TDA8025 Просмотр технического описания (PDF) - NXP Semiconductors.
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TDA8025 Datasheet PDF : 38 Pages
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NXP Semiconductors
TDA8025
IC card interface
The voltage on PORADJ (VPORADJ) can be calculated as: V PORADJ = α × V DD(INTF)
where:
• VDD(INTF) is the interface supply voltage
• ratio α
α = 1-----+--1----RR--------12---
(2)
An activation can be triggered if
V DD(INTF) × α > V th(max) ⇒ V DD(INTF) > V-----t-h---α(--m----a--x--)
(3)
where
• Vth(max) is the maximum rising external threshold voltage
The resistance spread of R1 between a minimum value R1min and a maximum value
R1max induces a spread of the ratio α. This is also true for R2. Based on this:
V DD(INTF)actmin = V-----tα-h---m(--m--i-n-a--x--)
(4)
where
αmin = -1----+------R-R--1-----1-2-----m-m------a-i---n--x
(5)
If ∆R1 is the maximum spread of R1 and ∆R2 is the maximum spread of R2 then:
R1max
=
R1nom + ∆R1
=
R
1n
om
⋅
1
+
-R--∆--1--R-n--o-1--m--
(6)
R2min
=
R2nom – ∆R2
=
R
2no
m
⋅
1
–
-R--∆--2--R-n--o-2--m--
(7)
αmin
=
1-----+------RR--------12------nn-----o-o----m-m---------⋅⋅----1-------1-1--------+-–----------R-R---------∆∆------2--1--------RR----nn---------o-o--21--------mm--------------
=
1-----+------RR--------12------n-n----o-o-----m1m---------⋅-⋅-----(-(----11---------+-–--------β-β-------))-
=
-----------V----t--h--(--m----a--x---)---------
V DD(INTF)actmin
(8)
where
• where β is the accuracy ratio of R1 and R2 (R1 and R2 are considered to be of the
same type).
Then
TDA8025_1
Product data sheet
Rev. 01 — 6 April 2009
© NXP B.V. 2009. All rights reserved.
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