TDA8034AT データシートの表示（PDF） - NXP Semiconductors.

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TDA8034AT

Smart card interface

NXP Semiconductors. 

NXP Semiconductors

8.2 Voltage supervisor

VDD(INTF)

VDD

TDA8034T; TDA8034AT

Smart card interface

VDD

REFERENCE

VOLTAGE

VDDP

5 V or 3 V

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Fig 3. Voltage supervisor circuit

The voltage supervisor monitors the voltage of the VDDP and VDD supplies providing both

Power-On Reset (POR) and supply drop-out detection during a card session. The

supervisor threshold voltages for VDDP and VDD are set internally. As long as VDD is less

than Vth + Vhys, the IC remains inactive irrespective of the command line levels. After VDD

has reached a level higher than Vth + Vhys, the IC remains inactive for the duration of tw.

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. (tw = 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 VDD or

VDDP falls below Vth.

Remark: fosc(int)low is the low frequency (or inactive) mode of the defined fosc(int)

parameter.

Vth + Vhys

Vth

VDD

ALARMN

(internal signal)

tw

power on

Fig 4. Voltage supervisor waveforms

tw

supply dropout

power off

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TDA8034T_TDA8034AT

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 3.1 — 13 December 2012

© NXP B.V. 2012. All rights reserved.

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