Tripath Technology, Inc. - Technical Information
Using the resistor values from above, the actual minimum over voltage turn off points will be:
VPP MIN_OV_TUR N_OFF = RVPP1 × IVPPSENSE (MIN_OV_TU RN_OFF)
VNN MIN_OV_TUR N_OFF = −(RVNN1 × IVNNSENSE (MIN_OV_TU RN_OFF)
)
The other three trip points can be calculated using the same formula but inserting the appropriate
IVPPSENSE (or IVNNSENSE) current value. As stated earlier, the usable supply range is the difference
between the minimum overvoltage turn off and maximum under voltage turn-off for both the VPP
and VNN supplies.
VPP RANGE = VPP MIN_OV_TUR N_OFF - VPP MAX_UV_TUR N_OFF
VNN RANGE = VNN MIN_OV_TUR N_OFF - VNN MAX_UV_TUR N_OFF
VN10 Supply and Switch Mode Power Supply Controller
VN10 is an additional supply voltage required by the TP2150. VN10 must be 10 volts more
positive than the nominal VNN. VN10 must track VNN. Generating the VN10 supply requires
some care.
The proper way to generate the voltage for VN10 is to use a 10V-postive supply voltage
referenced to the VNN supply. The TP2150 has an internal switch mode power supply
controller which generates the necessary floating power supply for the MOSFET driver stage
in the TP2150 (nominally 10V with the external components shown in Application / Test
Circuit). The SMPSO pin (pin 60) provides a switching output waveform to drive the gate of a
P channel MOSFET. The source of the P channel MOSFET should be tied to power ground
and the drain of the MOSFET should be tied to the VN10 through a 100uH inductor. The
performance curves shown in this datasheet as well as the efficiency measurements were
done using the internal VN10 generator. Tripath recommends using the internal VN10
generator to power the TP2150. Figure 6 shows how the VN10 generator should be
connected.
TP2150
RSWFB 1kΩ
59 SW-FB
CSWFB
VN10
0.1uF
Switchmode
LSW
QP
Power Supply
VNN
RPG 10Ω
100uH
60
SMPSO
VN10
+
DSW
B1100DICT
CSW
0.1uF
CSW
100uF
VNN
Figure 6: VN10 Generator
In some cases, though, a designer may wish to use an external VN10 generator. The
specification for VN10 quiescent current (200mA typical, 250mA maximum) in the Electrical
Characteristics section states the amount of current needed when an external floating supply is
used. If the internal VN10 generator is not used, Tripath recommends shorting SMPSO(pin 60) to
VNN(pin 42) and SW-FB(pin 59) to VNN(pin 42).
One apparent method to generate the VN10 supply voltage is to use a negative IC regulator to
drop PGND down to 10V (relative to VNN). This method will not work since negative regulators
24
TK2150 – Rev. 1.0/12.02
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
