ltc3717-1 Linear Technology Corporation, ltc3717-1 Datasheet
ltc3717-1
Related parts for ltc3717-1
ltc3717-1 Summary of contents
Page 1
... Semiconductor, Hitachi, IDT, Micron Technology, Inc. and Samsung 2.5V TO 5.5V + 150 F 6.3V Si7840DP 2 B320A V OUT 1.25V 0. 10A 180 Si7840DP B320A 37171 F01a LTC3717-1 Step-Down Controller memory termination. The controller and OUT Efficiency vs Load Current 100 V = 1.25V OUT 2.5V ...
Page 2
... LTC3717 ABSOLUTE AXI U RATI GS (Note 1) Boosted Topside Driver Supply Voltage (BOOST) ............................................... 42V to – 0. SW, SENSE Voltage .................. 36V to – 0. EXTV , DRV , RUN/SS, PGOOD (BOOST – SW) Voltages ............................ 7V to – 0. Voltages .......(INTV ON REF RNG Voltages...................................... 2.7V to – 0. TG, BG, INTV ...
Page 3
... Specifications over the – operating temperature range are assured by design, characterization and and power A correlation with statistical process controls. Note 5: R limit guaranteed by design and/or correlation to static DS(ON) test LTC3717-1 MIN TYP MAX UNITS – 0.8 1.5 ...
Page 4
... LTC3717 TYPICAL PERFOR A CE CHARACTERISTICS Efficiency vs Load Current 100 1.25V OUT FIGURE 1 CIRCUIT 0 0.01 0 LOAD CURRENT (A) 37171 G01 Load-Step Transient V OUT 200mV/DIV I L 5A/DIV V = 2.5V 20 s/DIV 1.25V OUT LOAD = 500mA TO 10A STEP FIGURE 1 CIRCUIT ...
Page 5
... RNG 180 160 140 120 100 –50 –30 – 110 130 70 TEMPERATURE ( C) 37171 G16 LTC3717-1 RUN/SS Latchoff Thresholds vs Temperature 3 2 PULL-DOWN CURRENT 1 0 PULL-UP CURRENT –1 –2 –50 – 125 100 TEMPERATURE ( C) 37171 G11 Maximum Current Sense Threshold ...
Page 6
... LTC3717 CTIO S V (Pin 1): On-Time Voltage Input. Voltage trip point for ON the on-time comparator. Tying this pin to the output voltage makes the on-time proportional to V comparator input defaults to 0.7V when the pin is grounded, 2.4V when the pin is tied to INTV CC PGOOD (Pin 2): Power Good Output. Open-drain logic output that is pulled to ground when the output voltage is not within 10% of the regulation point ...
Page 7
... REF REG SWITCH I REV LOGIC – SHDN RUN SS SHDN – + 1.2 A 0.6V C RUN/ 0. LTC3717 BOOST SENSE OUT B INTV VCC DRV OUT BG 19 ...
Page 8
... LTC3717-1 U OPERATIO Main Control Loop The LTC3717 current mode controller for DC/DC step-down converters. In normal operation, the top MOSFET is turned on for a fixed interval determined by a one-shot timer OST. When the top MOSFET is turned off, the bottom MOSFET is turned on until the current com- ...
Page 9
... Connecting the SENSE and SENSE The LTC3717-1 can be used with or without a sense resistor. When using a sense resistor placed between W U the source of the bottom MOSFET M2 and ground. Con- ...
Page 10
... Low frequency operation improves efficiency by reducing MOSFET switching losses but requires larger inductance and/or capacitance in order to maintain low output ripple voltage. The operating frequency of LTC3717-1 applications is determined implicitly by the one-shot timer that controls the on-time t of the top MOSFET switch. The on-time is ...
Page 11
... Kool registered trademark of Magnetics, Inc. LTC3717-1 R VON1 VON VON2 0.01 F 10k 10k LTC3717 2N5087 C C 37171 F03 (3b) ® cores. A variety of inductors designed for high Selection OUT is required to filter the square ...
Page 12
... Consult the MOSFET manufacturer for further guidelines. Minimum Off-time and Dropout Operation ) B The minimum off-time t time that the LTC3717-1 is capable of turning on the bottom MOSFET, tripping the current comparator and from INTV B CC turning the MOSFET back off. This time is generally about ...
Page 13
... Soft-Start and Latchoff with the RUN/SS Pin The RUN/SS pin provides a means to shut down the pin. A REF LTC3717-1 as well as a timer for soft-start and overcur- can be used to OUT rent latchoff. Pulling the RUN/SS pin below 0.8V puts the LTC3717-1 into a low quiescent current shutdown (I < ...
Page 14
... MOSFET gate drivers. Applica- tions using large MOSFETs with a high input voltage and high frequency of operation may cause the LTC3717 used as a exceed its maximum junction temperature rating or RMS SS current rating. Most of the supply current drives the ...
Page 15
... APPLICATIO S I FOR ATIO what is limiting the efficiency and which change would produce the most improvement. Although all dissipative elements in the circuit produce losses, four main sources account for most of the losses in LTC3717-1 circuits losses. These arise from the resistances of the MOSFETs, inductor and PC board traces and cause the efficiency to drop at high output currents ...
Page 16
... C is chosen for an RMS current rating of about The output capacitors are chosen for a low ESR 0.1 F RUN/ 11k 39k 100k PGOOD LTC3717 RNG C1 R 470pF C 20k 100pF SGND C 0.01 F ...
Page 17
... IN OUT compact area. It may help to have some components on the bottom side of the board. • Place LTC3717-1 chip with Pins facing the power components. Keep the components connected to Pins close to LTC3717-1 (noise sensitive components). • Use an immediate via to connect the components to ground plane including SGND and PGND of LTC3717-1 ...
Page 18
... VCC INTV ON CC DRV EXTV REF CC High Voltage Half (V ) Power Supply CMDSH-3 RUN/SS BOOST C B 0.22 F PGOOD TG LTC3717 RNG + SENSE I PGND TH – SENSE SGND BG C VCC INTV DRV ...
Page 19
... U UH Package 32-Lead Plastic QFN (5mm 5mm) (Reference LTC DWG # 05-08-1693) 0.57 0.05 PACKAGE OUTLINE 0.23 0.05 0.50 BSC 0.75 0.05 0.00 – 0.05 3.45 0.10 (4-SIDES) 0.200 REF LTC3717-1 BOTTOM VIEW—EXPOSED PAD R = 0.115 0.40 0.10 TYP (UH) QFN 0102 0.23 0.05 0.50 BSC sn37171 37171fs 19 ...
Page 20
... Burst Mode is a registered trademark of Linear Technology Corporation. Linear Technology Corporation 20 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 Typical Application 1.25V 1.4MHz D B CMDSH-3 RUN/SS BOOST C B 0.22 F PGOOD TG LTC3717 RNG + SENSE I PGND TH – SENSE SGND BG C VCC ...