Datasheet
MAX8647/MAX8648
Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
10 ______________________________________________________________________________________
Temperature Derating Function
The MAX8647/MAX8648 contain a derating function that
automatically limits the LED current at high temperatures
to help protect the LEDs from damage. The derating
function enables the safe usage of higher LED current at
room temperature, thus reducing the number of LEDs
required to backlight the display. The derating circuit
lowers the LED current at approximately 2.5%/°C once
the IC is above +60°C. The typical derating function
characteristic is shown in the
Typical Operating
Characteristics
.
Power-Up LED Detection and
Fault Protection
The MAX8648 contains special circuitry to detect short-
circuit conditions at power-up and disable the corre-
sponding current regulator to avoid wasting battery
current. Connect any unused LED_ to IN to disable the
corresponding current regulator. If an LED fails short
circuit, the current regulator continues the current regu-
lated operation until power to the IC is cycled and the
short circuit is detected. An open-circuit LED failure dri-
ves the voltage on the corresponding LED_ output
SDA CONTROL BYTE
COMMAND DATA
FUNCTION
C2 C1 C0 D4 D3 D2 D1 D0
Not used 0 0 0 —————
LED1 current 0 0 1 24.0mA to 0.1mA and off in 32 steps
LED2 current 0 1 0 24.0mA to 0.1mA and off in 32 steps
LED3 current 0 1 1 24.0mA to 0.1mA and off in 32 steps
LED4 current 1 0 0 24.0mA to 0.1mA and off in 32 steps
LED5 current 1 0 1 24.0mA to 0.1mA and off in 32 steps
LED6 current 1 1 0 24.0mA to 0.1mA and off in 32 steps
Not used 1 1 1 —————
Table 2. I
2
C Control Data Byte—Device Address 0x9A
Note: C2 is MSB and D0 is LSB. The power-on default settings for D4 to D0 are all 0, which indicates that all LED_ are off.
Table 3. MAX8647 I
2
C Data vs. LED Currents
D4 D3 D2 D1 D0 mA
1111124
1111022.4
1110120.8
1110019.2
1101117.6
1101016
1100114.4
1100012.8
1011111.2
101109.6
101018
101006.4
100115.6
100104.8
100014
100003.2
D4 D3 D2 D1 D0 mA
011112.8
011102.4
011012
011001.6
010111.4
010101.2
010011
010000.8
001110.7
001100.6
001010.5
001000.4
000110.3
000100.2
000010.1
00000OFF