LDS8681008-T2

LDS8681 800 mA, Dual Output LED Flash/PWM Dimming Lamp Driver FEATURES o o 1-x and 2-x Charge Pump modes Supply voltage range from 2.7 to 5.5 V o o o Low dropout PowerLite™ Current Regulator* Drives up to 2 LEDs at 400 mA simultaneously or one LED at 800 mA Power efficiency up to 90% o o Low current shutdown mode < 1 µA Short circuit current limiting o Thermal shutdown protection o Available 8-pin 2 x 3 x 0.8 mm 8-pin TDFN package LEDs at 400 mA each simultaneously or one LED at 800 mA. Low dropout PowerLite™ Current Regulator (PCR) increases device’s efficiency up to 90%. The EN logic input functions as a chip enable. The LEDs current is programmed at 400 mA for both channels in the factory. Please, consult factory about other current values. Each LED current can be programmed separately in the factory from 52 to 800 mA in 25 mA steps for LEDA and in the range from 52 to 400 mA for LEDB APPLICATION o The regulated charge pump supports a wide input voltage range from 2.7 V to 5.5 V. White LED photoflash for digital cameras, cell phones, Smart Phones, and other portable devices The device is available in 8-lead TDFN 2 mm x 3 mm package with a max height of 0.8 mm. DESCRIPTION The LDS8681 is a high efficiency regulated charge pump with low dropout voltage that can drive two TYPICAL APPLICATION CIRCUIT © 2009 IXYS Corp. Characteristics subject to change without notice 1 Doc. No. 8681_DS, Rev. N1.0 LDS8681 ABSOLUTE MAXIMUM RATINGS Parameter VIN, LEDx, C1± voltage V OUT voltage EN/SET voltage Storage Temperature Range Junction Temperature Range Soldering Temperature Rating 6 6 V IN + 0.7V -65 to +160 -40 to +125 300 Unit V V V °C °C °C RECOMMENDED OPERATING CONDITIONS Parameter Rating 2.7 to 5.5 -40 to +85 VIN Ambient Temperature Range Unit V °C Typical application circuit with external components is shown on page 1. ELECTRICAL OPERATING CHARACTERISTICS (Over recommended operating conditions unless specified otherwise) VIN = 3.6V, C1 = 2.2 µF, Cin = Cout = 1 µF, EN = High, TAMB = 25°C Name Standby Current Shutdown Current LED Current Accuracy LED Channel Matching Output Resistance (open loop) Conditions 1 Charge Pump Frequency Output short circuit Current Limit Input Current Limit 1-x to 2-x Transition Thresholds at any LED pin Transition Filter Delay Input current EN/SET Pin High Logic Level Low 1 Thermal Shutdown 1 Thermal Hysteresis Under Voltage Lockout (UVLO) Threshold Output Over Voltage protection 1-x mode 2 Flash LED Turn-on Time 2-x mode 3 PWM Frequency Note: Min V EN = 0V 1mA ≤ILED ≤400 mA (ILED - ILEDAVG) / ILEDAVG 1-x mode 2-x mode V OUT < 0.5V At 200 mA EN = 1.4 V, V IN = 5.5 V Typ 0.6 0.5 ±8 ±8 0.5 1.7 1 2 2 Max Units mA µA % % Ω MHz A A 150 mV 800 1 µs µA 1.4 0.4 160 25 2.3 5.6 °C 5.9 100 1.2 0.1 V 1 V V µs ms kHz 1. Sample test only 2. Measusured from EN LOW to HIGH transition to ILED current reaches 90% of regulated level 3. See Current setting Error vs. Duty Cycle and PWM Frequency at p.3 © 2009 IXYS Corp. Characteristics subject to change without notice 2 Doc. No. 8681_DS, Rev. N1.0 LDS8681 TYPICAL CHARACTERISTICS V IN = 3.6V, IOUT = 800 mA (2 LEDs at 400mA), C IN = C1= 1μF, COUT = 2 μF, TAMB = 25°C unless otherwise specified Power-Up in 1-x mode Power-Up in 2-x Mode V IN = 4.2 V, Ch1 – PWM, Ch2 – LED current (400 mA/div), Ch3 – Output voltage V IN = 3.6 V, Ch1 – PWM, Ch2 – LED current (400 mA/div), Ch3 – Output voltage Operating Waveforms at 1kHz PWM mode 10% Duty Cycle Operating Waveforms at 1kHz PWM mode 90% Duty Cycle V IN = 4.2 V, Ch1 – PWM, Ch2 – LED current (400 mA/div) V IN = 4.2 V, Ch1 – PWM, Ch2 – LED current (400 mA/div) LED Current Setting Error vs. Duty Cycle Power-Down Delay (1-x Mode) V IN = 4.2 V, Ch1 – PWM, Ch2 – LED current (400 mA/div) © 2009 IXYS Corp. Characteristics subject to change without notice 3 Doc. No. 8681_DS, Rev. N1.0 LDS8681 PIN DESCRIPTION Pin # 1 2 3 4 5 6 7 8 PAD Name V IN C1+ C1EN LEDB LEDA GND VOUT PAD Function Charge pump input, connect to battery or supply Flying capacitor 1 Positive terminal Flying capacitor 1 Negative terminal Device enable (active high) LEDB cathode terminal LEDA cathode terminal Ground Reference Charge pump output connected to the LED anodes Connect to GND on the PCB Top view: TDFN 8-lead 2 X 3 mm PIN FUNCTION VIN is the supply pin for the charge pump. A small 1 μF ceramic bypass capacitor is required between the V IN pin and ground near the device. The operating input voltage range is from 2.7 V to 5.5 V. If VIN falls below the under-voltage threshold, all LED channels disable and the device enters shutdown mode. GND is the ground reference