Precision Dual Voltage Regulator Controller ADM1052

Transcription

1 a FEAURES wo Independen Conrollers on One Chip wo V Oupus Shudown Inpus o Conrol Each Channel 2.5% Accuracy Over Line, Load, and emperaure Low Quiescen Curren Low Shudown Curren Works wih Exernal N-Channel MOSFEs for Low Cos Hiccup Mode Faul Proecion No Exernal Volage or Curren Seing Resisors Small, 8-Lead SO Package APPLICAIONS Deskop Compuers Servers Worksaions Precision Dual Volage Regulaor Conroller ADM052 GENERAL DESCRIPION he ADM052 is a dual, precision, volage regulaor conroller inended for power rail generaion and acive bus erminaion on personal compuer moherboards. I conains a precision.2 V bandgap reference and wo channels consising of conrol amplifiers driving exernal power devices. Each channel has a shudown inpu o urn off amplifier oupu and Hiccup Mode proecion circuiry for he exernal power device. he ADM052 operaes from a 2 V supply. his gives sufficien headroom for he amplifiers o drive exernal N-channel MOSFEs, operaing as source-followers, as he exernal series pass devices. his has he advanage ha N-channel devices are cheaper han P-channel devices of similar performance, and he circui is easier o sabilize han one using P-channel devices in a common-source configuraion. FUNCIONAL BLOCK DIAGRAM ADM052 BANDGAP REFERENCE CONROL AMPLIFIER FORCE 00 F SENSE V OU 50 A 2 00 F SHDN SHUDOWN CONROL HICCUP COMPARAOR CONROL AMPLIFIER 00 F V OU2 50 A 2 00 F SHDN2 SHUDOWN CONROL HICCUP COMPARAOR POWER-ON RESE CLK/DELAY GENERAOR CLOCK OSCILLAOR Informaion furnished by Analog Devices is believed o be accurae and reliable. However, no responsibiliy is assumed by Analog Devices for is use, nor for any infringemens of paens or oher righs of hird paries which may resul from is use. No license is graned by implicaion or oherwise under any paen or paen righs of Analog Devices. One echnology Way, P.O. Box 906, Norwood, MA , U.S.A. el: 78/ World Wide Web Sie: hp:// Fax: 78/ Analog Devices, Inc., 200

2 ADM052 SPECIFICAIONS ( = 2 V 6%, V IN = 3.3 V, A = 0 C o 70 C, boh channels, unless oherwise noed. See es Circui.) Parameer Min yp Max Uni es Condiions/Commens OUPU VOLAGE Channel, Channel V SHDN, SHDN2 Floaing OUPU VOLAGE ACCURACY % V IN = 3.0 V o 3.6 V, I OU = 0 ma o A Load Regulaion 5 +5 mv V IN = 3.3 V, I OU = 0 ma o A Line Regulaion 5 +5 mv V IN = 3.0 V o 3.6 V, I OU = A CONROL AMPLIFIER Conrol Amplifier Open-Loop Gain 00 db Conrol Amplifier Slew Rae 3 V/µs Closed-Loop Seling ime 5 µs I O = 0 ma o 2 A urn-on ime 5 µs o 90% of Force High Oupu Level (C L = 470 pf) Sense Inpu Impedance 50 kω Force Oupu Volage Swing, V F (High) 0 V R L = 0 kω o Force Oupu Volage Swing, V F (Low) 2 V R L = 0 kω o HICCUP MODE Hiccup Mode Hold-Off ime ms Figure 2 Hiccup Mode hreshold 0.8 V OU V Hiccup Comparaor Glich Immuniy 00 µs Hiccup Mode On-ime ms Hiccup Mode Off-ime ms Power-On Rese hreshold 6 9 V SHUDOWN, SHDN, SHDN2 Shudown Inpu Low Volage, V IL 0.8 V Shudown Inpu High Volage, V IH 2.0 V Supply Curren, Normal Operaion ma Shudown Inpus Floaing Supply Curren, Shudown Mode µa Boh Channels Shu Down NOES Guaraneed by design. Specificaions subjec o change wihou noice. 2

