1/4 rev. a structure silicon monolithi c integrated circuit product name 1ch dc dc converter controller ic with built-in synchronous rectifier type BD9121GUL features ? output voltage fixed(1.2v, 1.3v, 1.4v), output current 0.3a ? fast transient response with current mode pwm control system ? high efficiency with synchronous rectifier absolute maximum rating ta = 2 5 parameter symbol limit unit supply voltage v cc -0.3 +7 * 1 v pv cc -0.3 +7 * 1 v sel voltage sel -0.3 +7 v sw ? ith voltage sw, ith -0.3 +7 v sw output current i sw 0.5 * 1 a power dissipation 1 pd1 660 * 2 mw operating temperature range topr -25 +85 storage temperature range tstg -55 +150 maximum junction temperature tjmax +150 * 1 pd, aso, and tjmax=150 should not be exceeded. * 2 derating is 5.28mw/ for temperatures above ta=25 (when mounted on 50mm 58mm 1.6mm glass epoxy pcb). operating conditions ta = - 2 5 +85 parameter symbol min. typ. max. unit supply voltage v cc 2.55 3 3.6 v pv cc 2.55 3 3.6 v sw average output current i sw - - 0.3* 3 a * 3 pd and aso should not be exceeded.
2/4 rev. a electrical characteristics (unless otherwise specified, ta=25 , v cc =pv cc =3v, v out =1.3v parameter symbol limit unit condition min. typ. max. bias current i cc - 400 640 a output voltage1 v out 1 -2 - +2 % output voltage2 v out 2 -3 - +3 % ta = - 2 5 85 oscillation frequency1 f osc 1 2.4 3 3.6 mhz oscillation frequency2 f osc 2 2.1 3 3.9 mhz ta = 2 5 85 pch fet on resistance r onp - 0.3 0.6 p v cc =3v nch fet on resistance r onn - 0.2 0.4 p v cc =3v i th sink current i thsi 10 20 - a v out =2v, sel=open i th source current i thso 10 20 - a v out =0.8v, sel=open uvlo threshold voltage v uvlo 1 2.1 2.25 2.4 v v cc =3 0v uvlo release voltage v uvlo 2 2.12 2.3 2.5 v v cc =0 3v soft start time t ss 25 50 100 s timer latch time t latch 0.68 1.36 2.72 ms scp/tsd operational mode output short circuit threshold voltage v scp - 0.65 1 v v out =1.3 0v, sel=open physical dimension block diagram ? application circuit vcsp50l2 (unit:mm) 9 1 2 1 lot no. 3v input pv cc pgnd sw gnd output gm amp l v cc r s q osc uvlo tsd + 4.7 f v cc clk slope current comp soft start current sense/ protect + driver logic + vref ith vout r ith c ith scp sel 4.7 f 10 0.1 f
3/4 rev. a pin distribution [bottom view] b1 sw b2 pvcc b3 vcc b4 vout a1 pgnd a2 gnd a3 sel a4 ith setting the output voltage pin no. ?pin name sel output voltage v pin no. pin name gnd 1.2 a1 pgnd open 1.3 a2 gnd vcc 1.4 a3 sel cannot switch in operational mode. a4 ith b1 sw b2 pvcc b3 vcc b4 vout
4/4 rev. a notes for use (1) absolute maximum rating although the quality of this ic is rigorously controlled and will function properly in normal operating conditions, the ic may be destroyed when applied voltage or operating temperature ex ceeds its absolute maximum rating. because short mode or open mode cannot be specified when the ic is destroyed, it is important to take physical safety measures such as fusing if a special mode in excess of absol ute rating limits is to be implemented. (2) gnd potential make sure the potential for the gnd pin is always kept at the minimum, regardless of the operating mode. in addition, verify that the gnd voltage is lower than the potential of all terminals except sw, pgnd and gnd in all conditions, including electric transient events. (3) thermal design do not exceed the power dissipation (pd) of the package spec ification rating under actual operation. provide sufficient margin in the thermal design to account for the pd expected in actual use. (4) short-circuits between pins and incorrect mounting position when mounting the ic onto the set pcb, be extremely careful about the orientation and position of the ic. the ic may be destroyed if it is incorrectly positioned for mounting. do not short-circuit between pins, or between a pin and the power supply or ground terminal. note that in troducing foreign matter in these paths will cause shorts and may damage the ic. (5) operation in strong electromagnetic fields use in strong electromagnetic fields may cause malfunctions. use extreme c aution with electromagnetic fields. (6) aso (area of safe operation) do not exceed the maximum aso parameter or the absolute maximum ratings of the output driver. (7) tsd (thermal shutdown) circuit this product is provided with a built-in thermal shutdown (tsd ) circuit, which is activated when the ic chip temperature rises to the threshold value. in this case, tsd automatically latches output off. output is restored when uvlo is deactivated. note that the tsd circuit is provided for the exclusive purpose shut ting down the ic in the presence of extreme heat, and is not designed to protect the ic per se or guarantee performance when or after extreme heat conditions occur. therefore, do not operate the ic with t he expectation of continued use or subsequent operation once the tsd is activated. (8) gnd wiring pattern when both a small-signal gnd and high current gnd are pr esent, single-point grounding (at the standard point on the circuit set board) is recommended. this will separate the small- signal and high current patterns, and serves to ensure that the high current flow and wire impedance will not change the small-signal gnd voltage. in the same way, care must be taken to avoid wiring pattern fluctuations in any connec ted external component gnd. (9) operation in supply voltage range circuit functionality is guaranteed within t he operating ambient temperature, as long as the operation is within the supply voltage range. the standard electrical characteristics cannot be guaranteed. however, any variation in thes e values will be small, as long as the operation is within the supply voltage range. (10) the application schematic presented abov e is an example of recommended circuit la yout. although the circuit example is sound, actual circuit characteristics should be checked carefully before use. be sure to allow sufficient margins to accommodate variations between external devices and this ic when employing t he depicted circuit with other circuit constants modified. both static and trans ient characteristics shoul d be considered in establishing these margins. when switching noise is substantial and may impact the system, a low pass filter should be inserted between the vcc and pvcc pins, and a schottky barrier diode established between the sw and pgnd pins. (11) overcurrent protection circui t/output short protection circuit the overcurrent protection circuit is built in to output, and functions as the current limit. note that if the protection circuit operat es more than a specified time period (w hen the output short-circuit protection circuit detects a load short or other sim ilar state) the output will be latched off. output is restored when uvlo is deactivated. although the pr otection circuits effectivel y prevent ic destruction under fault conditions, they should not be employed continuously.
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