SSL21081AT Datasheet, PDF (10/22 Pages) NXP Semiconductors – Compact non-dimmable LED driver IC

NXP Semiconductors
SSL21082AT
Mains dimmable LED driver IC
8.5 VCC supply
The SSL21082AT can be supplied using three methods:
• Under normal operation, the voltage swing on the DVDT pin is internally rectified to
provide current on the VCC pin
• At start-up, there is an internal current source connected to the HV pin. The current
source provides internal power until either the dV/dt supply or an external current on
the VCC pin provides the supply.
• Using an auxiliary winding, the voltage can be rectified and connected to the VCC pin
via a series resistor.
The IC starts up when the voltage at the VCC pin exceeds V_CC(startup). The IC locks out
(stops switching) when the voltage on the VCC pin < V_CC(stop). The hysteresis between
the start and stop levels allows the IC to be supplied by a buffer capacitor until the external
supply is stable. The SSL21082AT has an internal V_CC clamp, which is an internal active
Zener (or shunt regulator). This internal active Zener limits the voltage on the supply VCC
pin to the maximum value of V_CC. If the maximum current of the supply minus the current
consumption of the IC (determined by the load on the gate drivers), is lower than the
maximum value of I_DD, an external Zener diode is not required in the supply circuit.
8.5.1 VCC regulator
During supply dips, the input voltage can drop too low to supply the required IC current.
Under these conditions, if the VCC voltage drops lower than the V_CC(swon)reg level, a
second regulator is started. Its function is to fill in the required supply current which the
external supply does not deliver. It prevents that the IC goes into UVLO. When the VCC
voltage exceeds V_CC(swon)reg level, the regulator is turned off.
8.6 DVDT pin supply (dV/dt)
The DVDT pin is connected to an internal single-sided rectification stage. When an
alternating voltage with sufficient amplitude is supplied to this pin, the IC can be powered
without another external power connection. This provides a compact and effective solution
without introducing high power losses and without requiring an additional inductor
winding.
8.7 NTC functionality and PWM dimming
The NTC pin can be used as a control method for LED thermal protection. Alternatively,
the pin can be used as an input to disable/enable light output using a digital signal (PWM
dimming). The pin has an internal current source that generates the current of I_offset(NTC).
An NTC resistor to monitor the LED temperature can be directly connected to the NTC
pin. Depending on the resistance value and the corresponding voltage on the NTC pin,
the converter reacts as shown in Figure 6.
During start-up, before V_CC reaches V_CC(startup) the voltage on the NTC pin must be less
than the minimum value of V_act(tmr)NTC. This is valid when the voltage on the NTC pin is
derived from the V_CC using a resistive divider and a PTC in series with the resistor
between pins VCC and NTC.
If an NTC resistor is connected between the NTC pin and ground, the voltage on the NTC
pin is 0 V when V_CC reaches V_CC(startup).
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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