1 datasheet high efficiency buck-boost regulator with 4.2a switches isl91108 the isl91108 is a highly-integrated buck-boost switching regulator that accepts input voltages either above or below the regulated output voltage. unlike other buck-boost regulators, this regulator automatically transitions between operating modes without significant output disturbance. this device is capable of delivering up to 2.7a of burst current (pvin = 3v, v out = 3.3v), and provides excellent efficiency due to its fully synchronous 4-switch architecture. no load quiescent current of only 27. 5a also optimizes efficiency under light-load conditions. forced pwm and/or synchronization to an external clock may also be selected for noise sensitive applications. the isl91108 is designed for standalone applications and supports a 3.3v fixed output voltage or variable output voltages with an external resist or divider. output voltages as low as 1v or as high as 5.2v are supported using an external resistor divider. the isl91108 requires only a single inductor and very few external components. power supply solution size is minimized by a 2.34mmx1.72mm wlcsp and a 2.6mhz switching frequency, which further redu ces the size of external components. related literature ? an1903 ?isl91108iia-evz/isl91108iin-evz evaluation board user guide? features ? accepts input voltages above or below regulated output voltage ? automatic and seamless transitions between buck and boost modes ? input voltage range: 1.8v to 5.5v ? output current: up to 1.6a dc (pvin = 2.8v, v out = 3.3v) ? burst current: up to 2.7a (pvin = 3v, v out = 3.3v, t on <600s, t = 4.6ms) ? high efficiency: up to 95% ? 27.5a quiescent current maxi mizes light load efficiency ? 2.6mhz switching frequency minimizes external component size ? selectable forced pwm mode and external synchronization ? fully protected for short-circuit, over-temperature, and undervoltage ? small 2.34mm x 1.72mm wlcsp applications ? smartphones and tablets ? wireless communication devices ? 2g/3g/4g power amplifiers figure 1. typical fixed output application figure 2. isl91108iinz efficiency vs output current vout fb c2 2x22f pvin v in = 1.8v to 5.5v vin mode en c 1 2x10f isl91108iinz gnd pgnd lx1 lx2 l1 1h v out = 3.3v efficiency (%) i out (a) 50 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 4.5vin 3.5vin 2.7vin 3.0vin 2.5vin november 12, 2014 fn8448.1 caution: these devices are sensitive to electrostatic discharge; follow proper ic handling procedures. 1-888-intersil or 1-888-468-3774 | copyright intersil americas llc 2013, 2014. all rights reserved intersil (and design) is a trademark owned by intersil corporation or one of its subsidiaries. all other trademarks mentioned are the property of their respective owners.
isl91108 2 fn8448.1 november 12, 2014 submit document feedback block diagram pin configuration isl91108 (20 bump wlcsp) top view osc error amp pvin pwm control pvin monitor lx1 v ref ref reverse current vout b1 b2 b4 lx2 gate drivers & anti- shoot thru d1 vin thermal shutdown current detect b5 vout monitor d2 en d5 fb b3 pgnd d4 gnd en en en en en en vout clamp c1 d3 mode c3 voltage prog. en soft discharge a1 c2 a2 c4 a4 a5 c5 a3 a1 a2 a3 a4 a5 b1 b2 b3 b4 b5 c1 c2 c3 c4 c5 d1 d2 d3 d4 d5 pin descriptions pin # pin names description a5, b5, c5 vout buck-boost output. connect 2x22f capacitor to pgnd. a4, b4, c4 lx2 inductor connection, output side. a3, b3, c3 pgnd power ground for high switching current. a2, b2, c2 lx1 inductor connection, input side. a1, b1, c1 pvin power input. range: 1.8v to 5.5v. connect 2x 10f capacitor to pgnd. d1 vin supply input. range: 1.8v to 5.5v. d2 en logic input, drive high to enable device. d3 mode/ sync logic input, high for auto pfm mode. low for forced pwm operation. also, this pin can be used with an external clock sync input. range: 2.75mhz to 3.25mhz. d4 gnd analog ground pin. d5 fb voltage feedback pin.
