CM9142 Datasheet, PDF (12/14 Pages) California Micro Devices Corp – Two Group, 4 and 2, WLED Driver, Different Current Settings

PRELIMINARY
CM9142
Application Information (cont’d)
Phone with Keyboard Backlight
The CM9142 can support a wireless phone with LCD
and a backlit keyboard. Group one can drive the back-
light to the LCD, and group two drive the keyboard
backlight. Each group can have a different current set-
ting, and individual PWM signals applied. One or both
groups can have their brightness controlled by a PWM
signal. In the example in Figure 11, both are controlled
with one PWM signal.
V_BATT
VIN
VOUT
R_SET2
R_SET1
ISET2
ISET1
LED1
LED2
LED3
LED4
CM9142
on
PWM
off
EN
GND
LED5
LED6
Main
Display
MENU
Camera Flash
The CM9142 can support a camera flash and a display
in digital still cameras as well as in camera equipped
smart phones and PDAs. A typical example would be
the main display is supplied by group 2, and the out-
puts of group 1 are used to support flash white LEDs.
See Figure 13. If less current is required for the Main
display drivers in group two, it can be allocated to
group one with the appropriate programming of the
R_SET resistors.
Enable
on ^{Display 1}
off
V_BATT
R_SET2
Flash
R_SET1
on ^Enable
off
VIN
ISET2
ISET1
VOUT
LED1
LED2
LED3
LED4
CM9142
EN
GND
LED5
LED6
WLED
Flash
Main
Display
Figure 11. Phone with Keyboard Backlight
PDA Backlight
The CM9142 can support larger displays such as color
LCDs for PDAs by utilizing both groups. Typically,
larger displays will require four or more WLED back-
lights. With all the drivers set at the same current, uni-
form backlighting can be achieved. EN can be used for
ON/OFF control PWM dimming. Figure 12 shows a
typical application.
V_BATT
VIN
VOUT
R_SET2
R_SET1
ISET2
ISET1
LED1
LED2
LED3
LED4
CM9142
on
PWM
off
EN
LED5
LED6
GND
PDA
Display
Figure 12. PDA Display Backlight
Figure 13. Display and Flash Application
If a full regulated flash current is needed, both display
outputs can be used to drive flash modules, as shown
in Figure 14. In this case, EN controls the flash,
enabling both outputs.
V_BATT
R_SET2
R_SET1
Flash
VIN
VOUT
ISET2
ISET1
LED1
LED2
LED3
LED4
CM9142
EN
GND
LED5
LED6
WLED
Flash
Figure 14. All Flash
Another option, which provides the maximum flash cur-
rent, can be implemented by pulling the cathode of the
flash LED to ground with a switch for the brief duration
of the flash. The example shown in Figure 15 shows an
example that allows the flash LED to be used as a
© 2006 California Micro Devices Corp. All rights reserved.
12 490 N. McCarthy Blvd., Milpitas, CA 95035-5112 l Tel: [phone] l Fax: [phone] l www.cmd.com
04/26/06