PRELIMINARY
CM9142
Two Group, 4 and 2, WLED Driver, Different Current Settings
Features
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2.9V to 6V input voltage range
Powers two display backlight and/or flash WLEDs
Low external parts count, requires no inductor and
ballast resistors
Low EMI and reflected ripple
Adaptive charge pump ratio (1x or 1.5x) maximizes
efficiency at both high and low input voltage
Precision current regulation for each output with
2% current matching at 20mA
Programmable LED current via ISET1 and ISET2
Independent Analog and PWM brightness control
Independent current setting for each group
Typical 500-kHz fixed switching frequency
Supports up to 300mA, drives six LEDs regulated
to 50mA each
Less than 10μA shutdown current
Over-current and over-temperature protection
Short circuit protection with auto shutdown
Undervoltage lockout
Soft-start limits start-up inrush current
16 lead TQFN package
Optional RoHS compliant lead free package
Product Description
The CM9142 is an adaptive fractional switched capaci-
tor (charge pump) regulator optimized for driving two
groups, 4 and 2, of white LEDs Each group features
individual ON/OFF controls and individually set current.
Each LED’s driver current is matched to within 2% for
uniform intensity. It supports an input voltage range of
2.9V to 6V, with undervoltage lockout. A failure detec-
tion circuit prevents the loss of power when one or
more LEDs fail (short or open). Internal over-tempera-
ture and over-current management provide short circuit
protection.
The CM9142 regulates up to 300mA of output current
to drive WLEDs, allowing up to 50mA per LED channel.
The maximum LED current for each group is pro-
grammed with external resistors. Master plus two inde-
pendent enable inputs allows for Analog and PWM
brightness control for each display. Either display can
also be used for a camera flash. In full shutdown mode,
the CM9142 draws only 10μA.
The CM9142 automatically selects the most efficient
charge pump ratio based on the operating voltage
requirement of the white LEDs. The proprietary design
architecture maintains high efficiency (> 80%), and at
low V
IN
provides longer battery life. With a high V
IN,
or
when the adapter is powered, it provides cool reliable
operation.
The CM9142 is available in a compact 16 lead TQFN
package. It can operate over the industrial temperature
range of -40°C to 85°C.
Applications
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Drive white LEDs for STN/TFT Color LCD back-
lighting
Cell phones, PDAs, with multiple displays
Digital Still Cameras
Flash for DSC
Typical Application
1.0uF
C1P C1N
VIN
1uF
1.0uF
C2P
C2N
VOUT
LED1
Display 1
2.9V to 6.0V
1uF
off
on
Enable
EN
ISET1
PhotonIC
TM
LED2
CM9142
LED3
LED4
LED5
LED6
Display 2
R
SET1
R
SET2
ISET2
GND
©
2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
1
PRELIMINARY
CM9142
Functional Block Diagram
C1P C1N
C2P C2N
VIN
OSC
500 kHz
Charge Pump x1, x1.5
VOUT
UVLO
Bandgap
LED1
Mode Select
LED2
Current
Sinks
LED3
LED4
LED5
LED6
EN
Failed LED
Condition
CM9142
GND
ISET1
ISET2
Pin Descriptions
PIN DESCRIPTIONS
LEAD(s)
NAME
DESCRIPTION
1
2
3
LED1
C1P
VIN
Cathode of LED1 pin.
This pin is the plus side of charge pump bucket capacitor C1. Connect a 1.0μF
ceramic capacitor with a voltage rating of 10V or greater between C1N and C1P.
Positive supply voltage input pin. This voltage should be between 2.9V and 6V.
This pin requires a 1.0μF or larger ceramic capacitor to ground.
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
4
ISET1
approximately:
0.66V –
(
LogicLow
)
-
I
LED
= ----------------------------------------------------
×
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.
©
2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
5
Microchip MCU
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