LM2825N-5.0

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1. Describe

LM2825N-5.0 is a complete 1A DC-DC step-down converter Packaged in 24-pin molded dual in-line integrated Circuit package. All activities included in the package and Passive components for high-efficiency step-down (Buck) switching regulator. Can be used for fixed output Voltages are 3.3V, 5V and 12V, and two Adjustable version, these devices can provide up to 1A load current, fully guaranteed electrical specifications. The converter is self-contained and can completely protect it from output fault conditions, such as excessive load current, short circuit, or excessive temperature.

2. Feature

    1. The shortest design time required

    2. 3.3V, 5V and 12V fixed output versions

    3. Two adjustable versions allow 1.23V to 15V output

    4. Wide input voltage range, up to 40V

    5. Low power consumption standby mode, IQ is usually 65 μA

    6. High efficiency, usually 80%

    7. ±4% output voltage tolerance

    8. Excellent line and load regulation

    9. TTL shutdown capability/programmable soft start

  10. Thermal shutdown and current limit protection

  11. −40°C to +85°C ambient temperature range

3. Application

    1. Simple and high-efficiency step-down (pressure reduction) Regulator

    2. Switching regulator on card

    3. High-efficiency pre-regulator for linear regulators

    4. Distributed power system

    5. DC/DC module replacement

4. Emphasize

    1. No need for external components (fixed output voltage version)

    2. Integrated circuit reliability

    3. MTBF exceeds 20 million hours

    4. Radiated EMI complies with CISPR 22 regulation B class

    5. High power density, 35 W/in3

    6. 24-pin PDIP package outline (1.25 x 0.54 x 0.26 inches)

5. Pin configuration

6. Optional external components

    1. Soft start capacitor

        CSS: The capacitor on this pin provides a soft start function (slow start) for the regulator. Drawn current The low average level and narrow pulses from the source start and rise in a controlled manner because The pulses extend to their steady-state width. This greatly reduces the starting current, and delays and slows down Reduce the output voltage rise time. It is particularly useful when the amount of current that the input power supply can provide is limited, Because you can avoid reducing the load of this type of power supply. Under certain operating conditions, a soft-start capacitor is required to work properly. The input voltage and ambient temperature conditions of the soft start capacitor may be required. This curve is a typical curve that fully guarantees the output current and can be used as a guide. As output current Reduced, the working area of the soft-start capacitor is reduced. The capacitance value between 0.1 μF and 1 μF is recommended. Tantalum or ceramic capacitors are suitable for this application.

    2. Input capacitor

        CIN: If the distance between the package and the main filter or bypass exceeds 6", an optional input capacitor is required Capacitor. It is recommended to use a low ESR aluminum or tantalum bypass capacitor between the input pin and ground To prevent large voltage transients at the input. In addition, to be conservative, the RMS current The rated value of the input capacitor should be at least ½ of the DC load current. With a 1A load, the recommended RMS current rating of a capacitor is at least 500 mA. The rated voltage should be approximately 1.25 times the maximum input voltage. Has a nominal input voltage 12V aluminum electrolytic capacitors (Panasonic HFQ series or Nichicon PL series or equivalent) require a rated voltage greater than 15V (1.25 × VIN). Solid tantalum input capacitors should only be used when the input source impedance current is limited. High The dV/dt applied to the input will cause excessive charging current through the low ESR tantalum capacitor. This high The charging current will cause a short circuit in the capacitor. It is recommended to pass the surge current test manufacturer. Both AVX's TPS series and Sprague's 593D series are surge currents test. Be careful when using ceramic capacitors for input bypass, as it may cause ringing on the VIN pin.

    3. Reduce output ripple

        When using adjustable parts, lower output ripple voltage can be achieved by short-circuiting the internal resistor LM2825. However, if the resistor is short-circuited, a feedforward capacitor must be used to keep the regulator stable. Therefore, the resistor must be kept open on all fixed output voltage versions, otherwise it will cause instability. Short-circuiting the internal resistance is achieved by short-circuiting pins 8 and 9 on the LM2825, and will usually reduce the output ripple by 25% to 33%.

    4. Feedforward capacitor selection (CFF)

        When using adjustable parts and pins 8 and 9 are shorted to reduce output ripple, the feedforward capacitor is Required. This capacitor is usually between 680 pF and 2700 pF.

    5. Thermal considerations

        LM2825 uses 24-pin through-hole PDIP. The package is a molded plastic with a copper lead frame. When the package is soldered to the PC board, the copper and the board are the heat sink of the LM2825.