MIC2846A Datasheet, PDF (10/19 Pages) Micrel Semiconductor – High Efficiency 6 Channel Linear WLED Driver with DAM™, Digital Control and Dual Low IQ LDOs

Micrel Inc.
Functional Diagram
MIC2846A
Figure 1. MIC2846A Functional Block Diagram
Functional Description
The MIC2846A is a six channel linear LED driver with
dual 150mA LDOs. The LED driver incorporates a
Dynamic Averaged Matching^TM (DAM^TM) technique
designed specifically to optimize on current accuracy
and matching across process variation. It can maintain
proper current regulation with LED current accuracy of
1.5% while the typical matching between the six
channels is 1.5% at room temperature. The LED
currents are independently driven from the input supply
and will maintain regulation with a dropout of 40mV at
20mA. The low dropout of the linear LED Drivers allows
the LEDs to be driven directly from the battery voltage
and eliminates the need for boost or large and inefficient
charge pumps. The maximum LED current for each
channel is set via an external resistor while a single-wire
digital interface controls dimming.
The MIC2846A has two LDOs with a dropout voltage of
150mV at 150mA and consume 35µA of current in
operation. Each LDO has an independent enable pin,
which reduces the operating current to less than 1µA in
shutdown. Both linear regulators are stable with just 1µF
of output capacitance.
Block Diagram
As shown in Figure 1, the MIC2846A consists of two
LDOs with six current mirrors set to copy a master
current determined by R_SET. The linear LED drivers have
a designated control block for enabling and dimming of
the LEDs. The MIC2846A dimming is controlled by the
Digital Control block that receives digital signals for
dimming. The LDOs each have their own control and are
independent of the linear LED drivers. Each LDO
consists of internal feedback resistors, an error amplifier,
a PFET transistor and a control circuit for enabling.
April 2010
10
M9999-041210-D