6.4 Device Functional Modes

Table 6-2 lists the ISO7842 functional modes.

Table 6-2. Function Table

VCCI

VCCO

INPUT

(INx)(2)

OUTPUT

ENABLE

(ENx)

OUTPUT

(OUTx)

COMMENTS

PU

PU

H

H or open

H

Normal Operation:

A channel output assumes the logic state of its input.

L

H or open

L

Open

H or open

Default

Default mode: When INx is open, the corresponding channel output goes to

its default logic state. Default= High for ISO7842 and Low for ISO7842F.

X

PU

X

L

Z

A low value of Output Enable causes the outputs to be high-impedance

PD

PU

X

H or open

Default

Default mode: When VCCI is unpowered, a channel output assumes the

logic state based on the selected default option. Default= High for IISO7842

and Low for ISO7842F.

When VCCI transitions from unpowered to powered-up, a channel output

assumes the logic state of its input.

When VCCI transitions from powered-up to unpowered, channel output

assumes the selected default state.

X

PD

X

X

Undetermined

When VCCO is unpowered, a channel output is undetermined (1).

When VCCO transitions from unpowered to powered-up, a channel output

assumes the logic state of its input

(1)

The outputs are undetermined when 1.7V < VCCI, VCCO < 2.25V.

(2)

A strongly driven input signal can weakly power the floating VCC through an internal protection diode and cause undetermined output.

6.4.1 Device I/O Schematics

Input (Device Without Suffix F)

Output

Enable

OUTx

VCCO

~20 W

INx

1.5 MW

985 W

Input (Device With Suffix F)

VCCI

VCCI

VCCI

INx

1.5 MW

985 W

VCCI

VCCI

VCCI VCCI

Enx

2 MW

1970 W

VCCO

VCCO

VCCO VCCO

Copyright © 2016, Texas Instruments Incorporated

Figure 6-3. Device I/O Schematics

www.ti.com

ISO7842, ISO7842F

SLLSEJ0H – OCTOBER 2014 – REVISED MARCH 2024

Copyright © 2024 Texas Instruments Incorporated

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Product Folder Links: ISO7842 ISO7842F