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LMH0324: Power Consumption

Charles Steinkuehler
Prodigy 140 points
Part Number: LMH0324
Other Parts Discussed in Thread: LMH1219

I am designing a power supply for 8x LMH0324 and I am looking for the worst-case power consumption.  We are using a 2.5V rail.

Per the data sheet, IDD is listed as 71 mA max at 2.5V (6.4 "Electrical Characteristing") HOWEVER there is a footnote (1) indicating this value is "Measured with RSV_L tied to VSS".

Elsewhere in the data sheet, it is indicated that RSV_L is tied to VGG for 2.5V operation (9 "Power Supply Recommendations").

Confusing things further, Figure 16 (8.2 "Typical Application") shows the LMH0325 with a 2.5V rail and RSV_L tied to ground (VSS), although this configuration is not discussed elsewhere that I can find.

So...is the 71 mA maximum current accurate if RSV_L is tied to 2.5V?

Is it legal to tie RSV_L to VSS when powered via 2.5V?

Is there a maximum current specification when running at 2.5V with RSV_L tied to 2.5V?

  • 0
    TI__Guru* 93670 points

    Hi Charles,

    LMH0324 is pin and register compatible with the LMH1219 device. This part - LMH1219 - has a CDR or retimer which is powered by 2.5V supply. In order to be compatible with LMH1219 part, we need to tie RSV_L to 2.5V supply(Actually RSV_L is the CDR VDD). Please refer to the LMH1219 data sheet and this could become more clear.

    1). LMH0324 can operate in either 1.8V supply mode(note figure 25 of the data sheet) or 2.5V mode(Figure 16 RSV_L tied to GND) of the data sheet. Data sheet foot note 1 refers to either 1.8V supply mode or 2.5V supply mode with RSV_L tied to GND. 71mA current consumption is with RSV_L tied to GND.

    2). If you are not going to use LMH1219 in future then in this case you can follow figure 16 of the data sheet. On the other hand, if there might be a case where you would use LMH1219 - 12G SDI - then you can follow figure 24 of the data sheet.

     3). Please note maximum power consumption with 2.5V supply and RSV_L tied to 2.5V has not been characterized. 

    Regards,, Nasser