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參數(shù)資料
| 型號： | 73M2921-IG |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Advanced Single Chip Modem |
| 中文描述： | 先進的單芯片調(diào)制解調(diào)器 |
| 文件頁數(shù)： | 36/41頁 |
| 文件大?。?/td> | 222K |
| 代理商： | 73M2921-IG |
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73M2921
Advanced Single
Chip Modem
Page 36 of 41
TDK Semiconductor
February 99 Rev M
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, and as easy to control as conventional digital bus peripherals.
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 tolerance. Following are additional
recommendations that should be taken into consideration when starting new designs. Additional information is
available in the 73M2921 Design Guide.
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 on the PC board, the more attention to noise control is needed.
The 73M2921 should be considered a high performance analog device. A 10
μ
F electrolytic capacitor in parallel
with a 0.1
μ
F Ceramic capacitor should be placed between VPD and VND as well as between VPA and VNA. A
0.1
μ
F ceramic capacitor should be placed between VREF and VNA as well as VBG and VNA. Liberal use of
ground planes and large traces on power are also highly recommended. High speed, digital circuits tend to
generate a significant amount of EMI (Electro-Magnetic Interference) which must be minimized in order to meet
regulatory agency limitations.
To accomplish this, 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. To avoid
problems, 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.
MODEM PERFORMANCE CHARACTERISTICS
The curves presented here define modem IC performance under a variety of line conditions typical of those
encountered over public service telephone lines.
BER vs. SNR (see Figure 9)
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 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 possible is desirable. The minimum Bell specification calls for 36dB of dynamic
range. 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.
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| 73M2AR0015F | 功能描述:RES 0.0015 OHM 1% 2W 2512 制造商:cts resistor products 系列:73M2A 包裝:帶卷（TR） 零件狀態(tài):在售 電阻值:1.5 MOhms 容差:±1% 功率（W）:2W 成分:金屬薄膜 特性:電流檢測 溫度系數(shù):±100ppm/°C 工作溫度:-55°C ~ 155°C 封裝/外殼:2512（6432 公制） 供應(yīng)商器件封裝:2512 大小/尺寸:0.248" 長 x 0.126" 寬（6.30mm x 3.20mm） 高度 - 安裝（最大值）:0.043"（1.10mm） 端子數(shù):2 故障率:- 標準包裝:4,000 |
| 73M2AR001F | 功能描述:RES 0.001 OHM 1% 2W 2512 制造商:cts resistor products 系列:73M2A 包裝:帶卷（TR） 零件狀態(tài):在售 電阻值:1 MOhms 容差:±1% 功率（W）:2W 成分:金屬薄膜 特性:電流檢測 溫度系數(shù):±100ppm/°C 工作溫度:-55°C ~ 155°C 封裝/外殼:2512（6432 公制） 供應(yīng)商器件封裝:2512 大小/尺寸:0.248" 長 x 0.126" 寬（6.30mm x 3.20mm） 高度 - 安裝（最大值）:0.043"（1.10mm） 端子數(shù):2 故障率:- 標準包裝:4,000 |
| 73M2AR0025F | 功能描述:RES 0.0025 OHM 1% 2W 2512 制造商:cts resistor products 系列:73M2A 包裝:帶卷（TR） 零件狀態(tài):在售 電阻值:2.5 mOhms 容差:±1% 功率（W）:2W 成分:金屬薄膜 特性:電流檢測 溫度系數(shù):±100ppm/°C 工作溫度:-55°C ~ 155°C 封裝/外殼:2512（6432 公制） 供應(yīng)商器件封裝:2512 大小/尺寸:0.248" 長 x 0.126" 寬（6.30mm x 3.20mm） 高度 - 安裝（最大值）:0.043"（1.10mm） 端子數(shù):2 故障率:- 標準包裝:4,000 |
| 73M2AR002F | 功能描述:RES 0.002 OHM 1% 2W 2512 制造商:cts resistor products 系列:73M2A 包裝:帶卷（TR） 零件狀態(tài):在售 電阻值:2 MOhms 容差:±1% 功率（W）:2W 成分:金屬薄膜 特性:電流檢測 溫度系數(shù):±100ppm/°C 工作溫度:-55°C ~ 155°C 封裝/外殼:2512（6432 公制） 供應(yīng)商器件封裝:2512 大小/尺寸:0.248" 長 x 0.126" 寬（6.30mm x 3.20mm） 高度 - 安裝（最大值）:0.043"（1.10mm） 端子數(shù):2 故障率:- 標準包裝:4,000 |
| 73M2AR003F | 功能描述:RES 0.003 OHM 1% 2W 2512 制造商:cts resistor products 系列:73M2A 包裝:帶卷（TR） 零件狀態(tài):在售 電阻值:3 mOhms 容差:±1% 功率（W）:2W 成分:金屬薄膜 特性:電流檢測 溫度系數(shù):±100ppm/°C 工作溫度:-55°C ~ 155°C 封裝/外殼:2512（6432 公制） 供應(yīng)商器件封裝:2512 大小/尺寸:0.248" 長 x 0.126" 寬（6.30mm x 3.20mm） 高度 - 安裝（最大值）:0.043"（1.10mm） 端子數(shù):2 故障率:- 標準包裝:4,000 |
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