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| SSL3401HN Datasheet, PDF (11/29 Pages) NXP Semiconductors – Low voltage dimmable controller for LED lighting | |||
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NXP Semiconductors
SSL3401HN
Low voltage dimmable controller for LED lighting
If the input power, based on the default input current, is lower than the
maximum LED power + system losses, the LED current PWM is adjusted. Otherwise, the
input current is adjusted to maintain the system power balance. The maximum LED power
is equal to VLED(max) ï´ ILED(max). ILED(max) is the maximum LED current when the LED
current PWM signal is continuously LOW. VLED(max) is the voltage across the LED string
when biased with ILED(max).
The optimum values of the LED current, the boost output capacitor Cbus, and the coil
current sensing resistor RICBST can be calculated with Equation 2 and Equation 3:
I---L---E---D-
Cbus
=
---0---.--2-----A-----
330 ïF
(2)
RICBST ï´ Cbus = 0.24 ï ï´ 330 ïF
(3)
8.8 Protection circuits
Several protection circuits are integrated to protect the device and the application against
defects.
The SSL3401HN embedded protection circuits are:
⢠OverVoltage Protection (OVP)
⢠Coil Current Limitation (CCL)
⢠OverTemperature Protection (OTP)
⢠Open LED protection (OLED)
⢠Shorted LED protection (SLED)
⢠Power-On Reset protection (POR)
8.8.1 Overvoltage protection
Every 41.667 ïs, the OVP detector checks if the voltage on the OVP pin exceeds a preset
threshold Vth(ovp).
If the voltage on the OVP pin exceeds Vth(OVP), the boost converter is disabled. Normal
operation is resumed once the voltage on the OVP pin drops to < Vth(ovp) ï Vovp(hys). When
OVP is active, the feedback loops and the LED current control are frozen.
8.8.2 Coil current limitation
The device is equipped with a peak coil current limiting function to avoid excessive current
in the inductor.
The voltage on the ACMPREF pin is limited. The limitation ensures that the average coil
current does not exceed Ilim(L)M = 1.1 A * 200 mï / RICBST. The coil current limitation
disregards the latching current. Thus, if a latching current is set, the maximum coil current
equals Ilim(L)M plus the input latching current.
SSL3401HN
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 â 28 January 2014
© NXP B.V. 2014. All rights reserved.
11 of 29
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