SEA05L Datasheet, PDF (8/12 Pages) STMicroelectronics – Advanced constant voltage and constant current controller with very efficient LED pilot-lamp driver

Application information
Figure 4. Output voltage versus output current
Vout
Voltage regulation
SEA05L
Io u t (V cc of the device independent from output voltage)
AM04987v1
2.2
Compensation
The voltage control transconductance operational amplifier can be fully compensated. Both
its output and negative input are directly accessible for external compensation components.
2.3
LD pin function
The device provides a unique feature that allows highly efficient driving of an LED pilot-lamp.
The main benefit of this new feature is to allow reducing the standby power consumption of
the SMPS with the LED pilot-lamp.
The LD pin is an open-drain output able to sink 5 mA (peak), driven by the internal oscillator
at 1 kHz (typ.) square waveform with 12.5% duty cycle (see Figure 6). The internal mosfet
starts to switch when V_CC is above the turn-on threshold (typ 3 V) and it is off (LD high
impedance) when V_CC is below the UVLO of the IC.
Connecting the LED pilot-lamp, with a resistor in series in order to limit the LED current, to
pin LD (as shown in Figure 5) reduces the power consumption of the LED while keeping the
same driving peak current. The LED driving current modulation frequency of 1 kHz (typ.)
eliminates the visual perception of flickering.
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Doc ID 18462 Rev 1