designed to meet high-current requirements at high efficiency in industrial and consumer applications; embedded core, memory, or logic supplies; tvs, vcrs, and office or telecommunications equipment, the SI-8120JD dc/dc step-down (buck) converter offers a constant 125 khz switching frequency essential for low emi noise. the npn switch is included on the die along with the oscillator, control, and logic circuitry requiring only four external components for a regulated 12 v output at up to 1.5 a. . a wide input voltage range and integrated thermal and overcurrent protection enhance overall system reliability. reference accuracy and excellent temperature characteristics are provided. an output-enable input gives the designer complete control over power up, standby, or power down. this device is supplied in a 5-lead surface-mount plastic package (to-263) with ground tab to provide a low-resistance path for maximum heat dissipation. a similar device in a flange-mounted (to-220-style) high-power package is the si-8120jf. features 11 v to 40 v input range 1.5 a output current at 12 v 2% output voltage tolerance foldback current limiting constant 125 khz switching frequency 200 a maximum standby current soft start prevents supply voltage dip remote voltage sensing exposed pad for superior heat dissipation thermal protection applications tvs, vcrs, electronic games embedded core, memory, or logic supplies printers and other office equipment industrial machinery telecommunications equipment step-down to 12.0 v, 1.5 a, dc/dc converter data sheet 27469.51 always order by complete part number, e.g., SI-8120JD-tl , where ?-tl? indicates tape and reel. absolute maximum ratings input voltage, v i . . . . . . . . . . . . . 43 v output current, i o . . . . . . . . . . . 1.5 a* enable input voltage, v oe . . . . . . . . . . . 6 v junction temperature, t j . . . . +125c storage temperature range, t s . . . . . . . . . . . . -40c to +125c * output current rating is limited by input voltage, duty cycle, and ambient tempera- ture. under any set of conditions, do not exceed a junction temperature of +125c. si-8120 jd sanken power devices from allegro microsystems switching regulators
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 switching regulators 2 functional block diagram copyright ? 2004 allegro microsystems, inc. recommended operating conditions min max units dc input voltage (i o 1 a) 14 15 v (i o 1.5 a) 15 40 v dc output current (v i 6.3 v) 0 1.5 a operating junction temp. -30 +125 c allowable package power dissipation this data sheet is based on sanken data sheet ssj-01967
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter www.allegromicro.com switching regulators 3 electrical characteristics at t a = +25c, v i = 24 v, i o = 0.5 a (unless otherwise noted). limits characteristic symbol test conditions min. typ. max. units output voltage v o 11.76 12.0 12.24 v ref. volt. temp. coeff. a vref ? 1.0 ? mv/c output short-circuit current i om see note 1.6 ? ? a efficiency ?88? % operating frequency f ? 125 ? khz line regulation ? v o( ? vi) v i = 18 v ~ 30 v, i o = 0.5 a ? 60 130 mv load regulation ? v o( ? io) v i = 24 v, i o = 0.2 a ~ 0.8 a ? 10 40 mv quiescent current i iq i o = 0 a ? 7.0 ? ma v ce = 0.3 v ? ? 200 a chip enable voltage v ce converter turn-off voltage ? ? 0.5 v soft-start current i ss v ss = 0 v ? ? -100 a typical values are given for circuit design information only. note: output short-circuit current is at point where output voltage has decreased 5% below v o(nom) . SI-8120JD test circuit c1 = 220 f/50 v c2 = 470 f/25 v c3 = 0.47 f/10 v l1 = 100 h d1 = sanken sfpb-66
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 switching regulators 4 typical characteristics (t a = 25c) efficiency overcurrent protection low-voltage behavior load regulation temperature stability
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter www.allegromicro.com switching regulators 5 applications information input capacitor (c1). capacitors with low impedance for high-frequency ripple current must be used. output capacitor (c2). capacitors with low impedance for high-frequency ripple current must be used. especially when the c2 impedance is high, the switching waveform may not be normal at low temperatures. film or tantalum capacitor for c2 may cause abnormal oscillations. catch diode (d1). diode d1 must be a schottky diode. other diode types will result in increased forward voltage spikes, reverse current flow, increased ic power dissipa- tion during the off period, and possible destruction of the ic. choke coil (l1) . if the winding resistance of the choke coil is too high, the circuit efficiency will decrease. as the overcurrent protection start current is approximately 2.5 a, attention must be paid to the heating of the coil by magnetic saturation due to overload. to reduce the output ripple, the inductor may be increased at the expense of excessive board area and cost. typical application SI-8120JD soft-start capacitor (c3). soft start for the converter is enabled by connecting a capacitor between terminal 5 and ground. the converter may be turned off by decreasing the terminal 5 voltage below 0.5 v with either an npn small-signal transistor or the output of open-collector ttl. if both a large soft-start capacitor and on/off control are desired, collector current limiting must be used to prevent transistor damage. no external voltage can be applied to terminal 5. parallel operation. parallel operation to increase load current is not permitted. overcurrent protection. the si-8000jd series has a built-in fold-back type overcurrent protection circuit, which limits the output current at a start-up mode. it thus cannot be used in applications that require current at the start-up mode such as: (1) constant-current load, (2) power supply with positive and negative outputs to common load (a center-tap type power supply), or (3) raising the output voltage by putting a diode or a resistor between the device ground and system ground.
