ncp5890 ON Semiconductor, ncp5890 Datasheet - Page 11

• Manufacturer Part Number: ncp5890
• Description: Light Management Ic Dedicated For Lcd Backlighting And Multi-led Fun Light Applications
• Manufacturer: ON Semiconductor

− First Byte = 0111 0000 ³ I2C address
Inductor Peak Current
application is set up by the external resistor R
connected between the I
mirror ratio (multiplier − kk −) typically equal to 9700. In
other words, to get a 750 mA maximum peak current in the
inductor, the reference current should be 750 mA/9700 =
79 mA. This current is used to calculate the resistor
connected between the I
79e−6 = 14.4 kW.
paragraph applies as well and care must be observed to
avoid any voltage source connection to the IPK pin.
Gradual Dimming
Decrease the brightness of the backlight / keyboard LED
upon command from the external MCU. The function is
activated and controlled by means of the I2C protocol.
time defined for each step, multiplied by the number of
steps. The number of step is derived from the value
associated with the target current.
information:
GDIMR[7..0] Gradual Dimming Target
Bits [B7:B5] : RFU
Bits [B4:B0] : ILED peak current setup or Gradual Dimming Timing
the start and end output current range: since the IPEAK
value is encoded in the ILEDREG [4:0] binary scale, a
maximum of 31 steps is achievable during a gradual
dimming operation.
Upward or Downward), one shall set−up the appropriate
register before to activate the sequence as depicted in the
example here below:
TDIM[7.0] Gradual Dimming Time per Step
Bits [B7:B5] : RFU
Bits [B4:B0] : Gradual Dimming Timing
NOTE:
The peak current flowing into the inductor during normal
The maximum I
The concept depicted in the ILED peak current
The purpose of this function is to gradually Increase or
The period (either upward or downward) is equal to the
To operate such a function, the MCU will provide three
The number of steps for a given sequence, depends upon
To select the direction of the gradual dimming (either
(assuming I2CADR = Low)
RESET
RESET
ms
ms
bit B0 = 2^14/F, with F = operating frequency (1.3 MHz typical)
PK
B7
B7
0
0
0
0
current is given by the internal current
PK
PK
pin and ground.
pin and GND: R
B6
B6
0
0
0
0
REF
B5
B5
0
0
0
0
= 1.144 /
http://onsemi.com
PCA
ILED5
200
B4
B4
11
0
0
− Second byte = 0000 0010 ³ select an ILED target
− Third byte = 0000 1111 ³ set I−LED =
− First Byte = 0111 0000 ³ I2C address
− Second byte = 0000 0100 ³ set Timing and start the
− Third byte = 0000 0010 ³ set Timing per step =
output current increases, according to the logarithmic
curve, from the existing start value to the end value. The
end current value is defined by the contents of the Upward
or Downward register, the width of each step is defined by
the third register, the number of steps being in the 1 to 32
range ($00 to $1F). In the event of a software error, the
system checks that neither the maximum output current
(25 mA), nor the zero level are forced out of their
respective bounds. Similarly, software errors shall not
force NCP5890 into an uncontrolled mode of operation.
encoded into the third byte of the I2C transaction.
selection = $01), the output current is set up to the level
defined by the contents of the related register upon
acknowledge of the output current byte.
new output current data byte is sent to the NCP5890. At this
point, the brightness sequence takes place when the new
data byte is acknowledged by the internal I2C decoder.
Since the six registers are loaded on independent byte flow
associated to the I2C address, any parameter of the
NCP5890 chip can be updated ahead of the next function.
When a new gradual dimming sequence is requested, the
The dimming is built with 32 steps and the time delay
When the gradual dimming is not requested (register
The gradual dimming sequence must be set up before a
UPWARD sequence
2.51% of the maximum range
(assuming I2CADR = Low)
sequence
20 ms/step
1. The target current level (either upward or
2. The time per step
3. The Upward or Downward mode of operation
downward)
ILED4
100
B3
B3
0
0
ILED3
B2
B2
50
0
0
ILED2
B1
B1
25
0
0
ILED1
12.5
B0
B0
0
0