Rainbow-electronics MAX8848Z Manual de usuario descargar pdf (Pagina 11)

High-Performance Negative Charge Pump

for 7 White LEDs in 3mm x 3mm Thin QFN

MAX8848Y/MAX8848Z

______________________________________________________________________________________ 11

for the LED current values and the corresponding ENA/

ENB pulse count. Figure 2 shows a timing diagram for

ENA/ENB.

If dimming control is not required, ENA/ENB works as

a simple on/off logic control. Drive ENA/ENB high for

at least 120Fs to enable the LED current regulators, or

drive ENA/ENB low for greater than 8ms (typ) to place

the LED current regulators in shutdown. The LED current

regulators operate at 100% brightness and off under

these conditions.

Figure 2. Timing Charateristics for LED Serial-Pulse Dimming Control

Table 2. ENA/ENB Serial-Pulse Dimming Count and Programmed LED_ Currents

EN_

LED_

SHDN

INITIAL t

INIT

> 120µs

1µs

TO 500

µs

> 1µs

SHDN

8ms (TYP)

24mA

22.4mA

1 2 3 4 5 26 27 28 29 30 31

20.8mA

19.2mA

17.6mA

16.0mA

0.6mA

0.5mA

0.4mA

0.3mA

0.2mA

0.1mA

24mA

22.4mA

EN_ PULSE

COUNT

PROGRAMMED LED_ CURRENT

(mA)

EN_ PULSE

COUNT

PROGRAMMED LED_ CURRENT

(mA)

Startup or EN_high 24.0 16 2.8

1 22.4 17 2.4

2 20.8 18 2.0

3 19.2 19 1.6

4 17.6 20 1.4

5 16.0 21 1.2

6 14.4 22 1.0

7 12.8 23 0.8

8 11.2 24 0.7

9 9.6 25 0.6

10 8.0 26 0.5

11 6.4 27 0.4

12 5.6 28 0.3

13 4.8 29 0.2

14 4.0 30 0.1

15 3.2 31 24.0

1 2 ... 6 7 8 9 10 11 12 13 14

MAX8848Y/MAX8848Z 1

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Rainbow-electronics MAX8848Z Manual de usuario Pagina 11

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