AAT2860 Datasheet, PDF (17/23 Pages) Advanced Analogic Technologies – Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

PRODUCT DATASHEET
AAT2860
ChargePump^TM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
REG4
D7
F_HI[3]²
D6
F_HI[2]²
D5
F_HI[1]
D4
F_HI[0]
D3
F_TIME[1]
D2
F_TIME[0]
D1
F_LO[1]²
Table 7: AAT2860-x Flash/Torch Control Register Allocation.
D0
F_LO[0]²
F_HI[3:0]
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100¹
1101
1110
1111
Flash Current (mA) per Output
AAT2860-2 or -3
600
560
520
480
440
400
360
320
280
240
200
160
120¹
80
40
OFF
AAT2860-4
300
280
260
240
220
200
180
160
140
120
100
80
60¹
40
20
OFF
Table 8: Flash LED Current Register, F_HI[3:0].
F_TIME[1:0]
00¹
01
10
11
Flash Time (sec)
2¹
1
0.5
Always ON
Table 9: Flash Safety Timer Data, F_TIME[1:0].
Total Output Torch Current (mA)
F_LO[1:0]
00
01
10
11¹
AAT2860-2 or -3
120
80
40
0¹
AAT2860-4
60
40
20
0¹
Table 10: Torch Data, F_LO[1:0].
Applications Information
LED Selection
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 (V_F) levels.
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.
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
handsets or other communication devices. The AAT2860-x
soft-start feature prevents noise transient effects associ-
ated with in-rush currents during the start up of the
charge pump circuit.
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.
1. Denotes the default (power-on-reset) value.
2. Denotes default value is "1" or ON.
2860.2008.05.1.0
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