general description the max8550 evaluation kit (ev kit) is designed to evalu- ate the max8550 ddr power-supply solution for note- books, desktops, and graphics cards. the ev kit board produces vddq at the output of the synchronous pwm buck, vtt at the output of the sourcing/sinking ldo linear regulator, and vttr at the output of the reference buffer. the vddq output is preset to 2.5v and sources up to 12a. the vtt output is always vddq/2 and can source/sink up to 3a of peak current and 1.5a of contin- uous current. the vttr output is also always vddq/2 and can source/sink up to 10ma. the max8550 ev kit was conveniently designed with jumpers to select the ovp/uvp, ton, skip , stby, and shdn_ modes. the board? default settings enable ovp (overvoltage protection), 600khz switching fre- quency, low-noise pwm mode, vddq, vtt, and vttr. the vin input accepts voltages from 9v to 20v and vdd requires a 5v bias supply. the ev kit comes with the max8550 installed. contact the factory for free samples of the max8550a or max8551 to evaluate these parts. features ? vddq preset to 2.5v/12a ? vtt 1.25v source/sink 1.5a continuous/3a peak ? vttr 1.25v source/sink 10ma ? vin range: 9v to 20v ? optimized switching frequency: 600khz ? overvoltage/undervoltage protection ? standby ? independent shutdown ? power ok evaluates: max8550/max8550a/max8551 max8550 evaluation kit ________________________________________________________________ maxim integrated products 1 19-3436; rev 1; 11/04 component list for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. ordering information part temp range ic package max8550evkit 0? to +70? 28 thin qfn 5mm x 5mm designation qty description c1 1 0.1? 10%, 50v x7r ceramic capacitor (0603) tdk c1608x7r1h104k c2, c4a, c4b, c4c, c4d, c4e, c4f 7 10? 10%, 6.3v x5r ceramic capacitors (1206) tdk c3216x5r0j106k or tdk c3216x5r0j106m c3, c6, c13 3 1? 10%, 10v x5r ceramic capacitors (0603) tdk c1608x5r1a105k c5 1 4.7? 20%, 6.3v x5r ceramic capacitor (0805) tdk c2012x5r0j475m c7, c10 2 0.22? 20%, 16v x7r ceramic capacitors (0603) tdk c1608x7r1c224m c8a, c8b, c8c 3 10? 20%, 25v x5r ceramic capacitors (1210) taiyo yuden tmk325bj106mm tdk c3225x5r1e106m designation qty description c8d 0 not installed 470? 20%, 25v aluminum electrolytic capacitor (10mm x 16mm) sanyo 25mv470wx c9 1 3900pf, 50v x7r ceramic capacitor (0603) kemet c0603c392k5rac c11, c12 2 150?, 4v, 25m ? low-esr pos capacitors (d2e) sanyo 4tpe150m c14 1 470pf 5%, 50v cog ceramic capacitor (0603) tdk c1608cog1h471j c15, c16 2 not installed (0603) d1 1 s chottky d i od e, 30v , 100m a ( s od - 3 23) central cmdsh-3 ju1, ju2 2 4-pin headers ju3?u6 4 3-pin headers note: to evaluate the max8550a, request a free sample of the max8550aeti when ordering the max8550 ev kit. to evaluate the max8551, request a free sample of the max8551eti when ordering the max8550 ev kit.
