TI中文支持网Part Number:LMX2492
we use LMX2492 + CHC2442 to generate 24G source signal, originally, 40MHz TCXO feeding to LMX2492, they works well for 24GHz source signal generation. However, when we switch to 100MHz VCXO feeding to LMX2492， they could not functionally be operating that the output signal is unlocked. For debugging, we use SG as OSCin, it is found that OSCin frequency less than 80MHz, they could work well, but LMX2492 could not lock the output when OSCin frequency is higher than 80MHz. we use TI official software tool for LMX2492 configuration， it should be OK for REGs setup. on datasheet, LMX2492 OSCin could be lower than 600MHz, so what's the problem of our case. REGs OK, 100MHz OSCin, but LMX2492 could not lock the output, while works well when OSCin below 80MHz. since it is a urgent case, would you please present us solution as soon as possible, thanks in advance.
Cherry Zhou：
Hi,
我们把您的问题升级到英文论坛看下，有答复尽快给您。
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? ??：
Mentioned POWERDOWN bit is set as 0x01, so it should be functionally operating.Further investigation suggested that if LMX2492 PD frequency is set as 50MHz, the OSCin could be 100MHz, even 200MHz. VCO output frequency could be locked. but if LMX2492 PD frequency is set as 100MHz, the Max OSCin is 85MHz, higher than that, CPout is measured as highest voltage so as not to lock the output frequency. Fin=1.5G
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Cherry Zhou：
What is the fpd frequency and VCO frequency?
