ZXLD381

Document overview

  • Manufacturer or author: Diodes Incorporated
  • PDF pages: 9

Technical content

Features

  • 85% Efficiency
  • User adjustable output current
  • Single cell operation (0.9V minimum)
  • Low saturation voltage switching transistor
  • SOT23-3 package
  • Available also in Die form
  • Simple Application circuit Application
  • LED flashlights and torches
  • LED backlights
  • White LED driver Pin Assignments SOT23-3 (Top View) Typical Application Circuit LED ZXLD381 GND VOUT VCC VIN

Document number: DS32188 Rev. 3 - 2 2 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated Block Diagram Fig 1. ZXLD381 Block Diagram Pin Description Pin No. Name Description

1 GND Ground

2 VOUT Switch output external inductor/LED

3 VCC Supply voltage, generally Alkaline, NiMH or NiCd single cell

1.5V LED Cof fCon Pulse Co ntro l Rsense

Document number: DS32188 Rev. 3 - 2 3 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated Absolute Maximum Ratings Parameter Rating Unit Supply Voltage (VCC) -0.6 to 10 V Output Voltage (VOUT) -0.6 to 20 V Supply Current 20 mA Output Switch Current 800 mA Power Dissipation SOT23-3 450 mW Power Dissipation Die 1 W Operating Temperature Range 0 to 85 °C Storage Temperature Range -55 to 150 °C Electrical Characteristics Measured at TAMB = 25°C, L = 4.7µH and VCC = 1.5V unless otherwise specified. Parameter Conditions Limits Units Min Typ. Max Supply Voltage Operating Range L = 10 μH 0.9 2.2 V Minimum Supply Start-up Voltage L = 10μ H 0.8 0.9 V Switch Current At turn-off 250 320 400 mA Switch Saturation Voltage IOUT = 200mA 100 300 mV Switch Leakage Current VOUT = 20V 40 70 120 µA Mean LED Current VLED = 3.5V 40 55 70 mA Efficiency VLED = 3.5V 85 % Operating Frequency VLED = 3.5V 350 kHz Discharge Pulse Width 0.7 1.5 2.5 µs

Document number: DS32188 Rev. 3 - 2 4 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated Device Description The ZXLD381 is a simple PFM, DC-DC controller combined with a high performance internal switching transistor, enabling the production of a high efficiency boost converter for use in single cell applications. A block diagram is shown for the ZXLD381 i n Fig 1. When power is applied, an oscillator within the pulse control block forces the internal switching transistor to switch on to st art an energy charge cycle. The low saturation voltage switch pulls the V OUT pin close to ground which forces the supply voltage across the external inductor L1. This causes a current to build up, storing energy in the inductor. During this phase, switch current and supply voltage are monitored and used by the pulse control circuit to determine the optimum drive conditions and on-time. At the end of the energy charge cycle, the internal sw itch is turned off rapidly, interrupting the current flow throug h L1 which causes the voltage on V OUT to rise dramatically. When the voltage on V OUT reaches the load LED's forward (on) voltage, the inductor current is transferred from the internal switch to the LED, star ting the energy discharge cycle. With the voltage across the inductor reversed, the current flowing through it (and the LED) now falls. When the inductor current reaches zero, the voltage on the V OUT pin falls back towards V CC. This action is sensed by the pulse control circuit, which initiates the next energy charge cycle. Except for low level losses, all the energy stored in the inductor during a charge cycle will be channeled to the load LED during the following discharge cycle. The current fed into the load LED has a sawtooth waveform, the average (DC) value of which is kept constant by the pulse control circuit for varying supply voltage and temperature. It is possible to change the output current given by the ZXLD381 by changing the value of inductor L1. The la rger the inductance of L1, the lower the output current. A table/graph showing the relationship between inductance and output current is given later in this datasheet. Since the output current of the ZXLD381 is a sawtooth waveform, its peak value is substantially larger than the DC/average value. The table also provides this data. The internal switching transistor has a minimum collector-emi tter breakdown voltage of 20V and this sets the maximum load voltage allowable. The minimum value is set by a feature of the pulse control circuit that requires the load voltage to be at least 0.8V greater than V CC. (The device will function with load voltages smaller than this but output current regulation will be impaired.) Higher than nominal load voltages will lower the average (DC) output current generated for a given inductor value.

Document number: DS32188 Rev. 3 - 2 5 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated Typical Characteristics 100 2.2µH 3.3µH 4.7µH 6.8µH 10µH 15µH 22µH 47µH I ( m A )OUT V ( V ) I vs. V for L = 2.2µH to 47µH CC OUT(A VE RAGE) CC 100 22µH 3.3µH 4.7µH 6.8µH 10µH 15µH 2.2µH Efficiency (%) V ( V ) Efficiency vs. V for L = 2.2µH to 47µH CC CC 47µH 100 150 200 250 300 350 V ( V ) I vs. V for L = 2.2µH to 47µH CC IN CC I ( m A )IN 2.2µH 3.3µH 4.7µH 6.8µH 10µH 15µH 22µH 47µH Channel-1 (Upper): I @ 100mA/cm Ch ann el-2 (Low er): V @ 1V/cm Timebase: 500ns/cm Operating Waveforms for L = 4.7µH, V = 1.5V LED OUT CC Notes: V LED = 3.5V for all graphs

Document number: DS32188 Rev. 3 - 2 6 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated Typical Characteristics (Cont.) 100 150 200 250 300 350 400 450 V ( V ) f vs. V for L = 47µH CC OSC CC f ( k H z )OSC Notes: V LED = 3.5V for all graphs

Document number: DS32188 Rev. 3 - 2 7 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated Application Examples Standard Operating Mode Notes: V LED = 3.5V Low Ripple LED Current Mode Notes: VLED = 3.5V, D1 = ZHCS1000, C1 = 1F (low ESR)

Document number: DS32188 Rev. 3 - 2 8 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of Diodes Incorporated

Ordering Information

Part Number Package Part Mark Tape Width (mm) Quantity (per reel) ZXLD381FHTA SOT23 381 8 3000 Package Outline Dimensions Dim. Millimeters Inches Dim. Millimeters Inches A - 1.12 - 0.044 e1 1.90 NOM 0.075 NOM e 0.95 NOM 0.037 NOM - - - - - E e L D A c E1L1 b 3leads

Document number: DS32188 Rev. 3 - 2 9 of 9 www.diodes.com May 2010 © Diodes Incorporated A Product Line of 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 rese rve the right to make modifications, enhanc ements, improvements, corrections or ot her changes without further notice to this document and any product descri bed herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or an y product described herein; neither does Di odes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or us er of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated 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 whatsoever in respect of any products purchased through unauthoriz ed sales channel. Should Customers purchase or use Diodes Inco rporated products for any unintended or una uthorized application, Customers shall i ndemnify and hold Diodes Incorporated and its representativ es harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated 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. LIFE SUPPORT Diodes Incorporated products are specifically not authorized for use as critical component s in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems 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 instructions 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 dev ice 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 ramifi cations 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 their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or s ystems-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 support devices or systems. Copyright © 2010, Diodes Incorporated www.diodes.com