evaluates: max8550/max8550a/max8551 max8550 evaluation kit 2 _______________________________________________________________________________________ recommended equipment 5vdc power supply (500ma rated) 9vdc to 20vdc power supply (5a rated) two digital voltmeters (dvm) quick start the max8550 ev kit is fully assembled and tested. follow these steps to verify board operation. do not turn on the power supplies until all connections are completed. 1) ensure a shunt is placed across pins 1-4 of jumper ju1 to enable ovp and uvp. 2) ensure a shunt is placed across pins 1-2 of jumper ju2 to set the switching frequency to approximately 600khz. 3) ensure a shunt is placed across pins 1-2 of jumper ju3 to enable low-noise pwm mode. 4) ensure a shunt is placed across pins 2-3 of jumper ju4 to disable the vddq buck output. 5) ensure a shunt is placed across pins 1-2 of jumper ju5 to enable the vtt and vttr outputs. 6) ensure a shunt is placed across pins 2-3 of jumper ju6 to set the board in normal operation mode. 7) connect the 5vdc power supply across the vdd pad and the pgnd pad nearest vin. 8) connect the 12vdc power supply across the vin pad and the corresponding pgnd pad. 9) turn on both of the power supplies. 10)set ju4 (1-2). this turns vddq on. 11)using one of the dvms, verify that the vddq voltage between the vddq and pgnd pads is 2.5v (?%). 12) using the other dvm, verify that the vtt voltage between the vtt and pgnd pads is 1.25v (?%). detailed description jumper selection component list (continued) designation qty description l1 1 1.0?, 20a, 1.6m ? power inductor (12.6mm x 12.6mm x 5.2mm) toko fda1254-1r0m q1 1 n-channel mosfet 30v, 9m ? (so-8) international rectifier irf7821 q2 1 n-channel mosfet 30v, 5m ? (so-8) international rectifier irf7832 r1 1 10 ? 5% resistor (0603) r2, r3 2 100k ? 5% resistors (0603) r4 1 75k ? 1% resistor (0603) r5 1 124k ? 1% resistor (0603) r6, r7, r8 2 not installed (0603) r9, r10, r11 3 0 ? resistors (0603) r12 1 not installed (1812) r13 1 20 ? 5% resistor (0603) u1 1 max8550eti (28-pin 5mm x 5mm thin qfn) none 6 shunts none 1 max8550 ev kit pc board jumper shunt position description ju1 1-2 disable ovp and uvp. ju1 1-3 enable uvp. disable ovp. ju1 1-4* enable ovp and uvp. ju1 open enable ovp. disable uvp. * default position. note: refer to the max8550/max8551 or max8550a data sheet for additional information on ovp/uvp. this mode does not directly apply to the max8551. table 1. overvoltage/undervoltage control input (ovp/uvp) component suppliers supplier phone website central semiconductor 631-435-1110 www.centralsemi.com international rectifier 310-322-3331 www.irf.com kemet 864-963-6300 www.kemet.com sanyo usa 619-661-6835 www.sanyo.com tdk 847-803-6100 www.component.tdk.com toko america 847-297-0070 www.tokoam.com note: indicate that you are using the max8550 when contact- ing these component suppliers.
setting the buck regulator output voltage (vddq) the output voltage of the buck regulator is preset to 2.5v on the max8550 ev kit for ddr memory applica- tions. to pin-strap the output voltage to 1.8v follow the steps below: 1) remove r9. 2) solder the 0 ? resistor from step 1 in the r7 location. refer to the max8550/max8551 data sheet to change the external components for optimum performance. low-side mosfet snubber circuit (buck) fast switching transitions cause ringing because of the resonating circuit formed by the parasitic inductance and capacitance at the switching lx node. this high- frequency ringing occurs at the lx node? rising and evaluates: max8550/max8550a/max8551 max8550 evaluation kit _______________________________________________________________________________________ 3 jumper shunt position description ju2 1-2* 600khz switching frequency ju2 1-3 450khz switching frequency ju2 1-4 200khz switching frequency ju2 open 300khz switching frequency * default position. note: refer to the max8550/max8551 or max8550a data sheet for additional information on ton. table 2. on-time selection input (ton) jumper shunt position description ju3 1-2* low-noise pwm mode. ju3 2-3 pulse-skipping mode. use only this position when evaluating the max8551. * default position. note: refer to the max8550/max8551 or max8550a data sheet for additional information on skip . caution: do not connect an external controller to the skip pad while a shunt is on jumper ju3. table 3. pulse-skipping control input ( skip ) jumper shunt position description ju4 1-2 the vddq buck output is enabled. ju4 2-3* the vddq buck output is shut down. * default position. note: refer to the max8550/max8551 or max8550a data sheet for additional information