ISL1904 Datasheet, PDF (19/21 Pages) Intersil Corporation – Dimmable AC Mains LED Driver with PFC and Primary Side Regulation

ISL1904
and can be estimated using Equation 21.
t_delay ≈ 73.33 + 10.2 ⋅ R_DELADJ(kΩ)
ns
(EQ. 21)
DHC (Dimmer Holding Current)
The DHC pin provides a method to pre-load a triac-based dimmer
during the period of time when the AC is blocked, with overlap at
each edge of the AC conduction period to ensure adequate
holding current. DHC is an open drain FET used to control an
external resistor to act as the load.
DHC controls a resistor on the external high voltage start-up bias
regulator. See “Typical Application - Dimmable Isolated Flyback”
on page 3 for an example of its usage. Note the series resistor
and diode connecting VDD to the gate of the start-up bias FET. It
is required to keep the device on when the AC voltage is near the
zero-crossing.
Gate Drive
The ISL1904 output is capable of sourcing and sinking up to 1A.
The OUT high level is limited to the OUT clamp voltage or VDD,
whichever is lower.
Thermal Protection
Internal die over-temperature protection is provided. An
integrated temperature sensor protects the device should the
junction temperature exceed +160°C. There is approximately
+10°C of hysteresis.
Ground Plane Requirements
Careful layout is essential for satisfactory operation of the device.
A good ground plane must be employed. VDD and VREF should
be bypassed directly to GND with good high frequency
capacitance.
19
FN8286.1
September 20, 2012