Other Parts Discussed in Thread: TPS22965-Q1
We got some questions from customer about TPS22918-Q1.
Could you help us?
They are considering to design under following condition.
QOD=connected to Vout directly(not use external resistor)
- How much is the recommended range of QOD external resistor in their condition? They need external resistor because of output capacitor exceeds 200uF.
So they want to know how to estimation.
- What does the maximum continuous switch current rating be related? If it is related only junction temperature, can the output current flow more than Imax at low thermal resistance board?
Thermal resistance of thier board is 50C/W. On their board, can the output current flow 1.8A at Ta=95C?
- Which is shorter, the delay time of QOD or toff? If QOD will active untill FET still ON, discharge current flow from VIN. Is there any possibility this phenomenon occur? When they simulated by PSPICE, they found this phenomenon.
- They are considering QOD fall time. What can we estimate from equation 2? What does the Vcap stand for?
We think fall time is CR-time constant. Can we estimate it from following equation?
QOD Fall time = Rpd * Cout
- CT capacitor is connected to gate of FET. So they are thinking CT is related to tF and ON/OFF delay time.
Does the CT capacitor be related to tF and ON/OFF delay time?
- Is there the variation data of Ron under the following condition?
Vin=3.15 to 3.46V
Ta=-30 to 95C
They should estimate the variation of output voltage as accurately as possible. They don't need guarantee. They only use for reference.