3 ADM052 ABSOLUE MAXIMUM RAINGS* ( A = 25 C unless oherwise noed) o V SHDN, SHDN2 o V o ( V) SENSE, SENSE2 o V o +5.5 V FORCE, FORCE Shor-Circui o or Coninuous Power Dissipaion ( A = 70 C) mw 8-Lead SOIC (Derae 8.3 mw/ C above 70 C) Operaing emperaure Range Commercial (J Version) C o 70 C Sorage emperaure Range C o +50 C Lead emperaure (Soldering, 0 sec) C *his is a sress raing only and funcional operaion of he device a hese or any oher condiions above hose indicaed in he operaion secions of his specificaion is no implied. Exposure o absolue maximum raing condiions for exended periods of ime may affec reliabiliy. HERMAL CHARACERISICS 8-Lead Small Ouline Package: JA = 50 C/W ORDERING GUIDE emperaure Package Package Model Range Descripion Opion ADM052JR 0 C o 70 C 8-Lead SOIC SO-8 PIN FUNCION DESCRIPIONS Pin No. Mnemonic Funcion Oupu of Channel 2 conrol amplifier o gae of exernal N-channel MOSFE. 2 Inpu from source of exernal MOSFE o invering inpu of Channel 2 conrol amplifier, via oupu volage-seing feedback resisor nework. 3 SHDN2 Digial Inpu. Acive-low shudown conrol wih 50 µa inernal pull-up. he oupu of Channel 2 conrol amplifier goes o ground when SHDN2 is aken low. 4 Device Ground Pin. 5 SHDN Digial Inpu. Acive-low shudown conrol wih 50 µa inernal pull-up. he oupu of Channel conrol amplifier goes o ground when SHDN is aken low. 6 SENSE Inpu from source of exernal MOSFE o invering inpu of Channel conrol amplifier, via oupu volage-seing feedback resisor nework. 7 FORCE Oupu of Channel 2 conrol amplifier o gae of exernal N-channel MOSFE. 8 2 V Supply. 2V PIN CONFIGURAION F PHD55N03L FORCE 00 F SHDN2 2 ADM OP VIEW 3 4 (No o Scale) 6 5 FORCE SENSE SHDN SENSE V OU 2 00 F SHDN LEAVE OPEN OR CONNEC O LOGIC SIGNALS IF SHUDOWN REQUIRED SHDN2 ADM052 MD3055VL 00 F V OU F Figure. es Circui CAUION ESD (elecrosaic discharge) sensiive device. Elecrosaic charges as high as 4000 V readily accumulae on he human body and es equipmen and can discharge wihou deecion. Alhough he ADM052 feaures proprieary ESD proecion circuiry, permanen damage may occur on devices subjeced o high-energy elecrosaic discharges. herefore, proper ESD precauions are recommended o avoid performance degradaion or loss of funcionaliy. WARNING! ESD SENSIIVE DEVICE 3

4 ADM052 ypical Performance Characerisics ek Sop: 25.0MS/s 56Acqs [ v OUPU V v 2.5 Ch 500mV BW Ch2 20.0mV BW M 2.00 s Ch 3.53V Ch3 20.0mV BW PC. Line ransien Response, Channel and Channel CURREN A PC 4. Load Regulaion, Channel V OU V OUPU V V IN V CURREN A PC 2. Line Regulaion, Channel PC 5. Load Regulaion, Channel V OU V RIPPLE REJECION db V IN V PC 3. Line Regulaion, Channel k 0k 00k M 0M FREQUENCY Hz PC 6. Supply Ripple Rejecion 4

5 ADM ek Sop: Single Seq 50.0MS/s [ OUPU V EMPERAURE C PC 7. Regulaor Oupu Volage vs. emperaure Ch 20.0mV BW M.00 s Ch 40mV PC 0. ransien Response Channel 2, 0 ma o 2 A Oupu Load Sep ek Sop: Single Seq 50.0MS/s [ ek Sop: Single Seq 50.0MS/s [ Ch 20.0mV BW M.00 s Ch 45.0mV Ch 20.0mV BW M.00 s Ch 37.6mV PC 8. ransien Response Channel, 0 ma o 2 A Oupu Load Sep PC. ransien Response Channel 2, 2 A o 0 ma Oupu Load Sep ek Sop: Single Seq 50.0MS/s [ ek Sop: 0.0kS/s 0Acqs [ Ch 20.0mV BW M.00 s Ch 5.2mV Ch 0.0mV BW M 5.00 s Ch 800mV PC 9. ransien Response Channel, 2 A o 0 ma Oupu Load Sep PC 2. Force Oupu In Hiccup Mode, Channel 5

