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您可以将您的电路发上来看一下。
The bq76200 can not directly support FETs in a common source configuration. If using CHG to control the gate of
the discharge FET, when off CHG will not go below BAT leaving the discharge FET operating as a source follower
with the source voltage approximately Vgsth below BAT (your last question). The DSG driving the discharge gate
would initially seem to be OK since it can swing from 0 up to VDDCP. If there is no load DSG will pull up the FET
gate and the source through the 10M resistor. Normally the load current from the 10M resistor is 10V/10M = 1uA. If
there is a load on DISCHARGE and no charger on CHARGE, if DSG were to rise to VDDCP at 50V as proposed, the load
would be 50V/10M = 5uA which would be within the capability of the charge pump, however the FET would not be happy
with a 50V Vgs. Also there is an internal clamp which will prevent the rise of DSG more than about 20V above the
PACK pin. The CVDDCP will discharge into the clamp and the driver will turn off and cycle.
As noted it may be possible to add a circuit to allow the common source charge FET gate to fall below
CHG. Consider a P-channel FET between CHG and BAT pins. If the charge FET needs to turn off fast consider a
circuit similar to figure 3 of www.ti.com/lit/slua795. Preventing turn on of CHG if CHARGE (the charger voltage)
is not present through system behavior should avoid dissipating the charge pump into an external gate clamp.
I've not tested a common source circuit, the part is recommended for common drain implementations.
