LT1765 Linear Technology Corporation, LT1765 Datasheet
LT1765
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LT1765 Summary of contents
Page 1
... LTC and LT are registered trademarks of Linear Technology Corporation. * Patent Pending CMDSH-3 0.18µF 1.5µH OUTPUT 3. 2. 4.7µF UPS120 2.2nF CERAMIC 1765 TA01 LT1765-3.3/LT1765-5 U Efficiency vs Load Current 10V OUT 1.0 0 0.5 1.5 2.0 SWITCH CURRENT (A) 1765 • ...
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... JA EXPOSED PAD (PIN 17) SOLDERED TO LARGE COPPER PLANE CONDITIONS 3.3V < V < 25V (Note 0V 25V SHDN < V < 25V, 0.4V < V < 0.9V LT1765 (Adj (Note 3) LT1765-1.8 LT1765-2.5 LT1765-3.3 LT1765-5 ORDER PART NUMBER TOP VIEW 16 GND LT1765EFE 15 NC LT1765EFE-1.8 14 SYNC LT1765EFE-2.5 ...
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... Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1765E is guaranteed to meet performance specifications from 0°C to 125°C. Specifications over the – 40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls ...
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... LT1765/LT1765-1.8/LT1765-2.5/ LT1765-3.3/LT1765 TYPICAL PERFOR A CE CHARACTERISTICS FB vs Temperature (Adj) 1.220 1.215 1.210 1.205 1.200 1.195 1.190 1.185 1.180 0 50 –50 – 100 TEMPERATURE (°C) 1765 G01 SHDN Threshold vs Temperature 1.40 1.38 1.36 1.34 1.32 1.30 –50 – TEMPERATURE (°C) 4 Switch On Voltage Drop ...
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... G10 Maximum Load Current 2.5V OUT 3 4.7µH 2 2.2µH 2 1.5µH 2.4 2 INPUT VOLTAGE (V) 1765 G12 LT1765-3.3/LT1765-5 Input Supply Current 1200 1000 UNDERVOLTAGE 800 LOCKOUT 600 400 200 0 1 INPUT VOLTAGE (V) Maximum Load Current OUT 3.0 2 4.7µH 2 ...
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... LT1765/LT1765-1.8/LT1765-2.5/ LT1765-3.3/LT1765 CTIO S FB: The feedback pin is used to set output voltage using an external voltage divider (adjustable version) that gen- erates 1.2V at the pin when connected to the desired output voltage. The fixed voltage 1.8V, 2.5V, 3.3V and 5V versions have the divider network included internally and the FB pin is connected directly to the output ...
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... W BLOCK DIAGRA The LT1765 is a constant frequency, current mode buck converter. This means that there is an internal clock and two feedback loops that control the duty cycle of the power switch. In addition to the normal error amplifier, there is a current sense amplifier that monitors switch current on a cycle-by-cycle basis ...
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... If operation is required close to the mini- mum input required by the output or the LT1765, a larger value may be required. This is to prevent excessive ripple causing dips below the minimum operating voltage result- ing in erratic operation. If tantalum capacitors are used, values in the 22µ ...
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... V = Maximum input voltage Switching frequency, 1.25MHz If an inductor with a peak current lower than the maximum switch current of the LT1765 is chosen a soft-start circuit in Figure 10 should be used. Also, short-circuit conditions should not be allowed because the inductor may saturate ) minus one half P resulting in excessive power dissipation. ...
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... SHUTDOWN AND UNDERVOLTAGE LOCKOUT Figure 4 shows how to add undervoltage lockout (UVLO) to the LT1765. Typically, UVLO is used in situations where the input supply is current limited , or has a relatively high source resistance. A switching regulator draws constant power from the source, so source current increases as source voltage drops ...
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... At switch off, this parasitic inductance produces a flyback spike across the LT1765 switch. When operating at higher currents and input voltages, with poor layout, this spike can generate voltages across the LT1765 that may exceed its absolute V IN LT1765-3.3/LT1765-5 LT1765 L1 V ...
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... Board layout also has a significant effect on thermal resistance. The exposed pad or GND pin is a continuous copper plate that runs under the LT1765 die. This is the best thermal path for heat out of the package as can be seen by the low θ ...
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... The LT1765 uses current mode control. This alleviates many of the phase shift problems associated with the ) inductor. The basic regulator loop is shown in Figure 7, with both tantalum and ceramic capacitor equivalent cir- cuits. The LT1765 can be considered as two g error amplifier and the power stage. LT1765 CURRENT MODE POWER STAGE ...
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... In systems with a primary and backup supply, for ex- ample, a battery powered device with a wall adapter input, the output of the LT1765 can be held up by the backup supply with its input disconnected. In this condition, the SW pin will source current into the V pole must C is held at ground, only the shutdown current of 6µ ...
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... L1B and C4. At switch off, the energy stored in both L1B and C4 supply the –5V rail. This reduces the current in L1A and changes L1B current waveform from square to triangular. For details on this circuit, including maximum output currents, see Design Note 100. LT1765-3.3/LT1765-5 CMDSH-3 5µH 3.3V, 2A ALTERNATE SUPPLY 4.7µ ...
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... SINGLE CORE WITH TWO WINDINGS COILTRONICS CTX5-1A † IF LOAD CAN GO TO ZERO, AN OPTIONAL PRELOAD MAY BE USED TO IMPROVE LOAD REGULATION D1, D3: B220A CMDSH-3 C2 0.18µF BOOST LT1765-5 SHDN FB SYNC GND 2.2µF 3.3k 25V CERAMIC 4700pF C4 4.7µ ...
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... SYNC V C UPS120 C3 C 22µF C 4700pF 16V X5R C F CERAMIC R 100pF C 6.8k L1: CDRH5D28-2R5 BOLD LINES INDICATE HIGH CURRENT PATHS Figure 13. Negative Boost Converter LT1765-3.3/LT1765 3µH C1 10µF 6.3V X5R CERAMIC D3 B220A OUTPUT – 1765 F12 D2 CMDSH-3 INPUT –5V L1 2.5µH C1 2.2µ ...
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... LT1765/LT1765-1.8/LT1765-2.5/ LT1765-3.3/LT1765-5 PACKAGE DESCRIPTIO 6.60 ±0.10 4.50 ±0.10 SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BB 3 ...
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... TYP .016 – .050 .014 – .019 (0.406 – 1.270) (0.355 – 0.483) TYP INCHES (MILLIMETERS) LT1765-3.3/LT1765-5 .189 – .197 (4.801 – 5.004) NOTE .150 – .157 (3.810 – 3.988) ...
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