c644ultrt Semtech Corporation, c644ultrt Datasheet - Page 14

• Manufacturer Part Number: c644ultrt
• Description: Light Management Unit With 4 Ldos And Sempulse Interface
• Manufacturer: Semtech Corporation

Applications Information (continued)
Notes:
() 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 specified in the
Main/Sub Backlight Fade register (09h). This procedure
must be followed regardless of the backlight grouping
configuration.
Fading Between Different 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
steps explicitly will ensure that the fade-in/fade-out oper-
ation will proceed with no interruption at the rate specified
in the Main/Sub Backlight Fade register (09h). This proce-
.
2.
3.
4.
5.
.
2.
Table 2 — Fade-Out from any On State to Off State
Disable fade for
the bank
Set Main and/or
Sub backlights to
0.5mA
Enable fade for
the bank
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 0h
Write to register 09h
Write to register 00h
Write to register 0h
Write to register 09h
Write to register 0h
and or 02h
and/or 02h
and/or 02h
Action
Action
()
Any value from 05h
Any value from 0h
Any value from 0h
xxxx0 , xxxx,
xx0xxx, xxxxx0,
Binary value
Binary value
through 3Fh
through Fh
through 3Fh
or xx0xx0
or xx0xx
Data
Data
04h
00h
dure must be followed regardless of the backlight
grouping configuration.
Additional Information
For more details about the Fade-in/Fade-out function,
refer to the SC644 Backlight Driver Software User’s Guide
and SemPulse Interface Specification document and to the
associated software drivers available for this device
(contact your sales office 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 specification is
possible at somewhat reduced accuracy (refer to the
typical characteristic section of this datasheet for load
regulation examples). LDO, LDO3, and LDO4 have iden-
tical specifications, with a programmable output ranging
from .5V to 3.3V. LDO2 is specified to operate with pro-
grammable output ranging from .2V to .8V. LDO2 also
has lower noise specifications so that it can be used with
noise sensitive circuits.
Shutdown Mode
The device is disabled when the SPIF pin is held low for
the shutdown time specified in the electrical characteris-
tics section. All registers are reset to default condition at
shutdown. Typical current consumption is this mode is
0.µA
Sleep Mode
When all backlights are off the charge pump is disabled,
and sleep mode is activated. This is a reduced current
mode that helps minimize overall current consumption.
In sleep mode, the SemPulse interface continues to
monitor its input for commands from the host. Typical
current consumption in this mode is 90µA.
.
2.
Enable fade
Set new value of
backlight current
Command
Table 3 — Fading between Different On States
Sequence
Write to register 09h
Write to register 0h
and/or 02h
Action
Any value from 05h
Any value from 0h
through 3Fh
through Fh
Data
4
4