NCP5623B

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9

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 NCP5623B . 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

NCP5623B chip can be updated ahead of the next function

as depicted in Table 2.

Table 2. Basic Programming Sequences

I2C Address

COMMAND Bits[7:0]

Operation

Note

$70

000X XXXX

System Shut Down

Bits[4:0] are irrelevant

$70

0010 0000

0011 1111

Set Up the ILED current

ILED register

Bits[4:0] contain the IMAX value as defined by the

Iref value

$70

0100 0000

0101 1111

Set Up the PWM1

PWM1

Bits[4:0] contain the PWM value

$70

0110 0000

0111 1111

Set Up the PWM2

PWM2

Bits[4:0] contain the PWM value

$70

1000 0000

1001 1111

Set Up the PWM3

PWM3

Bits[4:0] contain the PWM value

$70

1010 0000

1011 1111

Set Up the IEND Upward

UPWARD

Bits[4:0] contain the IEND value

$70

1100 0000

1101 1111

Set Up the IEND Downward

DWNWRD

Bits[4:0] contain the IEND value

$70

1110 0000

1111 1111

Set Up the Gradual Dimming time

and run the sequence

GRAD

Bits[4:0] contain the TIME value

The number of step for a given sequence, depends upon

the start and end output current range: since the IPEAK

value is encoded in the Bits[4:0] binary scale, a maximum

of 31 steps is achievable during a gradual dimming

operation.

The number of steps will be automatically recalculated by

the chip according to the equation:

Nstep = | existing step position − new step position |

As an example, assuming the previously programmed

step was 5 and the new one is 15, then we will have 10 steps

to run between the actual location to the end value. If the

timing was set at 16 ms, the total gradual dimming sequence

will be 160 ms.

To select the direction of the gradual dimming (either

Upward or Downward), one shall send the appropriate

register before to activate the sequence as depicted below:

1010 1111

³ 1110 0011 ³ select an UPWARD sequence

with 24 ms/step, the end IPEAK current being (IREF *

2400) / (31 − 16) mA.

1100 0001

³ 1110 0100 ³ select the DOWNWARD

sequence with 32 ms/step, the end IPEAK current being

(IREF * 2400) / (31 − 1) mA.

Table 3. Output Current Programmed Value (ILED = F(Step))

Step

ILED (mA)

Step

ILED (mA)

Step

ILED (mA)

Step

ILED (mA)

0 / $00

0

9 / $09

1.25

18 / $12

2.12

27 $1B

6.90

1 / $01

0.92

10 / $0A

1.31

19 / $13

2.30

28 / $1C

9.20

2 / $02

0.95

11 / $0B

1.38

20 / $14

2.50

29 / $1D

13.80

3 / $03

0.98

12 / $0C

1.45

21 / $15

2.76

30 / $1E

27.60

4 / $04

1.02

13 / $0D

1.53

22 / $16

3.06

31 / $1F

27.60

5 / $05

1.06

14 / $0E

1.62

23 / $17

3.45

6 / $06

1.10

15 / $0F

1.72

24 / $18

3.94

7 / $07

1.15

16 / $10

1.84

25 / $19

4.60

8 / $08

1.20

17 / $11

1.97

26 / $1A

5.52