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PDF AAT3122 Data sheet ( Hoja de datos )
| Número de pieza | AAT3122 | |
| Descripción | High Efficiency 1X/1.5X Fractional Charge Pump | |
| Fabricantes | AAT | |
| Logotipo |  |
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AAT3122
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
General Description
Features
ChargePump™
The AAT3122 is a low noise, constant frequency
charge pump DC/DC converter that uses a dual
• VIN Range: 2.7V to 5.5V
• <1µA of Shutdown Current
mode load switch (1X) and fractional (1.5X) con-
• 1 MHz Switching Frequency
version to increase efficiency in white LED applica-
• Dual Mode 1X and 1.5X Charge Pump for
tions. With input voltages ranging from 2.7V to
Maximum Efficiency
5.5V, the device can produce an output current of
• Only Four External Components
up to 120mA. A low external parts count (two 1µF
• Simple Serial Control (S2Cwire) Interface
flying capacitors and two small bypass capacitors
• Low Noise Constant Frequency Operation
at VIN and OUT) makes the AAT3122 ideally suited
for small battery-powered applications.
• 33% Less Input Current Than Doubler Charge
Pumps
AnalogicTech's Simple Serial Control™ (S2Cwire™)
interface is used to enable, disable, and set the
LED drive current with a 32-level logarithmic scale
LED brightness control. The AAT3122 has a ther-
mal management system to protect the device in
the event of a short-circuit condition on any of the
• Small Application Circuit
• Regulated Output Current
• Automatic Soft Start
• No Inductors
• TSOPJW-12 Package
• -40°C to +85°C Temperature Range
output pins. Built-in soft-start circuitry prevents
excessive inrush current during start-up. High
switching frequency enables the use of small exter-
nal capacitors. A low shutdown current feature dis-
Applications
connects the load from VIN and reduces quiescent
current to less than 1µA. The AAT3122 provides awww.DataSheet4U.com
single current source output that can be used to
•
•
Programmable Current Source
White LED Backlighting
drive up to six LEDs at 20mA each. The AAT3122
is available in a Pb-free TSOPJW-12 package.
Typical Application
VBATTERY
CIN COUT
1µF 1µF
EN/SET
VIN C1+
AAT3122
VOUT
C1-
C2+
C2-
EN/SET
D
GND
C1
1µF
C2
1µF
D1 D2 D3 D4 D5 D6
3122.2005.11.1.3
1
1 page  
AAT3122
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.6V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C.
Efficiency vs. VIN
(ID = 80mA)
100
95
90 VDIODE = 3.3V
85 VDIODE = 3.4V
80
75
70 VDIODE = 3.5V
65 VDIODE = 3.6V
60
55
50
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9
5.1
VIN (V)
IDIODE vs. VIN
90
VDIODE = 3.3V VDIODE = 3.4V VDIODE = 3.5V
85 VDIODE = 3.6V
80
75
70
65
60
55
50
45
40
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9
5.1
VIN (V)
Quiescent Current vs. VIN
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.50
VDIODE = 3.3V
VDIODE = 3.4V
VDIODE = 3.5V
VDIODE = 3.6V
3.00
3.50
4.00
VIN (V)
4.50
5.00
5.50
VIH and VIL vs. VIN
0.850
0.825
0.800
0.775
0.750
VIH
0.725
0.700
VIL
0.675
0.650
0.625
0.600
2.5 3.0 3.5 4.0 4.5 5.0 5.5
VIN (V)
3122.2005.11.1.3
5
5 Page 
AAT3122
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Additional Application Circuit
VBATTERY
VIN C1+
VOUT
C1-
C2+
CIN
1µF
COUT
1µF
AAT3122
C2-
C1
1µF
C2
1µF
D1 D2 D3 D4 D5 D6
D1
RB* RB* RB* RB* RB* RB*
EN/SET
EN/SET
GND
*In some applications, white LED forward voltages (VF) can vary significantly. Ballast resistors between the LED cathodes and ground are
recommended for balancing the forward voltage differences. The ballast resistor value may be approxiamted by the following equation:
RB
=
(VIN(MIN))1.5 - (VF(MAX)
IF(MAX)
+
250mV)
VF(MAX) = Maximum expected LED forward voltage at the given maximum forward current level. Refer to the LED manufacturers’
datasheet for maximum VF specifications.
IF(MAX) = Maximum forward current used to drive an individual LED.
VIN(MIN) = Minimum input supply voltage for the application.
RB = Ballast resistor value in ohms.
3122.2005.11.1.3
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet AAT3122.PDF ] | |
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