MAX8648 Maxim Integrated Products, MAX8648 Datasheet - Page 11

• Manufacturer Part Number: MAX8648
• Description: (MAX8647 / MAX8648) Ultra-Efficient Charge Pumps
• Manufacturer: Maxim Integrated Products

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below the switch over threshold enabling the inverting
charge pump.
For the MAX8647, program any unused LED_ to off
using the I
ed to IN or left unconnected.
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.
Table 4. MAX8648 Pulse Dimming Step vs. LED Currents
Figure 2. Definition of Timing for I
SCL
SDA
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
Six White/RGB LEDs in 3mm x 3mm Thin QFN
24.0
22.4
20.8
19.2
17.6
16.0
14.4
12.8
11.2
mA
9.6
8.0
6.4
5.6
4.8
4.0
3.2
t
SU_STA
2
C interface. Unused LED_ can be connect-
A
t
HD_STA
______________________________________________________________________________________
t
LOW
B
MAX8648 DIMMING STEPS
t
HIGH
Startup or EN_ high
2
C Bus
Thermal Shutdown
t
SU_DAT
10
11
12
13
14
15
C
1
2
3
4
5
6
7
8
9
Ultra-Efficient Charge Pumps for
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
D
E
F
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 C
2.2µF (or 4.7µF) cuts input ripple in half (or in fourth)
with only a small increase in footprint.
t
HD_DAT
G
24.0
mA
2.8
2.4
2.0
1.6
1.4
1.2
1.0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Applications Information
H
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
MAX8648 DIMMING STEPS
I
J
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
K
Input Ripple
t
SU_STO
L
t
BUF
M
IN
11
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