s s p p 6 6 6 6 6 6 9 9 1 1 . . 5 5 m m h h z z , , 6 6 0 0 0 0 m m a a s s y y n n c c h h r r o o n n o o u u s s s s t t e e p p d d o o w w n n c c o o n n v v e e r r t t e e r r rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 1/10 features ? up to 600ma output current ? up to 95% efficiency ? 1.5mhz constant frequency operation ? low dropout operation mode: 100% duty cycle ? output voltages as low as 0.6v ? no schottky diode required ? 200 a quiescent current (no load) ? excellent line and load transient response ? over-temperature protection ? 2.5v to 5.5v input voltage range ? lead free sot23-5 package applications ? cellular phones ? wireless networking ? digital cameras ? portable media players ? bluetooth devices ? portable instruments description the sp6669 is a 600ma synchronous buck converter using a constant frequency current mode architecture with pulse width modulati on (pwm) for low output voltage ripple and fixed frequency noise, a pulse skip mode (psm) for light load efficiency and a ldo mode for 100% duty cycle. with a 2.5v to 5.5v inpu t voltage range and a 1.5mhz switching frequency, the sp6669 allows the use of small surface mount inductors and capacitors ideal for battery powered portable applications. the internal synchron ous switch increases efficiency and eliminates the n eed for an external schottky di ode. low output voltages are easily supported with the 0.6v feedback refe rence voltage. the sp6669 is available in an adjustable output voltage version, using an exte rnal resistor divider ci rcuit, as well as fixed output voltage versions of 1.2v, 1.5v and 1. 8v. the sp6669 is available in a 5 pin sot-23 package. typical application circuit
block diagram rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 2/10 fig.1: sp6669 block diagram pin description sot23-5l pin number name description 1 en enable pin. do not leave the pin floating. v en <0.4v: shutdown mode v en >1.2v: device enabled 2 gnd ground signal pin. 3 sw switching node. 4 vin power supply pin. must be decoupled to ground with a 4.7f or greater ceramic capacitor. vfb adjustable version fe edback input pin. connect vfb to the center poin t of the resistor divider. 5 vout fixed output voltage version, output voltage pin. an internal resistive divider divides th e output voltage down for comparison to the internal reference voltage.
electrical characteristics rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 3/10 absolute maximum ratings these are stress ratings only and functional operation is not implied. exposure to absolute maximum ratings for prolonged time periods may affect device reliabil ity. all voltages are with respect to ground. input voltage v in ..........................-0.3v to 6v en v fb voltage ............................ -0.3v to v in sw voltage.................... -0.3v to (v in + 0.3v) pmos switch source current (dc) ........ 800ma nmos switch sink current (dc) ........... 800ma peak switch sink and source current ....... 1.3a operating junction temp. (not e 1)......... 125oc storage temp. range t stg ....... -65oc to 150oc lead temperature (sold. 10s) t lead ........ 240oc thermal resistance r ja ............................................... 250o c/w r jc .................................................90oc/w note 1: t j is a function of the ambient temperature t a and power dissipation p d (t j = t a + p d x 250c/w). recommended operating conditions operating temperature t op ....... -40oc to 85 oc input voltage v in ......................... 2.5v to 5.5v v in =3.6v, t a =25oc, unless otherwise specified ? boldface char acters apply over the full temperature range. parameter symbol conditions min typ. max unit feedback current i vfb 30 na regulated feedback voltage v fb t a =25c 0.588 0.600 0.612 v reference voltage line regulation v fb v in =2.5v to 5.5v 0.4 %/v output voltage accuracy v out % -3 +3 % v ovl = v ovl ? v fb (adj.) 20 50 80 mv output over-voltage lockout v ovl v ovl = v ovl ? v out (fixed) 2.5 7.8 13 % output voltage line regulation v out v in =2.5v to 5.5v 0.4 %/v peak inductor current i pk v in =3v, v fb =0.5v or v out =90%, duty cycle <35% 1.0 a output voltage load regulation v loadreg 0.5 % quiescent current (note 2) i q v fb =0.5v or v out =90% 200 340 a shutdown current i shtdwn v en =0v, v in =4.2v 0.1 1 a v fb =0.6v or v out =100% 1.2 1.5 1.8 mhz oscillator frequency f osc v fb =0v or v out =0v 290 khz r ds(on) of pmos r pfet i sw =100ma 0.45 0.55 ? r ds(on) of nmos r nfet i sw =100ma 0.40 0.50 ? sw leakage i lsw v en =0v, v sw =0v or 5v, v in =5v 1 a enable threshold 1.2 v shutdown threshold v en 0.4 v en leakage current i en 1 a note 1: the switch current limit is related to the duty cycle. please refer to figure 15 for details. note 2: dynamic quiescent current is higher due to the gate charge being delivered at the switching frequency.
