ncp5623b ON Semiconductor, ncp5623b Datasheet - Page 8

• Manufacturer Part Number: ncp5623b
• Description: Triple Output I2c Controlled Rgb Led Driver
• Manufacturer: ON Semiconductor

*Note: according to the I2C specifications, the physical address is based on 7 bits out of the SDA byte, the 8
11. The programmed current applies to the three LED simultaneously, the gradual dimming is not engaged
12. The bit values represent the steps count, not the ILED current: see equations 1 & 2, page 7, to derive the ILED value.
GRADUAL DIMMING
Decrease the brightness of the backlight LED upon
command from the external MCU. The function is activated
and controlled by means of the I2C protocol.
level, the period (either upward or downward) is equal to the
time defined for each step, multiplied by the number of
steps.
information:
1 – The target current level (either upward or downward)
2 – The time per step
Byte#1 : I2C Physical Address, based 7 bits : % 011 1000 ³ $38 *
Byte#2 : DATA register
Table 1. Internal Register Bits Assigment
Since the NCP5623B is a receiver only, the R/W command is 0 and the hexadecimal byte send by the MCU is %0111 0000 = $70
RLED2
B7
The contain of bits B[4:0] depends upon the type of function selected by bits B[7:5] as depicted in Table 1
The purpose of that function is to gradually Increase or
In order to avoid arithmetic division functions at silicon
To operate such a function, the MCU will provide three
0
0
0
0
1
1
1
1
B7
0
B6
0
0
1
1
0
0
1
1
RLED1
B5
0
1
0
1
0
1
0
1
B[7:5] : Internal Register Selection:
B6
1
B7
0
0
0
0
1
1
1
1
BPWM16
BPWM16
BPWM16
GDIM5
GDIM5
GDIM5
128 ms
B4
16
16
16
X
B6
0
0
1
1
0
0
1
1
RLED0
B5
1
B5
BPWM8
BPWM8
BPWM8
0
1
0
1
0
1
0
1
GDIM4
GDIM4
GDIM4
64 ms
B3
X
8
8
8
Chip Shut Down ³ all LED current = zero
Set up the maximum Output LED Current
PWM1 : LED1 control
PWM2 : LED2 control
PWM3 : LED3 control
Set the Upward Iend target
Set the Downward Iend target
Set the number of steps and activate the Gradual Dimming
BPWM4
BPWM4
BPWM4
GDIM3
GDIM3
GDIM3
BLED4
32 ms
B2
B4
X
4
4
4
1
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BPWM2
BPWM2
BPWM2
GDIM2
GDIM2
GDIM2
16 ms
8
B1
X
2
2
2
BLED3
3 – The Upward or Downward mode of operation
output current increases, according to an exponential curve,
from the existing start value to the end value. The end current
value is defined by the contain of the Upward or Downward
registers, the width of each step is defined by the third
register, the number of step being in the 1 to 30 range. In the
event of software error, the system checks that neither the
maximum output current (30 mA), nor the zero level are
forced out of their respective bounds. Similarly, software
errors shall not force the NCP5623B into an uncontrolled
mode of operation.
B3
0
When a new gradual dimming sequence is requested, the
Function
BPWM1
BPWM1
BPWM1
GDIM1
GDIM1
GDIM1
8 ms
B0
X
1
1
1
BLED2
B2
0
Shut down
Output LED Step, see Figure 4 (Note 11)
PWM1
PWM2
PWM3
Set Gradual Dimming
Upward Iend Target (Note 12)
Set Gradual Dimming
Downward Iend Target (Note 12)
Gradual Dimming
Step Number & run
th
bit representing the R/W command.
BLED1
B1
Comments
0
BLED0
R/W
B0