ACE716E

Max 38V, Variable Frequency Step-up DC/DC Converter

VER 1.1

8

VFB =Duty*200 mV

(2)

Where

Duty = duty cycle of the PWM signal, 200 mV = internal reference voltage

This PWM dimming eliminates the audible noise which often occurs when the output current is pulsed in

replica of the frequency and duty cycle of PWM control. Unlike other scheme which filters the PWM signal

for analog dimming, ACE716E regulation voltage is independent of the PWM logic voltage level which

often has large variations For optimum performance, use the PWM dimming frequency in the range of

25kHz to 100kHz.

APPLICATION INFORMATION

Inductor Selection

Using an inductor with a smaller inductance value forces discontinuous PWM when the inductor current

ramps down to zero before the end of each switching cycle. This reduces the boost converter’s maximum

output current, causes large input voltage ripple and reduces efficiency. Large inductance value provides

much more output current and higher conversion efficiency. For these reasons, a 15μH to 22μH inductor

value range is recommended. A 15μH inductor optimized the efficiency for most application while

maintaining low inductor peak to peak ripple. Below table lists the recommended inductor for the

ACE716E.

Recommended Inductors for ACE716E

L(uH)

Saturation Current (mA)

Vendor

4.7- 15

>1500

Sunlord

Schottky Diode Selection

A high-speed rectifying Schottky with low parasitic capacitance is recommended for ACE716E for

maximum efficiency due to its high switching frequency.

The diode average and peak current rating

must be larger than the average output current and peak inductor current to ensure reliability. In addition,

the diode’s reverse breakdown voltage must exceed the open LED protection voltage.

Input and Output Capacitor Selection

The output capacitor is mainly selected to meet the requirements for the output ripple and loop stability.

The output requires a capacitor in the range of 2.2μF to 10μF.