Datasheet AL5822 (Diodes) - 7

AL5822 Functional Descriptions
(Cont.)
Over Current Protection (OCP)
VS pin voltage will be limited to 0.2V (internal the IC), so the LED current will be limited at 0.2V/RS. When LED short or hot-plug, the current limit can protect the IC and MOSFET from a damage of over current. The internal current limit is prior to over-voltage protection, which means the limit of MOSFET drain voltage will not work if there’s LED over current condition.
Short Circuit Protection (SCP)
The AL5822 monitors the external MOSFET drain voltage, if the drain voltage exceeds VD_SHORT and this voltage keeps there for more than tSHT_DELAY, the IC will enter short circuit protection. When short circuit protection, the IC will turn off the external MOSFET for tSHT_HOLD period, after that, the IC will reset the SCP status and re-check the drain voltage, following the next protection cycle. The VD_SHORT voltage is set as:
T
VD_SHORT=2Vx(RLMT1/RLMT2+1)+40AxRLMT1
C U D O R
Short Protection
P
Threshold
W E N
LED Voltage VG 70s 70s 40ms Turn off Turn on Figure 9. SCP Waveform AL5822 7 of 10 January 2019 Document number: DS41708 Rev. 1 - 2
www.diodes.com
© Diodes Incorporated