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

• 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
Inductor Selection
A 68μH inductor or higher, is recommended for most AP8800A applications with input voltage at 12V.
Figure 3 displays the resulting switching frequency with various main circuit parameters: Supply voltage, Inductor value and
number of LEDs to be driven.
Capacitor Selection
A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in series with the supply
source impedance and lowers overall efficiency. This capacitor has to supply the relatively high peak current to the coil and
smooth the current ripple on the input supply. A minimum value of 1μF is acceptable if the DC input source is close to the
device, but higher values will improve performance at lower input voltages, especially when the source impedance is high.
The input capacitor should be placed as close as possible to the IC.
For AC input sources a bigger capacitor ( 300uF in the case of 12C AC) to guarantee the accuracy of the LED current.
For maximum stability over temperature and voltage, capacitors with X7R, X5R, or better dielectric are recommended.
Capacitors with Y5V dielectric are not suitable for decoupling in this application and should NOT be used.
Diode Selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance SBR diode with low reverse
leakage at the maximum operating voltage and temperature. The recommended diode for use with this part is the SBR1A40,
with a current rating above the peak coil current and a continuous current rating higher than the maximum output load current.
It is very important to consider the reverse leakage of the diode when operating above 85°C. Excess leakage will increase the
power dissipation in the device.
AP8800A
Document number: DS35100 Rev. 2 - 2
700
600
500
400
300
200
100
0
0
Figure 3. Switching Frequency Vs Supply voltage, Inductor, and number of LEDs
50
47
68
100
100
100
(Continued)
150
150
150
200
Inductor Value [uH]
(T
Switching Frequency
220
A
220
= 25°C unless otherwise stated)
www.diodes.com
250
COST EFFECTIVE 28V BUCK 1-W LED DRIVER
7 of 12
300
350
400
450
470
470
500
AP8800A
© Diodes Incorporated
12V - 1LED
24V - 3 LEDs
28V - 4LEDs
January 2011