MP3021 – 1X, 1.5X, 2X AUTO-ADJUST CHARGE PUMP WLED BACKLIGHT DRIVER
MP3021 Rev. 1.0 www.MonolithicPower.com 7
11/21/2007 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
OPERATION
The MP3021 uses a charge pump architecture
optimized to support white LED backlight driver
needs. To maximize power efficiency, it
automatically switches between 1X, 1.5X, and
2X modes. The device provides regulated
current for up to four backlight LEDs.
The charge pump automatically responds to
changing conditions such as supply voltage,
forward diode voltage and mode selection in
order to maintain LED current and maximize
efficiency.
The single pin interface provides on/off control,
individual WLED selection, and brightness
control for the backlight. A 5-bit backlight
brightness register provides 32 levels of current
(brightness) control. ISET controls the
maximum brightness of the backlights.
Furthermore, the MP3021 is equipped with a
low brightness backlight mode where the
backlight current can be accurately set down to
100µA.
Soft-start and mode changes limit the inrush
current in the MP3021. The MP3021 uses
charge pump derating over a period of 200µs to
limit inrush current. Before startup the part
checks for a shorted charge pump and
pre-charges its capacitors. This further prevents
inrush and over-current situations.
Single Pin Serial Port Operation
The DATA pin acts as a single wire port for
sending brightness data, LED selection and
LED control to the MP3021. The MPC
TM
protocol is very flexible and easy to use and is
based entirely on short and long pulses (see
Table1). Short pulses having a width within the
specified range are accepted as data. Polarity
of the data matches the pulse polarity. Long
pulses having a pulse width greater than the
minimum specified serve two purposes in the
communication. First, they are used to separate
two similar data values. For example, back-to-
back “1” data must be separated by a long low
pulse otherwise a “0” would be seen between.
Similarly, back-to-back “0”s must be separated
by a long high. Second, long pulses are used to
indicate end of communication by sending two
back-to-back long pulses. Any number of bits
up to a maximum of 11 can be entered during
one communication, always starting with bit 0.
The register value will not change until new
input is received or the register is reset.
Table 1—MPC™ Pulse Detail
Parameter Minimum Maximum Note
Tshort 1.5µs 3.5µs
Accepted
Pulse
Tlong 8µs NA
Ignored
Pulse
1
Begin on first
acceptable pulse
DATA LINE
Tshort
Send Pattern <11010010101>
End on back-to-back
long pulse
10 0 0 0 01111
Tlong Tlong Tlong Tlong
Tshort Tshort Tshort TshortTshort
Tshort Tshort Tshort Tshort Tshort
Figure 2—Protocol Waveforms
