LT1976B LINER [Linear Technology], LT1976B Datasheet
LT1976B
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LT1976B Summary of contents
Page 1
... Burst Mode operation at low currents, utilizing the output to bias the internal circuitry, and by using a supply boost capacitor to fully saturate the power switch. The LT1976B does not shift into Burst Mode operation at low currents, eliminating low frequency out- put ripple at the expense of efficiency. Patented circuitry maintains peak switch current over the full duty cycle range ...
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... SYNC PGFB, FB ................................................ 6V SS Operating JunctionTemperature Range LT1976EFE/LT1976BEFE (Note 2) ... – 40°C to 125°C LT1976IFE/LT1976BIFE (Note 2) ..... – 40°C to 125°C LT1976HFE (Note 2) ........................ – 40°C to 140°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ELECTRICAL CHARACTERISTICS operating temperature range, otherwise specifications are at T FB/PGFB = 1 ...
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... SHDN = 0V, BOOST = 0V, FB/PGFB = 0V BIAS = 0V 1.35V FB = 1.35V BIAS = 0V 1.15V 0.8V C BIAS = 5V 1.15V 0.8V C SYNC = 3. 1. 1.5A SW 3.3V < V < 60V VIN )= ±10μA dI 1.15V FB = 1.35V LT1976/LT1976B MIN TYP MAX UNITS ● 1.5 2.4 3.5 A 1.2 2 Ω ● 0.2 0.4 ● 180 200 230 kHz ...
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... It flows only during switch on time. Note 8: Gain is measured with a V Note 9: Switch on resistance is calculated by dividing V the forced current (1.5A LT1976, 1.2A LT1976B). See Typical Performance Characteristics for the graph of switch voltage at other currents. Note 10: The C threshold is defined as the value of current sourced into ...
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... Shutdown Supply Current 60V 42V V = 12V 125 150 –50 – 100 TEMPERATURE (°C) 1976 G05 LT1976B Efficiency and Power Loss vs Load Current 100 10 EFFICIENCY 3.3V 50 0.1 TYPICAL POWER LOSS 25 0.01 0 0.001 0.1 1 100 1000 10 LOAD CURRENT (mA) SHDN Threshold 1.40 1.35 1.30 1 ...
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... LT1976/LT1976B W U TYPICAL PERFOR A CE CHARACTERISTICS PGFB Threshold 1.20 1.18 1.16 1.14 1.12 1.10 1.08 1.06 1.04 1.02 1.00 – 100 125 150 –25 TEMPERATURE (°C) 1976 G08 Soft-Start Current Threshold vs FB Voltage 25° SOFT-START 30 DEFEATED 0.2 0.4 0.6 0.8 1.0 1.2 FB VOLTAGE (V) 1976 G11 LT1976 Supply Current vs Input Voltage ...
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... OUT BOOST DIODE = DIODES INC. B1100 5 LOAD CURRENT = 250mA 4 3 LOAD CURRENT = 1.25A 2.5 3 3.5 4 4.5 5 5.5 INPUT VOLTAGE (V) 1976 G24 LT1976B No Load Operation (Pulse-Skipping Mode) V OUT 50mV/DIV AC COUPLED I SW 100mA/DIV 12V TIME (10μs/DIV) IN 1976 G27 V = 3.3V OUT I = 1.6mA Q LT1976/LT1976B ...
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... LT1976/LT1976B W U TYPICAL PERFOR A CE CHARACTERISTICS CTIO S NC (Pins 1, 3, 5): No Connection. Pins are electrically isolated from the LT1976. They may be con- nected to PCB traces to aid in PCB layout. SW (Pin 2): The SW pin is the emitter of the on-chip power NPN switch. This pin is driven up to the input pin voltage during switch on time ...
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... C high impedance when the clamp is active. The PG pin has a typical sink capability of 200μA. See the Power Good section in Applications Information for details. LT1976/LT1976B . When PGFB , current ( sourced into ...
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... CLAMP 1. CLAMP Figure 1. LT1976/LT1976B Block Diagram delivered to the output rather than voltage. A voltage fed system will have low phase shift up to the resonant fre- quency of the inductor and output capacitor, then an abrupt 180° shift will occur. The current fed system will have 90° ...
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... The only difference between the LT1976 and the LT1976B is that the LT1976B does not shift into burst mode in light load situations, eliminating low frequency output ripple at the expense of light load efficiency. ...
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... OUT = • • nA For LT1976B aplications, the suggested value for R2 is 10k or less, eliminating output voltage errors due to feedback pin current and reducing noise susceptibility. LT1976 SOFT-START 200kHz FOLDBACK OSCILLATOR DETECT – ERROR AMP + Figure 2. Feedback Network ...
