Tripath Technology, Inc. - Technical Information
Thus, the supply voltage must be outside of the user defined supply range for greater than 200mS for
the TA2022 to be muted.
The equation for calculating RVPPSENSE is as follows:
VPP - 2.5V
R
VPPSENSE =
I
VPPSENSE
The equation for calculating RVNNSENSE is as follows:
1.25V - VNN
R
VNNSENSE =
I
VNNSENSE
where IVPPSENSE or IVNNSENSE can be any of the currents shown in the Electrical Characteristics
table for VPPSENSE and VNNSENSE, respectively.
Example: Nominal supply voltage – +/-32.5V +/-10%
From this information, a value of RVPPSENSE and RVNNSENSE can be calculated using the above
formulas.
VPP MAX = 32.5V ×1.1 = 35.75V use 36V
VNN MAX = −32.5V ×1.1 = −35.75V use - 36V
36V - 2.5V
R
VPPSENSE
=
= 242.75 kΩ use 243 kΩ,1%
138 µA
where IVPPSENSE is the minimum over-voltage turn off current for VPPSENSE.
1.25V - - 36V
R
VNNSENSE
=
= 245.1 kΩ use 249 kΩ,1%
152 µA
where IVNNSENSE is the minimum over-voltage turn off current for VNNSENSE.
Using the resistor values from above, the actual minimum over voltage turn off points will be:
VPP MIN_OV_TUR N_OFF = 243 kΩ × 138 µA + 2.5V = 36.03V
VNN MIN_OV_TUR N_OFF = 1.25V − 249kΩ ×152 µA = - 36.60V
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 = 243 kΩ × 87 µA + 2.5V = 23.64V
VNN MAX_UV_TUR N_OFF = 1.25V − 249kΩ × 95 µA = - 22.41V
25
TA2022 – KLI/1.2/07-04
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
