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NJU6049 PDF даташит

Спецификация NJU6049 изготовлена ​​​​«JRC» и имеет функцию, называемую «White LED Driver / VSP10».

Детали детали

Номер произв NJU6049
Описание White LED Driver / VSP10
Производители JRC
логотип JRC логотип 

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NJU6049 Даташит, Описание, Даташиты
www.DataSheet4U.com
NJU6049
PRELIMINARY
High Efficiency White LED Driver
! GENERAL DESCRIPTION
The NJU6049 is a high-efficiency white LED driver. It
contains a high-efficiency step-up DC/DC converter and an
output driver. The IC can output max.18V and drive as many
as 4 white LEDs in series with a constant current, which
guarantees the LEDs with uniform brightness.
The high frequency of the step-up converter permits the
use of small, low-profile inductors and capacitors to
minimize the footprint in space-conscious applications. The
NJU6049 also features low operating voltage of 1.7V and the
small package VSP10.
All of these benefits make the NJU6049 suitable for the
battery-powered portable applications such as cellular phones,
camcorders, PDAs, etc.
! PACKAGE OUTLINE
NJU6049R
! FEATURES
# Drives Up to 4White LEDs in Series
IOUT = 20mA(typical)
# Uses Small Inductor and Capacitors
# 1.7V to 6.5V Operating Voltage for Step-up Circuits (VDD)
# Low Switch RDS (ON)
VSW = 18V, RDS=0.8(ISW=150mA)
# OVP Function
# Shutdown terminal
# CMOS Technology
# Package
: VSP10
! PIN CONFIGURATION (TOP VIEW)
FB 1
NC 2
VSS 3
NC 4
SW 5
10 SHDNb
9 OVP
8 VSS
7 NC
6 VDD
Ver.2005-06-09
-1-









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NJU6049 Даташит, Описание, Даташиты
NJU6049
www.DataSheet4U.com
! PIN DESCRIPTIONS
No. SYMBOL
1 FB
3,8 VSS
5 SW
6 VDD
9 OVP
10 SHDNb
2,4,7
NC
TYPE
Input
Power
Input
Power
Input
Input
-
DESCRIPTION
Feedback Terminal
Ground Terminal
Switch Terminal
Power Supply terminal
Over Voltage protection Terminal
Shutdown Terminal Active “L” (Pull-up resistance On-chip)
“L” : Disable the device.
“H” : Enable the device.
NC Terminal
Electrical open.
! BLOCK DIAGRAM
VIN
C1
L1
VDD
SW
Bias
Shutdown
circuit
VSS
D1
VOUT
OVP
OVP
DC/DC
Control
-
+
FB
VREF
0.25V
RLED
C2
ILED
-2-
Ver.2005-06-09









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NJU6049 Даташит, Описание, Даташиты
www.DataSheet4U.com
! FUNCTIONAL DESCRIPTONS
NJU6049
(1) LED Current Control and Resistor RLED Selection
The NJU6049 incorporates the LED current control to regulate the LED current (ILED) , which is programmed
by the feedback resistor (RLED) connected between the FB and the VSS terminals. Typically, the reference voltage
VREF is internally regulated to 0.25V and is used as the positive input of the built-in comparator. Formula (1) is
used to choose the value of the RLED, as shown below.
RLED
= VREF
I LED
--- Formula (1)
VREF=0.25 (typical)
The ILED is the constant current programmed by the RLED. When the feedback voltage on the FB terminal
reaches above the reference voltage VREF (i.e., ILED is above the level programmed by RLED), the output capacitor
C2 delivers the ILED. Once the feedback voltage drops below the reference voltage (i.e., ILED drops below the level
programmed by the RLED), the MOS switch is turned on, then the current of the inductor L1 begins increasing.
When the switch current reaches 250mA, the MOS switch is turned off, then the L1 delivers current to the output
through the diode D1as the inductor current drops. After that, the MOS switch is turned on again and the switch
current increases up to 250mA. This switching cycle continues until the ILED reaches the level programmed by the
RLED, then the ILED current is maintained constant.
(2) Over Voltage Protection
OVP is designed to prevent the damage of internal NMOS switch in case the increased impedance of the
LED load (including the LED opened). Once the device detects over voltage at the output, the internal NMOS
switch is kept off until the output voltage drops below 14V.
(3) Inductor Selection
A 10uH inductor is recommended for most application. The selected inductor must have a saturation current
that meets the maximum peak current of the converter. Another important inductor parameter is the DC resistance.
The lower DC resistance the device has higher efficiency.
(4) Diode Selection
A Schottky diode with a low forward-voltage-drop and a fast switching-speed is ideal for the D1. And the D1
must have a rating greater than the output voltage and output current in the system.
(5) Capacitor Selection
A low ESR (Equivalent Series Resistance) capacitor should be used as the output capacitor C2 to minimize
output ripples. A multi-layer ceramic capacitor is the best selection for the NJU6049 application because of not
only the low ESR but also small package. Application requires good line regulation ±1%(typ) should use output
capacitor larger than 1uF. A ceramic capacitor is also recommended for the input decoupling-capacitor C1, and
should be placed as close to the NJU6049 as possible. A 4.7uF is sufficient for most applications.
Ver.2005-06-09
-3-










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