on shdna . shdna is shdn on the max8550a. caution: do not connect an external controller to the shdna pad while a shunt is on jumper ju4. table 4. shutdown control input a ( shdna ) jumper shunt position description ju5 1-2* the vtt and vttr outputs are enabled. ju5 2-3 the vtt and vttr outputs are shut down. * default position. note: refer to the max8550/max8551 or max8550a data sheet for additional information on shdnb . shdnb is tp0 on the max8550a. caution: do not connect an external controller to the shdnb pad while a shunt is on jumper ju5. table 5. shutdown control input b ( shdnb ) jumper shunt position description ju6 1-2 the vtt output is shut down. ju6 2-3* normal operation. * default position. note: refer to the max8550/max8551 or max8550a data sheet for additional information on stby. stby is stby on the max8550a. caution: do not connect an external controller to the stby pad while a shunt is on jumper ju6. table 6. standby control input (stby)
evaluates: max8550/max8550a/max8551 falling transitions and may interfere with circuit perfor- mance and generate emi. to dampen this ringing, an optional series rc snubber circuit is added across the low-side switch. below is a simple procedure for select- ing the value of the series rc for the snubber circuit: 1) connect a scope probe to the lx node labeled on the max8550 ev kit schematic and observe the ring- ing frequency, f r . 2) estimate the circuit parasitic capacitance (c par ) at lx by first finding a capacitor value, which, when connected from lx to pgnd1, reduces the ringing frequency by half. c par can then be approximated as 1/3 the value of the capacitor value found. 3) estimate the circuit parasitic inductance (l par ) from the equation: 4) calculate r12 for critical dampening from the equation: r12 = 2 f r x l par adjust the resistor value up or down to tailor the desired damping and the peak voltage excursion. 5) capacitor c15 should be at least 2 to 4 times the value of c par to be effective. the power loss of the snubber circuit (pwr_snub) is dissipated in the resistor and can be calculated as: pwr_snub = c15 x vin 2 x f sw where vin is the input voltage and f sw is the switching frequency. choose the power rating of r12 according to the specific application? derating rule for the power dissipation calculated in the equation above. recommended snubber values for this ev kit are 3 ? (r12) and 2.2nf (c15). l fc par r par = 1 2 2 () max8550 evaluation kit 4 _______________________________________________________________________________________
evaluates: max8550/max8550a/max8551 max8550 evaluation kit _______________________________________________________________________________________ 5 c4a 10 f c4b 10 f c4c 10 f c4d 10 f c4e 10 f vtt pgnd c4f 10 f c16 open vttr gnd c6 1 f ref a vdd ju1 4 1 3 2 4 3 1 2 ju2 pok1 r2 100k ? r3 100k ? pok2 a vdd c9 3900pf ref c10 0.22 f c14 470pf r4 75k ? 1% a vdd r5 124k ? 1% r7 open r6 open vddq r8 open r9 0 ? c2 10 f vddq r13 20 ? c1 0.1 f vddq skip ju3 1 2 3 r1 10 ? c3 1 f a vdd r10 0 ? d1 cmdsh-3 c7 0.22 f lx c5 4.7 f vdd (5v bias supply) q1 irf7821 7 8 6 5 4 1 2 3 lx 7 8 6 5 q2 irf7832 4 3 1 2 r11 0 ? r12 open c15 open l1 1 h c11 150 f c12 150 f c13 1 f vddq pgnd vddq 2.5 at 12a pgnd vin (9v to 20v) c8d open c8c 10 f c8b 10 f c8a 10 f vin a vdd ju4 1 2 3 shdna shdnb stby a vdd ju6 1 2 3 3 2 1 ju5 a vdd max8550 vtt vtts pgnd2 vttr ovp/uvp ton pok1 pok2 ss gnd ref ilim fb out 16 15 4 3 24 8 6 5 1 2 10 11 9 12 13 vtti 14 refin 25 skip av dd v dd bst lx v in dh dl pgnd1 shdna shdnb stby 7 28 27 23 21 18 17 19 20 22 26 stby shdna shdnb on/off control logic 01 1 01 0 11 1 00 1 00 0 vttr vddq vtt on on on off off on on on on on off off off off off a vdd ref figure 1. max8550 ev kit schematic
evaluates: max8550/max8550a/max8551 max8550 evaluation kit 6 _______________________________________________________________________________________ figure 2. max8550 ev kit component placement guide?omponent side figure 3. max8550 ev kit pc board layout?omponent side
evaluates: max8550/max8550a/max8551 max8550 evaluation kit _______________________________________________________________________________________ 7 figure 4. max8550 ev kit pc board layout?nner layer 2 (gnd, pgnd1 and pgnd2) figure 5. max8550 ev kit pc board layout?nner layer 3 (gnd, pgnd1 and pgnd2)
evaluates: max8550/max8550a/max8551 max8550 evaluation kit maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 _____________________ 8 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. figure 6. max8550 ev kit pc board layout?older side
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