BQ24171: Does a schottky diode on SW pin need in case of connecting AC Adapter?

user4292685

Part Number: BQ24171

In datasheet, there is a schottky diode on SW pin (page25,28,29 except for page30), especially in case of connecting AC adapter.

However this device is Synchronous Switched- Mode Charger with Integrated High/Low side MOSFETs.

Does this schottky diode on SW pin need for this device? If so, could you tell me the reason why?

Regards,

over 7 years ago

0 user4292685 over 7 years ago

Intellectual 945 points

Add typical application schematic with marking

0 Steven Bangdiwala over 7 years ago in reply to user4292685

TI__Expert 8690 points

Hi,

The schottky diode helps with the reverse recovery of the internal FET so that the freewheeling current in the inductor during the switching falling edge does not pass through the body diode of the low side FET and instead through the schottky diode (lower forward conducting voltage than internal FET), minimizing losses because of the slower reverse recovery time of the internal FET.

It is necessary if you are using charging currents higher than about 1A. I suggest you leave the space for the schottky diode in the layout in case you need it later.

Regards,
Steven

0 user4292685 over 7 years ago in reply to Steven Bangdiwala

Intellectual 945 points

Hi Steven,

Thank you for your quick reply. I understand the schottky diode helps the freewheeling current in the inductor.

However usually TI's Synchronous step-down voltage DCDC converter does not need this schottky diode on Low side FET.

Is there any difference between battery charger and DCDC converter?

Regards,

0 Steven Bangdiwala over 7 years ago in reply to user4292685

TI__Expert 8690 points

The two ICs are not the same die. They use different design for the internal FETs.

Regards,
Steven

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BQ24171: Does a schottky diode on SW pin need in case of connecting AC Adapter?