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| TOSHIBA TB62731FU TOSHIBA BiCD INTEGRATED CIRCUIT SILICON MONOLITHIC TB62731FU Step up DC-DC converter for LEDs FEATURES * The new driver incorporates a Pulse Current Drive Mode that raises efficiency over 90% while driving up to six white LEDs in a serial connection. In Direct Current Drive Mode white LEDs can be driven with very low noise and efficiencies over 85%. The TB62731FU uses bi-cadmium (BiCD) process technology. This SOT23 6pin new methodology allows for a reduction in the external component count therefore lowering costs and improving battery life. Newly developed temperature derating technology predicts environmental temperature, including heat dissipating from the driver IC itself, and adjusts current to optimize light emission. Ultra compact 6-pin SOT23 package. Ability to drive all wavelengths and materials. +3.0V to +5.5V supply voltage Adjustable output current (Up to 320mW output power) 20mA driving current can be supply for LEDs with 16V total Vf Internal switching MOSFET (1.5 ohm typ) Shutdown function * * * * * * * * * * * * * * TOSHIBA is continually working to improve the quality and reliability of its products. Nevertheless, semiconductor devices in general can malfunction or fail due to their inherent electrical sensitivity and vulnerability to physical stress. It is the responsibility of the buyer, when utilizing TOSHIBA products, to comply with the standards of safety in making a safe design for the entire system, and to avoid situations in which a malfunction or failure of such TOSHIBA products could cause loss of human life, bodily injury or damage to property. In developing your designs, please ensure that TOSHIBA products are used within specified operating ranges as set forth in the most recent TOSHIBA products specifications. Also, please keep in mind the precautions and conditions set forth in the "Handling Guide for Semiconductor Devices," or "TOSHIBA Semiconductor Reliability Handbook" etc.. The TOSHIBA products listed in this document are intended for usage in general electronics applications (computer, personal equipment, office equipment, measuring equipment, industrial robotics, domestic appliances, etc.). These TOSHIBA products are neither intended nor warranted for usage in equipment that requires extraordinarily high quality and/or reliability or a malfunction or failure of which may cause loss of human life or bodily injury ("Unintended Usage"). Unintended Usages include atomic energy control instruments, airplane or spaceship instruments, transportation instruments, traffic signal instruments, combustion control instruments, medical instruments, all types of safety devices, etc. Unintended Usage of TOSHIBA products listed in this document shall be made at the customer's own risk. The products described in this document are subject to the foreign exchange and foreign trade laws. The information contained herein is presented only as a guide for the applications of our products. No responsibility is assumed by TOSHIBA CORPORATION for any infringements of intellectual property or other rights of the third parties, which may result from its use. No license is granted by implication or otherwise under any intellectual property or other rights of TOSHIBA CORPORATION or others. Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA Block Diagram VCC 4 TB62731FU A 6 OSC S R Q Driver SHDN 3 STB E 0.11V R_lim 0.5 ohm K REF A 1 5 2 GND GND Pin Assignment PIN NO. 1 2,5 3 4 6 SYMBOL K GND SHDN VCC A FUNCTION Feedback input pin. Connect to the external LED driving current-sense resistor(R_sens). Ground pin Active "Low", shutdown control input pin. TB72731FU falls into shutdown mode, when SHDN=L. Supply voltage input pin. Bypass this pin with a capacitor to ground as close to the device as possible. Switching pin. Inductor connection to the Drain of internal N channel MOSFET. Both GND pins must be connected to external Ground. Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA Absolute Maximum Ratings (Ta = 25C) PARAMETER Power Supply Voltage Input Voltage Anode Current Anode Voltage Power Dissipation Saturated Thermal Resistance Operating Temperature Range Storage Temperature Range Junction Temperature TB62731FU Electrical Characteristics (VCC=3.0V~5.5V, Ta = +25C, unless otherwise specified.) PARAMETER SYMBOL TEST CONDITION Supply Voltage VCC Supply Current ICC(ON) VCC=3.6V Quiescent Current ICC(SHDN) SHDN=GND SHDN Input Current I_SHDN SHDN=VCC Internal MOSFET I(A)=220mA or less, Ron including R_lim ON-Resistance Anode Voltage V(A) Anode Current I(A) Anode Leak Current IOZ(A) SHDN=GND LED Current (average) Io(K) R_sens=1.8 ohm Io(K)=20mA, Derating Function Tder Ta=25C Start Temperature MIN. 3.0 TYP. 600 4.2 2.0 MAX. 5.5 900 0.5 7 2.5 30 220 0.5 20*1 (45)*2 1 22*1 UNIT V uA uA uA ohm V mA uA mA 18* 1 C Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA Typical Performance Characteristics S u p p ly C u r re n t v s . S u p p ly V o lta g e ( N o r m a l O p e r a tio n ) TB62731FU 900 VCC 800 ICC(ON) (uA) 700 600 500 400 3 3 .5 4 4 .5 5 5 .5 V C C (V ) S up p ly C urre nt vs . S up p ly V o lta g e (S hutd o w n M o d e ) 0 .5 0 .4 ICC(SHDN) (uA) 0 .3 0 .2 4 1 3 6 TB62731FU 2 5 VCC 4 1 3 6 TB62731FU 2 5 0 .1 0 3 3 .5 4 4 .5 5 5 .5 V C C (V ) Switching Frequency vs. Supply Voltage 400 VCC 380 Fs (kHz) 360 340 320 300 3 3.5 4 4.5 5 5.5 VCC (V) 1 4 3 6 To Monitor TB62731FU 2 5 Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA Operational Description TB62731FU TB62731FU is a pulse-skipping converter that uses a combined control scheme of voltage