LTC3718 Linear Technology, LTC3718 Datasheet
LTC3718
Available stocks
Related parts for LTC3718
LTC3718 Summary of contents
Page 1
... Si7440DP B340A IN2 4 4 VCC1 MBR0520 10 F L2: PANASONIC ELJPC4R7MF 3718 TA01 LTC3718 Low Input Voltage DC/DC Controller for U and V . The LTC3718 uses IN OUT ® compensation allows the is a SENSE Efficiency vs Load Current 100 1.25V OUT ...
Page 2
... RNG FB1 REF 50mV RNG FB1 REF V = INTV , 50mV RNG CC FB1 REF RUN/SS Pin Rising U W ORDER PART TOP VIEW NUMBER 1 BOOST 24 LTC3718EG SW1 + 4 21 SENSE – SENSE 6 19 PGND1 INTV IN1 ...
Page 3
... Falling FB1 V = Returning FB1 I = 5mA PGOOD ) V =0V SHDN 0 C < T < 1.5V < V < 10V IN2 0 C < T < (Note 300mA SHDN SHDN LTC3718 MIN TYP MAX UNITS 3.5 4.2 V – 0.5 –1.2 – 0.8 1 3.4 3.9 V 3.5 4 ...
Page 4
... TEMPERATURE ( C) 3718 G04 4 Note 3: The LTC3718 is tested in a feedback loop that adjusts V achieve a specified error amplifier output voltage (I and power Note 4: The LTC3718 is guaranteed to meet performance specifications A from Specifications over the – operating temperature range are assured by design, characterization and correlation with statistical process controls ...
Page 5
... G07 V OUT 1V/DIV 2A/DIV 3718 G10.eps On-Time vs Temperature 300 ION 250 200 150 100 50 0 –50 – TEMPERATURE ( C) LTC3718 Load Regulation 2. 1.25V OUT FIGURE 1 CIRCUIT LOAD CURRENT (A) 3718 G08 Start-Up Response I ...
Page 6
... LTC3718 W U TYPICAL PERFOR A CE CHARACTERISTICS www.DataSheet4U.com INTV Load Regulation CC 0 –0.1 –0.2 –0.3 –0.4 –0 INTV LOAD CURRENT (mA) CC 3718 G14 Undervoltage Lockout Threshold vs Temperature 4.0 3.5 3.0 2.5 2.0 –50 – 100 125 TEMPERATURE (C) 3718 G17 Maximum Current Sense Threshold ...
Page 7
... Reference voltage for output voltage, power good thresh- old, and short-circuit shutdown threshold. The output voltage is set to V /2. REF SHDN (Pin 10): Shutdown, Active Low. Tie more to enable boost converter portion of the LTC3718. Ground to shut down. V (Pin 12): Boost Converter Feedback. The V FB2 connected to INTV ...
Page 8
... LTC3718 CTIO AL DIAGRA S www.DataSheet4U.com 0.7V 2.4V V VON t = (10pF ION 20k + I CMP – 1.4V V RNG 4 0.7V 5 240k Q2 I THB – R2 80k V REF 9 R1 40k V 15 IN2 R5 40k V OUT2 R7 (EXTERNAL) V FB2 Q1 FB2 12 R8 (EXTERNAL) 11 SGND2 SWITCH ...
Page 9
... U OPERATIO www.DataSheet4U.com Main Control Loop The LTC3718 is a current mode controller for DC/DC step-down converters designed to operate from low input voltages. It incorporates a boost converter with a buck regulator. Buck Regulator Operation In normal operation, the top MOSFET is turned on for a fixed interval determined by a one-shot timer OST. When ...
Page 10
... Connecting the SENSE and SENSE The LTC3718 can be used with or without a sense resistor. When using a sense resistor placed between the source of the bottom MOSFET M2 and ground. Connect ...
Page 11
... MOSFET switching losses but requires larger inductance and/or capacitance in order to maintain low output ripple voltage. The operating frequency of LTC3718 applications is deter- mined implicitly by the one-shot timer that controls the on-time t of the top MOSFET switch. The on-time is set ...
Page 12
... The selection of C required to minimize voltage ripple and load step R VON1 VON VON2 0.01 F 10k 10k LTC3718 2N5087 C C 3718 F03 (3b) Selection OUT is required to filter the square IN V ...
Page 13
... Consult the MOSFET manufacturer for further guidelines Minimum Off-time and Dropout Operation The minimum off-time t time that the LTC3718 is capable of turning on the bottom from INTV B CC MOSFET, tripping the current comparator and turning the MOSFET back off. This time is generally about 250ns. The ...
Page 14
... MOSFET gate. Soft-Start and Latchoff with the RUN/SS Pin The RUN/SS pin provides a means to shut down the LTC3718 as well as a timer for soft-start and overcurrent latchoff. Pulling the RUN/SS pin below 0.8V puts the LTC3718 into a low quiescent current shutdown pin ...
Page 15
... INTV Supply CC The 5V supply that powers the drivers and internal cir- cuitry within the LTC3718 can be supplied by either an internal P-channel low dropout regulator if V than 5V or the internal boost regulator if V The INTV pin can supply up to 50mA RMS and must be CC bypassed to ground with a minimum of 4 ...
Page 16
... LTC3718 U U APPLICATIO S I FOR ATIO www.DataSheet4U.com losses. These arise from the resistances of the MOSFETs, inductor and PC board traces and cause the efficiency to drop at high output currents. In continuous mode the average output current flows through L, but is chopped between the top and bottom MOSFETs. If the two ...
Page 17
... V V REF IN1 10 15 SHDN V IN2 11 14 SGND2 PGND2 SW2 FB2 VCC1 R R 10k 37. 1000pF LTC3718 = I (ESR) L(MAX) = (2.6A) (0.005 ) = 13mV = I (ESR) = (6A) (0.005 ) = 30mV LOAD MHz ) V IN 2.5V C IN1 C IN2 22 F 330 F ...
Page 18
... IN OUT compact area. It may help to have some components on the bottom side of the board. • Place LTC3718 chip with Pins facing the power components. Keep the components connected to Pins close to LTC3718 (noise sensitive components). • Use an immediate via to connect the components to ground plane including SGND and PGND of LTC3718 ...
Page 19
... BSC (.009 – .015) * DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE MILLIMETERS (INCHES) ** DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE LTC3718 V IN 2.5V C IN1 22 F X5R C **** IN2 2 ...
Page 20
... F B X7R PGOOD SW1 SENSE RNG 10k – I SENSE TH C2 100pF 6 19 SGND1 PGND1 R ON 237k LTC3718 INTV FB1 REF F 499k 0 REF IN1 C VCC2 4 SHDN V IN2 X5R 11 ...