LTC1625 Linear Technology Corporation, LTC1625 Datasheet
LTC1625
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LTC1625 Summary of contents
Page 1
... Q and an output overvoltage comparator. An external ca- pacitor attached to the RUN/SS pin provides soft start capability for supply sequencing. A wide supply range allows operation from 3.7V (3.9V for LTC1625I) to 36V at the input and 1.19V LTC and LT are registered trademarks of Linear Technology Corporation and Burst Mode are trademarks of Linear Technology Corporation. ...
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... Peak Driver Output Current < (TG, BG) ............ 2A INTV Output Current ........................................ 50mA CC Operating Ambient Temperature Range LTC1625C............................................... LTC1625I (Note 5) .............................. – Junction Temperature (Note 2) ............................. 125 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL CHARACTERISTICS SYMBOL ...
Page 3
... I = 20mA, V Ramping Positive CC EXTVCC Ramping Positive Note 3: The LTC1625 is tested in a feedback loop that adjusts V achieve a specified error amplifier output voltage (I Note 4: Typical in application circuit with EXTV and FCB = INTV OUT to the gate charge being delivered at the switching frequency. See ...
Page 4
... LTC1625 W U TYPICAL PERFOR A CE CHARACTERISTICS Efficiency vs Load Current 100 BURST MODE 90 OPERATION CONTINUOUS MODE 10V OUT EXTV = V CC OUT 50 0.001 0.01 0.1 1 LOAD CURRENT (A) 1625 G01 Load Regulation 0 FIGURE 1 CIRCUIT – 0.05 – 0.10 – 0.15 – 0.20 – 0. LOAD CURRENT (A) ...
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... TEMPERATURE ( C) Transient Response (Burst Mode Operation) V OUT 50mV/DIV 500 s/DIV V = 20V OUT I = 50mA TO 1A LOAD FIGURE 1 CIRCUIT LTC1625 Oscillator Frequency vs Temperature 300 250 SYNC = 1.5V 200 SYNC = 0V 150 100 50 0 110 135 – 40 – TEMPERATURE ( C) 1625 G11 Soft Start: ...
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... LTC1625 PIN FUNCTIONS EXTV (Pin 1): INTV Switch Input. When the EXTV CC CC voltage is above 4.7V, the switch closes and supplies INTV power from EXTV . Do not exceed 7V at this pin SYNC (Pin 2): Synchronization Input for Internal Oscilla- tor. The oscillator will nominally run at 150kHz when open, 225kHz when tied above 1 ...
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... OSC 0.6V REV + S Q TOP – + 0.5V SLEEP B – SWITCH LOGIC/ DROPOUT COUNTER SHUTDOWN OVERVOLTAGE + – FCNT + 1.19V F – FCB EXTV 4 1 OSENSE LTC1625 – – – BOOST INTV VCC BG 10 PGND 9 1 ...
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... This forces continuous operation and can assist second- ary winding regulation. INTV /EXTV CC Power for the top and bottom MOSFET drivers and most . When this of the internal circuitry of the LTC1625 is derived from the SS INTV pin. When the EXTV CC 5.2V low dropout regulator supplies the INTV from V ...
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... U U APPLICATIONS INFORMATION The basic LTC1625 application circuit is shown in Figure 1. External component selection is primarily determined by the maximum load current and begins with the selection of the sense resistance and power MOSFETs. Because the LTC1625 uses MOSFET V sensing, the sense resistance DS is the R of the MOSFETs ...
Page 10
... Burst Mode Operation Considerations The choice of R the load current at which the LTC1625 enters Burst Mode operation. When bursting, the controller clamps the peak inductor current to approximately: I BURST PEAK 7V 1 ...
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... Under short-circuit conditions with very low duty cycle, the LTC1625 will begin skipping cycles in order to limit the short-circuit current. In this situation the bottom MOSFET R rather than the top MOSFET controlling the inductor current peak ...
Page 12
... CC An internal P-channel low dropout regulator produces the 5.2V supply which powers the drivers and internal cir where I cuitry within the LTC1625. The INTV OUT RMS to 50mA and must be bypassed to ground with a minimum of 4.7 F tantalum or low ESR electrolytic capacitance. Good bypassing is necessary to supply the high transient currents required by the MOSFET gate drivers ...
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... U U APPLICATIONS INFORMATION High input voltage applications in which large MOSFETs are being driven at high frequencies may cause the LTC1625 to exceed its maximum junction temperature rating. Most of the supply current drives the MOSFET gates unless an external EXTV source is used. The junction temperature ...
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... B Run/Soft Start Function The RUN/SS pin is a dual purpose pin that provides a soft start function and a means to shut down the LTC1625. Soft start reduces surge currents from V creasing the controller’s current limit I can also be used for power supply sequencing. ...
Page 15
... DS(ON) Minimum On-Time Considerations Minimum on-time t that the LTC1625 is capable of turning the top MOSFET on and off again determined by internal timing delays and the amount of gate charge required to turn on the top MOSFET. Low duty cycle applications may approach this minimum on-time limit and care should be taken to ensure ...
Page 16
... But before you connect, be advised: you are plug- )(C )(f) O(MAX) RSS ging into the supply from hell. The main battery line in an supply current. The V current is the connected to 5V, the LTC1625 will CC and the remaining 520 A will current results in a small ...
Page 17
... Note that the transient suppressor should not conduct during double-battery operation, but must still clamp the input voltage below breakdown of the converter. Although the LTC1625 has a maximum input voltage of 36V, most applications will be limited to 30V by the MOSFET V . ...
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... OSENSE 9 PGND PROG Figure 9. 3.3V/2A Fixed Output at 225kHz 3) The LTC1625 signal ground pin must return to the (–) plate of C ground at the source of the bottom MOSFET 4) Keep the switch node SW away from sensitive small- signal nodes. Ideally the switch node should be placed on the opposite side of the power MOSFETs from the LTC1625 ...
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... FCB BOOST VCC SGND INTV OSENSE PGND PROG Figure 10. LTC1625 Layout Diagram 5V/1.2A Fixed Output at 225kHz 16 EXTV SYNC TK 14 RUN/SS SW LTC1625 13 FCB BOOST TH C VCC 4 CMDSH-3 0 SGND ...
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... V OSENSE 8 V OPEN PROG C : AVX TPSE226M020R0300 AVX TPSD107M010R0065 OUT L1: SUMIDA CDRH125-150MC 1 EXTV EXT 0.1 F SYNC CLK 3 RUN/ LTC1625 4 R 2.2nF C OPEN FCB 10k 220pF 6 SGND 7 V OSENSE 8 V PROG C : SANYO 30SC10M SANYO 6SA150M OUT 20 2 ...
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... Adjustable Output BOOST C VCC 4 CMDSH-3 0 INTV PGND LTC1625 20V 30V 2 • 0.1 F 1:2. 100k SM4003TR* + 95.3k C SEC 1% 3 35V 11k M3 1% NDT410EL R1 4 ...
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... SANYO 20S68M SANYO 16SA100M OUT L1: 7A Kool-M 77120-A7, 15 TURNS, 17 GAUGE 22 – 5V/4.5A Positive to Negative Converter EXTV SYNC RUN/ LTC1625 4 13 0.22 F FCB BOOST CMDSH SGND INTV OSENSE + C VCC 4 ...
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... LTC1625 0.189 – 0.196* (4.801 – 4.978) 0.009 (0.229 REF 0.150 – 0.157** (3.810 – 3.988 ...
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... LTC1625 U TYPICAL APPLICATION 1 EXTV 0.1 F SYNC 3 RUN/ LTC1625 4 R 1nF C OPEN FCB 10k 100pF 6 SGND 7 V OSENSE 8 V PROG C : AVX TPSD156M035R0300 AVX TPSD107M010R0100 OUT L1: SUMIDA CDRH125-270MC RELATED PARTS PART NUMBER DESCRIPTION LTC1435A High Efficiency Synchronous Step-Down Controller ...