TSB41AB1PHP datasheet(31/71 Pages) TI1

31 / 71 page

TSB41AB1

IEEE 1394a2000 ONEPORT CABLE

TRANSCEIVER/ARBITER

SLLS423I − JUNE 2000 − REVISED MARCH 2005

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251−1443

APPLICATION INFORMATION

crystal selection (continued)

The layout of the crystal portion of the PHY circuit is important for obtaining the correct frequency, minimizing

noise introduced into the PHYs phase-lock loop, and minimizing any emissions from the circuit. The crystal and

two load capacitors should be considered as a unit during layout. The crystal and load capacitors should be

placed as close as possible to one another while minimizing the loop area created by the combination of the

three components. Varying the size of the capacitors may help in this. Minimizing the loop area minimizes the

effect of the resonant current (Is) that flows in this resonant circuit. This layout unit (crystal and load capacitors)

should then be placed as close as possible to the PHY XI and XO terminals to minimize trace lengths. Figure 16

depicts a layout that meets these guidelines.

C10

Figure 16. Recommended Crystal and Capacitor Layout

It is strongly recommended that part of the verification process for the design be to measure the frequency of

the SYSCLK output of the PHY. This should be done with a frequency counter with an accuracy of six digits or

better. If the SYSCLK frequency is more than the crystal tolerance from 49.152 MHz, the load capacitance of

the crystal may be varied to improve frequency accuracy. If the frequency is too high, add more load

capacitance; if the frequency is too low, decrease load capacitance. Typically, changes should be done to both

load capacitors (C9 and C10, see Figure 15) at the same time, and both should be of the same value. Additional

design details and requirements may be provided by the crystal vendor. For more information, see Selection

and Specification of Crystals for Texas Instruments IEEE 1394 Physical Layers, TI literature number SLLA051.

EMI guidelines

For

electromagnetic

interference

(EMI)

guidelines

and

recommendations,

check

the

web

site

http://www.ti.com/1394emi−guidelines

designing with the PowerPad package

The TSB41AB1 is housed in high-performance, thermally enhanced, 48/64-terminal PHP/PAP PowerPAD

packages. Use of a PowerPAD package does not require any special considerations except to note that the

PowerPAD, which is an exposed metallic pad on the bottom of the device, is a thermal and electrical conductor.

This exposed pad is connected inside the package to the substrate of the silicon die; it is not connected to any

terminal of the package. Therefore, if not implementing PowerPAD PCB features, the use of solder masks (or

other assembly techniques) may be required to prevent any inadvertent shorting by the exposed PowerPAD

of connection etches or vias under the package. The recommended option, however, is to not run any etches

or signal vias under the device, but to have only a grounded thermal land as explained below. Although the actual

size of the exposed die pad may vary, the minimum size required of the keep-out area is 8 mm

× 8 mm for the

64-terminal PAP PowerPAD package, and 5 mm

× 5 mm for the 48-terminal PHP PowerPAD package.

It is recommended that there be a thermal land, which is an area of solder-tinned-copper (see Figure 17),

underneath the PowerPAD package. The thermal land varies in size depending on the PowerPAD package

being used, the PCB construction, and the amount of heat that needs to be removed. In addition, the thermal

land may or may not contain numerous thermal vias depending on PCB construction.

TSB41AB1PHP bảng dữ liệu(PDF) 31 Page - Texas Instruments

TSB41AB1PHP bảng dữ liệu(HTML) 31 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

bảng dữ liệu tải về

Link URL