for the charge pump. The pin must be connected to the ground plane on the PCB. C1+, C1- are connected to each side of the ceramic flying capacitor C1 = 1 µF LEDA, LEDB provides the internal regulated current source for each of the LED cathodes. These pins enter high-impedance zero current state whenever the device is in shutdown mode. These pins may be teed together to provide sum of the currents set at every channel. EN is the enable control logic input for all LED channels. Guaranteed levels of logic high and logic low are set at 1.4 V and 0.4 V respectively. To place the device into zero current mode, the EN pin must be held low for more than 50 ms. PAD is the exposed pad underneath the package. For best thermal performance, the pad should be soldered to the PCB and connected to the ground plane VOUT is the charge pump output that is connected to the LED anodes. A small 2.2 μF ceramic bypass capacitor is required between the V OUT pin and ground near the device. © 2009 IXYS Corp. Characteristics subject to change without notice 4 Doc. No. 8681_DS, Rev. N1.0 LDS8681 BLOCK DIAGRAM Figure 2. LDS8681 Functional Block Diagram BASIC OPERATION driver’s efficiency. The LDS8681 monitors voltage drop Vd across PCR at every channel in ON state. If this voltage falls below 150 mV (typical) at any one channel, (channel with LED with highest forward voltage), the Mode Control Block changes charge pump mode to the next multiplication ratio. LDS8681 is a charge pump designed for converting at Li-Ion battery voltage to drive a white LED used in photo flash applications. The LEDs current is factory programmed at 400 mA for both channels. Consult factory about other current values. Every LED may be factory programmed separately in the range from 25 to 800 mA in 25 mA steps for LEDA and in the range from 25 to 400 mA for LEDB. Vd (LEDA/B) = VIN x M – VF – Rcp x IOUT , where Rcp is a Charge Pump Output Resistance at given mode, IOUT is sum of all LED currents, and M is a charge pump’ multiplication ratio. The LDS8681 is in standby mode after applying V IN voltage until logic HIGH level is applied to EN pin. The device requires approximately 100 µs to wake up. If the input voltage is insufficient or falls to a level where Vd ≤ 150 mV, and the regulated currents cannot be maintained, the low dropout PowerLite™ Current Regulator switches the charge pump into 2-x mode (after a fixed delay time of about 800μs). In 2-x mode, the charge pump’ output voltage is approximately equal to 2 times the input supply voltage (less any internal voltage losses). Device starts operating with soft-start at 1-x mode to minimize inrush current At 1-x mode, the V OUT is approximately equal to VIN (less any internal voltage losses). If the output voltage is sufficient to regulate all LED currents, the device remains in 1-x operating mode. LED Current Setting The charge pump has two modes of operation: 1-X, and 2-x. The device changes modes if the output voltage drops below the minimum needed to support the desired ILED current. The current in each of the two LED channels is factory programmed; however, average current value may be decreased using PWM pulses. Check LED Data sheet to avoid LED thermal damage at high current. . The low dropout PowerLite™ Current regulator (PCR) performs well at input voltages up to 150 mV above LED forward voltage V F significantly increasing © 2009 IXYS Corp. Characteristics subject to change without notice 5 Doc. No. 8681_DS, Rev. N1.0 LDS8681 Unused LED Channels LEDs with forward voltages (VF ) ranging from 1.6 V to 4 V may be used. Charge pump operates in highest efficiency when V F voltage is close to V IN voltage multiplied by switching mode, i.e. V IN x 1 or V IN x 2 For applications with only one LED, unused channel can be connected to VOUT or both channels may be teed together to provide sum of the currents set at each channel. External Components Protection Modes The driver requires three external ceramic capacitors (C1, CIN , and COUT ) X5R or X7R type. In 2-x charge pump mode, an input bypass capacitor of 1µF is sufficient. The LDS8681 has follow protection modes: 1. LED short to VOUT protection In 1x mode, the device operates in linear mode and does not introduce switching noise back onto the supply. If LED pin is shorted to VOUT , LED burned out becomes as short circuit, or LED pin voltage is within from VOUT to (VOUT - 1.5V) range, LDS8681 recognizes this condition as “LED Short” and disables this channel. If LED pin voltage is less than (Vout – 1.5V), LDS8681 restores LED current at this particular channel to programmed value. Recommended