6 ADM052 GENERAL DESCRIPION he ADM052 is a dual, precision, volage regulaor conroller inended for power rail generaion and acive bus erminaion on personal compuer moherboards. I conains a precision.2 V bandgap reference and wo channels consising of conrol amplifiers driving exernal power devices. Boh channels have an oupu of nominally V. Each channel has a shudown inpu o urn off amplifier oupu and proecion circuiry for he exernal power device. he ADM052 operaes from a 2 V supply. he oupu is disabled unil climbs above he rese hreshold (6 V 9 V). he oupu from he ADM052 is used o drive exernal N-channel MOSFEs, operaing as source-followers. his has he advanage ha N-channel devices are cheaper han P-channel devices of similar performance, and he circui is easier o sabilize han one using P-channel devices in a common-source configuraion. he exernal power devices are proeced by a Hiccup Mode circui ha operaes if he circui goes ou of regulaion due o an oupu shor-circui. In his case he power device is pulsed on/off wih a :40 duy cycle o limi he power dissipaion unil he faul condiion is removed. CIRCUI DESCRIPION CONROL AMPLIFIERS he reference volage is amplified and buffered by he conrol amplifiers and exernal MOSFEs, he oupu volage of each channel being deermined by he feedback resisor nework beween he sense inpu and he invering inpu of he conrol amplifier. A power-on rese circui disables he amplifier oupu unil has risen above he rese hreshold (6 V 9 V). Each amplifier oupu drives he gae of an N-channel power MOSFE, whose drain is conneced o he unregulaed supply inpu and whose source is he regulaed oupu volage, which is also fed back o he appropriae sense inpu of he ADM052. he conrol amplifiers have high curren-drive capabiliy so ha hey can quickly charge and discharge he gae capaciance of he exernal MOSFE, hus giving good ransien response o changes in load or inpu volage. SHUDOWN INPUS Each channel has a separae shudown inpu, which may be conrolled by a logic signal and allows he oupu of he regulaor o be urned on or off. If he shudown inpu is held high or no conneced, he regulaor operaes normally. If he shudown inpu is held low, he enable inpu of he conrol amplifier is urned off and he amplifier oupu goes low, urning off he regulaor. HICCUP MODE FAUL PROECION Hiccup mode faul proecion is a simple mehod of proecing he exernal power device wihou he added cos of exernal sense resisors or a curren sense pin on he ADM052. In he even of a shor-circui condiion a he oupu, he oupu volage will fall. When he oupu volage of a channel falls 20% below he nominal volage, his is sensed by he hiccup comparaor and he channel will go ino hiccup mode, where he enable signal o he conrol amplifier is pulsed on and off wih a :40 duy cycle. o preven he device inadverenly going ino hiccup mode during power-up or during channel enabling, he hiccup mode is held off for approximaely 60 ms on boh channels. By his ime he oupu volage should have reached is correc value. In he case of power-up, he hold-off period sars when reaches he power-on rese hreshold of 6 V 9 V. In he case of channel enabling, he hold-off period sars when SHDN is aken high. Noe ha he hold-off imeou applies o boh channels even if only one channel is disabled/enabled. As he 3.3 V inpu o he drain of he MOSFE is no moniored, i should ideally rise a he same or a faser rae han. A he very leas i mus be available in ime for V OU o reach is final value before he end of he power-on delay. If he oupu volage is sill less han 80% of he correc value afer he poweron delay, he device will go ino hiccup mode unil he oupu volage exceeds 80% of he correc value during a hiccup mode on-period. Of course, if here is a faul condiion a he oupu during power-up, he device will go ino hiccup mode afer he power-up delay and remain here unil he faul condiion is removed. he effec of power-on delay is illusraed in Figure 2, which shows an ADM052 being powered up wih a faul condiion. he oupu curren rises o a very high value during he poweron delay, he device goes ino hiccup mode, and he oupu is pulsed on and off a :40 duy cycle. When he faul condiion is removed, he oupu volage recovers o is normal value a he end of he hiccup mode off period. he load curren a which he ADM052 will go ino hiccup mode is deermined by hree facors: he inpu volage o he drain of he MOSFE, V IN he oupu volage V OU ( 20%) he on-resisance of he MOSFE, R ON I HICCUP = (V IN (0.8 V OU ))/R ON I should be emphasized ha he hiccup mode is no inended as a precise curren limi bu as a simple mehod of proecing he exernal MOSFE agains caasrophic faul condiions such as oupu shor circuis. 6

