LDS8681

LDS8681 IXYS | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 9

Technical content

Characteristics subject to change without notice 800 mA, Dual Output LED Flash/PWM Dimming Lamp Driver

FEATURES

o 1-x and 2-x Charge Pump modes o Supply voltage range from 2.7 to 5.5 V o Low dropout PowerLite™ Current Regulator* o Drives up to 2 LEDs at 400 mA simultaneously or one LED at 800 mA o Power efficiency up to 90% o Low current shutdown mode < 1 µA o Short circuit current limiting o Thermal shutdown protection o Available 8-pin 2 x 3 x 0.8 mm 8-pin TDFN package APPLICATION o White LED photoflash for digital cameras, cell phones, Smart Phones, and other portable devices

DESCRIPTION

The LDS8681 is a high efficiency regulated charge pump with low dropout voltage that can drive two 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 The regulated charge pump supports a wide input voltage range from 2.7 V to 5.5 V. The device is available in 8-lead TDFN 2 mm x 3 mm package with a max height of 0.8 mm. TYPICAL APPLICATION CIRCUIT

Characteristics subject to change without notice ABSOLUTE MAXIMUM RATINGS Parameter Rating Unit VIN, LEDx, C1± voltage 6 V VOUT voltage 6 V EN/SET voltage VIN + 0.7V V Storage Temperature Range -65 to +160 °C Junction Temperature Range -40 to +125 °C Soldering Temperature 300 °C RECOMMENDED OPERATING CONDITIONS Parameter Rating Unit VIN 2.7 to 5.5 V Ambient Temperature Range -40 to +85 °C Typical application circuit with external components is shown on page1. 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 Conditions Min Typ Max Units Standby Current 0.6 mA Shutdown Current VEN = 0V 0.5 µA LED Current Accuracy 1mA ≤ILED ≤ 400 mA ±8 % LED Channel Matching (ILED - ILEDAVG) / ILEDAVG ±8 % 1-x mode 0.5Output Resistance (open loop) 2-x mode 1.7 Ω Charge Pump Frequency 1 MHz Output short circuit Current Limit VOUT < 0.5V 2 A Input Current Limit 2 A 1-x to 2-x Transition Thresholds at any LED pin At 200 mA 150 mV Transition Filter Delay 800 µs Input current EN = 1.4 V, VIN = 5.5 V 1 µA High 1.4 EN/SET Pin Logic Level Low 0.4 V Thermal Shutdown1 160 Thermal Hysteresis1 25 °C Under Voltage Lockout (UVLO) Threshold 2.3 V Output Over Voltage protection 5.6 5.9 V 1-x mode 100 µsFlash LED Turn-on Time2 2-x mode 1.2 ms PWM Frequency3 0.1 1 kHz Note: 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

Characteristics subject to change without notice TYPICAL CHARACTERISTICS VIN = 3.6V, IOUT = 800 mA (2 LEDs at 400mA), CIN = C1= 1μF, COUT = 2 μF, TAMB = 25°C unless otherwise specified Power-Up in 1-x mode VIN = 4.2 V, Ch1 –PWM, Ch2 –LED current (400 mA/div), Ch3 –Output voltage Power-Up in 2-x Mode VIN = 3.6 V, Ch1 –PWM, Ch2 –LED current (400 mA/div), Ch3 –Output voltage Operating Waveforms at 1kHz PWM mode 10% Duty Cycle VIN = 4.2 V, Ch1 –PWM, Ch2 –LED current (400 mA/div) Operating Waveforms at 1kHz PWM mode 90% Duty Cycle VIN = 4.2 V, Ch1 –PWM, Ch2 –LED current (400 mA/div) LED Current Setting Error vs. Duty Cycle Power-Down Delay (1-x Mode) VIN = 4.2 V, Ch1 –PWM, Ch2 –LED current (400 mA/div)

Characteristics subject to change without notice PIN DESCRIPTION Pin # Name Function

1 VIN Charge pump input, connect to battery or supply

2 C1+ Flying capacitor 1 Positive terminal

3 C1- Flying capacitor 1 Negative terminal

4 EN Device enable (active high)

5 LEDB LEDB cathode terminal

6 LEDA LEDA cathode terminal

7 GND Ground Reference

8 VOUT Charge pump output connected to the LED anodes

PAD PAD 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 VIN 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. 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. VOUT is the charg e pump output that is connected to the LED anodes. A small 2.2 μF ceramic bypass capacitor is required between the VOUT pin and ground near the device. 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 cur rents set at every channel. 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

Figure 2. LDS8681 Functional Block Diagram range from 25 to 400 mA for LEDB. voltage until logic HIGH level is applied to EN pin. device remains in 1-x operating mode. pump mode to the next multiplication ratio. voltage (less any internal voltage losses).

Characteristics subject to change without notice Unused LED Channels 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. Protection Modes The LDS8681 has follow protection modes: 1. LED short to VOUT protection If LED pin is shorted to V OUT, LED burned out becomes as short circuit, or LED pin voltage is within from V OUT 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. 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 V OUT 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 VIN 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 V IN continues fall below 1.7 V, LDS 8681 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 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. LEDs with forward voltages (VF) ranging from 1.6 V to 4 V may be used. Charge pump operates in highest efficiency when VF voltage is close to VIN voltage multiplied by switching mode, i.e. VIN x 1 or VIN x 2 External Components The driver requires three external ceramic capa citors (C1, CIN, and C OUT) X5R or X7R type. In 2-x charge pump mode , an input bypass capacitor of 1µF is sufficient. In 1x mode, the d evice operates in linear mode and does not introduce switching noise back onto the supply. 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 pl ane 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 th e 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 ground plane on the bottom layer through two vias to imporove power dissipation.

Characteristics subject to change without notice PACKAGE DRAWING AND DIMENSIONS 8-PIN TDFN (HV3), 2mm x 3mm, 0.5mm PITCH SYMBOL MIN NOM MAX A 0.700 0.750 0.800 A1 - 0.000 0.050 A2 0.203 Ref. b 0.180 0.230 0.280 D 2.950 3.000 3.050 D1 1.750 1.800 1.850 E 1.950 2.000 2.050 E1 1.550 1.600 1.650 e 0.500 Bsc L 0.350 0.400 0.450 Note: 1. All dimensions are in millimeters 2. Complies with JEDEC Standard MO-220

Characteristics subject to change without notice

ORDERING INFORMATION

Part Number Package Package Marking LDS8681 008-T2 1) TDFN-8 2 x 3mm 2) 681 Notes: 1. Quantity per reel is 2000 2. Matte-Tin Plated Finish (RoHS-compliant) EXAMPLE OF ORDERING INFORMATION 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. Optional Company ID Package 008: 2x3 TDFN Prefix Device # Suffix LDS 681 008 T2 Product Number Tape & Reel T: Tape & Reel 2: 2000/Reel

Characteristics subject to change without notice IXYS Corp. 1590 Buckeye Dr., Milpitas, CA 95035-7418 Phone: 408.457.9000 Document No: 8681_DS Fax: 408. 496.0222 Revision: N1.0 http://www.ixys.com Issue date: 2/8/2011 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 int ended 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 theIXYS 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.