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参数资料
| 型号： | MAX2870EVKIT# |
| 厂商： | Maxim Integrated |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | EVAL KIT MAX2870 |
| 标准包装： | 1 |
| 系列： | * |
MAX2870
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer/VCO
REF_IN
X2
MUX
R COUNTER
DIVIDE-BY-2
MUX
PFD
Figure 3. Reference Input
Reference Input
The reference input stage is configured as a CMOS
inverter with shunt resistance from input to output. In
shutdown mode this input is set to high impedance to
prevent loading of the reference source.
The reference input signal path also includes optional x2
and ÷2 blocks. When the reference doubler is enabled
(DBR = 1), the maximum reference input frequency is lim-
ited to 100MHz. When the doubler is disabled, the refer-
ence input frequency is limited to 200MHz. The minimum
reference frequency is 10MHz. The minimum R counter
divide ratio is 1, and the maximum divide ratio is 1023.
Int, Frac, Mod, and R Counter
Relationship
The phase-detector frequency is determined as follows:
f PFD = f REF O [(1 + DBR)/(R x (1 + RDIV2))]
f REF represents the external reference input frequency.
DBR (register 2, bit 25) sets the f REF input frequency
doubler mode (0 or 1). RDIV2 (register 2, bit 24) sets
the f REF divide-by-2 mode (0 or 1). R (register 2,
bits 23:14) is the value of the 10-bit programmable
reference counter (1 to 1023). The maximum f PFD is
50MHz for frac-N mode and 105MHz for int-N mode. The
R-divider can be held in reset when RST (register 2,
bit 3) = 1.
The VCO frequency (f VCO ), N, F, and M can be deter-
mined based on desired RF output frequency (f RFOUTA )
as follows:
Set DIVA value property based on f RFOUTA and DIVA
register table (register 4[22.20])
f VCO = f RFOUTA x DIVA
If bit FB = 1, (DIVA is not in PLL feedback loop):
N + (F/M) = f VCO/ f PFD
If bit FB = 0, (DIVA is in PLL feedback loop) and DIVA
≤ 16:
N + (F/M) = (f VCO /f PFD )/DIVA
If bit FB = 0, (DIVA is in PLL feedback loop) and DIVA > 16:
N + (F/M) = (f VCO / f PFD )/16
Maxim Integrated
N is the value of the 16-bit N counter (16 to 65535),
programmable through bits 30:15 of register 0. M is the
fractional modulus value (2 to 4095), programmable
through bits 14:3 of register 1. F is the fractional division
value (0 to MOD - 1), programmable through bits 14:3 of
register 0. In frac-N mode, the minimum N value is 19 and
maximum N value is 4091. The N counter is held in reset
when RST = 1 (register 2, bit 3). DIVA is the RF output
divider setting (0 to 7), programmable through bits 22:20
of register 4. The division ratio is set by 2 DIVA .
The RF B output frequency is determined as follows:
If BDIV = 0 (register 4, bit 9), f RFOUTB = f RFOUTA .
If BDIV = 1, f RFOUTB = f VCO .
Int-N/Frac-N Modes
Integer-N mode is selected by setting bit INT = 1 (regis-
ter 0, bit 31). When operating in integer-N mode, it is also
necessary to set bit LDF (register 2, bit 8) to set the lock
detect to integer-N mode.
The device’s frac-N mode is selected by setting bit INT = 0
(register 0, bit 31). Additionally, set bit LDF = 0 (register
2, bit 8) for frac-N lock-detect mode.
If the device is in frac-N mode, it will remain in frac-N
mode when fractional division value F = 0, which can
result in unwanted spurs. To avoid this condition, the
device can automatically switch to integer-N mode when
F = 0 if the bit F01 = 1 (register 5, bit 24).
Phase Detector and Charge Pump
The device’s charge-pump current is determined by the
value of the resistor from pin RSET to ground and the
value of bits CP (register 2, bits 12:9) as follows:
I CP = 1.63/R SET x (1 + CP)
To reduce spurious in frac-N mode, set charge-pump
linearity bit CPL = 1 (register 1, bits 30:29). For int-N
mode, set CPL = 0. For lower noise operation in int-N
mode, set charge-pump output clamp bit CPOC = 1
(register 1, bit 31) to prevent leakage current onto the
loop filter. For frac-N mode, set CPOC = 0.
13
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| MAX2870EVKIT# | 功能描述:射频开发工具 MAX2870 Eval Kit RoHS:否 制造商:Taiyo Yuden 产品:Wireless Modules 类型:Wireless Audio 工具用于评估:WYSAAVDX7 频率: 工作电源电压:3.4 V to 5.5 V |
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| MAX2900EGI | 功能描述:射频发射器 RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel |
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