Technical Note
10/22
BD60A00NUX, BD60A60NUX
www.rohm.com
2011.12 - Rev.A
© 2011 ROHM Co., Ltd. All rights reserved.
・
LED terminal over voltage protection
When FB terminal becomes higher than 5.9V(typ), IC senses the situation trouble after 100us and then stops constant
current driver and DC/DC. Therefore IC becomes never heated, even if output and FB are both shorted. Moreover, if FB
terminal becomes lower than 5.9V(typ), IC senses normal condition and activates constant current driver.
・
Prevention of LED terminal over voltage protection malfunction
As the below diagrams show, voltage drop of FB terminal becomes slow when PWM operates by connecting capacitor on
a parallel with LED and decreasing LED current. At that time, LED terminal voltage protection works after condition of FB
terminal > 5.9V keeps more than 100us. LED terminal voltage protection might stop current driver and DC/DC and also
turns off LEDs, so that please set up coil selection and LED current setting less than 100us until FB terminal < 5.9V.
・
Low voltage detect protection (UVLO)
Supply voltage(VIN) becomes lower than low voltage detect voltage 2.2V(typ), IC stops DC/DC and constant current
driver. Moreover, this function can be off by boosting supply voltage up to more than hysteresis voltage.
DC/DC
Current Driver
VIN
reset
2.20 V
5%
0V
Active
Active
2.32 V
Current Driver
FB
reset
5.9 V
0V
Active
Active
DC/DC
Active
Active
Active
FB
VOUT
Current Driver
FB
reset
5.9 V
Active
DC/DC
Active
100us
reset
reset
reset
PWM
L
H
EN
L
H