NCP5623C

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8

B7

B6

B5

B4

B3

B2

B1

B0

Byte#1 : I2C Physical Address, based 7 bits : % 011 1001 ³ $39 *

0

1

1

1

0

0

1

R/W

Byte#2 : DATA register

RLED2

RLED1

RLED0

BLED4

BLED3

BLED2

BLED1

BLED0

Since the NCP5623C is a receiver only, the R/W command is 0 and the hexadecimal byte send by the MCU is %0111 0010 = $72

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 : LED1 control

0

1

1

PWM2 : LED2 control

1

0

0

PWM3 : LED3 control

1

0

1

Set the Upward Iend target

1

1

0

Set the Downward Iend target

1

1

1

Set the number of steps and activate the Gradual Dimming

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

Output LED Step, see Figure 4 (Note 11)

0

1

0

BPWM16

BPWM8

BPWM4

BPWM2

BPWM1

PWM1

0

1

1

BPWM16

BPWM8

BPWM4

BPWM2

BPWM1

PWM2

1

0

0

BPWM16

BPWM8

BPWM4

BPWM2

BPWM1

PWM3

1

0

1

GDIM5

16

GDIM4

8

GDIM3

4

GDIM2

2

GDIM1

1

Set Gradual Dimming

Upward Iend Target (Note 12)

1

1

0

GDIM5

16

GDIM4

8

GDIM3

4

GDIM2

2

GDIM1

1

Set Gradual Dimming

Downward Iend Target (Note 12)

1

1

1

GDIM5

128 ms

GDIM4

64 ms

GDIM3

32 ms

GDIM2

16 ms

GDIM1

8 ms

Gradual Dimming

Step Number & run

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

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 three

information:

1 – The target current level (either upward or downward)

2 – The time per step

3 – The Upward or Downward mode of operation

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 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 NCP5623C into an uncontrolled

mode of operation.