LTC3458 Linear Technology, LTC3458 Datasheet
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LTC3458
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LTC3458 Summary of contents
Page 1
... Burst Mode current threshold, peak current limit, and soft- start are externally programmable. Other features include <1µA shutdown current, antiringing control, and thermal limit. The LTC3458 is available in a low profile (0.75mm), 3mm × 4mm 12-pin DFN package. , LTC and LT are registered trademarks of Linear Technology Corporation. ...
Page 2
... IN V Current at 0V OUT V Current Switching OUT OUT R = 124k ILIM V = 3.3V 1MHz IN OSC R = 200k T www.DataSheet4U.com ORDER PART NUMBER 12 V OUT 11 BURST LTC3458EDE GND 8 COMP DE PART MARKING 7 FB 3458 MIN TYP MAX UNITS 1.4 1.5 1.4 1.7 ● 2.0 7.5 1.21 1.23 1.25 1.20 1.25 – 0.5 ...
Page 3
... ILIM Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 3: The LTC3458 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls ...
Page 4
... LTC3458 W U TYPICAL PERFOR A CE CHARACTERISTICS Frequency Accuracy 1. 200k 1.03 1.01 0.99 0.97 0.95 –45 –30 – TEMPERATURE (°C) 3458 G07 Maximum Load Current 1200 1.8 to 5.5V at 700kHz 124k OUT ILIM 1000 800 3.3V OUT 600 7.5V OUT 400 200 0 5.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.5 V (V) IN 3458 G10 25°C unless otherwise specified) ...
Page 5
... OUT L = 10µ 22µF OUT C = 22pF FF 200mA/DIV 2V/DIV 0mA LIMIT 100mV/DIV 5V/DIV 200mA/DIV 0mA 2V/DIV 2V/DIV 200mV/DIV 200mA/DIV 0mA LTC3458 www.DataSheet4U.com Fixed Frequency (FF) Continuous Current 3.3V 200ns/DIV OUT L = 10µH Burst Mode Operation V OUT 3.3V 50µs/DIV ...
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... LTC3458 W U TYPICAL PERFOR A CE CHARACTERISTICS Sync Operation at 1.33MHz SW 5V/DIV SYNC 2V/DIV I L 200mA/DIV 500ns/DIV OUT R = 200k OSC Burst Mode Operation 10mA to 50mA Load Step V OUT 200mV/DIV BURST 500mV/DIV LOAD I L 200mA/DIV V = 3.3V 200µs/DIV OUT L = 10µ 22µ ...
Page 7
... Output of the Synchronous Rectifier and OUT Internal Gate Drive Source for the Power Switches. ⎛ ⎞ OUT ⎜ ⎟ ⎝ ⎠ Exposed Pad (PGND) (Pin 13): Must be soldered to PCB ground, for electrical contact and optimum thermal performance. LTC3458 is in amps. 3458f 7 ...
Page 8
... High efficiency is achieved at light loads when Burst Mode operation is entered, where the IC’s quiescent current is a low 15µA typical The LTC3458 is designed to provide custom IN performance in a variety of applications with program- mable feedback, current limit, oscillator frequency, soft- start, and Burst Mode threshold ...
Page 9
... Output Disconnect and Inrush Limiting. The LTC3458 is designed to allow true output disconnect by eliminating body diode conduction of the internal P-channel MOSFET rectifier. This allows V shutdown, drawing no current from the input source ...
Page 10
... LTC3458 U U APPLICATIO S I FOR ATIO transition occurs using a single resistor. During Burst Mode operation, the oscillator is shut down, since the on time is determined by the time it takes the inductor current to reach a fixed peak current, and the off time is deter- mined by the time it takes for the inductor current to return to zero ...
Page 11
... U APPLICATIO S I FOR ATIO COMPONENT SELECTION Inductor Selection The high frequency operation of the LTC3458 allows for the use of small surface mount inductors. Since the internal slope compensation circuit relies on the inductor’s current slope and frequency, Table 1 should be used to select an inductor value for a given frequency of operation (± ...
Page 12
... The trade off is in efficiency, since the switching losses due to gate charge increase proportional with frequency. Thermal Considerations For the LTC3458 to deliver its full output power imperative that a good thermal path be provided to dissi- pate the heat generated within the package. This can be accomplished by taking advantage of the large thermal pad on the underside of the IC ...
Page 13
... ZERO 1 2 • R • π ≈ POLE 2 2 • R • π LTC3458 1.25V OUT + R1 ERROR FB AMP – COMP 8 CC1 CC2 R Z 3458 F01 Figure 2 13 3458f ...
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... ALKALINE LTC3458 2.2µF 1.8V to 3.3V GND/PGND SHDN ON OFF SYNC R T BURST I LIM 243k 124k Lithium-Ion Battery to 7V COEV 10µH DQ7545 V IN Li-Ion 2.2µF LTC3458 2.5V to 4.2V GND/PGND SHDN ON OFF SYNC R T BURST I LIM 200k 124k OUT V 5V OUT 450mA 10pF 1M FB COMP 324k 0.01µ ...
Page 15
... Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695) 0.58 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 3.30 ±0.05 (2 SIDES) 4.00 ±0.10 (2 SIDES 0.20 TYP 3.00 ±0.10 1.70 ± 0.10 (2 SIDES) (2 SIDES) 0.75 ±0.05 0.00 – 0.05 LTC3458 www.DataSheet4U.com R = 0.115 0.38 ± 0.10 TYP 7 12 PIN 1 NOTCH (UE12/DE12) DFN 0802 6 1 0.25 ± 0.05 0.50 BSC 3.30 ±0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD 15 ...
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... LTC3458 U TYPICAL APPLICATIO Dual Lumiled Application with BURST Pin Current Regulation Li-Ion C IN LTC3458 2.7V to 4.2V 2.2µF V GND/PGND OUT FB SHDN ON OFF COMP SYNC BURST I LIM 243k 124k TAIYO YUDEN JMK107BJ225MA R IN OUT D1, D2: LUXEON EMITTER LUMILED WHITE LXHLMW1D (2.9V AT 350mA) L1: Wurth 12µ ...