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LTC1736



LINEAR TECHNOLOGY CORPORATION 1999

1736f LT/TP 1299 4K • PRINTED IN USA

TYPICAL APPLICATIO

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900

●

FAX: (408) 434-0507

●

www.linear-tech.com

12A Converter with FCB Tied to PGOOD for CPU Power; Optimized for Output Voltages of 1.3V to 1.6V

OSC

RUN/SS

FCB

SGND

PGOOD

SENSE

–

SENSE

OSENSE

VID0

VID1

BOOST

INTV

PGND

EXTV

VIDV

VID4

VID3

VID2

LTC1736

1000pF

47pF

330pF

PGOOD

OSC

47pF

01.

33k

100k

INTV

4.7

CMDSH-3

D1
MBRS340T3

F/30V

OS-CON

0.22

M1
FDS6680A

1.2

SENSE

0.004

Ω

SGND

M2
FDS6680A

OUTPUT VOLTAGE
PROGRAMMING

OUT

: 4-180

F/4V PANASONIC EEFUEOG181R (AS SHOWN)

3-470

F/6.3V KEMIT T51CX447M006AS (ALTERNATE)

1-820

F/4V SANYO 4 1-180

F/4V PANASONIC EEFUE0G181R (ALTERNATE)

: SANYO OS-CON 305C22M

L1: PANASONIC ETQP6RZ1RZ0HFA

Ω

OPTIONAL:
CONNECT
TO 5V

1736 TA02

OUT

180

F/4V

OUT

1.35V TO 1.6V
12A

4.75V TO 24V

Ω

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are trademarks of Linear Technology Corporaton.

Содержание LTC1736

Страница 1: ...allowing maximum flexibility inoptimizingefficiency Theoutputvoltageismonitoredby a power good window comparator that indicates when the output is within 7 5 of its programmed value Protection feature...

Страница 2: ...TA 25 C VIN 15V VRUN SS 5V unless otherwise noted SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop VOSENSE Output Voltage Set Accuracy Note 3 See Table 1 1 VLINEREG Reference Voltage L...

Страница 3: ...n Note 9 Rise and fall times are measured using 10 and 90 levels Delay times are measured using 50 levels f C pF I I OSC OSC CHG DIS 8 477 10 11 1 1 11 1 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS...

Страница 4: ...30 95 EXTVCC OPEN VOUT 1 6V FIGURE 1 IOUT 5A IOUT 0 5A LOAD CURRENT A 0 NORMALIZED V OUT 0 2 0 1 8 1736 G05 0 3 0 4 2 4 6 12 10 0 FCB 0V VIN 15V FIGURE 1 Load Regulation LOAD CURRENT A 0 0 I TH VOLTA...

Страница 5: ...0 CURRENT SENSE THRESHOLD mV 30 50 70 90 2 1736 G13 10 10 20 40 60 80 0 20 30 0 5 1 1 5 2 5 VRUN SS V 0 0 V ITH V 0 5 1 0 1 5 2 0 2 5 1 2 3 4 1736 G15 5 6 VOSENSE 0 7V VITH vs VRUN SS TEMPERATURE C 4...

Страница 6: ...V IL 5A DIV 1736 G22 5ms DIV VIN 15V VOUT 1 6V RLOAD 0 16 VOUT RIPPLE Synchronized VOUT 10mV DIV IL 5A DIV 1736 G23 10 s DIV EXT SYNC f fO VIN 15V VOUT 1 6V VOUT RIPPLE Burst Mode Operation VOUT 20mV...

Страница 7: ...VFBis0 8Vwhen the output is in regulation This pin can be bypassed to SGND with 50pF to 100pF VOSENSE Pin 10 Receives the remotely sensed feedback voltage from the output VID0 to VID4 Pins 11 to 15 Di...

Страница 8: ...t com parator I2 or the beginning of the next cycle The top MOSFET driver is powered from a floating bootstrap capacitor CB This capacitor is normally re chargedfromINTVCC throughanexternalSchottkydio...

Страница 9: ...is resumed Burst Mode operation is disabled by comparator F when the FCB pin is brought below 0 8V This forces continuous operation and can assist second ary winding regulation When the FCB pin is dri...

