SM8132A Datasheet, PDF (10/18 Pages) Nippon Precision Circuits Inc – White LED Driver IC

SM8132A
V_OUT Output Circuit Mode Switching
The SM8132A 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 SM8132A switches from standby condition (power-save mode) to normal operating condition (×1.0/×1.5
mode) on the first rising edge of EN. Note that if the VIN supply voltage is applied when EN is HIGH, startup
occurs after the internal power-ON reset time (approximately 50µs) expires. At startup, 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 EN 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 EN is LOW when power is applied, the “CE” rising
edge occurs simultaneously with the first rising edge.
EN
input signal
EN
LED current
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.—10