BD83A44EFV-M BD83A44MUF-M
Description of Blocks - continued
13 Internal CLK
This circuit generates the internal reference clock. It is a clock of 2.3 MHz and used as a counter.
14 Dimming Control
This circuit controls the dimming rate during PWM dimming.
15 Current Driver / ISET
Current driver circuit for lighting LED. LED current can be set by connecting a resistor to the ISET pin.
In addition, the LED current can be controlled according to the input voltage of the ADIM pin.
16 PROTECT
Outputs the status of protective operation from the FAIL pin. Since this pin is an open drain output, connect it to the REG
pin with a resistor. If the status of protective operation is not monitored, turn the FAIL pin to OPEN or connect to the GND
pin.
16.1 UVLO (Under Voltage Lock Out)
Under Voltage Lock Out. When VCC pin voltage is 4.10 V or less or REG pin voltage is 3.95 V or less, Under
Voltage Lockout (UVLO) is activated, and the load switch (M1), DC/DC switching, and current driver turn OFF.
When VCC pin voltage is 4.25 V or more and REG pin voltage is 4.10 V or more, UVLO is released and the IC
restarts from Self Diagnosis. When UVLO is detected, output of the FAIL pin does not change. When the FAIL pin
is pulled up to the REG pin, FAIL pin voltage will also drop as REG pin voltage is decreased.
16.2 TSDLED (Thermal Shutdown for Current Driver)
This is a temperature protection circuit that monitors the vicinity of the current driver on the chip. Prevents chip
temperature from rising due to output current fault. When the chip temperature rises to 175 °C or more, the
temperature protection circuit (TSDLED) is activated, the load switch (M1), DC/DC switching, and current driver
are turned OFF. When TSDLED is detected, the FAIL pin goes Low. When the chip temperature falls 150 °C or
less, TSDLED is released, the IC restarts from Self Diagnosis.
16.3 TSDREG (Thermal Shutdown for REG)
This is a temperature protection circuit that monitors the vicinity of the REG pin on the chip. Prevents chip
temperature from rising due to the REG pin failure. When the chip temperature rises to 175 °C or more, the
temperature protection circuit (TSDREG) is activated, and REG pin voltage, load switch (M1), DC/DC switching,
and current driver turn OFF. When TSDREG is detected, the FAIL pin goes Low. When the chip temperature falls
150 °C or less, TSDREG is released and the IC restarts from Self Diagnosis.
16.4 OCPL (Over Current Protection for Low side)
When the current flowing through Low side FET (the SW pin) becomes 3.6 A or more, the overcurrent protection
(OCPL) is activated and only DC/DC switching is stopped. If the current is less than 3.6 A, the overcurrent
protection is released, and switching is resumed. When OCPL is detected, output of the FAIL pin does not change.
16.5 OVP (Over Voltage Protection)
Output overvoltage protection circuit. When OVP pin voltage (resistor division of DC/DC converter output voltage)
becomes to 1.21 V or more, the overvoltage protection circuit (OVP) activates and only DC/DC switching is
stopped. When OVP pin voltage falls 1.16 V or less, OVP is released. When OVP is detected, output of the FAIL
pin goes Low.
16.6 OPEN Det (LED Open Detection)
LED open protection circuit. When any of LED1 to LED4 pin voltages is 0.3 V or less and OVP pin voltage is 1.21
V or more, LED open protection (OPEN Det) is activated, and the current driver is latched OFF only for the LED
row that is open. OPEN Det is released when VEN = Low or UVLO is detected. When OPEN Det is detected, the
FAIL pin goes Low.
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TSZ22111 • 15 • 001
08.May.2023 Rev.001
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