SLLSEF8C August 2013 – November 2014 TLK111
PRODUCTION DATA.
Figure 7-1 shows the recommended circuit for a 10/100Mbs twisted pair interface. Below is a partial list of recommended transformers. Variations with PCB and component characteristics require that the application be tested to verify that the circuit meets the requirements of the intended application.
The TLK111 supports an external CMOS-level oscillator source or an internal oscillator with an external crystal.
If an external clock source is used, XI should be tied to the clock source and XO should be left floating. The amplitude of the oscillator should be a nominal voltage of 3.3V.
The use of a 25MHz, parallel, 20pF-load crystal is recommended if a crystal source is desired. Figure 7-2 shows a typical connection for a crystal resonator circuit. The load capacitor values will vary with the crystal vendors; check with the vendor for the recommended loads.
The oscillator circuit is designed to drive a parallel-resonance AT-cut crystal with a minimum drive level of 100μW and a maximum of 500μW. If a crystal is specified for a lower drive level, a current limiting resistor must be placed in series between XO and the crystal.
As a starting point for evaluating an oscillator circuit, if the requirements for the crystal are not known, set the values for CL1 and CL2 at 33pF, and R1 should be set at 0Ω. Specifications for a 25MHz crystal are listed in Table 7-3.
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT |
---|---|---|---|---|---|
Frequency | 25 | MHz | |||
Frequency Tolerance | Operational Temperature | ±50 | ppm | ||
Frequency Stability | 1 year aging | ±50 | ppm | ||
Rise / Fall Time | 10%–90% | 8 | nsec | ||
Jitter (Short term) | Cycle-to-cycle | 50 | psec | ||
Jitter (Long term) | Accumulative over 10 ms | 1 | nsec | ||
Symmetry | Duty Cycle | 40% | 60% | ||
Load Capacitance | 15 | 30 | pF |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT |
---|---|---|---|---|---|
Frequency | 50 | MHz | |||
Frequency Tolerance | Operational Temperature | ±50 | ppm | ||
Frequency Stability | 1 year aging | ±50 | ppm | ||
Rise / Fall Time | 10%–90% | 6 | nsec | ||
Jitter (Short term) | Cycle-to-cycle | 50 | psec | ||
Jitter (Long term) | Accumulative over 10 ms | 1 | nsec | ||
Symmetry | Duty Cycle | 40% | 60% |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT |
---|---|---|---|---|---|
Frequency | 25 | MHz | |||
Frequency Tolerance | Operational Temperature | ±50 | ppm | ||
At 25°C | ±50 | ppm | |||
Frequency Stability | 1 year aging | ±5 | ppm | ||
Load Capacitance | 10 | 40 | pF |
(Extended temperature (125°C) grade only)
The following thermal via guidelines apply to DOWN_PAD, pin 49:
Adherence to this guideline is required to achieve the intended operating temperature range of the device. Figure 7-3 illustrates an example layout.