ISO1228DFBR datasheet(30/44 Pages) TI1

30 / 44 page

required is 15V) and a value of 910Ω is recommended for RTHR in Type 2 systems. The Table 8-1 and Source

Mode RTHR Admissible Values (Ω) tables list range of RTHR values applicable for each mode. Use Equation 2

and Equation 3 to calculate the values for the typical VIH values and minimum VIL values, respectively.

VIH (typical) = 6.0 V + RTHR x IL (typical)

(2)

VIL (typical) = 5.0 V + RTHR x IL (typical)

(3)

VIH (max) = 6.4 V + RTHR x IL (max)

(4)

VIL (min) = 4.7 V + RTHR x IL (min)

(5)

Refer to the tables for RTHR values to achieve IEC 61131-2 Type 1, 2, 3 voltage thresholds. For Type 2

operation, it is recommended to use two channels in parallel, with RILIM = 1 kΩ and RPAR = 9.76 kΩ operation

in sink mode, resulting in a current limit of 7 mA (typical). RTHR values can be same as Type 3 operation in this

mode.

Table 8-1. Sink Mode RTHR Admissible Values (Ω)

SINK MODE

RILIM = 0Ω, RPAR = 13kΩ, RSURGE = 1kΩ, (IL = 2.5mA)

RILIM = 1kΩ, RPAR = 9.76kΩ, RSURGE = 1kΩ, (IL = 3.5mA)

Min

Typical

Max

Min

Typical

Max

Type 1

180

1000

2400

Type 1

110

910

1740

Type 3

180

1000

1300

Type 3

110

910

930

Table 8-2. Source Mode RTHR Admissible Values (Ω)

SOURCE MODE

RILIM = 0Ω, RPAR = 13kΩ (IL = 2.5mA)

RILIM = 1kΩ, RPAR = 9.76kΩ, (IL = 3.5mA)

Min

Typical

Max

Min

Typical

Max

Type 1

180

1000

2400

Type 1

2000

Type 3

180

1000

1300

Type 3

Not Supported

A tolerance of 5% is acceptable on RTHR. Surge resistant resistors is recommended for RTHR.

The values in the tables are back calculated from the VIH and VIL formulae mentioned above.

For example;

IEC 61131-2 Type 1 Sink Mode threshold calculations with RILIM. = 0kΩ,

VOFF_MAX (5V) < VIL(min) , VON_MIN (15V) > VIH(max), IL(min) = 2mA and IL(max) = 3.3mA,

Switching close to OFF state: VOFF_MAX =VIL(min): 5V = 4.7 V + RTHR x IL(min) => RTHR = 150Ω

With RTHR = 150Ω, VON = VIH(max) = 6.4V + 150Ω x IL(max) = 6.895V which is less than VON_MIN

( 180Ω in the table is a standard resistor to accommodate for 5% tolerance on RTHR)

Switching close to ON state: VON_MIN =VIH(max): 15V = 6.4V+ RTHR x IL(max) => RTHR = 2.6kΩ

With RTHR = 2.6kΩ, VOFF = VIL = 6.4 V + 2.6kΩ x IL(min) = 9.9V which is greater than VOFF_MAX

( 2400Ω in the table is a standard resistor to accommodate for 5% tolerance on RTHR)

Similarly, other values in the table are derived.

8.2.3.1.3 Wire-Break Detection

Each channel has a wire-break detection circuit which includes a secondary comparator to detect the integrity

of field sensor wiring. The sensor or a switch has a wire break resistor across it which passes a small current

above 240µA to the INx. If the input current is below the IWB, the WBx in the SPI register is set and it will

ISO1228

SLLSFN5A – JUNE 2023 – REVISED FEBRUARY 2024

www.ti.com

Submit Document Feedback

Product Folder Links: ISO1228

ISO1228DFBR Datasheet(PDF) 30 Page - Texas Instruments

ISO1228DFBR Datasheet(HTML) 30 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL