MAX8647ETE Ver la hoja de datos (PDF) - Maxim Integrated
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MAX8647ETE Datasheet PDF : 15 Pages
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Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
A
tLOW B tHIGH
C
D
EF
G
SCL
H
IJ
K
LM
SDA
tSU_STA tHD_STA
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
tSU_DAT
tHD_DAT
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE (OP/SUS BIT)
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
Figure 2. Definition of Timing for I2C Bus
tSU_STO tBUF
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
Table 4. MAX8648 Pulse Dimming Step vs. LED Currents
mA
MAX8648 DIMMING STEPS
mA
24.0
Startup or EN_ high
2.8
22.4
1
2.4
20.8
2
2.0
19.2
3
1.6
17.6
4
1.4
16.0
5
1.2
14.4
6
1.0
12.8
7
0.8
11.2
8
0.7
9.6
9
0.6
8.0
10
0.5
6.4
11
0.4
5.6
12
0.3
4.8
13
0.2
4.0
14
0.1
3.2
15
24.0
MAX8648 DIMMING STEPS
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
below the switch over threshold enabling the inverting
charge pump.
For the MAX8647, program any unused LED_ to off
using the I2C interface. Unused LED_ can be connect-
ed to IN or left unconnected.
Thermal Shutdown
The MAX8647/MAX8648 includes a thermal-limit circuit
that shuts down the IC above about +160°C. The IC
turns on after it cools by approximately 20°C.
Applications Information
Input Ripple
For LED drivers, input ripple is more important than out-
put ripple. The amount of input ripple depends on the
source supply’s output impedance. Adding a lowpass
filter to the input of the MAX8647/MAX8648 further
reduces input ripple. Alternatively, increasing CIN to
2.2µF (or 4.7µF) cuts input ripple in half (or in fourth)
with only a small increase in footprint.
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