User Guide

http://onsemi.com
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Fig. 6: Control panel for Flash PWM, VOUT (DCDC converter) and I_LED. Safety operating area included.
SOA area is implemented in the Strata GUI. Accepted at the conditions: NCV890204 VOUT=10.0V; f_PWM_flash=62Hz. LED
current levels below 0.7A are unavailable.
Thresholds:
- the IR LED (MPN: SFH 4725S) maximum specified LED current: 5A
- R
ETL
value: 15kOhm -> maximum T_ON time 6ms per the NCV7694 specs -> thus 5ms maximum T_ON time accepted
Power law: P=E/t=U*I
- SOA is accepted: 40mJ
- 40mJ=10V*I*t
- t involves duty cycle (i.e. T_ON time)
- thus: 40mC=I_LED*T_ON -> SOA envelope
How to start the DMS (example1): 1. set the LED current and turn the LED current button on. 2. Set the T_ON time and turn the
PWM FLASH (T_ON time) on.
How to start the DMS (example2): 1. set the T_ON time and turn the T_ON time button on (i.e. PWM FLASH). 2. set the LED
current and turn the LED current button on.
The NCV890204 output voltage variable can be adjusted afterwards the DMS runs (T_ON time is ON) with default value 10.0V.
This precaution is done to prevent the DMS malfunction just after it starts due to insufficient voltage is applied at the particular
working point.
If the working point is out of the SOA area that is the T_ON time is set too high in the example1, the GUI automatically adjust the
previous variable (i.e. LED current in the example1 above) to stay within the SOA. In such case the working point sits onto the
dashed orange curve (the SOA envelope). Consequently any change of the T_ON time or the LED current exceeding the SOA adjusts
the working point position onto the SOA envelope.