feedback loop and current limited feedback loop to operate constant LED driving current. Operation can be easily understood by referring to the Block Diagram and Switching Waveforms. The internal MOSFET is turned on when amplifier A senses that the average voltage at R_sens is lower than REF level. The N-channel MOSFET stays "turned on" until either the switching current peak reaches 220mA(typ), or the oscillator automatically turns it off at its maximum on-duty (83.3%). Once turned off, the MOSFET keeps off during the off-time. Subsequently, if the R_sens voltage is still lower than reference level, another switching cycle is started. Otherwise, the internal MOSFET remains turned off as long as the average R_sens voltage is higher than reference level. [Shutdown Mode] The TB62731FU falls into shutdown mode, when SHDN="L". In shutdown mode, the reference, control circuitry, oscillator and internal switching MOSFET are stopped and current consumption is reduced below 0.5uA. Connect SHDN to "VCC" for normal operation. Switching Waveforms Illustration V(A) Inductor current 220 mA I(A) LED current Average Current Fs=360 kHz Preset LED current level OSC on-duty(max)=83.3% Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA [Driving Current Derating Function] TB62731FU In order to avoid application problems, it is important to stay within the LED Lamps maximum ratings. This is especially critical when determining the maximum allowable driving current, which needs to be derated depending on atmospheric temperature. The TB62731FU has a built-in current derating function that helps light LED lamps safely and efficiently. TB62731FU's driving current derating function is designed to start working at 45C in Tj as shown in Figure 1. When the driving current is 20mA, derating is expected to start approximately at 25C in Ta. The difference between Tj and Ta depends on LED driving current, IC mounting conditions, PCB patterns, cooling conditions. The initial driving current level must be set carefully so as not to exceed the absolute maximum ratings of LEDs. With Toshiba's original derating function the TB62731FU can supply a higher LED driving current thus eliminating current limitations in high temperatures. Competitive ICs do not have this function, therefore this feature will contribute to a reduction in the amount of LED lamps used. FIGURE 1 Current Derating Function 25 LED Driving Current (mA) 20 15 10 5 0 0 20 40 60 80 Temperature Tj / Ta (C) Solid line; Tj operation, Dotted line; Ta operation Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA Application Information [Typical Application Circuit] Inductor Schottky Diode TB62731FU White LED VIN = 3V 5.5V Cin 1uF VCC ON A SHDN OFF Cout 1uF TB62731FU K GND GND R_sens E ffic ie nc y vs . S up p ly V o lta g e 100 Efficiency (%) 90 80 70 60 3 3 .5 4 4 .5 5 5 .5 V C C (V ) Efficiency data are taken under the following conditions; Loads four white LED lamps Inductor 47uH Schottky Diode Vf=0.35V@0.7A Io(K)=20mA (R_sens=1.8 ohm), Ta; 25 C Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA [Important Notice] TB62731FU In a Typical Application Circuit, the total Vf of LED lamps must be kept larger than VCC. As the external inductor, Schottky diode, LED lamps and R_sens are connected in a series, if the total Vf is below VCC, very high currents are likely to surge into the LED lamps. [Setting LED Driving Current] TB62731FU is a constant output current DC/DC converter. R_sens sets the average LED driving current. (See LED driving current, Total Vf vs. Feedback resistor in this section). Also maximum supply power is limited by the following equation: < Io(K) x Total Vf(max) = 320mW Where Io(K) is the average LED current. Therefore, 20mA driving current can be supplied for LEDs with the total Vf(max) of 16V and this current is given by R_sens of 1.8ohm. Note that Io(K) x Total Vf(max) over 320mW makes output voltage smaller than Total Vf(max) and turns the LED lamps off. 40 35 30 25 20 15 10 5 0 0.5 LED driving current, total Vf vs. Feedback resistor 24 20 16 12 8 total Vf(max.) (V) Io(K) (mA) 1 1.5 2 2.5 R_sens (ohm) 3 [Output Capacitor Selection] The LED current ripple level deeply depends on the output buffering capacitor value. Larger values help to reduce output ripple and noise. TB62731FU, however, monitors the average voltage at R_sens, therefore low ripple driving current, like a DC current, is not necessarily needed. The capacitor value is not critical as viewed from LED current controlability. The output capacitance value will be decided by peak level of LED current and noise. Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. TOSHIBA [Inductor Selection] TB62731FU A recommended inductance value is 47uH, however, values from 33uH to 56uH can also be acceptable. Low DC resistance inductors are preferable for minimizing power losses. [PCB Pattern Layout] When designing PCB patterns, minimize trace lengths to the inductor, pin A, Schottky diode and buffering capacitors. Also, as for feedback traces, keep them short and away from noisy traces, like an inductor's trace. Both buffering capacitors should be placed as close to the IC as possible. Package Dimension 2.8 - 0.3 1.6 - 0.1 +0.2 +0.2 2.9+0.2 - 1.9+0.2 - 0.95 0.95 1 2 3 6 5 4 +0.1 0.3 +0.1 - 1.1 - 0.1 0~0.1 +0.2 0.16 - 0.06 (Unit: mm) Marking Top View 1 2 3 4 6 5 Available from: Marktech Optoelectronics 120 Broadway * Menands, NY 12203 800.984.5337 FAX: 518.432.7454 Website: www.marktechopto.com Email: info@marktechopto.com The information contained herein is subject to change without notice. |
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