Tripath Technology, Inc. - Technical Information
MOSFET to the drain of the low side output MOSFET. This diode absorbs any high
frequency overshoots caused by the output inductor LO during high output current
conditions. In order for this diode to be effective it must be connected directly to the
drains of both the top and bottom side output MOSFET. An ultra fast recovery diode
that can sustain the entire VPP-VNN voltage should be used here. In most
applications a 150V or greater diode must be used.
DS
Source diode. This diode must be connected from the source of the high side
output MOSFET to the source of the low side output MOSFET. This diode absorbs
any high frequency undershoots caused by the output inductor LO during high output
current conditions. In order for this diode to be effective it must be connected
directly to the sources of both the top and bottom sides output MOSFETs. An ultra
fast recovery diode that can sustain the entire VPP-VNN voltage should be used
here. In most applications a 150V or greater diode must be used.
RB
CB
Output MOSFET snubber resistor. This resistor forms a low pass filter with CO with
a frequency of
. This RC filter removes any high frequency overshoots
fC = 1 (2πRBCB )
that can be present on the switching output waveform. This RC filter must be
connected right across the drain and source of the low side output MOSFET.
Output MOSFET snubber capacitor. This resistor forms a low pass filter with RB
with a frequency of
. This RC filter removes any high frequency
fC = 1 (2πRBCB )
overshoots that can be present on the switching output waveform. This RC filter
must be connected right across the drain and source of the low side output
MOSFET.
RS
Source resistor. This resistor is in series between HOCOM and the source of the
top side output MOSFET. This resistor serves to limit the voltage swing at the
HOCOM pin (pins 37 and 47 of the TP2350B) to protect the TP2350B during any
output overshoots/undershoots. Since this resistor alters the rise and fall times of
the gate on the high side output MOSFET an additional resistor of the same value is
placed in series with LOCOM and the source of the bottom side output MOSFET to
match the rise and fall times of the top side to the bottom side.
RPG
Gate resistor for the output MOSFET for the switchmode power supply. Controls
the rise time, fall time, and reduces ringing for the gate of the output MOSFET for
the switchmode power supply.
QB
Output MOSFET for the switchmode power supply to generate the VN10. This
output MOSFET must be a P channel device.
DSW
LSW
Flywheel diode for the internal VN10 buck converter. This diode also prevents
VN10SW from going more than one diode drop negative with respect to VNN.
VN10 generator filter inductor. This inductor should be sized appropriately so that
LSW pass 0.5A of current without saturation, and VN10 does not overshoot with
respect to VNN during TK2350 turn on.
CSW
VN10 generator filter capacitors. The high frequency capacitor (0.1uF) must be
located close to the VN10 pins (pin 41 and 43 of the TP2350B) to maximize device
performance. The bulk capacitor (100uF) should be sized appropriately such that
the VN10 voltage does not overshoot with respect to VNN during TK2350 turn on.
VN10 generator feedback resistor. This resistor sets the nominal VN10 voltage.
With RSWFB equal to 1kΩ, the VN10 voltage generated will typically be 11V above
VNN.
RSWFB
CSWFB
VN10 generator feedback capacitor. This capacitor, in conjunction with RSWFB, filters
the VN10 feedback signal such that the loop is unconditionally stable.
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TK2350, Rev 1.5/09.03
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