isl91108 3 fn8448.1 november 12, 2014 submit document feedback ordering information part number ( notes 1 , 2 , 3 ) part marking vout (v) temp range (c) package tape and reel (pb-free) pkg. dwg. # isl91108iinz-t gaza 3.3 -40 to +85 20 bump wlcsp w4x5.20f isl91108iinz-t7a gaza 3.3 -40 to +85 20 bump wlcsp w4x5.20f ISL91108IIAZ-T gaxa adj. -40 to +85 20 bump wlcsp w4x5.20f ISL91108IIAZ-T7a gaxa adj. -40 to +85 20 bump wlcsp w4x5.20f isl91108iin-evz evaluation board for isl91108iinz isl91108iia-evz evaluation board for isl91108iiaz notes: 1. please refer to tb347 for details on reel specifications. 2. these intersil pb-free plastic packaged products employ spec ial pb-free material sets, molding compounds/die attach materials , and 100% matte tin plate plus anneal (e3 termination finish , which is rohs compliant and compatible wi th both snpb and pb-free soldering opera tions). intersil pb-free products are msl classified at pb-fr ee peak reflow temperatures that meet or exceed the pb-free requirements of ipc/jed ec j std-020. 3. for moisture sensitivity level (msl), please see device information page for isl91108 . for more information on msl please see techbrief tb363 .
isl91108 4 fn8448.1 november 12, 2014 submit document feedback absolute maximum rating s thermal information pvin, vin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 6.5v lx1, lx2 ( note 6 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 6.5v fb (isl91108iiaz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 2.7v fb (isl91108iinz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 6.5v gnd, pgnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 0.3v all other pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 6.5v esd rating human body model (tested per jesd22-a114e) . . . . . . . . . . . . . . .2.5kv machine model (tested per jesd22-a115-a) . . . . . . . . . . . . . . . . . 200v charged device model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2kv latch up (tested per jesd-78b; class 2, level a) . . . . . . . . . . . . . . 100ma thermal resistance (typical) ? ja (c/w) ? jc (c/w) 2.34x1.72 wlcsp ( notes 4 , 5 ). . . . . . . . . . 66 1.0 maximum junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . .+125c storage temperature range. . . . . . . . . . . . . . . . . . . . . . . .-65c to +150c pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see tb493 recommended operating conditions temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40c to +85c supply voltage (v in ) range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8v to 5.5v load current (i out ) range (dc) . . . . . . . . . . . . . . . . . . . . . . . . . . 0a to 1.6a maximum burst current (t on <600s, t = 4.6ms) . . . . . . . . . . . . . . . . .2.7a caution: do not operate at or near the maximum ratings listed for extended periods of time. exposure to such conditions may adv ersely impact product reliability and result in failures not covered by warranty. notes: 4. ? ja is measured in free air with the componen t mounted on a high effective thermal conduc tivity test board with ?direct attach? fe atures. see tech brief tb379 5. for ? jc , the ?case temp? location is the center of the exposed metal pad on the package underside. 6. lx1 and lx2 pins can withstand switching tran sients of -1.5v for 100ns, and 7v for 20ms. analog specifications v in = pvin = en = 3.6v, v out = 3.3v, l 1 = 1h, c 1 = 2x 10f, c 2 = 2x 22f, t a = +25c. boldface limits apply across the recommended operating temperature ra nge, -40c to +85c and input voltage ranges. symbol parameter test conditions min ( note 7 ) typ max ( note 7 )units power supply vin input voltage range 1.8 5.5 v v uvlo v in undervoltage lockout threshold rising 1.725 1.775 v falling 1.550 1.650 v i vin v in supply current pfm mode, no external load on v out ( note 8 )27.5 60 a i sd v in supply current, shutdown en = gnd 0.4 1.0 a output voltage regulation vout output voltage range isl91108iiaz, i out = 100ma 1.00 5.20 v output voltage accuracy i out = 0ma, pwm mode -2 +2 % i out = 1ma, pfm mode -3 +4 % v fb fb pin voltage regulation for adjustable output version (isl91108iiaz) 0.788 0.80 0.812 v i fb fb pin bias current for adjustable output version (isl91108iiaz) 0.2 a ? vout / ? vin line regulation, pwm mode i out = 500ma, mode = gnd, v in step from 2.3v to 5.5v 0.005 mv/mv ? vout / ? i out load regulation, pwm mode v in = 3.7v, mode = gnd, i out step from 0ma to 500ma 0.005 mv/ma ? vout/ ? vin line regulation, pfm mode i out = 100ma, mode = v in , v in step from 2.3v to 5.5v 12.5 mv/v ? vout/ ? i out load regulation, pfm mode v in = 3.7v, mode = v in , i out step from 0ma to 100ma 0.4 mv/ma v clamp output voltage clamp rising 5.25 5.95 v output voltage clamp hysteresis 400 mv
isl91108 5 fn8448.1 november 12, 2014 submit document feedback dc/dc switching specifications f sw oscillator frequency v in = 3.6v 2.4 2.6 2.9 mhz t onmin minimum on time 80 ns i pfetleak lx1 pin leakage current -0.5 +0.5 a i nfetleak lx2 pin leakage current -0.5 +0.5 a soft-start and soft discharge t ss soft-start time time from when en signal asserts to when output voltage ramp starts. 1ms time from when output voltage ramp starts to when output voltage reaches 95% of its nominal value with device operating in buck mode. v in = 4v, i out = 200ma 1ms time from when output voltage ramp starts to when output voltage reaches 95% of its nominal value with device operating in boost mode. v in = 2v, i out = 200ma 2ms r dischg vout soft-discharge on-resistance en < v il 110 power mosfet r dson_p p-channel mosfet on-resistance i out = 200ma 90 m r dson_n n-channel mosfet on-resistance i out = 200ma 75 m i pk_lmt p-channel mosfet peak current limit 3.7 4.2 4.7 a pfm/pwm transition load current threshold, pfm to pwm 200 ma load current threshold, pwm to pfm 75 ma external synchronization frequency range 2% 2.75 3.25 mhz thermal shutdown 150 c thermal shutdown hysteresis 35 c logic inputs i leak input leakage 0.03 0.5 a v ih input high voltage 1.4 v v il input low voltage 0.4 v notes: 7. parameters with min and/or max limits are 100% tested at +25c , unless otherwise specified. te mperature limits established by characterization and are not production tested. 8. quiescent current measurements are taken when the output is not switching. analog specifications v in = pvin = en = 3.6v, v out = 3.3v, l 1 = 1h, c 1 = 2x 10f, c 2 = 2x 22f, t a = +25c. boldface limits apply across the recommended operating temperature ra nge, -40c to +85c and input voltage ranges. (continued) symbol parameter test conditions min ( note 7 ) typ max ( note 7 )units
isl91108 6 fn8448.1 november 12, 2014 submit document feedback functional description functional overview refer to the ? block diagram ? on page 2 . the isl91108 implements a complete buck-boost switching regulator, with pwm controller, internal switches, references, protection circuitry, and control inputs. the pwm controller automatically switches between buck and boost modes as necessary to maintain a steady output voltage with changing input voltages and dynamic external loads. internal supply and references referring to the ? block diagram ? on page 2 , the isl91108 provides two power input pins. the pvin pin supplies input power to the dc/dc converter, while the vin pin provides operating voltage source required for stable v ref generation. separate ground pins (gnd and pgnd) are provided to avoid problems caused by ground shift due to the high switching currents. enable input a master enable pin en allows the device to be enabled. driving en low invokes a power-down mode, where most internal device functions, including input and ou tput power-good detection, are disabled. soft discharge when the device is disabled by driving en low, an internal resistor between vout and gnd is activated. this internal resistor has a typical resistance of 110 . por sequence and soft-start bringing the en pin high allows the device to power-up. a number of events occur during the start- up sequence. the internal voltage reference powers up and stabilizes. the device then starts operating. there is a 1ms (typical ) delay between assertion of the en pin and the start of switching regulator soft-start ramp. the soft-start feature minimizes output voltage overshoot and input inrush currents. during soft -start, the reference voltage is ramped to provide a ramping vout voltage. while output voltage is lower than approximately 20% of the target output voltage, switching frequency is reduced to a fraction of the normal switching frequency to aid in prod ucing low duty cycles necessary to avoid input in-rush current spikes. once the output voltage exceeds 20% of the target voltage, switching frequency is increased to its nominal value. when the target output voltage is higher than the input voltage, there will be a transition from buck mode to boost mode during the soft-start sequence. at the time of this transition, the ramp rate of the reference voltage is decreased, such that the output voltage slew rate is decreased. this provides a slower output voltage slew rate. the vout ramp time is not consta nt for all operating conditions. soft-start into boost mode will take longer than soft-start into buck mode. the total soft-start time into buck operating mode is typically 2ms, whereas the typica l soft-start time into boost mode operating mode is typically 3ms. increasing the load current will increase these typical soft-start times. short circuit protection the isl91108 provides short-circuit protection by monitoring the fb voltage. when fb voltage is sensed to be lower than a certain threshold, the pwm oscillator fr equency is reduced in order to protect the device from damage. the p-channel mosfet peak current limit remains active during this state. undervoltage lockout the undervoltage lockout (uvlo) feature prevents abnormal operation in the event that the supply voltage is too low to guarantee proper operation. when the vin voltage falls below the uvlo threshold, the re gulator is disabled. thermal shutdown a built-in thermal protection feature protects the isl91108, if the die temperature reaches +150c (typical). at this die temperature, the regulator is completely shut down. the die temperature continues to be monitored in this thermal shutdown mode. when the die temperature falls to +115c (typical), the device will resume normal operation. when exiting thermal shutdown, the isl91108 will execute its soft-start sequence. external synchronization an external sync feature is provid ed. applying a clock signal with a frequency between 2.75mhz and 3.25mhz at the mode input forces the isl91108 to synchronize to this external clock. the mode input supports standard logic levels. buck-boost conversion topology the isl91108 operates in either buck or boost mode. when operating in conditions where vin is close to vout, the isl91108 alternates between buck and boost mode as necessary to provide a regulated output voltage. figure 3 shows a simplified diagram of the internal switches and external inductor. pwm operation in buck pwm mode, switch d is continuously closed and switch c is continuously open. switches a and b operate as a synchronous buck converter when in this mode. in boost pwm mode, switch a remains closed and switch b remains open. switches c and d operate as a synchronous boost converter when in this mode. figure 3. buck-boost topology pvin vout switch a switch d switch b switch c lx1 lx2 l1
isl91108 7 fn8448.1 november 12, 2014 submit document feedback pfm operation during pfm operation in buck mode, switch d is continuously closed and switch c is continuously open. switches a and b operate in discontinuous mode during pfm operation. during pfm operation in boost mode, the isl91108 closes switch a and switch c to ramp up the current in the inductor. when inductor current reaches a certain threshold, the device turns off switches a and 10 c, then turns on switches b and d. with switches b and d closed, output voltage increases as the inductor current ramps down. in most operating conditions, th ere will be multiple pfm pulses to charge up the output capacito r. these pulses continue until v out has achieved the upper thre shold of the pfm hysteretic controller. switching then stops, and remains stopped until v out decays to the lower threshold of the hysteretic pfm controller. operation with v in close to v out when the output voltage is close to the input voltage, the isl91108 will rapidly and smoothly switch from boost to buck mode as needed to maintain the regulated output voltage. this behavior provides excellent efficiency and very low output voltage ripple. output voltage programming the isl91108 is available in fixed and adjustable output voltage versions. to use the fixed output version (isl91108iinz), the vout pin must be connected directly to fb. in the adjustable output voltage version (isl91108iiaz), an external resistor divider is required to program the output voltage. the fb pin has very low input leakage current, so it is possible to use large value resistors (e.g., r 1 =187k and r 2 =60k ) in the resistor divider connected to the fb input. applications information component selection the fixed-output version of th e isl91108 requires only three external power components to implement the buck boost converter: an inductor, an input capacitor, and an output capacitor. the adjustable isl91108 versio ns require three additional components to program the output voltage. two external resistors program the output volt age, and a small capacitor is added to improve stab ility and response. an optional input supply filtering capacitor (?c 4 ? in figure 4 ) can be used to reduce the supply noise on the vin pin, which provides power to the internal reference. in most applications, this capacitor is not needed. output voltage prog ramming, adjustable version setting and controlling the output voltage of the isl91108iiaz (adjustable output version) can be accomplished by selecting the external resistor values. equation 1 can be used to derive the r 1 and r 2 resistor values: when designing a pcb, include a gnd guard band around the fb resistor network to reduce noise and improve accuracy and stability. resistors r 1 and r 2 should be positioned close to the fb pin. feed-forward capacitor selection a small capacitor (c 4 in figure 4 ) in parallel with resistor r 1 is required to provide the specified load and line regulation. the suggested value of this capacitor is 27pf for r 1 =187k . an npo type capacitor is recommended. nonadjustable version fb pin connection the fixed output versions of the isl91108 does not require external resistors or a capacitor on the fb pin. simply connect vout to fb, as shown in figure 5 . figure 4. typical isl91108iiaz application vout fb pvin v in = 1.8v to 5.5v vin mode en c 1 2x10f isl91108iiaz gnd pgnd lx1 lx2 l1 1h v out = 3.3v c 2 2x22f r 1 r 2 187k 60k c 4 27pf vout 0.8v 1 r 1 r 2 ------ - + ?? ?? ?? ? = (eq. 1) vout fb c 2 2x22f pvin v in = 1.8v to 5.5v vin mode en c 1 2x10f isl91108iinz gnd pgnd lx1 lx2 l1 1h v out = 3.3v figure 5. typical isl91108iinz application
