SC658ULTRT Semtech, SC658ULTRT Datasheet - Page 12

• Manufacturer Part Number: SC658ULTRT
• Description: Backlight Driver For 4 LEDs With SemPulseTM Interface
• Manufacturer: Semtech

Applications Information (continued)
must be followed regardless of which backlight grouping
configuration is being used. Note that it is only necessary
to set the BLEN bits for the main display.
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 Fade register (04h). 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 Fade register (04h). This procedure must be
followed regardless of the backlight grouping
configuration.
.
2.
3.
4.
5.
.
2.
Table 2 — Fade-Out from any On State to Off State
Disable fade
Set Main back-
lights to 0.5mA
Enable fade
Set BLEN bits
Set new value of
backlight current
Enable fade
Set Main back-
lights to 0mA
Command
Command
Sequence
Sequence
Table 1 — Fade-In from Off State
Write to register 04h
Write to register 0h
Write to register 04h
Write to register 00h
Write to register 0h
Write to register 04h
Write to register 0h
Action
Action
Any value from 0h
Any value from 05h
0h, 02h, or 03h
0h, 02h, or 03h
(but not 00h)
through 3Fh
through Fh
Data
Data
00h
04h
00h
Additional Information
For more details about the Fade-in/Fade-out function,
refer to the SC658 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).
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.
Sleep Mode
When all LEDs are disabled, sleep mode is activated. This
is a reduced current mode that helps minimize overall
current consumption by disabling the clock and the
charge pump while continuing to monitor the serial inter-
face for commands. An additional current savings can be
obtained by putting the serial interface in standby mode
(see SemPulse Interface, Standby Mode).
Protection Features
The SC658 provides several protection features to safe-
guard the device from catastrophic failures. These features
include:
Output Open Circuit Protection
Over-Voltage Protection (OVP) at the OUT pin prevents the
charge pump from producing an excessively high output
voltage. In the event of an open circuit between the OUT
pin and all current sinks (no loads connected), the charge
.
2.
•
•
•
•
Enable fade
Set new value of
backlight current
Command
Table 3 — Fading between Different On States
Sequence
Output Open Circuit Protection
Over-Temperature Protection
Charge Pump Output Current Limit
LED Float Detection
Write to register 04h
Write to register 0h
Action
Any value from 05h
0h, 02h, or 03h
through Fh
Data
2