Part Number:LM3492HC
Hi all
Would you mind if we ask LM3492HC?
There is the description "Current limit ICL= ICL(max) – 4290 × IILIM" on the datasheet P13.
<Customer's condtion>
Vin : 12V
Vout : 31.2V/each out 230mA(Iout1=Iout2=230mA)
L=15uH
Fsw=414kHz
<Question>
Our customer would like to configfure Iimitation=0.67A(=ICL).
So, according to equation,
0.67= 3.9 – 4290 × IILIM(5.5(VCC)-0.7/Rlim)
Rlim=6.4kohm
In case of Rlim=6.4kohm,
-Vout=29V, IOUTs did't output 230mA.
-Switching frequency was more than 1MHz.
So, if Rlim was 10kohm(1.84A), operation was normal condtion as follows;
-Vout=31V, IOUTs output 250mA.
-Switching frequency was 414kHz.
Therefore, the customer would like to know how much RLIM is correct for Customer's condtion and formula for it.
We assume that ICL=0.67 is difficult to configure it, because,,,
Vin=12V, Vout=31.2V/ Iout=230mA×2
-31.2V×0.46A×100/80(assumption of the worst efficiency)=17.942W
-17.942/Vin=12V=1.495A
So, in order to configure Vout=31.2V Iout=230mA×2, we assume that ICL requires more than 1.5A limitation.
Is it correct?
Kind regards,
Hirotaka Matsumoto
