PAM2805 document number: dsxxxxx rev. 1 - 0 1 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated 3-modes/ 3w wled driver with 1 or 2 cell battery description the PAM2805 is a step-up dc-dc wled driver with 3 modes cycling function (100% brightness,25% brightness and 8.5hz blinking). the unique 3 modes cycling function can eliminate the needs of extra functional mcu or ic. the PAM2805 can deliver up to 750ma output current by setting an external resistor. the PAM2805 switches at a 1.0mhz constant frequency, allowing for the use of small value external inductor and ceramic capacitors. a low 95mv feedback voltage reduces the power loss in the r s for better efficiency. with its internal 2a, 100m ? device can provide high efficiency even at heavy load. the PAM2805 is available in tsot26 package. features ? 3 modes cycling function: bright dimming blinking power off <5s power off <5s power off <5s ? reset to bright mode if power off time more than 5s ? adjustable output current: up to 750ma ? 8.5hz blinking mode ? low start-up voltage: 0.9v(typ) ? low sw on resistance: 100m ? ? over temperature protection ? over voltage protection ? tsot26 package ? pb-free package pin assignments applications ? white led torch (flashlight) typical applications circuit iled + 95mv/r s top view tsot26
PAM2805 document number: dsxxxxx rev. 1 - 0 2 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated pin description pin number pin name function 1 vin input voltage 2 gnd power ground 3 blk connect a 1f cap for blinking 4 fb feedback 5 vout output voltage 6 sw connected to an internal nmos switch block diagram absolute maximum ratings (@t a = +25c, unless otherwise specified.) these are stress ratings only and functional operation is not implied. exposure to absolute maximum ratings for prolonged time periods may affect device reliability. all voltages are with respect to ground. parameter rating unit supply voltage 6 v output voltage 6 storage temperature range -65 to +150 c lead temperature (soldering, 5 sec) 300 recommended operating conditions (@t a = +25c, unless otherwise specified.) parameter rating unit operation temperature range -40 to +85 c junction temperature range -40 to +125
PAM2805 document number: dsxxxxx rev. 1 - 0 3 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated thermal information parameter symbol package max unit thermal resistance (junction to case) jc tsot26 130 c/w thermal resistance (junction to ambient) ja tsot26 250 internal power dissipation @ t a = 25c p d tsot26 400 mw electrical characteristics (@t a = +25c, l = 2.2h, c in = 10f, c out = 10f, c blk = 1f, v f = 3.4v unless otherwise specified.) parameter symbol test conditions min typ max units input voltage range v in 0.9 v f -0.2 (note 1) v feedback voltage v fb 90 95 100 mv start-up voltage v start v in : 0v 3v, i led = 200ma 0.9 v hold voltage v hold v in : 3v 0v, i led : 750ma 100ma 0.7 v oscillator frequency f osc 0.85 1.0 1.15 mhz over temperature shutdown ots 150 c over temperature hysteresis oth 30 c maximum output current range i o(max) v in = 2.4v 750 ma quiescent current i q i led = 0ma, vo = 3.4v, device switching at 1mhz 1 3 ma switch on resistance r ds(on) v o = 3.4v 0.1 ? current limit i lim v o = 3.4v 2 a over voltage protection (vout) v ovp 4.5 v blinking frequency f blk c blk = 1f 8.5 10 hz note: 1. v f ---led forward voltage
PAM2805 document number: dsxxxxx rev. 1 - 0 4 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated typical performance characteristics (@t a = +25c, l = 2.2f, c in = 10f, c out = 10f, c blk = 1f, unless otherwise specified.)
PAM2805 document number: dsxxxxx rev. 1 - 0 5 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated typical performance characteristics (cont.) (@t a = +25c, l = 2.2f, c in = 10f, c out = 10f, c blk = 1f, unless otherwise specified.)