electrical characteristics rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 4/10 typical characteristics fig. 2: efficiency vs output current (ma) fig. 3: efficiency vs output current (ma) fig. 4: efficiency vs output current (ma) fig. 5: efficiency vs output current (ma) fig. 6: output voltage vs load current fig. 7: reference voltage vs temperature
electrical characteristics rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 5/10 fig. 8: r ds(on) vs temperature fig. 9: r ds(on) vs input voltage fig. 10: dynamic supply current vs temperature fig. 11: dynamic supply current vs supply voltage fig. 12: oscillator frequency vs temperature fig. 13: oscillator frequency vs supply voltage
electrical characteristics rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 6/10 fig. 14: discontinuous operation fig. 15: start-up from shutdown fig. 16: load step fig. 17: load step fig. 17: load step fig. 18: load step
theory of operation rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 7/10 detailed description applications the typical application circuit of the adjustable output vo ltage option and the fixed output voltage option are shown below. fig. 18: adjustable output voltage version typical application circuit fig. 19: fixed output voltage version typical application circuit inductor selection inductor ripple current and core saturation are two factors considered to select the inductor value. eq. 1: ? ? ? ? ? ? ? ? ? ? = in out out l v v v l f i 1 1 equation 1 shows th e inductor ripple current as a function of the frequency, inductance, v in and v out . it is recommended to set the ripple current to 40% of the maximum load current. a low esr inductor is preferred. c in and c out selection a low esr input capacitor can prevent large voltage transients at v in . the rms current rating of the input capacitor is required to be larger than i rms calculated by: eq. 2: () in out in out omax rms v v v v i i ? ? the esr rating of the capacitor is an important parameter to select c out . the output ripple v out is determined by: eq. 3: ? ? ? ? ? ? ? ? ? ? + ? out l out c f esr i v 8 1 higher values, lower cost ceramic capacitors are now available in smaller sizes. these capacito rs have high ripple currents, high voltage ratings and low esr that makes them ideal for switching regulator applications. as c out does not affect the internal control loop stability, its value can be optimized to balance very low output ripple and circuit size. it is recommended to use an x5r or x7r rated capacitors which have the best temperature and voltage characteristics of all the ceramics for a given value and size. output voltage ? adjustable version the adjustable output voltage version is determined by: eq. 4: ? ? ? ? ? ? ? ? + ? = 1 2 1 6 . 0 r r v v out thermal considerations allthough the sp6669 has an on board over temperature circuitry, the total power dissipation it can support is based on the package therma l capabilities. the formula to ensure safe operation is given in note 1. pcb layout the following pcb layout guidelines should be taken into account to ensure proper operation and performance of the sp6669: 1- the gnd, sw and v in traces should be kept short, direct and wide. 2- v fb pin must be connected directly to the feedback resistors. the resistor divider network must be connected in parallel to the c out capacitor. 3- the input capacitor c in must be kept as close as possible to the v in pin.
theory of operation rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 8/10 4- the sw and vfb nodes should be kept as separate as possibl e to minize possible effects from the high frequency and voltage swings of the sw node. 5- the ground plates of c in and c out should be kept as close as possible. ouptut voltage ripple for v in close to v out when the input voltage v in is close to the output voltage v out , the sp6669 transitions smoothly from the switching pwm converter mode into a ldo mode. the following diagram shows the output voltage ripple versus the input voltage for a 3.3v output setting and a 200ma current load. fig.20: v out ripple voltage for v in decreasing close to v out design example in a single lithium-ion battery powered application, the v in range is about 2.7v to 4.2v. the desired outp ut voltage is 1.8v. the inductor value needed can be calculated using the following equation ? ? ? ? ? ? ? ? ? ? = in out out l v v v i f l 1 1 subsituting v out =1.8v, v in =4.2v, i l =240ma and f=1.5mhz gives h l 86 . 2 = a 2.2h inductor can be choosen with this application. an inductor of greater value with less equivalent series resistance would provide better efficiency. the cin capacitor requires an rms current rating of at least i load(max) /2 and low esr. in most cases, a ceramic capacitor will satisfy this requirement.
package rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 9/10 sot23-5l unit: mm
ordering information rev e ? 05/20/2008 sp6669 1.5mhz 0.6a sync. step down converter ? 2008 exar corporation 10/10 adjustable output voltage version part number voltage option operating temperature range package marking packing quantity sp6669aek-l/tr adjustable -40oc to +85oc sot23-5 qbww 3,000/t&r ?ww? = work week fixed output voltage version part number voltage option operating temperature range package marking packing quantity sp6669bek-l/tr 1.2v -40oc to +85oc sot23-5 rbww 3,000/t&r sp6669cek-l/tr 1.5v -40oc to +85oc sot23-5 sbww 3,000/t&r sp6669dek-l/tr 1.8v -40oc to +85oc sot23-5 tbww 3,000/t&r ?ww? = work week notice exar corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. exar corporatio n assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or ot her right, and makes no representation that the circuits are free of patent infringement. charts and schedules contai ned here in are only for i llustration purposes and may vary depending upon a user?s specific application. whil e the information in this publication has been carefully checked; no responsibility, howeve r, is assumed for inaccuracies. exar corporation does not recommend the use of any of it s products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. products are not authorized for use in such applications unless exar corporation receives, in writing, assurances to its satisf action that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potent ial liability of exar corporat ion is adequately protected under the circumstances. reproduction, in part or whole, without the prior written consent of exar corporation is prohibited. exar corporation headquarters and sales offices 48720 kato road fremont, ca 94538 ? usa tel.: +1 (510) 668-7000 fax: +1 (510) 668-7030 www.exar.com
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