Hello i'm trying to build the circuit showed on the datasheet of the SM72445 but i have the following questions:
1- If I set the pin A2 to 3.44 V to opperate in low frequency and to use the H-bridge for PM operation. Does that means that the PM_OUT pin becomes useless and i can avoid using the whole circuit related to it? I mean the PM driver and the 2 Transistors?
2- Wich H-Bridge driver would yo recomend me to use? ir2110 is ok? Idon't know if i can use bootstrap because the high side of the bridge couln't opperate in ON state continuously.Could you suggest me a circuit?
thats not very clear on the datasheet isn't it?
1- Correct, the whole bypass switch composed of the two FETs and the associated driver can be omitted in this operation mode
2-What is your switch node voltage and current driving requirement? The SM72295 has all the four necessary gate drivers, can deliver 3A (sink/source) with a switch node up to 100V. The SM72445 will pulse the low side FET of the Buck switch node and Boost switch node momentarily (about 100ns) to refresh the bootstrap capacitors of both switch nodes regardless of the operation (obviously the associated high side FET will be OFF at that time).
Thank you very much for you fast reply, it was very usefull.
I'll order some samples of the SM72295 to try it.
One more question, but this time it's about the SM72295. May i put 5V at VDD and VCCA/B inputs using the same supply? i make that question because in the datasheet they use 10V to feed VCC.
No there is an undervoltage threshold setting of around 7V (up to 7.8V depending on temperature and tolerance, see page 8 of the datasheet) on VCCA and VCCB. Additionnally there is up to 0.9V drop in the internal bootstrap diode used to recharge the bootstrap capacitor. For proper operation, and for correct drive of the FETs (reduced RDSon) the VCCA and VCCB pins should be driven with a 10V source.
Thank you, ill take that into account. Now i need a step up because i had a 5V supply, i'll solve it using a LM2731.
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