The major requirements of such designs are: reproducible performance during normal operation, an option to force all LEDs on, low power consumption, disabling the used LDO regulator during a fault, loading the LED driver before enabling it etc. Additionally, the requirements can vary from one manufacturer to another. Moreover, usually in automotive applications, TSSOP ICs are usually preferred due to their robustness as compared to QFN ICs since these are known to be prone to solder fatigue issues especially in harsh environments. Fortunately for this automotive application, Dialog Semiconductor provides a suitable GreenPAK™ IC, namely SLG46620, available in both QFN and TSSOP packages.
All of the requirements for the animated indicator LED patterns are currently met in the automotive industry using discrete ICs. However, the level of flexibility provided by the IC is unmatched and can easily cater to varying requirements of several manufacturers without any change in hardware design. Moreover, significant PCB footprint reduction and cost savings are also achieved.
The turn signal patterns shown in this article are currently implemented in the automobile industry using a number of discrete ICs to control the sequence of automotive indicator LED patterns. The selected GreenPAK IC SLG46620 would replace at least the following components in the current industrial design:
• 1 No. 555 Timer IC (e.g. TLC555QDRQ1)
• 1 No. Johnson Counter (e.g. CD4017)
• 2 No. D-Type Positive-Edge-Triggered Flip-Flop (e.g. 74HC74)
• 1 No. OR gate (e.g. CAHCT1G32)
• Several passive components i.e. inductors, capacitors, resistors etc.
Figure 1: Scheme 1 with Single Channel Drive
Figure 1 shows the diagram of the first proposed scheme. The major components of the scheme include a LDO voltage regulator, an automotive LED driver, an SLG46620, 11 logic-level MOSFETs and 10 LEDs. The LDO voltage regulator ensures that appropriate voltage is provided to the IC and if the battery voltage drops from a certain level the IC gets reset through