SM8132A

NIPPON PRECISION CIRCUITS INC.—11

Switching to power-save mode

The internal circuit operating mode switches from

×1.0/×1.5 mode to power-save mode when EN goes LOW

and do not switch HIGH for an interval of 1.63ms (max). This function turns the LEDs OFF and automatically

transfers internal circuit control to power-save mode, suppressing current consumption.

I

If the EN input signal is held for an interval greater than the “CE” hold time 1.63ms (max), the SM8132A

switches to power-save mode. The internal circuits are reset on the “CE” falling edge, and the current setting

must be re-established before restart.

Switching from

×1.0 mode to ×1.5 mode

If the LEDs can be driven solely by the current determined by RSET and EN pulse input without boosting the

×1.0 mode reduces the total power dissipation and extends the battery drive time. And if low “VF” LEDs are

used or the LED drive current setting is LOW, the operating time in

×1.0 mode is also extended.

the charge pump boosts the output voltage. This occurs even if only one LED low-current condition is detected

among the 4-channel LED drive circuits, thus it is recommended that LEDs have small “VF” variation to opti-

mize the total efficiency.

EN input signal and internal enable signal “CE”

CE hold time 1.63ms (max)

EN

Internal

enable (CE)

Power

save

Power

save

1.0 or 1.5

High

High VF LED

Low VF LED

1.0 mode

(high efficiency)

VIN input

1.5 mode

(low efficiency)

1.5 mode

(low efficiency)

Low

1.0 mode

(high efficiency)