BD94121F Datasheet, PDF (12/28 Pages) Rohm – PFC Direct current resonance type White LED Driver for Large LCD

BD9412F
PIN.6 IS
This is input pin of LED current feedback (IS pin) error amplifier. Please set up as normal voltage (ADIM/4.4)V
(Typ). When IS pin voltage becomes less than (ADIM/8.8)V (Typ) or higher than 1.0V, the output will be stopped
and latched.
50uA
FB
R2
IS
12kΩ
R1
ADIM
_
+
Gain
1/4.4
Error Amp
Figure. 17 IS Block Diagram
50µA (Typ) current flows from IS pin to external resistor during OFF period of burst brightness adjustment.
Considering Min value of IS source current during burst brightness adjustment, please set that total resistance
from IS Pin to GND is from 8kΩ to 22kΩ. When R2 is 12kΩ in above diagram, please set 8kΩ < R1 + R2 < 22kΩ.
PIN.7 VS
This is input pin of Open LED voltage feedback (VS pin) error amplifier. It has to be 1.25V during LED is open.
When LED is ON, it will be 0.5V to 1.0V. When VS pin becomes over 1.25V, protection circuit will start operation,
and if it becomes more than CP timer set up time (Timer Latch), it will shut down.
Connector
8
7
6
5
FB
R1
VS
R2 R3
Error Amp
_
+
1. 25 V
Figure. 18 VS Block Diagram
Please set C1, C2, R1, R2, and R3 value to input 1.25V to VS pin during LED bar’s connector disconnects.
PIN.8 PWMCMP
PWMCOMP pin voltage is fixed by DUTY of drive output N1, N2 in comparison with a saw wave of IC inside. This
pin has 100µA sink/source current capability and when external capacitor is connected between PWMCMP and
GND, IC will operate PWM at brightness start up stage. When N1 and N2 only drive at MaxDuty, please set
PWMCMP=open.
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TSZ22111 • 15 • 001
12/24
TSZ02201-0F5F0C100100-1-2
22.Feb.2016 Rev.001