aoz1977 Alpha & Omega Semiconductor, aoz1977 Datasheet - Page 4

• Manufacturer Part Number: aoz1977
• Description: High Voltage Led Driver Ic
• Manufacturer: Alpha & Omega Semiconductor

PIN 11: DPWM
This is the driver output for the gate of the LED current
control NMOS switch. DPWM = low if PIN13: DBRT
signal is low or fault condition is triggered. DPWM = high
if PIN 13: DBRT signal is high under normal operation.
The high voltage is equal to VDD voltage. It is
recommended to add a 1 Ω resistor between this pin and
the NMOS gate. The resistor value can be optimized
depending on the switching frequency and selection of
the NMOS.
PIN 12: OVP
This is the input for LED Over-Voltage Protection.
OVP monitors the LED output voltage through a resistor
divider. When the voltage at this pin is higher than 1 V,
the controller will stop switching immediately until the
voltage at this pin is below 0.8 V.
PIN 13: DBRT
This is the input for digital brightness control. A PWM
logic signal is applied to this pin to vary the brightness of
the LED. The brightness of the LED is proportional to the
duty cycle of the PWM logic signal. The input signal will
control the output driver at DPWM pin. This input pin
cannot be left floating.
Rev. 1.0 July 2011
www.aosmd.com
PIN 14: COMP
This is for
the error amplifier that controls PWM logic for the boost
controller. An RC network should be used to generate the
compensation for boost feedback loop.
PIN 15: ISET
This is for full scale LED current setting. A reference
voltage between 0.5 V and 0.8 V should be applied to this
pin. The voltage can be derived from a resistor divider
from the 1.2 V reference voltage at PIN 10: VREF.
To minimize power consumption, it is recommended that
the total resistance for the divider is approximately 20 kΩ.
The FB voltage will regulate to this voltage level. The full
scale LED current is derived by the FB voltage divided by
the Sense resistor.
PIN 16: FB
This is the feedback input for boost controller. This pin
should connect to a resistor that senses the LED current.
The FB voltage will be regulated to ISET voltage to
determine the desired LED current when LED current
control NMOS switch is on.
feedback loop compensation. It is the output of
AOZ1977
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