AP8800AWT-7 Diodes Inc, AP8800AWT-7 Datasheet - Page 8

• Manufacturer Part Number: AP8800AWT-7
• Description: LED Drivers 28V 1-W LED Driver DC/DC Converter
• Manufacturer: Diodes Inc
• Series: -r

Specifications of AP8800AWT-7

• Constant Current: Yes
• Constant Voltage: -
• Topology: PWM, Step-Down (Buck)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: General Purpose
• Type - Secondary: -
• Frequency: 600kHz
• Voltage - Supply: 8 V ~ 28 V
• Voltage - Output: -
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5 Thin, TSOT-23-5
• Operating Temperature: -40°C ~ 105°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Applications Information
LED Current Dimming
The LED current can be dimmed in two ways; either by applying a dc signal to the CTRL pin or by applying a Pulse Width
Modulated (PWM) signal to the CTRL pin.
A dc signal from 0.3V to 2.5V applied to the CTRL pin will vary the LED current from 24% to 200% of nominal LED current.
This gives an approximate 8:1 dimming range; care, however, should be exercised when overdriving the CTRL pin to 200%
LED current not to exceed the power dissipation of the package.
A PWM signal with a max resolution of 8bit can be applied to CTRL regulate the output current to a value below the nominal
average value set by resistor R
average LED currents than by applying dc voltage to the CTRL pin to achieve average LED current dimming.
The recommended method of driving the CTRL pin and controlling the amplitude of the PWM waveform is to use a small
NPN switching transistor as shown below:
This scheme uses the 50k resistor between the ADJ pin and the internal voltage reference as a pull-up resistor for the external
transistor eg MMBT3904.
AP8800A
Document number: DS35100 Rev. 2 - 2
SET
. PWM dimming gives a wider average LED current variation and is more accurate at lower
(Continued)
(T
A
= 25°C unless otherwise stated)
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COST EFFECTIVE 28V BUCK 1-W LED DRIVER
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AP8800A
© Diodes Incorporated
January 2011