MP3001 – AUTO-ADJUST CHARGE PUMP WLED BACKLIGHT AND FLASH DRIVER

MP3001 Rev. 0.91

www.MonolithicPower.com

6

9/21/2007

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2007 MPS. All Rights Reserved.

OPERATION

The MP3001 uses a charge pump architecture

optimized to support both white LED backlight

and flash 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

and one flash LED.

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, mode selection, and

brightness control for the backlight. A 5-bit

backlight brightness register provides 32 levels

of current (brightness) control. ISET1 controls

the maximum brightness of the backlights,

ISET2 sets the brightness of the flash and

ISET3 sets the brightness for preview mode.

Furthermore, the MP3001 is equipped with a

low brightness backlight mode where the

backlight current can be set accurately down to

100µA.

Soft-start and mode changes limit the inrush

current in the MP3001. The MP3001 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 in the part.

Single Pin Serial Port Operation

The DATA pin acts as a single wire port for

sending brightness data, LED selection and

protocol is very flexible and easy to use and is

based entirely on short and long pulses, see

Table 1 below. 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

0

11

1

1

Tlong

Tlong

Tlong

Tlong

Tshort

Tshort

Tshort

Tshort

Tshort

Tshort

Tshort

Tshort

Tshort

Tshort

Figure 1—Protocol Waveforms