SSL2103T NXP [NXP Semiconductors], SSL2103T Datasheet - Page 6

• Manufacturer Part Number: SSL2103T
• Description: SMPS controller IC for dimmable LED lighting
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
SSL2103
Product data sheet
8.3 Duty factor control
8.4 Bleeder for dimming applications
A typical RC waveform is shown in
by the BRIGHTNESS pin.
To ensure that the capacitor can be charged within the charge time, the value of the
oscillator capacitor should be limited to 1 nF. Due to leakage current, the value of the
resistor connected between the RC pin and the ground should be limited to a maximum of
220 k.
The duty factor is controlled by an internally regulated voltage and the oscillator signal on
pin RC. The internal regulation voltage is set by the voltage on the PWMLIMIT pin.
A low PWMLIMIT voltage will results in a low on-time for the external power switch. The
minimum duty factor of the switched mode power supply can be set to 0 . The maximum
duty factor is set to 75 .
The SSL2103 IC contains some circuitry intended for mains dimmer compatibility. This
circuitry can drive two external current sinks, called bleeders. A strong bleeder is used for
zero-cross reset of the dimmer and TRIAC latching. A weak bleeder is added to maintain
the hold current through the dimmer.
Fig 3.
Fig 4.
BRIGHTNESS
rc_threshold
Brightness control block
Brightness timing waveform
Voltage
(mV)
75 mV
All information provided in this document is subject to legal disclaimers.
5 V
Rev. 2 — 25 November 2010
24 μA
OSCILLATOR
V
V
Figure
RC voltage
rc_threshold
SMPS controller IC for dimmable LED lighting
4. The RC switch-over threshold is controlled
Comparator
RC
RC2
time
R2
10 kΩ
SSL2103
© NXP B.V. 2010. All rights reserved.
001aam657
014aab108
C1
330 pF
R1
220 kΩ
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