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PDF AIC1842 Data sheet ( Hoja de datos )
| Número de pieza | AIC1842 | |
| Descripción | High Efficiency 1.5X charge Pump | |
| Fabricantes | Analog Intergrations Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AIC1842 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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AIC1841/2
High Efficiency 1.5X charge Pump
For White LEDs Backlighting
FEATURES
1MHz Switching Frequency
2.7V to 5.5V Input Voltage Range
Low Shutdown Current: ≦1µA
Regulated 20mA Full-Scale Output Current
32-Position Linear Scale with Digital Control
High Accuracy Brightness Matching
33% Less Input Current Than Doubler Charge
Pump
No Inductors Required
Build-in Soft-Start
Current Limit and Over Temperature Protection
12-Pin (AIC1841) and 16-Pin (AIC1842) QFN
Package
APPLICATIONS
Cellular Phones
PDAs
Digital Still Cameras
Handheld Devices
White LED Backlighting
GENERAL DESCRIPTION
The AIC1841 and AIC1842 provide 4 and 6 LED
current source outputs with regulated constant
current for uniform intensity. The AIC1841/2 is the
low noise, constant frequency charge pump
DC/DC converter that uses 1.5X conversion to
increase efficiency in white LED applications. The
devices can be used to produce current levels up
to 20mA for each output from a 2.7V to 5.5V input.
Low external parts counts (two 1 μ F flying
capacitors and two small bypass capacitors at VIN,
and OUT) make the AIC1841/2 ideal for small,
battery-powered applications.
EN/SET interface is used to enable, disable and
set the LED current for a 32 level logic scale LED
brightness control. Built-in current limiting, with
thermal shutdown provide protection to the
AIC1841/2 against fault conditions. Automatic soft-
start circuitry prevents excessive inrush current
during start-up. 1MHz high switching frequency is
enable to use tiny external components.
The AIC1841 is available in a 12-pin thin QFN
package, and the AIC1842 is available in a space-
saving 16-pin QFN package.
Analog Integrations Corporation 3A1, No.1 Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan
TEL: 886-3-5772500
FAX: 886-3-5772510 www.analog.com.tw
DS-1842P-02 041707
1
1 page  
AIC1841/2
TYPICAL PERFORMANCE CHARACTERISTICS
VEN
Vo
VD
IIN
Vin=3.6V
Fig1: Enable Transient Response
VIN
Vo
VEN
Vo
VD
IIN
Vin=3.6V
Fig2: Shutdown Timeout
VIN
Vo
VD VD
Fig3: 80mA load at Vin=3.0V
VIN
Vo
VD
Fig4: 100mA load at Vin=3.0V
VIN
Vo
VD
Fig5: 80mA load at Vin=3.6V
Fig6: 120mA load at Vin=3.6V
5
5 Page 
AIC1841/2
the lowest current scale, 0.625mA, and Code 32
is full scale, 20mA. The LED current appears
linear with each increasing code. The first rising
edge enables the device and sets the LED output
current to the lowest setting level, 0.625mA. After
20
18
16
14
12
10
8
6
4
2
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31
Digital Code
EN/SET Interface
The EN/SET timing is as the diagram shown
below. The first rising edge enables the device
and sets the LED output current to the lowest
setting level. The AIC1841/2 reaches full capaciity
after typically 400us soft start time. During the soft
start period, multiple clock pulses may be inserted,
they will be missed cause the counter of EN/SET
interface will work after soft start time. The 2nd
32nd clock, the LED output returns to state 1. The
EN/SET pin has to remain high to keep the LED
output current to programmed level when the final
clock is input.
Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
WLED Current
0.625
1.250
1.875
2.500
3.125
3.750
4.375
5.000
5.625
6.250
6.875
7.500
8.125
8.750
9.375
10.000
Code
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
WLED Current
10.625
11.250
11.875
12.500
13.125
13.750
14.375
15.000
15.625
16.250
16.875
17.500
18.125
18.750
19.375
20.000
pulse should be later than 1st pulse for a soft start
time to maintain a correct LED output current level.
The counter can be clocked up to 1MHz, so the
intermediate scales are not visible.The EN/SET
has to hold high to keep the output LED current to
programmed level when the final clock is input.
When the EN/SET keeps a low for the tSHDN
timeout period or longer, the AIC1841/2 is
shutdown.
EN
t (LO)
0.3us to 75us
t (SOFT-START)
400us
I(LED)
SHDN
1BIT 2
3
4
5
6
Current Setting Diagram
7
t (HI)
8
9
10
11
>50ns
12
....
29 30
31 32
123
t (SHDN)
300us
4
SHDN
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet AIC1842.PDF ] | |
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