Datasheet

TDA8034HN All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 3.2 — 25 March 2014 6 of 30
NXP Semiconductors
TDA8034HN
Low power smart card interface
8.2 Voltage supervisor
The voltage supervisor monitors the voltage of the V
DDP
, V
DD
and V
DD(INTF)
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, and for
V
DD(INTF)
externally by pin PORADJ. 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 TDA8034HN. 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
, V
DDP
or V
DD(INTF)
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
001aal138
REFERENCE
VOLTAGE
V
DD
V
DD
PORADJ
VCC_SEL2
V
DDP
V
DD(INTF)
R1
R2
001aak993
t
w
t
w
power on supply dropout power off
V
th
+ V
hys
V
th
V
DD
ALARMN
(internal signal)