NCP5608 ON Semiconductor, NCP5608 Datasheet - Page 10

• Manufacturer Part Number: NCP5608
• Description: Multiple LED Charge Pump Driver
• Manufacturer: ON Semiconductor

OUTPUT LED PROGRAMMING SEQUENCE
external resistor (see Load Current Calculation paragraph
above), the I2C protocol can be used to dynamically adjust
the brightness of the selected block.
the content of the appropriate register (PWRLD_BK[4..0]
or PWRLED_FL[6..0]). The LED current can be
calculated according to the digital value stored into the
registers.
The LED can be programmed in four steps:
PHYSICAL ADDRESS
controller must fulfill the I2C protocol to drive the chip: see I2C−BUS SPECIFICATION, Version 2.1. The NCP5608
operates as a Slave only and never takes over the I2C control.
in the industry. Basically, the DATA is transferred from the
MCU to the NCP5608 registers by means of the SDA
message associated to the SCL clock. The MCU presents
MPU send bit
MPU enables clock
NOTE: See I2C−BUS SPECIFICATION, Version 2.1, January 2000, for further timing details.
Table 3. NCP5608 Operation Truth Table
CLOCK
DATA
Once the maximum output current has been set up by the
At this point, the dimming of each block depends upon
The physical I2C address dedicated to the NCP5608 to support the I2C protocol is: 0111 001X → $72. The external
The I2C protocol is based on the standard format defined
PWRLED_BK (0−7)
1. Define the maximum ILEDBK−MAX and
ILEDFL−MAX currents requested by the Back
Light and Flash applications (set by external
resistors). This is the maximum current that will
be reached when the registers will be at their
respective full range (PWRLD_BK[4..0] = $1F =
31 Decimal, PWRLED_FL[6..0] = $7F= 127
decimal).
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$00
X
Start
B7
PWRLED_FL (0−7)
B6
The NCP5608 reads one bit
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$00
B5
X
X
PHYSICAL ADDRESS FRAME
B4
B3
The NCP5608 send ACK
Forced to zero
Vfbk + Vsense
Vfbk + Vsense
Vffl + Vsense
Figure 5. Basic I2C Timings
B2
Output Voltage
http://onsemi.com
B1
NCP5608
B0
10
ACK
the 8 bits during the low state of the SCK signal and the
peripheral device ( in our case, the NCP5608) shall reads
the bits during the high state of the same clock. The transfer
is MSB first as depicted in Figure 5.
B7
DC−DC = OFF
DC−DC = ON, LED1 to LED4 active
DC−DC = ON, LED1 to LED3 active
DC−DC = ON
2. Calculate the reference current (Irefbk and Ireffl ):
3. Calculate the external resistor value
4. The dimming of flash and backlight LED will be
B6
Irefbk = ILED−BK/1200 and
Ireffl = ILED−FL/4000
RBK = 0.6/Irefbk
RFL = 0.6/Ireffl
now achieved by changing the PWRLD_BK[4..0]
and PWRLED_FL[6..0] registers content to get the
operating LED current along the curves 0 mA to
ILED−BK−MAX mA and 0 mA to ILED−FL mA:
BK−NSteps = number of steps stored into the
PWRLD_BK register (value, in decimal, of the
PWRLD_BK[4..0] register)
FL−NSteps = number of steps stored into the
PWRLED_FL register (value, in decimal, of the
PWRLD_FL[6..0] register)
ILEDBK = (ILEDBK−MAX/31) * BK−NSteps
ILEDFL = (ILEDFL−MAX/127) * FL−NSteps
B5
LED4 deactivated
DATA FRAME
B4
B3
Comments
B2
B1
B0
ACK
Stop