LT1936 Linear Technology, LT1936 Datasheet
LT1936
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LT1936 Summary of contents
Page 1
... PWM step-down DC/DC converter with an internal 1.9A power switch, packaged in a tiny, thermally enhanced 8-lead MSOP . The wide in- put range of 3.6V to 36V makes the LT1936 suitable for regulating power from a wide variety of sources, including automotive batteries, 24V industrial supplies and unregu- lated wall adapters ...
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... COMP Voltage .................................................6V C Operating Temperature Range (Note 2) LT1936E ............................................... –40°C to 85°C LT1936I .............................................. –40°C to 125°C LT1936H ............................................ –40°C to 150°C Maximum Junction Temperature LT1936E, LT1936I ............................................. 125°C LT1936H ........................................................... 150°C Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C ...
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... Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT1936E is guaranteed to meet performance specifi cations from 0°C to 70°C. Specifi cations over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation TYPICAL PERFORMANCE CHARACTERISTICS Effi ...
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... LT1936 TYPICAL PERFORMANCE CHARACTERISTICS Maximum Load Current 1 OUT 1 15μH 1 10μH 1.2 1 INPUT VOLTAGE (V) 1936 G04 Feedback Voltage 1.210 1.205 1.200 1.195 1.190 1.185 –50 – 100 125 TEMPERATURE (°C) 1936 G07 Frequency Foldback 700 T = 25° ...
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... OUT L = 10μH C OUT Error Amp Output Current –20 –40 – 100 125 150 0 1936 G18 LT1936 www.DataSheet4U.com Switch Current Limit 3.0 2.5 2.0 1.5 1.0 0.5 0 1000 –50 – TEMPERATURE (°C) 1936 G14 1936 G17 = 12V 1μs/DIV = 3.3V = 50mA = 22μ ...
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... GND (Pin 4): Tie the GND pin to a local ground plane below the LT1936 and the circuit components. Return the feedback divider to this pin. SHDN (Pin 5): The SHDN pin is used to put the LT1936 in shutdown mode. Tie to ground to shut down the LT1936. Tie to 2.3V or more for normal operation. If the shutdown feature is not used, tie this pin to the V provides a soft-start function ...
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... OPERATION (Refer to Block Diagram) The LT1936 is a constant frequency, current mode step- down regulator. A 500kHz oscillator enables an RS fl ip-fl op, turning on the internal 1.9A power switch Q1. An ampli- fi er and comparator monitor the current fl owing between the V and SW pins, turning the switch off when this ...
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... Absolute Maximum Ratings of the V and BOOST pins. IN The minimum input voltage is determined by either the LT1936’s minimum operating voltage of ~3.45V or by its maximum duty cycle. The duty cycle is the fraction of time that the internal switch is on and is determined by the input and output voltages: V ...
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... LT1936 to ~3.7V. Output Capacitor The output capacitor has two essential functions. Along with the inductor, it fi lters the square wave generated by the LT1936 to produce the DC output. In this role it determines the output ripple, and low impedance at the (1 – DC). OUT switching frequency is important. The second function is to store energy in order to satisfy transient loads and stabilize the LT1936’ ...
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... The LT1936 uses current mode control to regulate the output. This simplifi es loop compensation. In particular, the LT1936 does not require the ESR of the output capacitor for stability, so you are free to use ceramic capacitors to achieve low output ripple and small circuit size. ...
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... C OUT (4TPC150M) (2d) COMP Figure 2. Transient Load Response of the LT1936 with Different Output Capacitors as the Load Current is Stepped from 200mA to 800mA. V current proportional to the voltage at the V the output capacitor integrates this current, and that the capacitor on the V output current, resulting in two poles in the loop. In most ...
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... For proper start-up, the minimum input voltage is also limited by the boost circuit. If the input voltage is ramped slowly, or the LT1936 is turned on with its SHDN pin when the output is already in regulation, then the boost capacitor may not be fully charged. Because the boost capacitor is charged ...
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... LOAD CURRENT (mA) Figure 4. The Minimum Input Voltage Depends on Output Voltage, Load Current and Boost Circuit RUN RUN 15k 0.22μF Figure 5. To Soft-Start the LT1936, Add a Resistor and Capacitor to the SHDN Pin 12V OUT RC time constant, the peak start-up current can be reduced to the current that is required to regulate the output, with no overshoot ...
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... C COMP GND FB Figure 6. Diode D4 Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output; It Also Protects the Circuit from a Reversed Input. The LT1936 Runs Only When the Input is Present PCB Layout For proper operation and minimum EMI, care must be taken during printed circuit board layout. Figure 7 shows the recommended component placement with trace, ground plane and via locations ...
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... Figure 8. A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation When the LT1936 is Connected to a Live Supply input voltage, possibly exceeding the LT1936’s rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LT1936 into an energized supply, the input network should be designed to prevent this overshoot ...
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... BOOST pin. The 12V circuit shows how to overcome this limitation using an additional Zener diode. 3.3V Step-Down Converter BOOST 0.22μF IN SHDN SW C1 LT1936 D1 4.7μF COMP FB V GND R2 C 10k www.DataSheet4U.com D2 L1 10μH V OUT 3 ...
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... C3 L1 4.7μH V OUT 1.8V 1. 10k C2 R2 47μF 20k ×2 1936 TA05a C3 L1 3.3μH V OUT 1.2V 1. 100k 47μF ×2 1936 TA06a LT1936 www.DataSheet4U.com D2 L1 15μH V OUT 5V 1.2A R1 31.6k C2 22μF 1936 TA04 Effi ciency, 1.8V Output 90 2 1.8V OUT T = 25° 1 12V ...
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... COMP FB V GND R2 C 10k D1: DFLS140L D2: MBRO540 L1: TOKO D63CB 1.5 1936 TA07b 12V Step-Down Converter BOOST IN 0.22μF SHDN ON OFF LT1936 2.2μF COMP FB V GND R2 C 20k D1: MBRM140 D2: 1N4148 D3: CMDZ5235B www.DataSheet4U.com OUT 6.2μH 2.5V 1.2A T > 0° 11k C2 47μF ...
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... MAX SEATING PLANE 0.22 – 0.38 (.009 – .015) 0.65 TYP (.0256) BSC LT1936 www.DataSheet4U.com 2.06 ± 0.102 (.081 ± .004) 0.29 REF 1.83 ± 0.102 (.072 ± .004) 0.05 REF DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. DETAIL “B” ...
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... LT1936 TYPICAL APPLICATION 2.5V Step-Down Converter 3.6V TO 20V V BOOST 0.22μF IN SHDN ON OFF SW C1 LT1936 4.7μF COMP FB V GND C D1: DFLS140L D2: 1N4148 L1: TOKO D63CB RELATED PARTS PART NUMBER DESCRIPTION LT1676 60V, 440mA (I ), 100kHz, High Effi ciency Step-Down OUT DC/DC Converter LT1765 25V, 2.75A (I ), 1.25MHz, High Effi ...