Tripath Technology, Inc. - Technical Information
The two additional resistors, RVPP2 and RVNN2 compensate for the internal bias points. Thus, RVPP1
and RVNN1 can be used for the direct calculation of the actual VPP and VNN trip voltages without
considering the effect of RVPP2 and RVNN2
.
Using the resistor values from above, the actual minimum over voltage turn off points will be:
VPP MIN_OV_TUR N_OFF = 261kΩ × 138 µA = 36.02V
VNN MIN_OV_TUR N_OFF = −237kΩ ×152 µA = - 36.24V
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
Using the resistor values from above, and the maximum under voltage trip currents shown in the
Electrical Characteristics table, the maximum under voltage turn off points will be:
VPP MAX_UV_TUR N_OFF = 261kΩ × 87 µA = 22.71V
VNN MAX_UV_TUR N_OFF = −237kΩ × 95 µA = - 22..51V
and the resultant minimum supply ranges will be:
VPP RANGE = 36.02 − 22.71V = 13.31V
VNN RANGE = −36.24 − − 22.51V = -13.73V
By adding a total of 2 additional resistors (1 for VPPSENSE and 1 for VNNSENSE), the minimum
supply range is now about 3% different as opposed to 13% for the “single resistor” sense case. In
addition, the VPP range has been increased by nearly one volt. This represents a 7% improvement
in supply range for VPP. As in the single resistor case, the tolerance of the RVPP1 and RVPP2 (or RVNN1
and RVNN2) resistors will affect the trip voltages and thus, the usable supply range. As the nominal
supply voltage is decreased, the effect of RVPP2 and RVNN2 becomes more pronounced. To minimize
the additional variance Tripath recommends 1% tolerance resistors. It is possible to calculate the
effect of resistor tolerances for the “two resistor” sense circuit, but ultimately, 1% resistors should be
used for the sense circuit in all, but the tightest regulated supply schemes.
Over Temperature Protection
An over-temperature fault occurs if the junction temperature of the part exceeds approximately
165°C. The thermal hysteresis of the part is approximately 30°C, therefore the fault will automatically
clear when the junction temperature drops below 135°C.
HMUTE (pin 32)
The HMUTE pin is a 5V logic output that indicates various fault conditions within the device. These
conditions include: over-current, overvoltage and undervoltage. The HMUTE output is capable of
directly driving an LED through a series 2kΩ resistor.
Heat Sink Requirements
most applications it will be necessary to fasten the TA2022 to a heat sink. The determining factor is
that the 150°C maximum junction temperature, TJ(max) cannot be exceeded, as specified by the
following equation:
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TA2022 – KLI/1.2/07-04
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
