lt3688fe Linear Technology Corporation, lt3688fe Datasheet
lt3688fe
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lt3688fe Summary of contents
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... Industrial Power Supplies n High-Reliability μProcessor Systems L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 5V and 3.3V Regulator with Power-On Reset and Watchdog Timers ...
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... EXPOSED PAD (PIN 25) IS GND, MUST BE ELECTRICALLY CONNECTED TO PCB PART MARKING* PACKAGE DESCRIPTION LT3688FE 24-Lead Plastic TSSOP LT3688FE 24-Lead Plastic TSSOP LT3688FE 24-Lead Plastic TSSOP 24-Lead (4mm × 4mm) Plastic QFN 3688 24-Lead (4mm × 4mm) Plastic QFN 3688 http://www.linear.com/leadfree/ http://www ...
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ELECTRICAL CHARACTERISTICS junction temperature range, otherwise specifi cations are at T SYMBOL PARAMETER V Undervoltage Lockout IN Quiescent Current from V IN Quiescent Current from BIAS FB Voltage FB Pin Bias Current FB Voltage Line Regulation Switching Frequency Minimum Off-Time ...
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LT3688 ELECTRICAL CHARACTERISTICS junction temperature range, otherwise specifi cations are at T SYMBOL PARAMETER RST Pull-Up Current (Note 6) WDO Pull-Up Current (Note 6) CONFIG Low Level Input Voltage CONFIG High Level Input Voltage CONFIG Pin Voltage When Open Maximum ...
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TYPICAL PERFORMANCE CHARACTERISTICS No-Load Supply Current (Input) 160 OUT1 V = 3.3V OUT2 140 120 100 (V) IN 3688 G04 Maximum Load Current (3.3V ...
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LT3688 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency 2.5 2.0 1.5 1.0 0 100 150 R (kΩ) T 3688 G13 EN/UVLO Pin Current ...
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TYPICAL PERFORMANCE CHARACTERISTICS Power-On Reset Threshold vs Temperature 0.730 0.725 0.720 0.715 0.710 –50 – 100 125 150 TEMPERATURE (°C) 3688 G23 Reset Timeout Period (t vs Temperature 4700pF POR 20 15 ...
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LT3688 PIN FUNCTIONS (QFN/TSSOP) RT (Pin 1/Pin 22): The RT pin is used to set the internal oscillator frequency. Tie a resistor from RT to GND to set the switching frequency. SYNC (Pin 2/Pin 23): Drive the SYNC pin with ...
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PIN FUNCTIONS (QFN/TSSOP (Pins 23, 21/Pins 20, 18): Place a capacitor POR1 POR2 between this pin and ground to set the power-on-reset timeout period. C (Pin 24/Pin 21): Place a capacitor between this pin WDT and ground ...
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LT3688 OPERATION The LT3688 is a constant-frequency, current mode step- down regulator with two reset timers and a watchdog timer that perform microprocessor supervisory functions. Operation can be best understood by referring to the Block Diagram. Keeping the EN/UVLO pin ...
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TIMING DIAGRAMS t < t WDL WDI WDO Power-On Reset Timing V OUT RST RST Watchdog Timing t t WDTO WDU LT3688 t WDTO 3686 TD01 3688f 11 ...
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LT3688 TIMING DIAGRAMS V OUT1 RST1 V OUT2 RST2 WDO WDI V OUT1 V OUT2 RST1 RST2 WDO WDI V OUT1 RST1 V OUT2 RST2 WDO WDI RST1 RST2 t WDU STARTUP TIMING ...
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APPLICATIONS INFORMATION Setting the Output Voltage The output voltage is programmed with a resistor divider between the output and the FB pin. Choose the 1% resistors according to: ⎛ ⎞ V OUT ⎝ ⎜ ⎠ ⎟ R1= R2 – 1 ...
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LT3688 APPLICATIONS INFORMATION The LT3688 will regulate the output voltage at input volt- ages greater than V . For example, an application IN(PS) with an output voltage of 3.3V and switching frequency of 2.1MHz has 12.7V, as ...
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APPLICATIONS INFORMATION Table 2. Inductor Vendors VENDOR PART SERIES TYPE Murata LQH55D Open TDK SLF7045 Shielded SLF10145 Shielded Toko DC62CB Shielded D63CB Shielded D75C Shielded D75F Open Sumida CR54 Open CDRH74 Shielded CDRH6D38 Shielded CR75 Open The optimum inductor for ...
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LT3688 APPLICATIONS INFORMATION additional bulk capacitance may be necessary. This can be provided with a lower performance electrolytic capacitor. Step-down regulators draw current from the input supply in pulses with very fast rise and fall times. The input capacitor is ...
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APPLICATIONS INFORMATION Table 4. Capacitor Vendors V R Part Number (V) On Semiconductor MBR0520L 20 MBR0540 40 MBRM120E 20 MBRM140 40 Diodes Inc. B0530W 30 B120 20 B130 30 B140HB 40 DFLS140 40 Ceramic Capacitors Ceramic capacitors are small, robust ...
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LT3688 APPLICATIONS INFORMATION Low Ripple Burst Mode Operation To enhance effi ciency at light loads, the LT3688 operates in low ripple Burst Mode operation that keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. ...
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APPLICATIONS INFORMATION age source. However, the full benefi the BIAS pin is not realized unless least 3V. Ensure that the maximum voltage ratings of the BST and BIAS pins are not exceeded. The minimum operating ...
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LT3688 APPLICATIONS INFORMATION will charge these pins to ~2V. The RUN/SS pins provide a soft-start function that limits peak input current to the circuit during start-up. This helps to avoid drawing more current than the input source can supply or ...
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APPLICATIONS INFORMATION Output Voltage Monitoring The LT3688 provides power supply monitoring for microprocessor-based systems. The features include power-on reset (POR) and watchdog timing. A precise internal voltage reference and glitch immune precision POR comparator circuits monitor the LT3688 output voltages. ...
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LT3688 APPLICATIONS INFORMATION If WDO is low and RST goes low, then WDO will go high. The WDE pin allows the user to turn on and off the watchdog function. Leaving this pin open is okay and will automatically enable ...
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APPLICATIONS INFORMATION ⎛ ⎞ • 200 ⎝ ⎜ ⎠ ⎟ POR RST ms This equation is accurate for reset timeout periods of 1ms, or greater. To program faster timeout periods, see the Reset Timeout Period vs ...
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LT3688 APPLICATIONS INFORMATION D4 BIAS V V BOOST IN IN LTC3688 SW DA EN/UVLO FB GND Figure 13. Diode D4 Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output; It Also Protects the Circuit from a ...
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TYPICAL APPLICATIONS 36V ON OFF L1 V 18μH OUT1 5V 800mA C6 R1 10pF 523k C4 R2 22μF 100k μP RESET C1-C5: X5R OR X7R D1, D2: DIODES INC. B140 5V and 3.3V Regulator with Power-On ...
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LT3688 TYPICAL APPLICATIONS 36V ON OFF L1 8.2μH V OUT1 5V 800mA C6 R1 10μF 523k C4 R2 10μF 100k C1-C5: X5R OR X7R D1, D2: DIODES INC. B140 2MHz Switching Frequency, 5V and 3.3V Regulator ...
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... RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...
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... High Effi ciency Step-Down DC/DC OUT Converter with only 2.5uA of Quiescent Current LT3990 60V, 350mA (I ), 2MHz, High Effi ciency Step-Down DC/DC OUT Converter with only 2.5uA of Quiescent Current Linear Technology Corporation 28 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● C1 4.7μF ...