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PDF ACT6310 Data sheet ( Hoja de datos )
| Número de pieza | ACT6310 | |
| Descripción | White LED Step-Up Converter | |
| Fabricantes | Active-Semi | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de ACT6310 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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ACT6310
Datasheet
Rev 0, 1/2005
PRELIMINARY
ACT6310
White LED Step-Up Converter
FEATURES
Inherently Matched LED Current
Pin Compatible with ‘1937 with Higher
Efficiency (Up to 86%)
30V High Voltage Switch
1.2MHz Switching Frequency
Uses 0.22µF Output Capacitor
SOT23-5 Package
APPLICATIONS
Cellular Phones
Digital Cameras
PDAs, Handheld Computers
MP3 Players
GPS
GENERAL DESCRIPTION
The ACT6310 step-up DC/DC converter
drives white LEDs with a programmable constant
current. The device is capable of driving two,
three or four white LEDs in series from a
Lithium-Ion battery. Current matching and
uniform brightness is inherent in series
connection.
The ACT6310 incorporates a 30V high
voltage switch. Operating at 1.2MHz, the device
allows the use of very few tiny external
components. The low feedback voltage of 95mV
minimizes power loss in the current setting
resistor for better efficiency.
The ACT6310 is available in SOT-23 package
and requires very few external devices for
operation.
Figure 1. ACT6310 Supplying 3 White LEDs
Active-Semi, Inc.
-1-
1 page  
ACT6310
DIODE SELECTION
The ACT6310 requires a Schottky diode as
the rectifier. Select a low forward voltage drop
Schottky diode with forward current (IF) rating of
100mA to 200mA and sufficient peak repetitive
reverse voltage (VRRM). The required minimum
VRRM is 4.5V multiplied by the number of white
LEDs. Some suitable Schottky diodes are listed
in Table 2.
Table 2. Recommended Schottky Diodes
PART
NUMBER
IF (mA)
VRRM (V) SUPPLIER
CMDSH-3
100
30 Central
CMDSH2-3
200
30 Central
BAT54
200
30 Zetex
LED CURRENT SETTING
The LED current is determined by the value of
the feedback resistor R1. Because the IC’s FB
input is regulated to 95mV, the LED current is
ILED = 95mV / R1. The value of R1 for different
LED current is shown in table 3.
Table 3. R1 Resistor Value Selection
ILED (mA)
5
R1 (Ω)
19.1
10 9.53
12 7.87
15 6.34
20 4.75
DIMMING CONTROL METHODS
The following are dimming control methods
for the ACT6310:
1. PWM Signal Driving SHDN
When a PWM signal is connected to the SHDN
pin, the ACT6310 is on and off alternatively
under the control of the PWM signal. And the
current through the LEDs is either zero or full. By
changing the duty cycle of the PWM signal
(typically 1kHz to 10kHz), a controlled average
current is obtained.
2. DC Voltage Control
Figure 3 shows an application in which a DC
voltage is used to adjust the LED current. The
LED current increases when VDC is lower than
VFB and decreases when VDC is higher than VFB.
In Figure 3, the LED current range of 15mA to 0
is controlled by VDC = 0 to 2V.
3. Filtered PWM Control
Figure 4 shows an application using a filtered
PWM signal to control dimming.
4. Logic Control
A logic signal can be used to adjust the LED
current in a discrete step, as shown in Figure 5.
Figure 3. DC Voltage Controlled Dimming
Figure 4. Filtered PWM Controlled Dimming
Figure 5. Logic Controlled Dimming
Active-Semi, Inc.
- 5 - wwww.active-semi.com
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet ACT6310.PDF ] | |
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