Hello.
I am a newbie in DC/DC design, so have some problem with LM2704. Design requirements:
Input voltage -- 3,3 V
Output voltage -- 12 V
Output current -- 40 mA max.
Output load -- 2 relay coil, 20 mA per one.
Main purpose of this design -- generate voltage to control two 12 V relay coil from 3,3 V powered CPU. Circuit on Figure 6 in datasheet was used as reference .
After checking on real PCB I see some strange behaviour of output voltage. Both relay are ON -- otput voltage is 12V. One relay ON, other relay OFF -- 16 V on output. Both relay are OFF -- voltage jump to 30 V. May be I missunderstand LM2704 datasheet, and this IC work only as current source for LED's ? What DC/DC IC in SOT-23 package in this case suitable for my requirements ?
Circuit with used parts designation in attachment.
Best regards, Volodymir.
