Advanced Power

Electronics Corp.

APE1612

APPLICATION INFORMATION

Setting the ILED Current

Over Voltage Protection

Under Voltage Lockout (UVLO)

Input Capacitor Selection

Output Capacitor Selection

4

The output capacitor is required to keep the output voltage ripple small and to ensure

regulation loop stability. The output capacitor must have low impedance at the switching

frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their

low ESR and high ripple current. A 1uF ceramic capacitors works for most of the

applications. Higher capacitor values can be used to improve the load transient response.

Application circuit item shows the basic application circuit with APE1612 adjustable

output version. The external resistor sets the LED output current according to the following

equation:

⎟

⎠

⎞

⎜

⎝

⎛

=

3

3

.

0

R

V

I

LED

To avoid mis-operation of the device at low input voltages an under voltage lockout is

included that disables the device, if the input voltage falls below (2.25V-100mV).

The input capacitor reduces the surge current drawn from the input and switching

noise from the device. The input capacitor impedance at the switching frequency shall be

less than input source impedance to prevent high frequency switching current passing to

the input. A low ESR input capacitor sized for maximum RMS current must be used.

Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their

low ESR and small temperature coefficients. A 4.7 µ F ceramic capacitor for most

applications is sufficient. For a lower output power requirement application, this value can

be decreased.

20mA

15Ω

6mW

350mA

0.857Ω

105mW

R3

OV measure the output voltage for open circuit protection. Connect OV pin to the