View EUP2561JIR1_4129156.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

26V Step-Up Converters
EUP2561
for Two to Six White LEDs
DESCRIPTION
The EUP2561 is a constant current step-up converter specially designed for driving white LEDs. The step-up converter topology allows series connection of the white LEDs so the LED currents are identical for uniform brightness. The EUP2561 can drive 6 LEDs in series. The brightness of the LEDs can be adjusted through a voltage level on the CTRL pin or by applying a PWM signal to CRTL pin. 1MHz current-mode, pulse-width modulated (PWM) operation allows for small input and output capacitors and a small inductor while minimizing ripple on the input supply/battery. Programmable soft-start eliminates inrush current during startup. The EUP2561 is available in a space-saving, 8-pin 3mm x 3mm DFN package.
FEATURES
2.6V to 5.5V Input Range 26V (max) Output with Overvoltage Protection Up to 87% Efficiency Flexible Analog or PWM Dimming Control Internal High Power 30V MOSFET Switch < 1A shutdown Current Fast 1MHz PWM Operation Small, Low-Profile Inductors and Capacitors 3mm x 3mm DFN-8 Package RoHS Compliant and 100% Lead (Pb)-Free
APPLICATIONS
Cell Phones and Smart Phones PDAs, Palmtops, and Wireless Handhelds e-Books and Subnotebooks White LED Display Backlighting
Typical Application Circuit
Figure 1. White LED Application
DS2561 Ver1.0 Dec. 2006
1
EUP2561
Pin Configurations
Package Type Pin Configurations (Top View)
DFN-8
Pin Description
PIN OUT IN CTRL CS COMP GND PGND LX Pin 1 2 3 4 5 6 7 8 Regulated Output Voltage. Input Supply Voltage. Brightness Control Input. LED brightness is controlled by the voltage applied to CTRL. Varying the voltage from 0.24V to 1.62V adjusts the brightness from dim to bright, respectively. Any voltage above 1.62V does not increase brightness. Current-Sense Feedback Input. Connect a resistor from CS to GND to set the LED bias current. The voltage at CS regulates to VCTRL / 10 or 0.162V, whichever is lower. Compensation Input. Connect a 0.1F capacitor (CCOMP) from COMP to GND. CCOMP stabilizes the converter and controls soft-start. CCOMP discharges to GND when in shutdown. Common Ground. Connect to PGND and the exposed pad directly under the IC. Power Ground. Connect to GND and the exposed pad directly under the IC. Inductor Connection. This pin is high impedance during shutdown. DESCRIPTION
DS2561 Ver1.0
Dec. 2006
2
EUP2561
Ordering Information
Order Number EUP2561JIR1 Package Type DFN-8 Marking Operating Temperature range -40 C to 125C
xxxx 2561A
EUP2561
1/4
1/4
1/4
1/4
Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type J: DFN-8
Block Diagram
Figure 2.
DS2561 Ver1.0 Dec. 2006
3
EUP2561
Absolute Maximum Ratings
IN to GND -------------------------------------------------------------------------- -0.3V to 6V PGND to GND ---------------------------------------------------------------------- -0.3V to 0.3V LX,OUT to GND ------------------------------------------------------------------- -0.3V to 30V CTRL to GND -------------------------------------- -0.3V to the lower of 6V or (VIN +0.5V) COMP,CS to GND ---------------------------------------------------------- -0.3V to (VIN +0.3V) ILX ------------------------------------------------------------------------------------- 1A Thermal Resistance DFN-8 -------------------------------------------------------------------------------- 50C /W Junction Temperature ---------------------------------------------------------------- 150C Storage Temperature Range ------------------------------------------------------ -65C to 150C Lead Temperature (Soldering, 10sec.) --------------------------------------------- 260C
Recommended Operating Conditions
Supply Voltage, VIN ---------------------------------------------------------------- 2.6V to 5.5V Operating Temperature Rang ----------------------------------------------------- -40C to 85C
Electrical Characteristics
(VIN = 3V, VOUT = 20V, COUT = 0.1F, CCOMP = 0.15F, RSENSE = 7.5, VCTRL = 1.5V, Figure 2, TA =-40C to +85C, unless otherwise noted.)
Parameter
Supply Voltage UVLO Threshold Quiescent Current OVLO Threshold OUT Input Bias Current Output Voltage Range ERROR AMPLIFIER CTRL to CS Regulation CTRL Input Resistance CTRL Dual-Mode Threshold CTRL Shutdown Enable Delay CS-to-COMP Transconductance OSCILLATOR Operating Frequency Maximum Duty Cycle N-CHANNEL SWITCH LX On-Resistance LX Current Limit
Conditions
VIN rising or falling No Switching VOUT rising VOUT=26V,VCTRL> 0.24V VOUT=VIN, CTRL=GND
EUP2561 Min Typ Max.
2.6 2.20 26 12 (VIN-VD1) 2.40 0.39 27.5 22 0.01 5.5 2.60 0.60 29 35 1 25.5 0.100 400 180 7.5 0.105 700 260
Unit
V V mA V A V V k[ mV mS
VCTRL = 1V, VIN= 2.6V to 5.5V VCTRL 1.0V Rising
0.095 200 100
Vcomp=1.0V
21 0.78
52 1.05 92 1.6
85 1.3 96 2.4 1000
S MHz % [ mA
CTRL=IN CS=GND
88
Duty cycle=90%
550
750
DS2561 Ver1.0
Dec. 2006
4
EUP2561
Typical Operating Characteristics
DS2561 Ver1.0
Dec. 2006
5
EUP2561
DS2561 Ver1.0
Dec. 2006
6
EUP2561
Application Information