Layout In charge pump mode, the driver switches internally at a high frequency. It is recommended to minimize trace length to all capacitors. A ground plane should cover the area under the driver IC as well as the bypass capacitors. Short connection to ground on capacitors CIN and COUT can be implemented with the use of multiple via. A copper area matching the TDFN exposed pad (PAD) must be connected to the ground plane underneath. The use of multiple via improves the package heat dissipation (see figure below). The ground plane on the top layer is connected to the 2. VOUT Over-Voltage Protection The charge pump’ output voltage VOUT automatically limits at about 5.9 V maximum. This is to prevent the output pin from exceeding its absolute maximum rating. 3. VOUT Short Circuit Protection If VOUT is shorted to ground before LDS8681 is enabled, input current may increase up to 1 A within 20 µs after enable and is limited to ~ 90 mA after that. 4. Over-Temperature Protection If the die temperature exceeds +160°C, the driver will enter shutdown mode. Device restores normal operation after die temperature falls below 135°C. 5. Input Voltage Under-Voltage Lockout If V IN falls below 2.3 V but above 1.7 V (typical value), LDS8681 will restart when input voltage rises above 2.3 V called lockout mode. If VIN continues fall below 1.7 V, LDS8681 device will enter shutdown mode.. To restart device, set EN pin logic low for more than 50 ms and logic high after that.. 6. Open LED Definition ground plane on the bottom layer through two vias to imporove power dissipation. When LED becomes an open circuit, device will enter into 2-x mode unless this unused LED channel is connected to VOUT directly. LED Selection If the power source is a Li-ion battery, LEDs with lowest forward voltages are recommended to achieve highest efficiency and extended operation on a single battery charge. © 2009 IXYS Corp. Characteristics subject to change without notice 6 Doc. No. 8681_DS, Rev. N1.0 LDS8681 PACKAGE DRAWING AND DIMENSIONS 8-PIN TDFN (HV3), 2mm x 3mm, 0.5mm PITCH SYMBOL A A1 A2 b D D1 E E1 e L MIN 0.700 0.180 2.950 1.750 1.950 1.550 0.350 NOM 0.750 0.000 0.203 Ref. 0.230 3.000 1.800 2.000 1.600 0.500 Bsc 0.400 MAX 0.800 0.050 0.280 3.050 1.850 2.050 1.650 0.450 Note: 1. All dimensions are in millimeters 2. Complies with JEDEC Standard MO-220 © 2009 IXYS Corp. Characteristics subject to change without notice 7 Doc. No. 8681_DS, Rev. N1.0 LDS8681 ORDERING INFORMATION Part Number LDS8681 008-T2 Notes: 1. 2. Package 1) TDFN-8 2 x 3mm Package Marking 2) 681 Quantity per reel is 2000 Matte-Tin Plated Finish (RoHS-compliant) EXAMPLE OF ORDERING INFORMATION Prefix LDS Device # Suffix 681 008 Product Number Optional Company ID Package T2 Tape & Reel T: Tape & Reel 2: 2000/Reel 008: 2x3 TDFN Notes: 1) All packages are RoHS-compliant (Lead-free, Halogen-free). 2) The standard lead finish is Matte-Tin. 3) The device used in the above example is a LDS8681 008–T2 (2x3 TDFN, Tape & Reel). 4) For additional package and temperature options, please contact your nearest IXYS Corp. Sales office. © 2009 IXYS Corp. Characteristics subject to change without notice 8 Doc. No. 8681_DS, Rev. N1.0 LDS8681 Warranty and Use IXYS CORP. MAKES NO WARRANTY, REPRESENTATION OR GUARANTEE, EXPRESS OR IMPLIED, REGARDING THE SUITABILITY OF ITS PRODUCTS FOR ANY PARTICULAR PURPOSE, NOR THAT THE USE OF ITS PRODUCTS WILL NOT INFRINGE ITS INTELLECTUAL PROPERTY RIGHTS OR THE RIGHTS OF THIRD PARTIES WITH RESPECT TO ANY PARTICULAR USE OR APPLICATION AND SPECIFICALLY DISCLAIMS ANY AND ALL LIABILITY ARISING OUT OF ANY SUCH USE OR APPLICATION, INCLUDING BUT NOT LIMITED TO, CONSEQUENTIAL OR INCIDENTAL DAMAGES. IXYS Corp. products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the IXYS Corp. product could create a situation where personal injury or death may occur. IXYS Corp. reserves the right to make changes to or discontinue any product or service described herein without notice. Products with data sheets labeled "Advance Information" or "Preliminary" and other products described herein may not be in production or offered for sale. IXYS Corp. advises customers to obtain the current version of the relevant product information before placing orders. Circuit diagrams illustrate typical semiconductor applications and may not be complete. IXYS Corp. 1590 Buckeye Dr., Milpitas, CA 95035-7418 Phone: 408.457.9000 Fax: 408. 496.0222 http://www.ixys.com © 2009 IXYS Corp. Characteristics subject to change without notice Document No: 8681_DS Revision: N1.0 Issue date: 2/8/2011 9 Doc. No. 8681_DS, Rev. N1.0