ZXLD1370_11 DIODES [Diodes Incorporated], ZXLD1370_11 Datasheet - Page 25

• Manufacturer Part Number: ZXLD1370_11
• Description: 60V HIGH ACCURACY BUCK/BOOST/BUCK-BOOST LED DRIVER CONTROLLER
• Manufacturer: DIODES [Diodes Incorporated]

For example,
Over-Temperature Shutdown
The ZXLD1370 incorporates an over-temperature shutdown circuit to protect against damage caused by excessive die
temperature. A warning signal is generated on the STATUS output when die temperature exceeds 125°C nominal and the
output is disabled when die temperature exceeds 150°C nominal. Normal operation resumes when the device cools back
down to 125°C.
ZXLD1370
Document number: DS32165 Rev. 3 - 2
Applications Information
T
The ‘Thermal control’ circuit monitors the voltage on the T
below 625mV. An external NTC thermistor and resistor can therefore be connected as shown below to set the voltage on
the T
temperature and a falling current above it as shown in the graph. The temperature threshold can be altered by adjusting the
value of Rth and/or the thermistor to suit the requirements of the chosen LED.
The Thermal Control feature can be disabled by connecting T
Here is a simple procedure to design the thermal feedback circuit:
ADJ
1)
2)
3)
1)
2)
3)
pin - Thermal control of LED current
ADJ
Select the temperature threshold T
Select the Thermistor TH1 (both resistive value at 25˚C and beta)
Select the value of the resistor R
Temperature threshold T
TH1 = 10kΩ at 25˚C and beta= 3500
R
th
pin to 625mV at the required temperature threshold. This will give 100% LED current below the threshold
= TH at T
threshold
= 3.3kΩ
threshold
(Continued)
th
= 70˚C
Figure 33. Thermal feedback network
threshold
as R
th
= TH at T
at which the current must start to decrease
TH = 3.3kΩ @ 70˚C
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ADJ
threshold
ADJ
pin and reduces output current if the voltage on this pin falls
to REF.
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© Diodes Incorporated
ZXLD1370
February 2011