7 ADM052 POR HRESHOLD 6V 9V 2V SUPPLY V REF URN-ON HRESHOLD SUPPLY O EXERNAL MOSFE DRAIN GAE DRIVE O EXERNAL MOSFE MOSFE GAE HRESHOLD CHANNEL OR CHANNEL 2 OUPU VOLAGE NORMAL OUPU VOLAGE OUPU < 0.8 V REG FAUL REMOVED HICCUP MODE HOLD-OFF IME DEVICE ENERS HICCUP MODE FAUL CURREN CHANNEL OR CHANNEL 2 OUPU CURREN 2 AMPS OFF ON :40 DUY CYCLE Figure 2. Power-On Rese and Hiccup Mode APPLICAIONS INFORMAION PCB LAYOU For opimum volage regulaion, he loads should be placed as close as possible o he source of he oupu MOSFEs and feedback o he sense inpus should be aken from a poin as close o he loads as possible. he PCB racks from he loads back o he sense inpus should be separae from he oupu racks and no carry any load curren. Similarly, he ground connecion o he ADM052 should be made as close as possible o he ground of he loads, and he ground rack from he loads o he ADM052 should no carry load curren. Correc and incorrec layou pracice is illusraed in Figure 3. 2V 2V FORCE FORCE SENSE SENSE V OU V IN I V IN I 2 V OU V OU2 LOAD LOAD 2 I I 2 LOAD LOAD 2 V OU2 VOLAGE DROP BEWEEN OUPU AND LOAD I + I 2 CORREC VOLAGE DROP IN GROUND LEAD INCORREC Figure 3. Correc and Incorrec Layou Pracice 7

8 ADM052 LEAVE OPEN OR CONNEC O LOGIC SIGNALS IF SHUDOWN REQUIRED SHDN SHDN2 2V ADM052 F FORCE SENSE Figure 4. ypical Applicaion Circui 00 F V OU 2 00 F 00 F V OU F SUPPLY DECOUPLING he supply o he drain of an exernal MOSFE should be decoupled as close as possible o he drain pin of he device, wih a 00 µf capacior o ground. he oupu from he source of he MOSFE should be decoupled as close as possible o he source pin of he device. Decoupling capaciors should be chosen o have a low Equivalen Series Resisance (ESR). Wih he MOSFEs specified and wo 00 µf capaciors in parallel, he circui will be sable for load currens up o 2 A. he pin of he ADM052 should be decoupled wih a µf capacior o ground, conneced as close as possible o he and pins. In pracice, he amoun of decoupling required will depend on he applicaion. PC moherboards are nooriously noisy environmens, and i may be necessary o employ disribued decoupling o achieve accepable noise levels on he supply rails. CHOICE OF MOSFE As previously discussed, he load curren a which an oupu goes ino hiccup mode depends on he on-resisance of he exernal MOSFE. If he on-resisance is oo low his curren may be very high. While he es Circui (Figure ) shows he use of he lower resisance PHD55N03L from Philips on Channel and he use of he higher resisance MD3055VL from Moorola on Channel 2, he MD3055VL is, in fac, suiable for boh channels. Similarly, he PHBN06L from Philips is also suiable for boh channels. HERMAL CONSIDERAIONS Hea generaed in he exernal MOSFE mus be dissipaed and he juncion emperaure of he device kep wihin accepable limis. he power dissipaed in he device is, of course, he drain-source volage muliplied by he load curren. he required hermal resisance o ambien is given by JA = J(MAX) AMB(MAX) /(V DS(MAX) I OU(MAX) ) Surface-moun MOSFEs such as hose specified mus rely on hea conducion hrough he device leads and he PCB. One square inch of copper (645 sq. mm) gives a hermal resisance of around 60 C/W for a SO-223 surface-moun package and 80 C/W for a SO-8 surface-moun package. For higher power dissipaion han can be accommodaed by a surface-moun package D 2 PAK or O-220 devices are recommended. hese should be mouned on a heasink wih a hermal resisance low enough o mainain he required maximum juncion emperaure. C /0 (rev. A) OULINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Small Ouline Package (Narrow Body, SO-8) (4.00) (3.80) PIN (0.25) (0.0) SEAING PLANE (5.00) (4.80) (.27) BSC (0.49) (0.35) (6.20) (5.80) (.75) (.35) (0.25) (0.9) (0.50) (0.25) (.27) (0.4) PRINED IN U.S.A. 8