Cypress CY8C28243-24PVXI, Руководство пользователя

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CY3280-28XXX Universal CapSense® Controller Development Kit Guide, Spec. # 001-57457 Rev. ** 19
3. Hardware Design Notes
3.1 CY3280-28XXX Universal CapSense
®
Controller Board Features
The CY3280-28XXX Universal CapSense Controller Board is used to demonstrate the features of
the CY8C28XXX family of PSoC
®
devices. To demonstrate some features of the CY8C28XXX fam-
ily, a special circuit is needed.
3.1.1 PSoC Power Supplies
There are two kinds of power supplies for PSoC VCC, fixed 5V or variable Vadj. The JP3 is used to
select the power supply. If pin 2 is shorted to pin 3, the fixed 5V is selected for the PSoC VCC. If
pin 2 is shorted to pin 1, the variable Vadj is selected for the PSoC VCC.
Figure 3-1. Schematics
Vadj is the output of the regulator (LP3875ES-ADJ). According to the schematics, the output can be
calculated from the following formula.
RV1 varies from 0
Ω
to 10 k
Ω
, so the maximum voltage and minimum voltage of Vadj can be calcu-
lated individually.
Vadj
1.216 1
R 58
R 23 R 57
+
RV 1
||
------------------------------------------
+
⎝ ⎠
⎛ ⎞
×
=
Vadj
max
1.216 1
R 58
R 23 R 57 RV 1
min
||
+
--------------------------------------------------
+
⎝ ⎠
⎛ ⎞
×
1.216 1
3.9 k
1.5 k
----------
+
⎝ ⎠
⎛ ⎞
×
4.38 V
= = =
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