NCP5623 Просмотр технического описания (PDF) - ON Semiconductor
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NCP5623 Datasheet PDF : 10 Pages
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NCP5623
B[7:5] : Internal Register Selection:
B7
B6 B5
Function
0
0
0 Chip Shut Down ³ all LED current = zero
0
0
1 Set up the maximum Output LED Current
0
1
0 PWM1 : Red LED control
0
1
1 PWM2 : Green LED control
1
0
0 PWM3 : Blue LED control
1
0
1 Set the Upward Iend target
1
1
0 Set the Downward Iend target
1
1
1 Gradual Dimming Step Time and Run
The contain of bits B[4:0] depends upon the type of function selected by bits B[7:5] as depicted in Table 1
Table 1. Internal Register Bits Assigment
B7 B6 B5
B4
B3
B2
B1
B0
Comments
0
0
0
X
X
X
X
X
Shut down
0
0
1
16
8
4
2
1
LED Current Step, see Figure 5 (Note 9)
0
1
0 BPWM16 BPWM8 BPWM4
BPWM2
BPWM1 Red PWM
0
1
1 BPWM16 BPWM8 BPWM4
BPWM2
BPWM1 Green PWM
1
0
0 BPWM16 BPWM8 BPWM4
BPWM2
BPWM1 Blue PWM
1
0
1
GDIM5
16
GDIM4
8
GDIM3
4
GDIM2
2
GDIM1
1
Set Gradual Dimming
Upward Iend Target (Note 10)
1
1
0
GDIM5
16
GDIM4
8
GDIM3
4
GDIM2
2
GDIM1
1
Set Gradual Dimming
Downward Iend Target (Note 10)
1
1
1
GDIM5
GDIM4
GDIM3
128 ms
64 ms
32 ms
GDIM2
16 ms
GDIM1
8 ms
Gradual Dimming
Time & run
9. The programmed current applies to the three LED simultaneously, the gradual dimming is not engaged
10. The bit values represent the steps count, not the ILED current: see equations 1 & 2, page 6, to derive the ILED value.
GRADUAL DIMMING
The purpose of that function is to gradually Increase or
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.
In order to avoid arithmetic division functions at silicon
level, the period (either upward or downward) is equal to the
time defined for each step, multiplied by the number of
steps.
To operate such a function, the MCU will provide two
information:
1 – The target current level (either upward or downward)
2 – The time per step and run
When a new gradual dimming sequence is requested, the
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 Time and
run register, the number of step being in the 1 to 31 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 NCP5623 into an uncontrolled
mode of operation.
The dimming is built with 30 steps and the time delay
encoded into the second byte of the I2C transaction: see
Table 1.
When the gradual dimming is deactivated (B7 = B6 = 0,
B5 = 1), the output current is straightforwardly set up to the
level defined by the contain of the related register upon
acknowledge of the output current byte.
The gradual dimming sequence must be set up before a
new output current data byte is send to the NCP5623 . 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 NCP5623 chip can
be updated ahead of the next function as depicted in Table 2.
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