CS1610/11/12/13
When exiting reset, the chip enters startup and the ADC
quickly (<5ms) tracks the external temperature to check if it is
below the 110°C reference code before the boost and second
stages are powered up. If this check fails, the rest of the
system will not be initialized until the external temperature is
below 110C.
The CS1610/11/12/13 uses the calculated value of the
second low-pass filter to scale output LED current ILED, as
shown in Figure 15.
100%
50%
0
For external overtemperature protection, a second low-pass
filter with a time constant of two minutes filters the ADC output
and uses it to scale down the internal dim level of the system
(and hence LED current ILED) if the temperature exceeds
95°C (see Figure 15). The large time constant for this filter
ensures that the dim scaling does not happen spontaneously
and is not noticeable (suppress spurious glitches).
Current ILED starts reducing when resistor RNTC is
approximately 6.3k (assuming a 14k 1% tolerance,
series resistor), which corresponds to a temperature of 95°C
for a 100k NTC (100k at 25°C). LED current ILED is scaled
until the NTC value reaches 2.5k (125°C).
125
25
95
Temperature (°C)
Figure 15. LED Current vs. eOTP Temperature
If the measured temperature exceeds 125°C, the IC shuts
down using the mechanism discussed above. If the external
overtemperature protection feature is not required, connect
the eOTP pin to GND using a 50k-to-500k resistor to
disable the eOTP feature.
DS929F6
13
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