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... Mother Nature on ESR. If you find a tiny 22μF solid tantalum capacitor, it will have high ESR and output ripple voltage could be unacceptable. Table 3 shows some ratings. The IN typical solid tantalum surface mount capacitors. LT1976/LT1976B pin of IN 1976bfg 13 ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO Table 3. Surface Mount Solid Tantalum Capacitor ESR and Ripple Current E CASE SIZE ESR MAX (Ω) AVX TPS 0.1 to 0.3 D CASE SIZE AVX TPS 0.1 to 0.3 C CASE SIZE AVX TPS 0.2 Many engineers have heard that solid tantalum capacitors are prone to failure if they undergo high surge currents ...
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... EMI, fault current in the inductor, saturation and of course cost. The following procedure is suggested as a way of han- dling these somewhat complicated and conflicting requirements. LT1976/LT1976B = 5V and L = 20μ – ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO 1. Choose a value in microhenries from the graph of maximum load current. Choosing a small inductor with lighter loads may result in discontinuous mode of operation, but the LT1976 is designed to work well in either mode. Table 4. Inductor Selection Criteria VENDOR/ PART NUMBER VALUE (μ ...
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... Typical Performance Characteristics) and is defeated for FB voltages greater than 0.9V (typical). The output dV/dt can be approximated by but actual values will vary due to start-up load conditions, compensation values and output capacitor selection. LT1976/LT1976B pin, the LT1976 will skip C /( ratios > OUT ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO C = GND SS V OUT 0.5V/DIV C = 0.1μ 47μF TIME (1ms/DIV) OUT I = 200mA LOAD V = 12V IN Figure 4. V dV/dt OUT Burst Mode OPERATION (LT1976 ONLY) To enhance efficiency at light loads, the LT1976 automati- cally switches to Burst Mode operation which keeps the output capacitor charged to the proper voltage while mini- mizing the input quiescent current ...
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... BOOST voltage the LT1976 sees can be reduced by placing a Zener diode in 1088μA 84.5% series with the BOOST diode (Figure 7a option). LT1976/LT1976B current into the diode rail. This can IN above V to drive the output ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO OPTIONAL V V BOOST IN IN LT1976 GND SW V – BOOST SW OUT BOOST(MAX) IN OUT (7a BOOST IN IN LT1976 GND SW V – BOOST BOOST(MAX) IN (7b BOOST IN IN LT1976 GND – BOOST ...
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... Synchronizing the LT1976 during Burst Mode operation may alter the natural burst frequency which can lead to jitter and increased ripple in the burst waveform. Synchronizing the LT1976B during pulse skip operation may also increase output ripple synchronization is required this pin should be con- nected to ground ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO (I ) from the C pin into the external capacitor. When the CT T voltage on the external capacitor reaches an internal clamp (V ), the PG pin becomes a high impedance node. The CT V OUT 500mV/DIV PG 100k 500mV/DIV V SHDN 2V/DIV TIME (10ms/DIV) Figure 9 ...
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... NC SYNC PGFB BOOST BIAS GND GND Figure 12. Suggested Layout LT1976/LT1976B V OUT C1 LOAD 1976 F11 KELVIN SENSE FEEDBACK TRACE AND KEEP SEPARATE FROM BIAS TRACE 1976 F12 1976bfg 23 ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO Board layout also has a significant effect on thermal resistance. Pin 8 and the exposed die pad, Pin 17, are a continuous copper plate that runs under the LT1976 die. This is the best thermal path for heat out of the package. ...
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... IN OUT tion the theoretical analysis considers only first order non- ideal component behavior. For these reasons important that a final stability check is made with production layout and components. LT1976/LT1976B and high f may not be achievable in OUT OSC , low V IN can result in an unacceptably short ...
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... LT1976/LT1976B U U APPLICATIO S I FOR ATIO The LT1976 uses current mode control. This alleviates many of the phase shift problems associated with the inductor. The basic regulator loop is shown in Figure 12. The LT1976 can be considered as two g amplifier and the power stage. Figure 13 shows the overall loop response with a 330pF V capacitor and a typical 100μ ...
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... BSC 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT MILLIMETERS (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE LT1976/LT1976B LT1976B Efficiency and Power Loss vs Load Current 100 EFFICIENCY 75 5V 3.3V 50 TYPICAL POWER LOSS ...
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... LT1976/LT1976B RELATED PARTS PART NUMBER DESCRIPTION LT1074/LT1074HV 4. 100kHz, High Efficiency Step-Down DC/DC Converters OUT LT1076/LT1076HV 1. 100kHz, High Efficiency Step-Down DC/DC Converters OUT LT1676 60V, 440mA (I ), 100kHz, High Efficiency Step-Down DC/DC OUT Converter LT1765 25V 1.25MHz, High Efficiency Step-Down DC/DC OUT Converter LT1766 60V, 1. 200kHz, High Efficiency Step-Down DC/DC ...