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73M2901-32IH 参数 Datasheet PDF下载

73M2901-32IH图片预览
型号: 73M2901-32IH
PDF下载: 下载PDF文件 查看货源
内容描述: 先进的单芯片调制解调器 [Advanced Single Chip Modem]
分类和应用: 调制解调器
文件页数/大小: 17 页 / 316 K
品牌: TDK [ TDK ELECTRONICS ]
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73M2901/3.3V  
Advanced Single  
Chip Modem  
transformer directly (with the required impedance  
matching series resistor). Used in this configuration,  
there is loss associated in both the receive path and  
transmit path.  
The line interface circuit shown on the following  
page represents the basic components and values3  
for interfacing the TDK 73M2901/3.3V analog pins to  
the telephone line.  
DESIGN CONSIDERATIONS  
TDK Semiconductor’s single chip modem solutions  
include all the basic modem functions. This makes  
these devices adaptable to a variety of applications.  
Unlike digital logic circuitry, modem designs must  
contend with precise frequency tolerances and verify  
low level analog signals, to ensure acceptable  
performance. Using good analog circuit design  
practices will generally result in a sound design.  
The crystal oscillator should be held to a 50ppm  
MODEM PERFORMANCE  
CHARACTERISTICS  
tolerance.  
Following  
are  
additional  
recommendations that should be taken into  
consideration when starting new designs.  
The curves presented in this data sheet define  
modem IC performance under a variety of line  
conditions typical of those encountered over public  
service telephone lines.  
LAYOUT CONSIDERATIONS  
Good analog/digital design rules must be used to  
control system noise in order to obtain high  
performance in modem designs. The more digital  
circuitry present in the application, the more  
attention to noise control is needed.  
BER VS. SNR  
This test represents the ability of the modem to  
operate over noisy lines with a minimum amount of  
data transfer errors. Since some noise is generated  
in the best dial up lines, the modem must operate  
with the lowest signal to noise ratio (SNR) possible.  
Better modem performance is indicated by test  
curves that are closest to the BER axis. A narrow  
spread between curves representing the four line  
High speed, digital devices should be locally  
bypassed, and the telephone line interface and the  
modem should be located next to each other near  
where the telephone line connection is accessed. It  
is recommended that power supplies and ground  
traces should be routed separately to the analog and  
digital portions on the board. Digital signals should  
not be routed near low level analog or high  
impedance analog traces.  
The 73M2901/3.3V should be considered a high  
performance analog device. A 10µF electrolytic  
capacitor in parallel with a 0.1µF Ceramic capacitor  
should be placed between VPD and VND as well as  
between VPA and VNA. A 0.1µF ceramic capacitor  
should be placed between VREF and VNA as well  
as VBG and VNA. Use of ground planes and large  
traces on power is recommended.  
The 73M2901/3.3V is the first of a series of parts  
with different and/or additional features. In order to  
insure full lay out compatibility for all the series, it is  
recommended to implement three additional  
resistors in the schematics as shown in the  
recommended schematics arrangement (R11, R12  
and R13).  
parameters  
indicates  
minimal  
variation  
in  
performance while operating over a range of  
aberrant operating conditions. Typically a DPSK  
modem will exhibit better BER performance test  
curves receiving in the low band (answer mode)  
than in the high band (originate mode).  
BER VS. RECEIVE LEVEL  
This test measures the dynamic range of the  
modem. Because signal levels vary widely over dial  
up lines, the widest possible dynamic range is  
desirable. The SNR is held constant at the indicated  
values as the Receive level is lowered from very a  
very high to a very low signal level. The width of the  
bowl of these curves, taken at the BER point is the  
measure of the dynamic range.  
TELEPHONE LINE INTERFACE  
Transmit levels at the line are dependent on the  
interface used between the pins and the line. In  
order to save having to provide external op-amps to  
drive the line coupling transformer, the analog  
outputs (TXAP and TXAN) have the capability to be  
used as the hybrid drivers for connecting to the  
3
TDK73M2901 Demo boards use the line interface shown on the  
following page. Other designs may have different requirements  
and thus will require different component values or a different  
configuration. With the shown configuration, there is  
approximately an 8dB loss in the transmit path, and approximately  
a 5dB loss in the receive path.  
10