|
|
PDF SGM3124 Data sheet ( Hoja de datos )
| Número de pieza | SGM3124 | |
| Descripción | White LED Charge Pump Current Source | |
| Fabricantes | Shengbang Microelectronics | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de SGM3124 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
|
No Preview Available !
SGM3124
White LED Charge Pump Current
Source with PWM Brightness Control
GENERAL DESCRIPTION
The SGM3124 is a charge pump with PWM brightness
control for white LED supplies in LCD display backlight
applications. The supply voltage ranges from 2.7V to
5.5V, it is ideally suited for all applications powered by a
single Li-ion battery cell or three to four NiCd, NiMH, or
alkaline battery cells.
The device provides a constant current for each LED,
and the initial current value can be set by an external
resistor. High efficiency is achieved by utilizing a 1×/1.5×
fractional conversion technique in combination with very
low dropout current sources.
The SGM3124 is capable of driving up to three channels
of LEDs at 30mA per channel from a 2.7V to 5.5V input.
Additionally, the current controlled charge pump ensures
low input current ripple and EMI. A low external part
count (two 0.47µF flying capacitors and two small 1µF
capacitors at VIN and VOUT) makes this part ideally
suited for small, battery-powered applications.
The SGM3124 is available in a Green, space-saving
TQFN-3×3-16L package, and is rated over the -40℃ to
+85℃ temperature range.
FEATURES
Input Voltage Range: 2.7V to 5.5V
Drives up to 3 LEDs at 30mA Each
LED Brightness Control Through PWM Control
Signal
High Efficiency by Fractional Conversion with 1×
and 1.5× Modes
Switching Frequency: 1MHz
Regulated Output Current with 0.5% Matching
Internal Soft-Start Limits Inrush Current
Low Input Ripple and Low EMI
Over-Current and Over-Temperature Protected
Under-Voltage Lockout With Hysteresis
Green TQFN-3×3-16L Package
APPLICATIONS
Cellular Phones
Smart Phones
Digital Cameras
Handheld PCs
Camcorders
PDAs
Keypad Backlight
SG Micro Corp
www.sg-micro.com
REV. A. 1
1 page  
SGM3124
White LED Charge Pump Current
Source with PWM Brightness Control
FUNCTIONAL BLOCK DIAGRAM
1µF
0.47µF
0.47µF
VIN
C1+
C1-
C2+
C2-
VOUT
Charge
Pump
1µF
Reference
EN1
EN2
PGND
GND
Current
Sinks
Control
D3
D2
D1
ISET
RSET
SG Micro Corp
www.sg-micro.com
5
5 Page 
SGM3124
White LED Charge Pump Current
Source with PWM Brightness Control
THEORY OF OPERATION/DESIGN PROCEDURE
Capacitor Selection
Ceramic capacitors such as X5R or X7R are recommended to be used with the SGM3124. For the two flying capacitors
C1 and C2, it is important to use low ESR capacitors to avoid unnecessary efficiency losses. Low ESR capacitors on
VOUT reduce the ripple voltage on the supply of the current sources. Table 3 lists capacitor types that have been tested
with the SGM3124.
Table 3. Capacitors
PART
C1608X5R1A105M
C1608X5R1A474M
C2012X7R1C105M
LMK107BJ105MA
LMK107BJ474MA
LMK212BJ105MG
VALUE
1μF
0.47μF
1μF
1μF
0.47μF
1μF
VOLTAGE
10V
10V
16V
10V
10V
10V
MANUFACTURER
TDK
Taiyo Yuden
SIZE
0603
0603
0805
0603
0603
0805
WEBSITE
www.componnent.tdk.com
www.t-yuden.com
Power Dissipation
The maximum power dissipation inside the SGM3124
can be calculated based on the following equation:
PD_MAX = [(1.5× VIN) - VO + 0.4 V] × IO
The maximum power dissipation occurs when the input
voltage is just low enough to operate in 1.5× mode, with
a forward voltage of the white LED at maximum. This is
typically for VIN = 4.2V and a forward voltage of 3.6V.
This needs to be lower than the maximum allowed power
dissipation of the package, which can be calculated using
the following equation:
PD_MAX, package =
TJmax - TA
RθJA
For example, the worst case power dissipation occurs at
the input voltage level where the charge pump switches
from the 1× mode to the 1.5× mode. At this operating
point, the supply voltage to the current sources is at its
maximum and the current sources must drop the most
voltage in order to maintain a regulated output current.
The worst case power dissipation occurs when all 3 LED
outputs are fully loaded with 30mA of LED current.
With: VIN = 4.2V, Vf = 3.6V, IO = 75mA (1.5× mode)
PD_MAX = 0.203W
Power Efficiency
The power conversion efficiency of the SGM3124 can be
calculated by adding up the products of each LED current
and voltage and dividing it by the product of the input
voltage and current. With a fully charged battery where
the input voltage is typically above the LED forward
voltage, the charge pump operates in the 1× mode and
efficiency is very high. As the battery discharges, there is
a point where the current sources no longer have enough
voltage overhead to maintain a constant current
regulation.
At that point, the charge pump switches into the 1.5×
mode. The conversion efficiency is lowest at the
crossover. As the battery discharges further, the
efficiency again increases until at about 3.2V where it
reaches a second maximum. Below 3.2V input voltage,
the maximum current per LED is less than 30mA.
SG Micro Corp
www.sg-micro.com
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet SGM3124.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| SGM3122 | White LED Charge Pump Current Source | Shengbang Microelectronics |
| SGM3123 | White LED Driver | Shengbang Microelectronics |
| SGM3124 | White LED Charge Pump Current Source | Shengbang Microelectronics |
| SGM3127 | White LED Driver | Shengbang Microelectronics |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |