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Part Number: LM27222
We am trying to use LM27222 as a standard push pull driver, driving two N-Ch FETs into a load of 2A. The input to PWM pin is either DC or pulsed - when pulsed, its a frequency of ~ 100Hz with high period of ~100usec. The output switching needs to be fast, changing within 100nsec of the PWM input rise/fall edges. The VCC as well as PWM input levels are 5V. The high side mosfet Vin is also 5V.
My queries are:
1) Can the device handle this kind of a switching, as the datasheet mainly intends to show this only in a buck regulator configuration.
2) We will chose a low Rdson mosfet (~40mOhm) to minimize drop over the high mosfet and have almost 5V appear at the output. Is that ok?
3) There shall be no L/C configuration at the switching node SW. The output shall directly be fed to the load. Is that ok?
In reply to Richard Herring:
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
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In reply to Gaurav Agrawal1:
The solution worked fine for us, and the noise issue was resolved with the change in the HB cap.
We are now implementing this in our PCB where multiple such circuits will be needed to drive an array of switching loads. My query is if a single SN6505B isolated source acting as the bootstrap can be used across multiple LM27222 circuits, all of which have the same high side FETs.
It is good to hear the LM27222 with the floating bias is working in your application.
Regarding the multiple LM27222 circuits and the shared bias. The floating high side bias needs to be referenced to the CB and SW pins of each respective driver, so if there are multiple MOSFET's and drivers with the same connection to the high side MOSFET source the bias can be shared. But in that case the same driver may possibly be used to drive MOSFET's in parallel if the driving capability is adequate.
If there are multiple LM27222 drivers and MOSFETs connected to difference SW nodes in the power circuit, a common floating bias cannot be shared since it needs to be referenced to the SW node.
Thanks Richard! We can close this thread now.
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