tda8025hn NXP Semiconductors, tda8025hn Datasheet - Page 9

• Manufacturer Part Number: tda8025hn
• Description: Ic Card Interface
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA8025_1
Product data sheet
8.2.4.1 R1 and R2 resistor value calculation
8.2.3 V
8.2.4 V
The TDA8025 remains in inactive mode irrespective of the levels on the command lines
when
In both cases, this lasts for the duration of t
and V
voltages (V
An external resistor bridge can be used to divide V
detection threshold when monitoring the microcontroller interface supply voltage.
Connecting the external resistor bridge as illustrated in
to V
voltage V
The threshold voltage on pin V
where
When the resistor bridge is not used, pin PORADJ must be connected to pin V
This section describes how to calculate the values for resistors R1 and R2, taking into
account the IC detector threshold spread and the external resistance, while ensuring
reliable activation.
If for example, the controller is supplied by a regulator at 3.3 V
triggered above V
threshold is defined as V
activation can always be triggered.
In addition to this external input, activation is permitted provided all the following
conditions are met (see
and V
V
•
•
•
•
•
DD(INTREGD)
DD(INTF)
th
V
Pin PORADJ (monitoring V
V
for the digital part of the TDA8025
V
information.
DD(INTF)
V
on pin V
DD(INTREGD)
DD(INTREGD)
DD(INTF)
bg
DD(INTF)
DD(INTREGD)
is the bandgap voltage
th
voltage supervisor with external divider on pin PORADJ
th
on pin V
and R2 connected to GND) to pin PORADJ overrides the internal threshold
DD INTF
) are set by the hardware as follows:
threshold voltage: is set to 1.24 V; see
(on pin V
voltage supervisor with pin PORADJ connected to V
is less than V
threshold voltage: is set to the minimum supply voltage (2.7 V) specified
DD(INTF)
supplies, etc.
DD(INTF)
=
DD(INTF)
V
Rev. 01 — 6 April 2009
Table 8 on page
DD(INTF)actmin
bg
= 3.3 V
.
1
--------------- -
+ 1
R2
) have reached a level higher than V
DD(INTF)
th
DD(INTF)
R
+ V
20 % (in this example 2.64 V). This activation
hys
; i.e. the minimum value of V
) is less than V
is calculated as follows:
(on pin V
23): card presence, IC temperature, V
w(POR)
DD(INTREGD)
after V
DD(INTF)
Table 8 on page 23
th
Figure 4 on page 8
+ V
DD(INTREGD)
on pin PORADJ to adapt the
hys
)
20 %. Activation can be
DD(INTF)
th
+ V
(on pin V
TDA8025
© NXP B.V. 2009. All rights reserved.
hys
IC card interface
for detailed
above which
. Two threshold
(R1 connected
DD(INTF)
DD(INTREGD)
DD(INTF)
DD(INTF)
9 of 38
.
(1)
)