SSL21081AT Datasheet, PDF (8/22 Pages) NXP Semiconductors – Compact non-dimmable LED driver IC

NXP Semiconductors
SSL21082AT
Mains dimmable LED driver IC
8.4 Protective features
The IC has the following protective features:
• UnderVoltage LockOut (UVLO)
• Leading-Edge Blanking (LEB)
• OverCurrent Protection (OCP)
• Internal OverTemperature Protection (OTP)
• Brownout protection
• LED OverTemperature Control (OTC) and overtemperature protection
• An optional output OverVoltage Protection (OVP) circuit is implemented using
external components and the NTC pin.
• Output Short Protection (OSP)
The internal OTP and LED overtemperature protections are safe-restart protections. The
IC halts, causing V_CC to drop below V_CC(stop) and triggers a start-up. When V_CC drops to
below V_CC(rst), the IC resets the latch protection mode. If V_CC drops to below V_CC(stop), the
IC halts. Switching starts only when no fault condition exists.
8.4.1 UnderVoltage LockOut (UVLO)
When the voltage on the VCC pin < V_CC(stop), the IC stops switching. An attempt is then
made to restart by supplying V_CC from the HV pin voltage.
8.4.2 Leading-Edge Blanking (LEB)
To prevent false detection of the overcurrent, a blanking time following switch-on is
implemented. When the MOSFET switch switches on there can be a short current spike
due to capacitive discharge of voltage over the drain and source and the charging of the
gate to source capacitance. During the LEB time (t_leb), the spike is disregarded.
8.4.3 OverCurrent Protection (OCP)
The SSL21082AT contains a highly accurate peak current detector. It triggers when the
voltage on the SOURCE pin reaches the peak level V_{th(ocp)SOURCE}. The current through
the switch is sensed using a resistor connected to the SOURCE pin. The sense circuit is
activated following LEB time t_leb. As the LED current is half the peak current (by design), it
automatically provides protection for maximum LED current during operation. There is a
propagation delay (t_d(ocp-swoff)) between the overcurrent detection and the actual switching
off of the switch. Due to the delay, the actual peak current is slightly higher than the OCP
level set by the resistor in series to the SOURCE pin.
8.4.4
OverTemperature Protection (OTP)
When the internal OTP function is triggered at a certain IC temperature (T_th(act)otp), the
converter stops operating. The OTP safe-restart protection and the IC restart with
switching resuming when the IC temperature drops below T_th(rel)otp.
SSL21082AT
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 6 — 3 October 2013
© NXP B.V. 2013. All rights reserved.
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