CM9142 Datasheet, PDF (6/14 Pages) California Micro Devices Corp – Two Group, 4 and 2, WLED Driver, Different Current Settings

PRELIMINARY
CM9142
Pin Descriptions (cont’d)
PIN DESCRIPTIONS
Current set and shutdown pin for drivers, active low.Pull high to shutdown the
group.
To set the LED current, a resistor, R_SET, is connected between this pin and ground.
The regulated LED current is 1000x the current flowing in R_SET, and is
5
ISET2
approximately:
I_LED
=
0----.-6---6---V------–-----(_{--L----o----g---i--c---L----o---w-----}) _{× 1000}
R_SET
If this resistor is tied to directly ground (and enable function not used) Logic Low =
0, otherwise subtract the voltage drop of the device that drives this pin low.
6
NC
Cathode of LED5 pin.
7
NC
Cathode of LED6 pin.
8
C2N
This pin is the minus side of charge pump bucket capacitor C2. Connect a 1.0μF
ceramic capacitor between C2N and C2P.
9
EN
PWM/Analog input pin. Can be used as second Enable pin, active high. Should tied
high when not used.
10
GND
Ground terminal pin.
11
C1N
This pin is the minus side of charge pump bucket capacitor C1. Connect a 1.0μF
ceramic capacitor between C1N and C1P.
12
LED4
Cathode of LED4 pin.
13
C2P
This pin is the plus side of charge pump bucket capacitor C2. Connect a 1.0μF
ceramic capacitor between C2N and C2P.
14
LED3
Cathode of LED3 pin.
15
VOUT
Charge pump output voltage pin, which connects to the anodes of all LEDs. A 1μF
capacitor to ground is recommended.
16
LED2
Cathode of LED2 pin.
Application Information
The CM9142 is a switched capacitor, charge pump
voltage converter ideally suited for driving white LEDs
to backlight LCD color displays in portable devices.
The CM9142 charge pump is the perfect driver for por-
table applications such as cellular phones, digital still
cameras, PDAs and any application where small
space, compact overall size, low system cost and mini-
mal EMI are critical.
The CM9142 requires only two external switched
(bucket) capacitors, plus an input and an output capac-
itor, providing for a compact, low profile design. In
many applications, these can all be conveniently the
same value of 1.0µF, available in a compact 0805 sur-
face mount package.
The adaptive conversion ratio selects the most efficient
operating mode. When V_IN is higher than the needed
V_OUT (V_LED+V_{CURRENT_SINK}), the 1x mode is set.
When the input voltage is below the LED forward volt-
age and a voltage boost is needed, the 1.5x mode is
automatically selected. The 1.5x mode uses a frac-
© 2006 California Micro Devices Corp. All rights reserved.
6 490 N. McCarthy Blvd., Milpitas, CA 95035-5112 l Tel: [phone] l Fax: [phone] l www.cmd.com
04/26/06