madid87
Newbie level 1
Hi,
I'm designing a Li-Ion battery (4.2 - 3V) to 4V output boost regulator. **broken link removed** has an automatic bypass function which will bypass the input when higher or equal to output. The price is also very good at 1000pcs.
I need to power a GPRS modem which draws 2A peak transient current. In the MIC's datasheet there is a load transient graph were it is shown that the voltage will drop by 600mV with 1.2A step! This is totally unacceptable for my application.
My questions:
1) They used only 22uF output capacitor. Is it valid to expect that more output capacitance will drastically improve the transient response? I would put 10uF ceramic + 100uF low ESR aluminum. My concern is that big output capacitor will create a pole at low frequency and slow the regulator even more? Is my reasoning sound? Is it even possible to design a 300mV@2A transient response with this regulator?
2) Besides start-up inrush problem, what can be expected from current mode control SMPS's with high capacitive load? Let's say I put 1000uF aluminum, can this make the loop response very slow that 10uF output cap would provide better transient performance?
3) Any out suggestion for Li-Ion to GPRS voltage (4.4 - 3.4V) with 2A peak current with similar price?
Thank you very much.
I'm designing a Li-Ion battery (4.2 - 3V) to 4V output boost regulator. **broken link removed** has an automatic bypass function which will bypass the input when higher or equal to output. The price is also very good at 1000pcs.
I need to power a GPRS modem which draws 2A peak transient current. In the MIC's datasheet there is a load transient graph were it is shown that the voltage will drop by 600mV with 1.2A step! This is totally unacceptable for my application.
My questions:
1) They used only 22uF output capacitor. Is it valid to expect that more output capacitance will drastically improve the transient response? I would put 10uF ceramic + 100uF low ESR aluminum. My concern is that big output capacitor will create a pole at low frequency and slow the regulator even more? Is my reasoning sound? Is it even possible to design a 300mV@2A transient response with this regulator?
2) Besides start-up inrush problem, what can be expected from current mode control SMPS's with high capacitive load? Let's say I put 1000uF aluminum, can this make the loop response very slow that 10uF output cap would provide better transient performance?
3) Any out suggestion for Li-Ion to GPRS voltage (4.4 - 3.4V) with 2A peak current with similar price?
Thank you very much.