sc643 Semtech Corporation, sc643 Datasheet - Page 14

• Manufacturer Part Number: sc643
• Description: Light Management Unit With 4 Ldos And Sempulse Interface
• Manufacturer: Semtech Corporation

Applications Information (continued)
Notes:
(1) Write only to the banks which will fade
Fade-Out from any On State to Off State
Fading the backlight LEDs from any active state to the off
state follows a simple procedure. The sequence of com-
mands for this action is shown in Table 2. Following these
steps explicitly will ensure that the fade-out operation will
proceed with no interruption at the rate specifi ed in the
Main/Sub Backlight Fade register (09h). This procedure
must be followed regardless of the backlight grouping
confi guration.
Fading Between Diff erent On States
Fading from one backlight level to another (up or down)
also follows a simple procedure. The sequence of com-
mands for this action is shown in Table 3. Following these
1.
2.
3.
4.
5.
1.
2.
Table 2 — Fade-Out from any On State to Off State
Disable fade for
the bank
Set the bank to
0.5mA
Enable fade
Set BLEN bits
Set new value of
backlight current
for the bank
Enable fade
Set Main and/or
Sub backlights to
0mA
Command
Command
Sequence
Sequence
Table 1 — Fade-In from Off State
Write to register 09h
Write to register 01h
Write to register 09h
Write to register 00h
Write to register 01h
Write to register 09h
Write to register 01h
and/or 02h
and/or 02h
and/or 02h
Action
Action
(1)
Any value from 01h
Any value from 05h
Any value from 01h
xx1xx0, xx1xx1,
(but not 00h)
Binary value
through 1Fh
through 1Fh
through 3Fh
or xx0xx1
Data
Data
00h
04h
00h
steps explicitly will ensure that the fade-in/fade-out oper-
ation will proceed with no interruption at the rate specifi ed
in the Main/Sub Backlight Fade register (09h). This proce-
dure must be followed regardless of the backlight
grouping confi guration.
Additional Information
For more details about the Fade-in/Fade-out function,
refer to the SC643 Backlight Driver Software User’s Guide
and SemPulse Interface Specifi cation document and to the
associated software drivers available for this device
(contact your sales offi ce for more details).
Programmable LDO Outputs
Four low dropout (LDO) regulators are included to supply
power to peripheral circuits. Each LDO output voltage
setting has ±3.5% accuracy over the operating tempera-
ture range. Output current greater than specifi cation is
possible at somewhat reduced accuracy (refer to the
typical characteristic section of this datasheet for load
regulation examples). LDO1, LDO3, and LDO4 have iden-
tical specifi cations, with a programmable output ranging
from 1.5V to 3.3V. LDO2 is specifi ed to operate with pro-
grammable output ranging from 1.2V to 1.8V. LDO2 also
has lower noise specifi cations so that it can be used with
noise sensitive circuits.
LDO4 is controlled by both the enable pin ENL4 and the
LDO4 control register. ENL4 may be permanently con-
nected to V
sequencing logic may be used to enable LDO4 via the
ENL4 pin after writing to the LDO4 control register.
1.
2.
Enable fade
Set new value of
backlight current
Command
Table 3 — Fading between Diff erent On States
Sequence
IN
for software-only control. Alternately, power
Write to register 09h
Write to register 01h
and/or 02h
Action
Any value from 01h
Any value from 05h
(but not 00h)
through 3Fh
through 1Fh
Data
SC643
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