I want to use the BD18327EFV-M IC from ROHM for a LED driving application.
On page 22 of the datasheet they give an application example, but calculations are not given.
Can you please tell me how they arrived at the values of RCRT1, RCRT2 and CCRT?
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- \$\begingroup\$ Ah, let me see. (1) BD18327EFV-M datasheet rohm.com/products/power-management/led-drivers/… (2) BD18327EFV-M 50V 1.5A 1ch LED Driver for 2Wheeler Turn Indicator. It has built-in CR Timer for LED blinking control. The IC provides high reliability because it has LED open detection, short circuit protection, over voltage protection. In case of LED open detection, output blinking rate is doubled. Under high input voltage condition, output PWM ON Duty reduces to control heat dissipation across the IC and protect LED load. \$\endgroup\$tlfong01– tlfong012023-04-05 08:10:25 +00:00Commented Apr 5, 2023 at 8:10
- 3\$\begingroup\$ p.12 and 13 explains timing-related details. Why not use 555 and MOSFETs with regulators instead? Okay, the IC houses all of them but it looks too complicated to me. \$\endgroup\$Rohat Kılıç– Rohat Kılıç2023-04-05 08:20:10 +00:00Commented Apr 5, 2023 at 8:20
- 1\$\begingroup\$ @RohatKılıç,it looks complicated to me also.Can you please share the details of 555 and MOSFETs with regulators.I am ready to explore this option if it reduces the cost \$\endgroup\$Confused– Confused2023-04-05 09:11:11 +00:00Commented Apr 5, 2023 at 9:11
- 1\$\begingroup\$ @tlfong01,May I know what is CR timer \$\endgroup\$Confused– Confused2023-04-05 09:12:48 +00:00Commented Apr 5, 2023 at 9:12
- \$\begingroup\$ @Hari: Ah, "CR" is short for Capacitor Resistor. \$\endgroup\$tlfong01– tlfong012023-04-05 14:49:14 +00:00Commented Apr 5, 2023 at 14:49
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1 Answer
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1 The "CR" timer is what is almost always called an "RC" timer, ie, one made from a resistance and a capacitance. As noted in comments, unless you need the complexities of this chip (all to do with safety if used on a vehicle), you might be much better off with a MOSFET driver and timing from a 555 or a microcontroller.
The timing calculations are given in the datasheet:
and in the tables:
- \$\begingroup\$ ,if I use MOSFET driver method will I get these functionalities ,LED open detection, short circuit protection, over voltage protection. In case of LED open detection, output blinking rate is doubled \$\endgroup\$Confused– Confused2023-04-05 16:24:49 +00:00Commented Apr 5, 2023 at 16:24