T E C H N I C A L I N F O R M A T I O N
The equation for calculating RVNNSENSE is as follows:
VNN
R
VNN1
=
I
VNNSENSE
Set RVNN2 3 RVNN1 .
=
×
IVPPSENSE or IVNNSENSE can be any of the currents shown in the Electrical Characteristics table
for VPPSENSE and VNNSENSE, respectively.
The two 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 = 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
VN10 is an additional supply voltage required by the TA3020. 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. Figure 5 shows the correct way to power the TA3020:
VPP
V5
VPP
5V
AGND
VN10
PGND
VNN
10V
VNN
F. BEAD
Figure 5: Proper Power Supply Connection
TA3020, Rev 2.1, 01.01
23
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