Soft-Start The EUP2561 attain soft-start by charging CCOMP gradually with a current source. When VCOMP rises above 1.25V, the internal MOSFET begins switching at a reduced duty cycle. When VCOMP rises above 2.25V, the duty cycle is at its maximum. See the Typical Operating Characteristics for an example of soft-start operation. Shutdown The EUP2561 enter shutdown when VCTRL is less than 100mV for more than 8.2ms. In shutdown, supply current is reduced to 0.3A by powering down the entire IC except for the CTRL voltage-detection circuitry. CCOMP is discharged during shutdown, allowing the device to reinitiate soft-start when it is enabled. Although the internal N-channel MOSFET does not switch in shutdown, there is still a DC current path between the input and the LEDs through the inductor and Schottky diode. The minimum forward voltage of the LED array must exceed the maximum input voltage to ensure that the LEDs remain off in shutdown. However, with two or more LEDs, the forward voltage is large enough to keep leakage current low, less than 1A(typ). Typical shutdown timing characteristics are shown in the Typical Operating Characteristics. Overvoltage Protection Overvoltage lockout (OVLO) occurs when VOUT is above 27V.The protection circuitry stops the internal MOSFET from switching and causes VCOMP to decay to 0V. The device comes out of OVLO and into softstart when VOUT falls below 25V. Adjusting LED Current Adjusting the EUP2561 output current changes the brightness of the LEDs. An analog input (CTRL) and the sense-resistor value set the output current. Output current is given by:
VCTRL I LED = 10 x R SENSE
PWM Dimming Control CTRL is also used as a digital input allowing LED brightness control with a logic-level PWM signal applied directly to CTRL. The frequency range is from 200Hz to 200kHz, while 0% duty cycle corresponds to zero current and 100% duty cycle corresponds to full current. The error amplifier and compensation capacitor form a lowpass filter so PWM dimming results in DC current to the LEDs without the need for any additional RC filters; see the Typical Operating Characteristics. Capacitor Selection The exact values of input and output capacitors are not critical. The typical value for the input capacitor is 2.2F and the typical value for the output capacitor is 0.1F. Larger value capacitors can be used to reduce input and output ripple, but at the expense of size and higher cost. CCOMP stabilizes the converter and controlls soft-start. Connect a 0.1F capacitor from COMP to GND. For stable operation, COUT must not exceed 10 times CCOMP. Inductor Selection Inductor values range from 10H to 47H. A 22H inductor optimizes the efficiency for most applications while maintaining low 15mVP-P input ripple. With input voltages near 5V, a larger value of inductance can be more efficient. To prevent core saturation, ensure that the inductor-saturation current rating exceeds the peak inductor current for the application. Calculate the peak inductor current with the following formula:
I PEAK = + VOUT(MAX) x I LED(MAX) 0.8 x VIN(MIN)
VIN(MIN) x 0.8s 2x L
Schottky Diode Selection The EUP2561 high switching frequency demands a high-speed rectification diode (D1) for optimum efficiency. A Schottky diode is recommended due to its fast recovery time and low forward-voltage drop. Ensure that the diode's average and peak current rating exceed the average output current and peak inductor current. In addition, the diode's reverse breakdown voltage must exceed VOUT. The RMS diode current can be calculated from:
I DIODE(RMS) I OUT x I PEAK
The VCTRL voltage range for adjusting output current is 0.24V to 1.62V. To set the maximum current, calculate RSENSE when VCTRL is at its maximum as follows:
R SENSE = 1.62V 10 x I LED(MAX)
Power dissipation in RSENSE is typically less than 5mW, making a standard chip resistor sufficient.
DS2561 Ver1.0 Dec. 2006
7
EUP2561
PC Board Layout Due to fast switching waveforms and high-current paths, careful PC board layout is required. An evaluation kit is available to speed design. When laying out a board, minimize trace lengths between the IC and RSENSE, the inductor, the diode, the input capacitor, and the output capacitor. Keep traces short, direct, and wide. Keep noisy traces, such as the LX node trace, away from CS. The IN bypass capacitor (CIN) should be placed as close to the IC as possible. PGND and GND should be connected directly to the exposed paddle underneath the IC. The ground connections of CIN and COUT should be as close together as possible. The traces from IN to the inductor and from the Schottky diode to the LEDs may be longer.
DS2561 Ver1.0
Dec. 2006
8
EUP2561
Packaging Information
DFN-8
SYMBOLS A A1 b D D1 E E1 e L
MILLIMETERS MIN. MAX. 0.70 0.90 0.00 0.05 0.20 0.40 2.85 3.15 2.30 2.85 3.15 1.50 0.65 0.25 0.45
INCHES MIN. 0.028 0.000 0.008 0.112 0.090 0.112 0.059 0.026 0.010 0.018 0.124 MAX. 0.035 0.002 0.016 0.124
DS2561 Ver1.0
Dec. 2006
9

▲Up To Search▲

Price & Availability of EUP2561JIR1

	To Download EUP2561JIR1 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .