LTC1929 LINER [Linear Technology], LTC1929 Datasheet
![no-image](/images/no-image-200.jpg)
LTC1929
Available stocks
Related parts for LTC1929
LTC1929 Summary of contents
Page 1
... F SW2 S S BG2 INTV – + SENSE2 + – SENSE2 Figure 1. High Current 2-Phase Step-Down Converter Final Electrical Specifications LTC1929 Switching Regulator August 1999 U 1929 is a 2-phase, single output, synchronous 28V 35V CERAMIC L1 0.002 OUT 1.6V/40A L2 0 ...
Page 2
... Peak Output Current <1 s(TGL1,2, BG1,2) ................ 3A INTV RMS Output Current ................................ 50mA CC Operating Ambient Temperature Range LTC1929C .................................................. LTC1929I .............................................. – Junction Temperature (Note 2) ............................. 125 C Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T ...
Page 3
... DIFFOUT Op Amp Mode Op Amp Mode; 0V < V < Amp Mode; 6V < V < 30V IN Op Amp Mode DIFFOUT Op Amp Mode 1mA DIFFOUT Op Amp Mode 1mA DIFFOUT Op Amp Mode LTC1929 MIN TYP MAX UNITS 1 – 99 ...
Page 4
... The normal voltage range of this pin is from 0V to 2.4V 4 Note 3: The LTC1929 is tested in a feedback loop that servos V specified voltage and measures the resultant V and power Note 4: Dynamic supply current is higher due to the gate charge being A delivered at the switching frequency ...
Page 5
... OUT DET BOT FORCE BOT SHDN I1 – – 4 SLOPE 45k COMP V IN 1.2 A SHDN 4 LTC1929 (Pin 22): External Power Input to an Internal Connection in the Applica EXTVCC INTVCC INTV BOOST TOP SW SWITCH INTV CC LOGIC BG BOT PGND INTV ...
Page 6
... TH value continues to charge leased allowing normal operation to resume. When the RUN/SS pin is low, all LTC1929 functions are shut down has not reached 70% of its nominal value when C OUT has charged to 4.1V, an overcurrent latchoff can be invoked as described in the Applications Information section ...
Page 7
... The amplifier is not capable of sinking current and therefore must be resistively loaded APPLICATIO S I FOR ATIO The basic LTC1929 application circuit is shown in Figure 1 on the first page. External component selection is driven by the load requirement, and begins with the selection Once R ...
Page 8
... LTC1929 U U APPLICATIO S I FOR ATIO A graph for the voltage applied to the PLLFLTR pin vs frequency is given in Figure 2. As the operating frequency is increased the gate charge losses will be higher, reducing efficiency (see Efficiency Considerations). The maximum switching frequency is approximately 310kHz. 2.5 2.0 1.5 1.0 0.5 0 120 170 ...
Page 9
... Selection criteria for the power MOSFETs include the “ON” resistance R , reverse transfer capacitance C DS(ON) input voltage, and maximum output current. When the LTC1929 is operating in continuous mode the duty factors for the top and bottom MOSFETs of each output stage are given by ...
Page 10
... LTC1929 U U APPLICATIO S I FOR ATIO of the bottom MOSFET from turning on, storing charge during the dead-time, and requiring a reverse recovery period which would reduce efficiency (depend- ing on output current) Schottky diode is generally a good compromise for both regions of operation due to the relatively small average current ...
Page 11
... U High input voltage applications in which large MOSFETs are being driven at high frequencies may cause the maxi- mum junction temperature rating for the LTC1929 to be exceeded. The supply current is dominated by the gate charge supply current, in addition to the current drawn from the differential amplifier output. The gate charge is dependent on operating frequency as discussed in the Efficiency Considerations section ...
Page 12
... If the input current does not change then the efficiency has not changed either. Output Voltage The LTC1929 has a true remote voltage sense capablity. The sensing connections should be returned from the load to an output- CC back to the differential amplifier’ ...
Page 13
... The time for the output current to ramp up is then: t IRAMP By pulling both RUN/SS controller pins below 0.8V the , the LTC1929 is put into low current shutdown (I CC RUN/SS pins can be driven directly from logic as shown in Figure 6. Diode D1 in Figure 6 reduces the start delay but allows C SS function ...
Page 14
... At this stable operating point the phase comparator output is INTV open and the filter capacitor C CC LTC1929 PLLIN pin must be driven from a low impedance source such as a logic gate located close to the pin. RUN/SS ...
Page 15
... Minimum On-Time Considerations Minimum on-time t is the smallest time duration ON(MIN) that the LTC1929 is capable of turning on the top MOSFET determined by internal timing delays and the gate charge required to turn on the top MOSFET. Low duty cycle applications may approach this minimum on-time limit ...
Page 16
... U switch input minimum capacitance having a maxi- CC current mum of 10m to 20m of ESR. The LTC1929 2-phase IN architecture typically halves this input capacitance re- quirement over competing solutions. Other losses includ- ing Schottky conduction losses during dead-time and inductor core losses generally account for less than 2% total additional loss ...
Page 17
... Although the LT1929 has a maximum input voltage of 36V, most applications will be limited to 30V by the MOSFET BV . DSS 50A I RATING 12V LTC1929 TRANSIENT VOLTAGE SUPPRESSOR GENERAL INSTRUMENT 1.5KA24A Figure 8. Automotive Application Protection LTC1929 1929 F08 17 ...
Page 18
... LTC1929 U U APPLICATIO S I FOR ATIO Design Example (Using Two Phases design example, assume (nominal (max 1.8V 20A and f = 310kHz, OUT MAX A R and R can immediately be calculated: SENSE1 SENSE2 50mV/10A = 0.005 SENSE1 SENSE2 the actual value of the ripple current for ...
Page 19
... Keep the switching nodes, SW1 (SW2), away from RMS sensitive small-signal nodes. Ideally the switch nodes should be placed at the furthest point from the LTC1929. 7) Use a low impedance source such as a logic gate to drive the PLLIN pin and keep the lead as short as possible. ...
Page 20
... LTC1929 U U APPLICATIO S I FOR ATIO The diagram in Figure 9 illustrates all branch currents in a 2-phase switching regulator. It becomes very clear after studying the current waveforms why it is critical to keep the high-switching-current paths to a small physical size. High electric and magnetic fields will radiate from these “ ...
Page 21
... Figure 9. Instantaneous Current Path Flow in a Multiple Phase Switching Regulator CIN I COUT SW1 R SENSE1 D1 SW2 L2 R SENSE2 D2 SINGLE PHASE SW1 V SW2 CIN I COUT Figure 10. Single and 2-Phase Current Waveforms LTC1929 V OUT C OUT + DUAL PHASE RIPPLE 1929 F10 R L 1929 F09 21 ...
Page 22
... LTC1929 U TYPICAL APPLICATIO S 22 ...
Page 23
... BSC 0.010 – 0.015 (0.25 – 0.38) LTC1929 40 0.397 – 0.407 0.301 – 0.311 (7.65 – 7.90 0.068 – 0.078 (1.73 – 1.99) 0.002 – 0.008 (0.05 – 0.21) G28 SSOP 0694 ...
Page 24
... Adaptive Power and Burst Mode are trademarks of Linear Technology Corporation. Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear-tech.com TG1 0. – SW1 25 BOOST1 LTC1929 BG1 22 EXTV F,25V INTV CC 4 PGND 6.3V 19 BG2 18 – BOOST2 ...