Tripath Technology, Inc. – Preliminary Technical Information
Figure 4 shows the proper connection for the Over / Under voltage sense circuit for both the VPPSENSE
and VNNSENSE pins.
V5
VNN
RVNN2
RVNN1
VNNSENSE
V5
VPP
RVPP1
RVPP1
VPPSENSE
Figure 4 - Over / Under voltage sense circuit
The equation for calculating RVPP1 is as follows:
VPP
R
VPP1
=
VPPSENSE
I
Set RVPP2 = RVPP1 .
The equation for calculating RVNNSENSE is as follows:
VNN
R
VNN1
=
VNNSENSE
I
Set
.
R
VNN2 = 3 × RVNN1
I
VPPSENSE 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
41
TCD6001 – JL/Rev. 0.9/07.05
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
