## LM2653-5.0 Overview The **LM2653** is a high-efficiency, monolithic step-down (buck) DC-DC converter designed by Texas Instruments (formerly National Semiconductor). The "05" suffix typically indicates a fixed output version of **5.0V**. It is widely used in battery-powered systems due to its high efficiency and integrated features. --- ### Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Topology** | Step-Down (Buck) | | **Output Voltage** | 5.0V (Fixed) | | **Input Voltage Range** | 4V to 14V | | **Maximum Output Current** | 1.5A | | **Switching Frequency** | 300 kHz (Internal) | | **Efficiency** | Up to 97% | | **Package** | TSSOP-16 | --- ### Internal Electronic Components The LM2653 integrates several critical electronic functions within its silicon to reduce external component count: 1. **Power MOSFETs:** It contains two internal N-Channel MOSFETs (High-side and Low-side) for synchronous rectification. Synchronous rectification significantly reduces power loss compared to using a Schottky diode. 2. **Pulse Width Modulator (PWM) Control:** The chip uses a current-mode control scheme, which provides excellent line and load transient response. 3. **Bootstrap Circuitry:** Includes internal drive circuitry to provide the gate voltage necessary to turn on the high-side N-channel MOSFET. 4. **Protection Circuits:** * **Over-Current Protection:** Limits the peak current through the MOSFETs. * **Thermal Shutdown:** Shuts the device down if the junction temperature exceeds safe limits (approx. 150°C). * **Under-Voltage Lockout (UVLO):** Ensures the device stays off if the input voltage is too low to operate reliably. --- ### Critical External Components While the LM2653 is highly integrated, it requires a few high-quality external components to function correctly: * **Inductor ($L$):** Typically ranges from $10\mu H$ to $22\mu H$. It stores energy during the "on" cycle and releases it during the "off" cycle. * **Input Capacitor ($C_{IN}$):** Low ESR (Equivalent Series Resistance) capacitors are required to filter the high-frequency pulses from the input supply. * **Output Capacitor ($C_{OUT}$):** Works with the inductor to smooth the output voltage ripple. * **Bootstrap Capacitor ($C_{BST}$):** Usually a $0.1\mu F$ ceramic capacitor connected between the BOOT and SW pins to provide the drive voltage for the high-side switch. --- ### Typical Pin Configuration (TSSOP-16) ```text 1. NC - No Connection 2. PGND - Power Ground 3. SW - Switch Node (Connects to Inductor) 4. VIN - Input Supply Voltage 5. BOOT - Bootstrap Supply for high-side driver 6. NC - No Connection 7. FB - Feedback (Connected to Vout for fixed versions) ... 16. SD - Shutdown Pin (Logic High = Run, Logic Low = Off) ```