isl91108 8 intersil products are manufactured, assembled and tested utilizing iso9001 quality systems as noted in the quality certifications found at www.intersil.com/en/suppor t/qualandreliability.html intersil products are sold by description only. intersil corporat ion reserves the right to make changes in circuit design, soft ware and/or specifications at any time without notice. accordingly, the reader is cautioned to verify that data sheets are current before placing orders. information furnished by intersil is believed to be accurate and reliable. however, no responsi bility is assumed by intersil or its subsid iaries for its use; nor for any infringem ents of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of i ntersil or its subsidiaries. for information regarding intersil corporation and its products, see www.intersil.com fn8448.1 november 12, 2014 for additional products, see www.intersil.com/en/products.html submit document feedback inductor selection an inductor with high frequency core material (e.g., ferrite core) should be used to minimize core losses and provide good efficiency. the inductor must be able to handle the peak switching currents without saturating. a 1h inductor with 4.0a saturation cu rrent rating is recommended. select an inductor with low dcr to provide good efficiency. in applications where radiated noise must be minimized, a toroidal or shielded inductor can be used. pvin and v out capacitor selection the input and output capacitors sh ould be ceramic x5r type with low esl and esr. the recommended input capacitor value is 2x 10f. the recommended v out capacitor value is 2x22f. recommended pcb layout correct pcb layout is critical for proper operation of the isl91108. the input and output capacitors should be positioned as closely to the ic as possible. the ground connections of the input and output capacitors should be kept as short as possible and should be on the component layer to avoid problems that are caused by high switching currents flowing through pcb vias. about intersil intersil corporation is a leading provider of innovative power ma nagement and precision analog so lutions. the company's product s address some of the largest markets within the industrial and infrastr ucture, mobile computing and high-end consumer markets. for the most updated datasheet, application notes, related documentatio n and related parts, please see the respective product information page found at www.intersil.com . you may report errors or suggestions for improving this datasheet by visiting www.intersil.com/ask . reliability reports are also av ailable from our website at www.intersil.com/support table 1. inductor vendor information manufacturer series dimension (mm) website toko 1277as-h-1r0m 3.2x2.5x1.2 www.toko.com fdsd0312-h-1r0m 3.2x3.0x1.2 coilcraft xfl4020-102me 4.0x4.0x2.1 www.coilcraft.com table 2. capacitor vendor information manufacturer series website avx x5r www.avx.com murata x5r www.murata.com taiyo yuden x5r www.t-yuden.com tdk x5r www.tdk.com revision history the revision history provided is for informational purposes only and is believed to be accurate, but not warranted. please go t o web to make sure you have the latest revision. date revision change november 12, 2014 fn8448.1 -2nd paragraph: changed from "this device is capable of delivering up to 2.7a output current (pvin = 3 v, vout = 3.3v)...," to ?this device is capable of delivering up to 2.7a burst current (pvin = 3v, vout = 3.3v) ? -features section (bullet point #4) : changed from outp ut current: up to 1.5a (pvin = 3v, vout = 3.3v) to ?output current: up to 1.6a dc (pvin = 2.8v, vout = 3.3v)? -updated load current (i out ) range (dc) spec under ?recommended operating conditions? on page 4 from ?0a to 1.5a? to ?0a to 1.6a?. -figures 1, 4 and 5: removed the text "up to 2.7a" that appears next to the vout pin november 6, 2013 fn8448.0 initial release
isl91108 9 fn8448.1 november 12, 2014 submit document feedback package outline drawing w4x5.20f 20 ball wafer level chip scale package (wlcsp 0.4mm pitch) rev 0, 5/13 notes: dimensions and tolerance per asme y 14.5m - 1994. dimension is measured at the maximum bump diameter parallel to primary datum z . primary datum z and seating plane are defined by the spherical crowns of the bump. bump position designation per jesd 95-1, spp-010. there shall be a minimum clearance of 0.10mm between the edge of the bump and the body edge. 3. 2. 4. 1. 5. bottom view top view side view recommended land pattern 1.720.030 2.3350.030 pin 1 (a1 corner) (4x) 0.10 x y 1.200 0.400 20x 0.2650.035 1.600 0.3675 0.260 0.200 abcd 1 2 3 4 5 package outline 0.290 0.400 0.240 0.040 bsc (backside coating) seating plane 3 z 0.05 z 0.2650.035 x20 zxy z 0.10 0.05 m m 0.2000.030 0.5400.050
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