データシートサーチシステム |
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SL1466 データシート(PDF) 6 Page - Zarlink Semiconductor Inc |
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SL1466 データシート(HTML) 6 Page - Zarlink Semiconductor Inc |
6 / 18 page 5 SL1466 The SL1466 is normally used as a type 2 second order loop and can be represented by the above diagram. for such a system the following loop parameters apply. T 1 = C1 R1 T 2 = C1 R2 and T 1 = K o K D / ω n 2 T 2 =2 ξ/ω n where: K O is the VCO gain in radians seconds per volt K D is the phase detector gain in volts per radian ω n is the natural loop bandwidth ξ is the loop damping factor From these factors the loop 3dB bandwidth can be determined from the following expression; which approximates to ω 3dB = 2 ξω n , when ξ >>1 N.B. VCO gain within the PLL is three times higher than at the video drive pin due to gain in the output stage. NOTE: R1 is the loop amplifier input resistor. R2 and C2 are the generic designators for the loop components R7-R9 and C9, C14 on the circuit diagram. AGC FACILITY A sophisticated two stage level detect circuit has been provided which will control both internal IF AGC and external tuner AGC amplifiers in order to maintain a fixed level to the input of the phase detector of around –20dBm for optimum threshold performance. The internal AGC amplifier provides 50dB of gain adjust and the external AGC control provides for 15dB of gain adjust, thus covering 65dB of dynamic range at the tuner input. The RF output current RF AGC CONTROL can be converted to a positive gradient control voltage by an external resistor. AFC FACILITY The SL1466 contains a digital frequency error detect circuit, which generates an output consisting of two logic flags, DIGFHI and DIGFLO, dependant on whether the LO frequency is above or below the input frequency. These flags have an overlap region where both are high; this is equivalent to the deadband window. The function of the AFC outputs is shown in Fig. 7 and the accompanying Table. ω2 = ω2(2ξ2 + 1) + ω2 √ ((2ξ2 + 1) + 1 3dB n n Fig. 4 RF AGC control current and AGC time cinstant voltage vs Input power AGC TIME CONSTANT (V) -10 400 350 300 250 200 150 100 50 0 -90 -70 -50 -30 RFCONT TC Pin dBm RFC AGC CONTROL CURRENT ( µA) 4V 3V 2V 1V |
同様の部品番号 - SL1466 |
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同様の説明 - SL1466 |
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