SM8131B Datasheet, PDF (9/21 Pages) Nippon Precision Circuits Inc – The SM8131B is a charge pump DC/DC converter that switches between 1 and 1.5 automatically.

SM8131B
V_OUT Output Circuit Mode Switching
The SM8131B switches between 3 output states: power-save mode (standby state), ×1.0 mode (VIN through
mode), and ×1.5 mode (×1.5 charge pump boost). This automatically adjusts the VOUT output to match the
drive LED characteristics and reduces the total power dissipation. Switching to and from ×1.0 and ×1.5 mode
occurs automatically in an internal circuit, and cannot be controlled using an external input.
Power-ON internal reset time
The SM8131B switches from standby condition (power-save mode) to normal operating condition (×1.0/×1.5
mode) on the first rising edge of either EN1 or EN2. Note that if the VIN supply voltage is applied when EN1
or EN2 is HIGH, startup occurs after the internal power-ON reset time (approximately 50µs) expires. At star-
tup, operation commences in ×1.5 mode for a fixed interval during the soft-start time in order to determine
whether a LED is connected to each DIN pin.
VIN
power source
(1)
VIN
Power on
POR time
reset output
typ: 50µs
(2)
Internal
enable (CE)
Power save
mode
Soft start time
(3)
1.5 mode
Power-ON reset operation
(1) VIN voltage rises when power is applied.
(2) Power-ON reset (POR) circuit resets internal circuits approximately 50µs after the power is applied.
(3) If EN1 or EN2 is HIGH when power is applied, the internal circuits start operating when the internal “CE”
signal rising edge occurs after the power-ON reset time. If EN1 and EN2 are LOW when power is applied,
the “CE” rising edge occurs simultaneously with the first rising edge.
EN1
input signal
LED current
EN1
Dimming pulses enable
Soft start time
typ: 1.3ms
(1)
LED ON (2)
Soft start time and LED current
(1) If the EN signals are input after POR time is expired, the soft start time begin from the first EN input rising
edge. The current setting can be adjusted during the soft-start time.
(2) LED current starts flow immediately before the soft start time expires.
NIPPON PRECISION CIRCUITS INC.—9