SM8134AB datasheet(13/19 Pages) NPC

13 / 19 page

SM8134A

SEIKO NPC CORPORATION —13

For example, if the VIN voltage is low and the VOUT output voltage in ×1.0 mode does not provide sufﬁcient

drive current, then the mode reset will cause a LED undercurrent condition. The LED undercurrent detector

circuit will output an LED undercurrent signal immediately after the switch to

×1.0 mode, but the output will

stay in

×1.0 mode and not return to ×1.5 mode for the duration of the mode hold time. Consequently, the VOUT

output is not boosted during the 85

µs (min) to 200µs (max) mode hold time and the voltage drops and the LED

brightness is reduced. However, the LEDs are OFF for a maximum of 200

µs only, and this is not discernible to

the naked eye and thus is not a problem.

VOUT drop due to the mode reset single

Mode reset

(1.4sec/cycle)

Mode hold

(H: hold)

Low ILED detector

(H: low ILED)

VOUT

output voltage

VIN input voltage

1.4sec

max

200

µS

1.0

1.5 threshold

4.9V

VOUT mode

(H: 1.5, L: 1.0)

SM8134AB Datasheet(PDF) 13 Page - Nippon Precision Circuits Inc