PRODUCT DATASHEET
AAT2860
TM
ChargePump
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
D7
D6
D5
D4
D3
D2
D1
D0
F_HI[3]2
F_HI[2]2
F_HI[1]
F_HI[0]
F_TIME[1]
F_TIME[0]
F_LO[1]2
F_LO[0]2
REG4
Table 7: AAT2860-x Flash/Torch Control Register Allocation.
Applications Information
Flash Current (mA) per Output
F_HI[3:0]
AAT2860-2 or -3
AAT2860-4
LED Selection
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
11001
1101
1110
1111
600
560
520
480
440
400
360
320
280
240
200
160
1201
80
300
280
260
240
220
200
180
160
140
120
100
80
The AAT2860-x is specifically intended for driving white
LEDs. However, the device design will allow the AAT2860-x
to drive most types of LEDs with forward voltage specifi-
cations ranging from 2.0V to 4.7V. LED applications may
include mixed arrangements for display backlighting,
color (RGB) LEDs, infrared (IR) diodes and any other load
needing a constant current source generated from a vary-
ing input voltage. Since the BL1 to BL5/BL6(FL1)/
BL7(FL2) constant current sinks/channels are matched
with negligible voltage dependence, the constant current
channels will be matched regardless of the specific LED
forward voltage (VF) levels.
601
40
20
40
OFF
The current sinks/channels in the AAT2860-x maximize
performance and make it capable of driving LEDs with high
forward voltages. Multiple channels can be combined to
obtain a higher LED drive current without complication.
OFF
Table 8: Flash LED Current Register, F_HI[3:0].
F_TIME[1:0]
Flash Time (sec)
001
01
10
11
21
1
Device Switching Noise Performance
The AAT2860-x operates at a frequency of approximate-
ly 1MHz to control noise and limit harmonics that can
interfere with the RF operation of cellular telephone
handsetsorothercommunicationdevices. TheAAT2860-x
soft-start feature prevents noise transient effects associ-
ated with in-rush currents during the start up of the
charge pump circuit.
0.5
Always ON
Table 9: Flash Safety Timer Data, F_TIME[1:0].
Total Output Torch Current (mA)
F_LO[1:0]
AAT2860-2 or -3
AAT2860-4
00
01
10
111
120
80
40
01
60
40
20
01
Power Efficiency and Device Evaluation
Charge-pump efficiency discussion in the following sec-
tions accounts only for the efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT2860-x, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Table 10: Torch Data, F_LO[1:0].
1. Denotes the default (power-on-reset) value.
2. Denotes default value is "1" or ON.
w w w . a n a l o g i c t e c h . c o m
2860.2008.05.1.0
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