise
Parameter
Operating Voltage Output High Voltage Output Low Voltage Output High Voltage (CMOS Level) Operating Supply Current Short Circuit Current VIN, VCXO Control Voltage
Symbol
VDD VOH VOL VOH IDD IOS VIA
Conditions
IOH = -12 mA IOL = 12 mA IOH = -4 mA Output = 12 MHz, no load
Min.
3.15 2.4
Typ.
Max.
3.45 0.4
Units
V V V V
VDD-0.4 5 50 0 3.3
mA mA V
AC Electrical Characteristics
VDD = 3.3 V 5%, Ambient Temperature 0 to +70 C, unless stated otherwise
Parameter
Output Frequency Crystal Pullability, Note 2 VCXO Gain Output Rise Time Output Fall Time Output Clock Duty Cycle Maximum Output Jitter, short term
Symbol
FO FP
Conditions
0V< VIN < 3.3 V, Note 1 VIN = VDD/2 1 V, Note 1
Min.
12 115
Typ.
Max. Units
36 MHz ppm
140 0.8 0.8 40 50 100 1.5 1.5 60
ppm/V ns ns % ps
tOR tOF tD tJ
0.8 to 2.0 V, CL=15 pF 2.0 to 0.8 V, CL=15 pF Measured at 1.4 V, CL=15 pF CL=15 pF
Note 1: External crystal device must conform with Pullable Crystal Specifications listed on page 3.
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Package Outline and Package Dimensions (6-pin TSOT-23-6)
Package dimensions are kept current with JEDEC Publication No. 95
Millimeters Symbol Min Max Inches Min Max
A A1 A2 b c D E E1 e e1 L L1 L2
aaa
0.90 1.45 0 0.15 0.90 1.30 0.35 0.50 0.09 0.22 2.80 3.00 2.60 3.00 1.50 1.75 0.95 BASIC 1.90 BASIC 0.35 0.55 0.50 0.70 0.25 BASIC 0 10 -- 0.10
.0354 .0571 0 .0059 .0354 .0512 .0138 .0197 .0036 .0087 .1102 .1181 .1024 .1181 .0591 .0689 0.0374 BASIC 0.0748 BASIC .0138 .0217 .0197 .0276 .0098 BASIC 0 10 -- .0039
Ordering Information
Part / Order Number
ICS726T ICS726TT ICS726TLF ICS726TLFT
Marking
726 726 726 726
Shipping Packaging
Tubes Tape and Reel Tubes Tape and Reel
Package
6-pin TSOT-23-6 6-pin TSOT-23-6 6-pin TSOT-23-6 6-pin TSOT-23-6
Temperature
0 to +70 C 0 to +70 C 0 to +70 C 0 to +70 C
Parts that are ordered with a "LF" suffix to the part number are the Pb-Free configuration and are RoHS compliant. While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems (ICS) assumes no responsibility for either its use or for the 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.
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