Datasheet

TDA8034T_TDA8034AT All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 3.1 — 13 December 2012 6 of 30
NXP Semiconductors
TDA8034T; TDA8034AT
Smart card interface
8.2 Voltage supervisor
The voltage supervisor monitors the voltage of the V
DDP
and V
DD
supplies providing both
Power-On Reset (POR) and supply drop-out detection during a card session. The
supervisor threshold voltages for V
DDP
and V
DD
are set internally. As long as V
DD
is less
than V
th
+ V
hys
, the IC remains inactive irrespective of the command line levels. After V
DD
has reached a level higher than V
th
+ V
hys
, the IC remains inactive for the duration of t
w
.
The output of the supervisor is sent to a digital controller in order to reset the
TDA8034T/TDA8034AT. This defined reset pulse of approximately 8 ms, i.e. (t
w
= 1024 
1
⁄
fosc(int)low
), is used internally to maintain the IC in the Shutdown mode during the supply
voltage power on; see Figure 4
. A deactivation sequence is performed when either V
DD
or
V
DDP
falls below V
th
.
Remark: f
osc(int)low
is the low frequency (or inactive) mode of the defined f
osc(int)
parameter.
Fig 3. Voltage supervisor circuit
Fig 4. Voltage supervisor waveforms
001aak991
REFERENCE
VOLTAGE
V
DD
V
DD
V
DD(INTF)
5 V or 3 V
V
DDP
001aak993
t
w
t
w
power on supply dropout power off
V
th
+ V
hys
V
th
V
DD
ALARMN
(internal signal)