MAX22192 datasheet(21/50 Pages) MAXIM

21 / 50 page

Detailed Description

The MAX22192 senses the state (on, high or off, low) of

eight digital inputs. The voltages at the IN1 to IN8 input

pins are compared against internal references to deter-

mine whether the sensor is ON (logic 1) or OFF (logic 0).

All eight inputs are simultaneously latched by the asser-

tion of either LLATCH or LCS, and the data made avail-

able in a serialized format using the isolated SPI interface.

Placing a 7.5kΩ current-setting resistor between REFDI

and GNDF, and a 1.5kΩ resistor between each field input

and the corresponding IN_ input pin ensures that the cur-

rent at the ON and OFF trip points, as well as the voltage

at the trip points, satisfy the requirements of IEC 61131-2

for Type 1 and Type 3 inputs. The current sunk by each

input pin rises linearly with input voltage until the level

set by the current limiter is reached; any voltage increase

beyond this point does not increase the input current.

Limiting the input current ensures compliance with IEC

61131-2 while significantly reducing power dissipation

compared to traditional resistive inputs.

The current-setting resistor RREFDI can be calculated

using this equation:

RREFDI = 17.63V / IINLIM

Input Filters

Each input (IN1–IN8) has a programmable filter and input

data can be filtered to reduce noise, or it can be read

directly for more rapid response. The input is sampled

and data is updated at 1MHz (typ) when the input filter

is disabled. When the digital filter is enabled, the input

is sampled at 200kHz (typ). Bit FBP in the correspond-

ing FLT_ register is used to bypass the filter or to enable

the filter. One of eight filter delays (50µs, 100µs, 400µs,

800µs, 1.6ms, 3.2ms, 12.8ms, 20ms) can be indepen-

dently selected for each channel. Noise rejection is

accomplished through a nonrollover up-down counter

where the state of the field input controls the counting

direction (up or down). The filter uses an up-down coun-

ter fed by a 200kHz clock. If the input is high, it counts

up; if the input is low, it counts down. The filter output is

updated when the counter hits the upper or lower limit,

with the upper limit depending on the selected filter delay

and the lower limit being zero regardless of the filter delay.

The low-to-high transition of the filter occurs when the

counter reaches the upper limit. The high-to-low transi-

tion occurs when the counter reaches the lower limit.

There is no rollover; counting simply stops when the

upper or lower limit is hit. The filter delay is the time it

takes to reach the upper/lower limit in response to a step

input when the counter starts from the lower/upper limit.

Figure 4. Switching Characteristics for IEC 61131-2 Type 1, 2, and 3 24VDC Digital Inputs

MAX22192

Octal Industrial Digital Input with

Diagnostics and Digital Isolation

www.maximintegrated.com

Maxim Integrated │ 21

VLMIN

TYPE

LIMIT

TYPE 1 LIMITS

TYPE 2 LIMITS

TYPE 3 LIMITS

OFF REGION TRANSITION

ON REGION

OFF REGION

TRANSITION

ON REGION

OFF REGION TRANSITION

ON REGION

(V)

(mA)

(V)

(mA)

(V)

(mA)

(V)

(mA)

(V)

(mA)

(V)

(mA)

(V)

(mA)

(V)

(mA)

(V)

(mA)

MAX

15/5

11/5

MIN

-3

0.5

-3

1.5

IIN (mA)

VIN (V)

OFF REGION

ON REGION

TRANSITION REGION

VHMAX

VHMIN or VTMAX

IHMIN

IHMAX

ILMIN

ILMAX

VLMAX or VTMIN

ITMIN

ITMAX

STANDARD OPERATING RANGE FOR 24V DC DIGITAL INPUTS (CURRENT SINKING)

VLMAX

ND = NOT DEFINED

MAX22192 Datasheet(PDF) 21 Page - Maxim Integrated Products

MAX22192 Datasheet(HTML) 21 Page - Maxim Integrated Products

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 45 46 47 48 49 50

Datasheet Download

Link URL