E522.31_16 Datasheet, PDF (15/20 Pages) ELMOS Semiconductor AG – CHANNEL SWITCHED MODE CONSTANT CURRENT CONTROLLER

1 CHANNEL SWITCHED MODE CONSTANT CURRENT CONTROLLER
PRODUCTION DATA - JUL 21, 2016
E522.31/33
Operation _{No Operation}
with f_{RT ERRBx set}
Operation
with f_OSCIN
0
f_RT
No Operation
ERRBx set
f_OSCIN
0
f_RT
Wobbling disabled for proper
f_OSCIN Detection
0
f_RT
Figure 1. OSCIN Failure Check
f_OSCIN
f_OSCIN
5.10 Short Circuit Monitoring for floating LED Loads
The circuitry shown in (Figure 2) can be used to detect
LED chain short circuit in floating output topologies (e.g.
boost-to-battery). The resistors R_SC1,2 are used to adapt
the threshold for short circuit detection to a threshold
of V_SC,DETECT=U(BE)*(1+R_SC1/R_SC2), with U(BE) being the
base-emitter voltage of the bipolar transistor devices.
Choose R_SC1 value sufficiently high to prevent unintend-
ed discharge of the converter output during dimming
cycles. The negative thermal coefficient of this topolo-
gy can be used to partially compensate the temperatur
dependent characteristic of the load. With the connec-
tion to ERRB of E522.3x, the combined feedback signal
includes all failures detected by E522.3x together with
the short circuit (or under-voltage) information of the
highside load. An additional capacitor parallel to R_SC2
may be useful to implement debouncing of the feed-
back signal or to increase of EMI of the circuit.
Dimming
(if used)
R_SC1
Feedback
Channel
(incl. Pull-up)
ERRB
R_SC2
Figure 2. Exemplary shown circuit monitoring in Boost-to-Battery application
Elmos Semiconductor AG reserves the right to change the detail specifications as may be required to permit improvements in the design of its products.
Elmos Semiconductor AG
Data Sheet
QM-No.: 25DS0085E.01
15/20