PAM2805 document number: dsxxxxx rev. 1 - 0 6 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated application information inductor selection the PAM2805 can use small value inductors due to its switching frequency of 1 mhz. the value of inductor will focus in the rang e of 2.2h to 4.7h for most PAM2805 applications. in typical high current whit e led applications, it is recommended to use a 4.7h inductor. the inductor should have low dcr (dc resist ance) to minimize the i 2 r power loss, and it requires a current rating of 2a to handle the peak inductor current without saturating. capacitor selection an input capacitor is required to reduc e the input ripple and noise for proper oper ation of the PAM2805. for good input decoupl ing, low esr (equivalent series resistance) capacitors should be used at the input. at least 2.2f input capacitor is recommended for most a pplications. a minimum output capacitor value of 6.8f is recommended unde r normal operating conditions, while a 10f-22f capacitor may be required for higher power led current. a reasonable value of the output capaci tor depends on the led current. the esr of the output cap acitor is the important parameter to determine the output voltage ripple of t he converter, so low esr capacitors should be used at the output to reduce the output voltage ripple. the small size of ceramic capacitors is an excellent choice for PAM2805 applications. the x5r and x7r ty pes are preferred because they maintain capacitance over wide voltage and temperature ranges. diode selection it's indispensable to use a scho ttky diode rated at 2a with the PAM2805. using a schottky diode with a lower forward voltage dr op is better to improve the power led efficiency, and its voltage rating shoul d be greater than the output voltage. ss22 is recommended schottk y diode for rectifier. led current setting the led current is set by the single exter nal rs resistor connected to the fb pin as shown in the typical application circuit o n page 1. the typical fb reference is internally regulated to 95mv. the led current is 95mv/r1. it's recommended to use a 1% or better precision resi stor for the better led current accuracy. the formula for r s selection is shown as follows: ?? ? ? v3 v atma i /mv95 r in led s ? ?? typically, for 1w(330ma) and 3w(750ma) led light applications, the r s are 0.288 ? and 0.127 ? respectively. 3 modes cycling the PAM2805 has three modes: 100% brightness, 25% brightness and blinking (typical 8.5hz). the mode change is triggered by power on /off actions and cycles in the following se quence: bright, dimming, blinking and back t o bright mode. the PAM2805 will reset to the bright mode after being power off for more than 5 seconds. low voltage start-up and soft-start the PAM2805 has a build-in low voltage startup circuit for the best battery life solution. it can start up at 0.9v v in typically when the preset led current is 200ma. the soft-start function is made by clamping the output voltage of error amplifier with another voltage source which increases s lowly from zero to near v in dur ing the soft-start period. therefore, the duty cycle of the pwm will be increased from zero to maximum in this period. the charging time of the inductor will be limited by the smaller duty so that the inrush current can be reduced to an acceptable value. over voltage protection the output voltage of PAM2805 is monitored by over voltage protection circuit. once v out goes over v ovp , typically 4.5v, the power nmos is turned off and sw pin stops switching. then, the v out is clamped to around v ovp . over current protection the inductor current during charging period is detected by a curr ent sensing circuit. when the va lue is larger than current lim iting i lim , the power nmos is turned off so that the inductor will be forced to leav e charging stage and enter discharging stage. therefore, the indu ctor peak current will not exceed i lim , whose minimum value is 2a.
PAM2805 document number: dsxxxxx rev. 1 - 0 7 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated application information pcb layout guidelines as for all switching power supplies, the layout and components pl acement of the PAM2805 is an important step in the design; esp ecially at high peak currents and high switching frequencies. the input capacitor and output capacitor shoul d be placed respectively as close as possible to the input pin and output pin of the ic; the inductor and schottky diode should be placed as close as possible to the switch pin by us ing wide and short traces for the main current path; the current sense resistor should be placed as close as possible between the ground pin and feedback pin. ordering information part number marking package type standard package PAM2805af ecxyw tsot26 3000 units/tape&reel marking information top view tsot26
PAM2805 document number: dsxxxxx rev. 1 - 0 8 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated package outline dimensions (all dimensions in mm.) tsot26
PAM2805 document number: dsxxxxx rev. 1 - 0 9 of 9 www.diodes.com july 2013 ? diodes incorporated PAM2805 a product line o f diodes incorporated important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries reserve the right to ma ke modifications, enhancements, im provements, corrections or ot her changes without further notice to this document and any product described herein. diodes incorporated does not assume any liability ari sing out of the application or use of this document or any product described herein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or user of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes incorporat ed and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability wh atsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes inco rporated products for any unintended or unauthorized application, customers shall i ndemnify and hold diodes incorporated and its representat ives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death a ssociated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. this document is written in english but may be translated into mu ltiple languages for reference. only the english version of t his document is the final and determinative format released by diodes incorporated. life support diodes incorporated products are specifically not authorized for use as critical comp onents in life support devices or systems without the express written approval of the chief executive offi cer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when proper ly used in accordance with inst ructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support devic e or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning the ir products and any use of diodes incorporated products in such safety-critica l, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporate d and its representatives against any damages arising out of the use of diodes incorporated products in such safety-critical, life suppor t devices or systems. copyright ? 2013, diodes incorporated www.diodes.com
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