Tripath Technology, Inc. - Technical Information
V5
VNN
TA2022
RVNN2
RVNN1
18
19
VNNSENSE
V5
VPP
RVNN2
RVPP1
VPPSENSE
Figure 10: Two Resistor Sense Circuit
The equation for calculating RVPP1 is as follows:
VPP
VPPSENSE
R
VPP1 =
I
Set RVPP2 RVPP1
.
=
The equation for calculating RVNNSENSE is as follows:
VNN
VNNSENSE
R
VNN1 =
I
Set
.
R
VNN2 = 3 × RVNN1
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 RVPP1, RVPP2, RVNN1, and RVNN2 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
R
VPP1
=
= 260.87 kΩ use 261kΩ,1%
138 µA
Set
.
VPP2 = 261kΩ,1%
R
where IVPPSENSE is the minimum over-voltage turn off current for VPPSENSE.
36V
R
VNN2
=
= 236.84 kΩ use 237 kΩ,1%
152 µA
Set
.
R
VNN2 = 715 kΩ,1%
where IVNNSENSE is the minimum over-voltage turn off current for VNNSENSE.
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TA2022 – KLI/1.2/07-04
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