Страница 10: ...ever lower frequency operation re quires more inductance for a given amount of ripple current TheLTC1736usesaconstant frequencyarchitecturewith the frequency determined by an external oscillator capac...

Страница 11: ...uehasadirecteffectonripplecurrent The inductor ripple current IL decreases with higher induc tance or frequency and increases with higher VIN or VOUT I f L V V V L OUT OUT IN 1 1 Accepting larger valu...

Страница 12: ...the MOSFETs as well most of the logic level MOSFETs are limited to 30V or less SelectioncriteriaforthepowerMOSFETsincludethe ON resistance RDS ON reverse transfer capacitance CRSS input voltage and ma...

Страница 13: ...te and slow down the response The minimum capacitance to assure the inductors energy is adequately absorbed is C L I V V OUT OUT 2 2 where I is the change in load current Largerdiodescanresultinadditi...

Страница 14: ...a tions of different capacitor types have proven to be a very cost effective solution Remember also to include high frequency decoupling capacitors They should be placed as close as possible to the po...

Страница 15: ...to the LTC1735 data sheet for details The charge pump has the advantage of simple magnetics Output Voltage Programming Theoutputvoltageisdigitallysettolevelsbetween0 925V and 2 00V using the voltage i...

Страница 16: ...cross the gate source of the MOSFET This enhances the MOSFET and turns on the topside switch The switch node voltage SW rises to VIN and the BOOST pin rises to VIN INTVCC The value of the boost capaci...

Страница 17: ...Latchoff The RUN SS pin also provides the ability to shut off the controller and latchoff when an overcurrent condition is detected The RUN SS capacitor CSS is used initially to turn on and limit the...

Страница 18: ...ple current is determined by the minimum on time tON MIN of the LTC1736 less than 200ns the input voltage and inductor value IL SC tON MIN VIN L The resulting short circuit current is I mV R I SC SENS...

Страница 19: ...forced In this case the top and bottom MOSFETs continue to be driven synchronously regardless of the load on the main output Burst Mode operation is disabled and current reversal is allowed in the ind...

Страница 20: ...Efficiency 100 L1 L2 L3 APPLICATIO S I FOR ATIO W U U U where L1 L2 etc are the individual losses as a percent age of input power Although all dissipative elements in the circuit produce losses four m...

Страница 21: ...behavior but also provides a DC coupled and AC filtered closed loop response test point The DC step rise time and settling at this test point truly reflects the closed loop response Assuming a pre dom...

Страница 22: ...oad This offset is limited to 30mV at the input of the error amplifier The resulting change in output voltage is the product of input offset and the feedback voltage divider ratio Figure 6 shows a CPU...

Страница 23: ...fset ITH OUT DC L ITH ITH 2 At full load current V A A V A V V ITH MAX P P 15 5 2 0 084 0 3 1 77 At minimum load current V A A V A V V ITH MIN P P 0 2 2 2 0 084 0 3 0 40 In this circuit VITH changes f...

Страница 24: ...siderably with active voltage positioning Refer to Design Solutions 10 for more information about active voltage positioning Automotive Considerations Plugging into the Cigarette Lighter As battery po...

Страница 25: ...paral leled Choosing Fairchild FDS6680A MOSFETs yields a parallel RDS ON of 0 0065 The total power dissipaton for both bottom MOSFETs again assuming T 50 C is P V V V A mW SYNC 22 1 6 22 12 1 1 0 0065...

Страница 26: ...NSE and SENSE should be as close as possibletotheLTC1736 Ensureaccuratecurrentsens ing with kelvin connections as shown in Figure 11 Series resistance can be added to the SENSE lines to increase noise...

Страница 27: ...onofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights G24 SSOP 1098 0 13 0 22 0 005 0 009 0 8 0 55 0 95 0 022 0 037 5 20 5 38 0 205 0 212 7 65 7 90 0 301 0 311 1 2 3 4 5 6 7 8 9 10 11...

Страница 28: ...ep Down Controllers 100 DC Burst Mode Operation VIN 20V LTC1149 High Efficiency Synchronous Step Down Controller 100 DC Std Threshold MOSFETs VIN 48V LTC1159 High Efficiency Synchronous Step Down Cont...

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