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 switching regulators 6 layout guideline applications information (cont.) thermal protection. circuitry turns off the switching transistor when the junction temperature rises above 150c. it is intended only to protect the device from failures due to excessive junction temperatures and should not imply that output short circuits or continuous overloads are permitted. heat radiation and reliability. the reliability of the ic is directly related to the junction temperature (t j ) in its operation. accordingly, careful consideration should be given to heat dissipation. the inner frame on which the integrated circuit is mounted is connected to the gnd terminal (pin 3). therefore, it is very effective for heat radiation to enlarge the copper area that is connected to the gnd terminal. the graph illus- trates the effect of the copper area on the junction-to- ambient thermal resistance (r ja ). the junction temperature (t j ) can be determined from either of the following equations: t j = (p d r ja ) + t a or t j = (p d r jc ) + t c where p d = v i i i ? v o i o ? v f i o (1 ? [v o /v i ]) or the adjacent graph, v f = the schottky diode forward voltage, and r jc =3c/w.
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter www.allegromicro.com switching regulators 7 dimensions in millimeters notes: 1. dimensions do not include mold protrusions. 2. ( ) is reference. 3. [ ] is assembly out quality. 4. heat sink side flash: 0.8 mm max. 5. terminal finish: pure sn (category e3) 6. product weight: approximately 1.48 g tab temperature (t t ) measured here recommended land pattern
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 switching regulators 8 tape and reel dimensions in millimeters tape specifications 1. material: conductive polystyrene. 2. allowable camber: 1 mm/100 mm maximum. 3. a0 (10.6 mm) and b0 (15.7 mm) measured on a plane 0.3 mm above the bottom of the pocket. 4. k0 (4.9 mm) is measured from a plane on the inside bottom of the pocket to the surface of the carrier. 5. ten pitches cumulative tolerance on tape 0.2 mm. 6. the space between parts and cavity must not exceed 0.3 mm from its normal position in any direction. 7. surface resistivity of embossment: 10 7 ohm/cm 2 max. 8. k1 = 3.9 mm. detail c
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter www.allegromicro.com switching regulators 9 inner box 2 reels per box, 800 pieces per reel outer box maximum 3 inner boxes per outer box shipping container dimensions in millimeters
SI-8120JD step-down to 12.0 v, 1.5 a, dc/dc converter 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 switching regulators 10 the products described herein are manufactured in japan by sanken electric co., ltd. for sale by allegro microsystems, inc. sanken and allegro reserve the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. therefore, the user is cautioned to verify that the information in this publication is current before placing any order. when using the products described herein, the applicability and suitability of such products for the intended purpose shall be reviewed at the users responsibility. although sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. users of sanken products are requested to take, at their own risk, preventative measures including safety design of the equipment or systems against any possible injury, death, fires or damages to society due to device failure or malfunction. sanken products listed in this publication are designed and intended for use as components in general-purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). their use in any application requiring radiation hardness assurance (e.g., aerospace equipment) is not supported. when considering the use of sanken products in applications where higher reliability is required (transportation equipment and its control systems or equipment, fire- or burglar-alarm systems, various safety devices, etc.), contact a company sales representative to discuss and obtain written confirmation of your specifications. the use of sanken products without the written consent of sanken in applications where extremely high reliability is required (aerospace equipment, nuclear power-control stations, life-support systems, etc.) is strictly prohibited. the information included herein is believed to be accurate and reliable. application and operation examples described in this publica- tion are given for reference only and sanken and allegro assume no responsibility for any infringement of industrial property rights, intellectual property rights, or any other rights of sanken or allegro or any third party that may result from its use.
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