13

LED Current Input with Hysteresis

The detector has optical receiver input stage with built in Schmitt trigger to provide logic compatible waveforms, elimi-

nating the need for additional wave shaping. The hysteresis (Figure 5) provides differential mode noise immunity and

minimizes the potential for output signal chatter.

Thermal Model for ACPL-P347/W347 Stretched SO6 Package Optocoupler

Definitions:

Ambient Temperature: Junction to Ambient Thermal Resistances were measured approximately 1.25 cm above opto-

coupler at ~23

°C in still air

Thermal Resistance

°C/W

135

27

39

47

This thermal model assumes that an 6-pin single-channel plastic package optocoupler is soldered into a 7.62 cm x 7.62

cm printed circuit board (PCB) per JEDEC standards. The temperature at the LED and Detector junctions of the optocou-

pler can be calculated using the equations below.

Using the given thermal resistances and thermal model formula in this datasheet, we can calculate the junction tem-

perature for both LED and the output detector. Both junction temperatures should be within the absolute maxi¬mum

rating.

LED junction temperature,

= (135 * 0.017 + 27 * 0.214) + 85

= 93.1

°C

Output IC junction temperature,

= (39 *0.017 + 47 * 0.214) + 85

= 95.7

°C