Document
LTC3417 Dual Synchronous 1.4A/800mA 4MHz Step-Down DC/DC Regulator
FEATURES
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DESCRIPTIO
High Efficiency: Up to 95% 1.4A/800mA Guaranteed Minimum Output Current No Schottky Diodes Required Programmable Frequency Operation: 1.5MHz or Adjustable From 0.6MHz to 4MHz Low RDS(ON) Internal Switches Short-Circuit Protected VIN: 2.25V to 5.5V Current Mode Operation for Excellent Line and Load Transient Response 125µA Quiescent Current in Sleep Mode Ultralow Shutdown Current: IQ < 1µA Low Dropout Operation: 100% Duty Cycle Power Good Output Phase Pin Selects 2nd Channel Phase Relationship with Respect to 1st Channel Internal Soft-Start with Individual Run Pin Control Available in Small Thermally Enhanced (5mm × 3mm) DFN and 20-Lead TSSOP Packages
The LTC®3417 is a dual constant frequency, synchronous step-down DC/DC converter. Intended for medium power applications, it operates from a 2.25V to 5.5V input voltage range and has a constant programmable switching frequency, allowing the use of tiny, low cost capacitors and inductors 2mm or less in height. Each output voltage is adjustable from 0.8V to 5V. Internal synchronous low RDS(ON) power switches provide high efficiency without the need for external Schottky diodes. A user selectable mode input allows the user to trade off ripple voltage for light load efficiency. Burst Mode® operation provides high efficiency at light loads, while Pulse Skip mode provides low ripple noise at light loads. A phase mode pin allows the second channel to operate in-phase or 180° out-of-phase with respect to channel 1. Out-ofphase operation produces lower RMS current on VIN and thus lower RMS derating on the input capacitor. To further maximize battery life, the P-channel MOSFETs are turned on continuously in dropout (100% duty cycle) and both channels draw a total quiescent current of only 100µA. In shutdown, the device draws <1µA.
, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131, 6144194
U APPLICATIO S
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PDAs/Palmtop PCs Digital Cameras Cellular Phones PC Cards Wireless and DSL Modems
TYPICAL APPLICATIO
VIN 2.5V TO 5.5V 10µF 1.5µH 22pF VIN 511k VFB1 22µF 412k ITH1 5.9k 2200pF FREQ SW1 RUN1 VOUT1 1.8V 1.4A
OUT2 Efficiency (Burst Mode Operation)
100 REFER TO FIGURE 4 10 95
VIN
EFFICIENCY (%)
2.2µH SW2 RUN2 LTC3417 VFB2 VIN 866k 412k ITH2 GND 2.87k 6800pF
3417 TA01
22pF
VOUT2 2.5V 800mA
90 0.1 85 0.01 80 75 70 0.001 POWER LOSS VIN = 3.6V VOUT = 2.5V FREQ = 1MHz 0.01 0.1 LOAD CURRENT (A) 1
3417 TA01a
10µF
U
1 EFFICIENCY
U
POWER LOSS (W)
0.001
0.0001
3417f
1
LTC3417
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ABSOLUTE
AXI U
RATI GS (Note 1)
Operating Ambient Temperature Range (Note 2) ..........................................