LMZ12003TZ-ADJ

The LMZ12003TZ-ADJ is a complete 3A step-down DC-DC power module from Texas Instruments SIMPLE SWITCHER family. This device integrates the switching regulator controller, power MOSFETs (both high-side and low-side for synchronous operation), and a shielded inductor into a single, easy-to-use TO-PMOD package.

What sets the LMZ12003 apart from discrete buck converter solutions is its extreme ease of use. With the inductor already integrated and internal compensation handling loop stability, designers need only add an input capacitor, output capacitor, and two feedback resistors to create a complete 3A power supply. This dramatically reduces design time, PCB layout complexity, and the risk of design errors.

The device operates from 4.5V to 20V input and provides an adjustable output from 0.8V to 6V. Synchronous rectification delivers high efficiency — up to 92% — reducing thermal requirements and extending battery life in portable applications. The 500kHz fixed switching frequency balances component size with efficiency.

The TO-PMOD package features a large exposed thermal pad on the bottom that provides a low thermal resistance path to the PCB, enabling reliable 3A operation without a heat sink. The package style is similar to a standard TO-263, making it compatible with standard PCB assembly processes. The LMZ12003 is fully supported by TI WEBENCH Power Designer for fast and accurate design.

The LMZ12003 is a synchronous buck power module with integrated inductor, operating on the following principles:

1. Control Architecture: The device uses voltage-mode control with internal Type III compensation. The feedback voltage (from an external resistor divider on the FB pin) is compared against the internal 0.8V bandgap reference by the error amplifier. The error signal drives a PWM comparator that generates the timing for both high-side and low-side MOSFETs.

2. Synchronous Rectification: Unlike non-synchronous buck converters that use a Schottky diode for freewheeling, the LMZ12003 uses a second (low-side) N-MOSFET that conducts during the off-time. This reduces conduction losses significantly, improving efficiency especially at low output voltages and high load currents.

3. Switching Cycle (On-Time): The high-side N-MOSFET is turned on, and current flows from VIN through the integrated inductor to the output. The inductor current ramps up linearly at di/dt = (VIN – VOUT)/L. The output capacitor filters the ripple current.

4. Switching Cycle (Off-Time): The high-side MOSFET turns off, and the low-side MOSFET turns on after a brief dead time (to prevent shoot-through). The inductor current flows through the low-side MOSFET, still delivering current to the output. The inductor current ramps down at di/dt = -VOUT/L.

5. Integrated Inductor: A shielded ferrite inductor is integrated within the module package. Shielding reduces EMI radiation and provides predictable performance. The inductor value is optimized for 500kHz operation and 3A output current.

6. Protection: Cycle-by-cycle current limit protects both MOSFETs and the inductor. Output overvoltage protection clamps excessive output voltage. Thermal shutdown disables switching if the die temperature exceeds safe limits. Soft-start gradually ramps the output voltage to prevent inrush current at power-up.

• Point-of-load regulators for FPGA, ASIC, and DSP power
• 12V to 3.3V / 2.5V / 1.8V / 1V core supply
• Telecom and datacom line card power supplies
• Industrial PLC and embedded system power
• Rapid-prototyping and evaluation board designs