MIC2845 Datasheet, PDF (1/21 Pages) Micrel Semiconductor – 6 Channel High Side Current Source WLED driver

MIC2845/6
6 Channel High Side Current Source
WLED driver with Dual Low I_Q LDOs
General Description
The MIC2845 and MIC2846 are all-in-one integrated
circuits designed for driving White LEDs (WLEDs) for
display backlighting, camera flash, and other modules in
mobile devices. The MIC2845/6 uses 6 channels of current
sinks to maintain constant current for up to 6 WLEDs. It
features a typical dropout of less than 50mV at 20mA and
guarantees less than 100mV over all conditions, thus
allowing the WLEDs to be driven directly from the battery
without the use of extra capacitors in a large and costly
charge pump. The current sinks are accurate up to 95%
while the matching between each channel is guaranteed
above 96.5% at room temperature. The superior matching
of MIC2845/6 insures clear and uniform display brightness
under all conditions.
The brightness of WLEDs is be externally preset by a
resistor or internally programmed using pulse width
modulation (PWM) on the MIC2845 or single-wire digital
control on the MIC2846. The PWM brightness control on
the MIC2845 will operate down to less than 1% duty cycle
for an accurate and a high dynamic brightness range. The
MIC2846 dimming features a single-wire digital interface
which takes commands from digital programming pulses to
change the brightness in a logarithmic scale similar to the
eye’s perception of brightness. The single-wire digital
brightness control is divided into two modes of operation
for full brightness mode or battery saving mode for a total
of 32 total brightness steps.
The MIC2845/6 also features two independently enabled
low quiescent current LDOs. Each LDO offers ±3%
accuracy from the nominal voltage over temperature, low
dropout voltage (150mV @ 150mA), and low ground
current at all load conditions (typically 25µA). Both LDOs
can be turned off to draw virtually no current.
The MIC2845/6 are both available in the 2.5mm x 2.5mm
14-pin Thin MLF^® leadless package with a junction
temperature range of -40°C to +125°C.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• Input voltage range: 3.0V to 5.5V
WLED Driver
• Current source dropout of less than 50mV guaranteed
at 20mA
• Accuracy better than ±95% (-40°C to +125°C)
• Mismatching lower than ±3.5% (20°C)
• Maintains proper regulation regardless of how many
channels are utilized
• Flash LED driver paralleling 6 channels
• Two methods of dimming control
– MIC2845 – PWM operation to <1% duty cycle
– MIC2846 – Single wire digital control
LDOs
• Very low ground current – <25µA each @ 150mA
• Stable with 1µF ceramic output capacitor
• Dropout at 150mV at 150mA
• Thermal shutdown and current limit protection
Applications
• Mobile handsets
• Digital cameras
• Portable media/MP3 players
• Portable navigation devices (GPS)
• Portable applications
MLF and MicroLeadFrame are registered trademark Amkor Technology Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
January 2008
M9999-010808-A