SLUSE53 December 2024 BQ25751
PRODUCTION DATA
請參考 PDF 數(shù)據(jù)表獲取器件具體的封裝圖。
External N-channel MOSFETs are used for power path transfer. Those on the VAC side are called ACFETs and those on the VBAT side are called BATFETs.
The proper trade off for selecting these MOSFETs depends on the SOA characteristics. All FETs follow the same trend hence the same FET can be used at all places for regular operation and power path handover. It is essential to select a MOSFET that offers close to 10A Drain Current at 30V VDS at DC and also has the capability to offer 100A Drain Current at 30V VDS at 10 μs without breaking. Furthermore, the SOA characteristics should be such that the maximum junction temperature should be at least 125°C. The FETs selected for this application are AON6276 and can withstand a voltage swing of up-to 30V from VAC to VBAT and vice-versa.
Even though rugged high SOA MOSFETs are being used, it is still essential to limit the maximum amount of current that is allowed to flow from the battery to the system load. This is done by setting the power path overcurrent protection to a limit of 15A. This means that the maximum load for which we can achieve a successful power path transfer from VAC to VBAT is 15A. Furthermore, it should be noted that in cases where VAC > VBAT, the ACUV should be set to a value between VAC and VBAT. For cases where VBAT > VAC, the ACUV should be set just below VAC.
In some special cases, the battery has to be plugged into the system suddenly at a very high voltage which causes a large inrush current. This is called a battery hot plug. In such an application is desired, our recommendation is to replace the BATFETs with NTMFSC4D2N10MC FETs. These FETs have a higher threshold voltage which is desirable for hot plug applications. For hot plug applications, R9 and C36 on the EVM must be populated with a 10Ω resistor and 10nF capacitor respectively. This prevents a sudden rise and shoot through of the current and protects the FETs from being damaged.