CS1680 datasheet(13/16 Pages) CIRRUS

13 / 16 page

CS1680

DS1055F1

When exiting reset, the chip enters startup and the ADC

quickly (<15ms) tracks the external temperature to check

if it is below 120°C reference code before the controller is

powered up. If this check fails, the chip will wait until this

condition becomes true before initializing the rest of the

system; that is, until the resistance (RS+RNTC) rises above

17.02k

.

For example, a 14k

 (±1% tolerance) series resistor is

required to allow measurements of up to 130°C to be

within the eOTP tracking range when a 100k

 NTC with a

Beta of 4275. If the temperature exceeds 95°C,

thermistor RNTC is approximately 6.3k and series

resistor RS is 14k, so the eOTP pin has a total resistance

of 20.3k

. The eOTP pin initiates protective dimming

action by reducing the power dissipation. At 125°C, the

thermistor RNTC has 2.6k plus a series resistor RS equal

to 14k

 present a resistance of 16.6k at the eOTP pin

reaching the point where a thermal shutdown fault

intervenes. The CS1680 fault state is not cleared until the

power to the IC is recycled (see Figure 15).

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.

Temperature (°C)

125

50%

100%

Figure 15. LED Current vs. eOTP Temperature

CS1680 Fiches technique(PDF) 13 Page - Cirrus Logic