最近有用到DDR2的内存,看到了里面有一个阻抗要求。 ODT DC Electrical Characteristics (TC = 0°C to +85°C, VDD, VDDQ = 1.8V ± 0.1V) Parameter Symbol min. typ. max. Unit Note Rtt effective impedance value for EMRS (A6, A2) = 0, 1; 75 Ω Rtt1 (eff) 60 75 90 Ω 1 Rtt effective impedance value for EMRS (A6, A2) = 1, 0; 150 Ω Rtt2 (eff) 120 150 180 Ω 1 Rtt effective impedance value for EMRS (A6, A2) = 1, 1; 50 Ω Rtt3 (eff) 40 50 60 Ω 1 Deviation of VM with respect to VDDQ/2 ΔVM −6 ⎯ +6 % 1 Note: 1. Test condition for Rtt measurements. Measurement Definition for Rtt (eff) Apply VIH (AC) and VIL (AC) to test pin separately, then measure current I(VIH(AC)) and I(VIL(AC)) respectively. VIH(AC), and VDDQ values defined in SSTL_18. ( ( )) ( ( )) ( ) ( ) ( ) I VIH AC I VIL AC Rtt eff VIH AC VIL AC − = − Measurement Definition for ΔVM Measure voltage (VM) at test pin (midpoint) with no load. 100 1 - 2 × ⎟⎠ ⎞ ⎜⎝ Δ = ⎛ × VDDQ VM VM OCD Default Characteristics (TC = 0°C to +85°C, VDD, VDDQ = 1.8V ± 0.1V) 这个里面的讲的那个阻抗是对全部的数据和地址线要求的阻抗还是对那个ODT管脚的引出线要求的阻抗呢 请高手解答 [em08][em06] |