SSL21084T(2013) 查看數據表（PDF） - NXP Semiconductors.

零件编号

产品描述 (功能)

生产厂家

SSL21084T
(Rev.:2013)

Mains driver LED driver IC

NXP Semiconductors. 

NXP Semiconductors

SSL21084T

Mains dimmable LED driver IC

During start-up, before VCC reaches VCC(startup) the voltage on the NTC pin must be less

than the minimum value of Vact(tmr)NTC. This is valid when the voltage on the NTC pin is

derived from the VCC 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 VCC reaches VCC(startup).

Peak current

Ipk

Vth(ocp)SOURCE = 500 mV

Ipk / 2

Vth(ocp)SOURCE = 250 mV

1

23

4

5 VNTC

001aan700

Fig 6. NTC control curve

When the voltage on the NTC pin exceeds Vth(high)NTC (see Figure 6 (4)), the converter

delivers nominal output current. When the voltage is lower than this level, the peak current

is gradually reduced until Vth(low)NTC is reached (see Figure 6 (3)). The peak current is

now half the peak current of nominal operation. When Vact(tmr)NTC is passed (see Figure 6

(2)) a timer starts to run to distinguish between the following situations:

• If the low-level Vdeact(tmr)NTC is not reached within time tto(deact)NTC (see Figure 6 (1))

LED overtemperature is detected. The IC stops switching and attempts to restart from

the HV pin voltage. The converter restarts from an NTC protection shutdown when the

voltage on the NTC pin exceeds Vth(high)NTC (see Figure 6 (4)). It is assumed that the

reduction in peak current does not result in a lower NTC temperature and LED OTP is

activated.

• If the low-level Vdeact(tmr)NTC is reached within the time tto(deact)NTC (see Figure 6 (1)) it

is assumed that the pin is pulled down externally. The restart function is not triggered.

Instead, the output current is reduced to zero. PWM dimming can be implemented this

way. The output current rises again when the voltage is higher than Vth(low)NTC.

8.7.1 Soft-start function

The NTC pin can be used to make a soft start function. During switch-on, the level on the

NTC pin is low. By connecting a capacitor (in parallel with the NTC resistor), a time

constant can be defined. The time constant causes the level on the NTC pin to increase

slowly. When passing level Vth(low)NTC (see Figure 6 (3)), the convertor starts with half of

the maximum current. The output current slowly increases to maximum when Vth(high)NTC

(see Figure 6 (4)) is reached.

SSL21084T

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.

11 of 22

Share Link: