1 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation low power voltage conversion +2.4v to +5.5v input range 99% voltage conversion efficiency typical 60 a supply current requires only three external capacitors includes low power shutdown option ideal in portable applications such as handheld instruments cellular phones personal digital assistants laptops and notebooks pin compatible upgrade to microchip's tc682 sp682 micro power inverting charge pump typical application circuit corporation applications the sp682 is a monolithic charge pump voltage converter that produces a doubled, negative voltage from a single positive supply. the sp682 charge pump outputs a ?10v voltage from a +5v input. three external charge pump capacitors are required to support the voltage conversion and voltage doubling process. an internal oscillator generates a 12khz clock which cycles the internal switching that charges the storage and transfer capacitors. the charge pump architecture is fabricated using a low power bicmos process technology. the sp682 charge pump is ideal for low power applications requiring a typical +3v battery source such as a lithium cell. typical applications are handheld instruments, notebook and laptop computers, cellular phones, and data acquisition or gp systems. the sp682 is packaged in either 8-pin nsoic, 8-pin msop for surface mount applications, and 8 pin pdip. +2.4v to +5v 1 f + gnd v out 6 v cc 4 sp682 c1+ c1? c2+ c2? c1 c2 7 1 3 5 2 c out sd 8 v out - lcd display negative bias supply for op amps serial interface protocol circuits description 1 2 3 4 5 6 7 8 c1- sp682 8 pin msop gnd v out c2+ sd c1+ c2- v cc now available in lead free packaging
2 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation these are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. v cc ...........................................................................+7v v out ........................................................................?11v storage temperature..........................-65 ? c to +150 ? c t a = t min to t max and v cc = +5v. charge pump cap = 3.3 f, unless otherwise noted. min. typ. max. units conditions supply current charge pump capacitors: 3.3 f i cc 60 120 ar l = , t a = +25 c 200 ar l = in shutdown 1 at a = +25 o c, sd = +5v charge pump output charge pump capacitors: 3.3 f v out ?9.9 ?9.99 volts r l = ?9.0 ?9.5 volts r l = 2k ? source resistance r out 140 180 ? i l = 10ma, t a = +25 c 230 ? i l = 10ma 380 450 ? i l = 5ma, v cc = +2.8v oscillator frequency f osc 12 20 khz f osc = 2 x f c1+ conversion efficiency v out eff 99 99.9 % r l = v out eff 90 95 % r l = 2k ? start-up timing v out power on delay 12 ms r l = 2k ? shutdown timing shutdown to v out delay 5 ms r l = 2k ? supply voltage v cc +2.4 +5.5 volts operating temperature range - c 0 +70 o c - e -40 +85 o c electrical characteristics power dissipation: 8-pin nsoic......................................500mw 8-pin msop......................................320mw 8-pin pdip......................................750mw package derating: 8-pin nsoic: ? ja ..................................................128 c/w 8-pin msop: ? ja ..................................................216 c/w 8-pin pdip: ? ja ..................................................97 c/w absolute maximum ratings
3 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation about 12khz (20khz maximum) which con- serves power as opposed to higher frequency which operation typically draws more power from v cc . the external charge pump capacitors specified are 3.3 f but the absolute minimum should be 1 f. efficiency information a charge pump theoretically produces a doubled voltage at 100% efficiency. however in the real world, there is a small voltage drop on the output which reduces the output efficiency. the sp682 can usually run 99.9% efficient without driving a load. while driving a 1k ? load, the sp682 remains over 90% efficiency. output voltage efficiency = v out / (?*v cc ); v out = ?*v cc + v drop v drop = (i out )*(r out ) power loss = i out *(v drop ) the efficiency changes as the external charge pump capacitors are varied. larger capacitor values will strengthen the output and reduce output ripple. although smaller capacitors will cost less and save board space, lower values will reduce the output drive capability and also in- crease the output ripple. figure 3. charge pump phase 2 figure 2. charge pump phase 1 the sp682 's charge pump design is a simpli- fied version of sipex 's original patented charge pump design (5,306,954) except that it only generates a negative output. the charge pump utilizes external capacitors to store the charge. figure 1 shows the waveform found on the negative side of capacitor c2. there is a free running oscillator, running at 12khz, that con- trols the two phases of the voltage shifting. a description of each phase follows. phase 1 v out charge storage ?during this phase of the clock cycle, the positive side of capacitors c 1 and c 2 are initially charged to +5v. c l + is then switched to ground and the charge on c 1 is transferred to c 2 . since c 2 + is connected to +5v, the voltage potential across capacitor c 2 is now 10v. phase 2 v out transfer ?phase two of the clock con- nects the negative terminal of c 2 to the v out storage capacitor and the positive terminal of c 2 to ground, and transfers the generated ?0v to c 3 . simultaneously, the positive side of capacitor c 1 is switched to +5v and the nega- tive side is connected to ground. the oscillator frequency or clock rate for the charge pump is designed for low power opera- tion. the oscillator operates at a frequency of figure 1. charge pump waveform v cc = +5v ?5v ?5v +5v c 1 c 2 ++ ? ? v out storage capacitor c 3 + ? v cc = +5v ?10v c 1 c 2 ++ ? ? v out storage capacitor c 3 + ? theory of operation
4 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation table 1. r out .vs. c1, c2 table 2. c3 .vs. v ripple shutdown feature the sp682 charge pump includes a shutdown feature (pin 8) which disables the charge pump when the v out is not needed. a logic "1" will activate the shutdown mode. if shutdown is not needed, it can be left open where an internal pull-down resistor will always keep the charge pump active. typical input current for the shutdown pin is 3 a. the shutdown feature is another option for conserving power in portable applications, reducing current to only 1 a. parallel devices multiple sp682 charge pumps can be connected in parallel. however, the effective output resis- tance now is the output resistance of a single device divided by the number of devices. con- necting multiple pumps allows the user to save on the storage capacitor. the charge pump capacitors still must be separate for each device. applications information the sp682 charge pump produces a doubled, inverted voltage from the v cc input. as such, it can serve in many applications where a negative ?v to ?0v output is needed. typical applica- tions include powering analog switches, and biasing lcd displays and panels. the esr of the charge pump capacitors also determine the output resistance. assuming that switch resistances are approximately equal, the output resistance can be derived as shown be- low: r out = 16*(r sw1-4 ) + 4*( esr c1 + esr c2 ) + esr c3 + 1 / (f osc * c1) + 1 / (f osc * c2) r out is typically 140 ? at +25 c with vcc at +5v using 3.3 f capacitors. the total internal switch resistance (16*r sw ) is approximately 90 ? . the table below shows the comparison of r out versus c1&c2. c1, c2 ( f) rout ( ? ) 0.05 4085 0.10 2084 0.47 510 1.00 285 3.30 140 4.70 125 10.00 105 22.00 94 the output voltage ripple is also affected by the capacitors, specifically c out . larger values will reduce the output ripple for a given output current load of current. the formula represen- tation is: v ripple = {1 / [2 * (f osc * c3)] + 2 * (esr c3 )} * i out to minimize the output ripple, the c out storage capacitor can be increased to over 10 f whereas the pump capacitors can range from 1 f to 5 f. table 2 shows the typical v ripple for given c out values. c out ( f) v ripple (mv) 0.50 1020 1.00 520 3.30 172 4.70 120 10.00 70 22.00 43 theory of operation
5 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation package: 8 pin nsoic a a1 a2 side view seating plane section b-b with plating symbol min nom max a1.35- 1.75 a1 0.1 - 0.25 a2 1.25 - 1.65 b0.31- 0.51 c0.17- 0.24 d e e1 e l0.4-1 .27 l1 l2 ?0o-8o ?1 5o - 15o note: dimensions in (mm) 8 pin nsoic jedec mo-012 (aa) variation 4.90 bsc 6.00 bsc 3.90 bsc 1.27 bsc 1.04 ref 0.25 bsc gauge plane l1 l ? 1 ? seating plane l2 view c to p view b see view c b b e e/2 e1 index area (d/2 x e1/2) e1/2 d 1 e c base metal b
6 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation package: 8 pin msop l1 l r1 ?1 r ?1 seating plane 1 e1 2 e/2 e d gauge plane l2 pin #1 indentifier must be indicated within this shaded area (d/2 * e1/2) e a2 a a1 b e1 b b symbol min nom max a-- 1.1 a1 0 - 0.15 a2 0.75 0.85 0.95 b 0.22 - 0.38 c 0.08 - 0.23 d e e1 e e1 l 0.4 0.6 0.8 l1 l2 n-8- r 0.07 - - r1 0.07 - - ?0o-8o ?1 0o - 15o note: dimensions in (mm) 0.65 bsc 1.95 bsc 0.95 ref 0.25 bsc 8 pin msop jedec mo-187 (aa) variation 3.00 bsc 4.90 bsc 3.00 bsc c with plating base metal b section b-b
7 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation package: 8 pin pdip index area b n 1 23 n/2 c d1 ea eb e symbol min nom max a- - 0.21 a1 0.15 - - a2 0.115 0.13 0.195 b 0.014 0.018 0.022 b2 0.045 0.06 0.07 b3 0.3 0.039 0.045 c 0.008 0.01 0.014 d 0.355 0.365 0.4 d1 0.005 - - e 0.3 0.31 0.325 e1 0.24 0.25 0.28 e ea eb - - 0.43 l 0.115 0.13 0.15 note: dimensions in (mm) .100 bsc .300 bsc 8 pin pdip jedec ms-001 (ba) variation e e1 d a l a2 a1 b b2 e b3 c
8 date: 11/29/04 sp682 micro power inverting charge pump ? copyright 2004 sipex corporation sipex corporation reserves the right to make changes to any products described herein. sipex does not assume any liability aris ing out of the application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others. corporation analog excellence part number temperature range package types sp682cn ............................................. -0 c to +70 c ................................................................. 8-pin nsoic sp682cn/tr ....................................... -0 c to +70 c ................................................................. 8-pin nsoic sp682cp ............................................. -0 c to +70 c .................................................................... 8-pin pdip sp682cu ............................................. -0 c to +70 c .................................................................. 8-pin msop sp682cu/tr ....................................... -0 c to +70 c .................................................................. 8-pin msop sp682en ........................................... -40 c to +85 c ................................................................. 8-pin nsoic sp682en/tr ..................................... -40 c to +85 c ................................................................. 8-pin nsoic sp682ep ........................................... -40 c to +85 c .................................................................... 8-pin pdip sp682eu ........................................... -40 c to +85 c .................................................................. 8-pin msop sp682eu/tr ..................................... -40 c to +85 c .................................................................. 8-pin msop ordering iformation /tr = tape and reel pack quantity is 2,500 for nsoic and msop. sipex corporation headquarters and sales office 233 south hillview drive milpitas, ca 95035 tel: (408) 934-7500 fax: (408) 935-7600 click here to order samples
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