SSL2109T

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© NXP B.V. 2012. All rights reserved.

Product data sheet

Rev. 2 — 26 April 2012

5 of 19

NXP Semiconductors

SSL2109T

GreenChip controller for LED lighting

8.

Functional description

8.1 Introduction

The SSL2109T is an IC intended for small form factor retrofit SSL lamps and separate

LED drivers.

8.2 Converter operation

The converter in the SSL2109T is a Boundary Conduction Mode (BCM), peak current

controlled system. For the basic application diagram see Figure 3, for the waveforms see

Figure 4. This converter type operates at the boundary between continuous and

discontinuous mode. Energy is stored in inductor L each period that the switch is on. The

is on. When the MOSFET switch is switched off, the current continues to flow through the

freewheel diode and the output capacitor. The current then falls at a rate proportional to

8.3 Conversion frequency

The conversion frequency must be limited to below 200 kHz. Therefore, select an

inductance value so that the conversion frequency is always within limits, given the supply

voltage, LED voltage and component spread.

8.4 Driver pin

The SSL2109T is equipped with an external driver that can control an external switch. The

During transition from low to high and back, there is a controlled switching slope

steepness. This controlled condition limits the high frequency radiation from the circuit to

the surrounding area.

Fig 3.

Basic application diagram SSL2109T

SSL2109

HV

DVDT

VCC

DRAIN

NTC

DRIVER

GND

NTC

LEDs

SOURCE

aaa-001743

1

2

3

7

5

4

6

8

Rinrush

Rsense

Vsec