s1f81310f0a Epson Electronics America, Inc., s1f81310f0a Datasheet - Page 13

• Manufacturer Part Number: s1f81310f0a
• Description: Charge-pump Type White Led Driver.
• Manufacturer: Epson Electronics America, Inc.

S1F81310F0A (Rev.1.0)
enable (CE)
[Switching to power-save mode]
[Switching from 1.0 × mode to 1.5 × mode]
EN1+EN2
The internal circuit operating mode switches from 1.0x/1.5x mode to power-save mode when both EN1 and
EN2 go 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.
If the LEDs can be driven solely by the current determined by RSET and EN pulse input without boosting
the VIN input voltage, the VOUT output operates in 1.0x mode. In other words, if sufficient current flows
even with the LED forward-direction voltage drop VF, then VOUT is less than 4.2V. Operation in the more
efficient 1.0x mode reduces the total power dissipation and extends the battery drive time. And if low VF
LEDs are used or the LED current setting is low, the operating time in 1.0x mode is also extended.
internal
input
High VF
LED
Low VF
LED
input
EN1
EN2
VOUT mode switching time comparison due to drive LED VF variation
Power
High
Save
1.0x mode
(high efficiency)
1.0x mode
(high efficiency)
VIN
EN input signal and internal enable signal CE
1.0x or 1.5x
1.63ms (max)
CE hold time
EPSON
VIN input
1.5x mode
(low efficiency)
Power
Save
8. FUNCTIONAL DESCRIPTION
1.5x mode
(low efficiency)
If the internal enable signal CE goes
from HIGH to LOW and are held for an
interval greater than the CE hold time
1.63ms (max), the SM8131 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.
If the EN signals are input after power is
applied and the POR time has expired,
the internal enable signal CE switches
with the EN1+EN2 signal.
Low
9