preamble
Power supply circuit design is important, in order to better give the people who have the need for hardware design, the basic process of power supply design is described.
This describes the design of a commonly used 12V to 5V circuit 3A.
TPS54331 (DC-DC Regulator)
summarize
The TPS54331 device is a 28V, 3A non-synchronous buck converter with an integrated low RDS(on) high-side MOSFET that automatically activates the pulse-skipping Eco-mode feature for improved efficiency at light loads. In addition, a 1µA shutdown supply current allows the device to be used in battery-powered applications. Current-mode control with internal ramp compensation simplifies external compensation calculations and reduces component count while allowing the use of ceramic output capacitors. A resistor divider programs the hysteresis of the input undervoltage lockout. Overvoltage transient protection circuitry limits voltage overshoot during startup and during transient conditions. A cycle-by-cycle current limiting scheme, frequency foldback, and thermal shutdown features apply protection to the device and load during overload conditions.
The TPS54331 devices are available in 8-pin SOIC packages and 8-pin SOPowerPAD integrated circuit packages that are internally optimized for improved thermal performance.
characterization
- 3.5V to 28V input voltage range
- Adjustable output voltage down to 0.8V
- Integrated 80mΩ high-side MOSFET supports up to 3A continuous output current
- High Efficiency at Light Loads with Pulse Jump Eco-mode
- 570kHz Fixed switching frequency
- 1μA shutdown quiescent current (typical)
- Adjustable slow start to limit inrush current
- Programmable UVLO Threshold
- Overvoltage transient protection
- Cycle-by-cycle current limiting, frequency foldback and thermal shutdown protection
- Available in easy-to-use SOIC8 package or thermally enhanced SOIC8PowerPAD™ integrated circuit package
- Using the TPS54331 and Creating Customized Designs with WEBENCH® PowerDesigner
- Using the TPS62933 to achieve higher frequency, lower IQ, and improved
30V Input Voltage Converter into EMI
appliance
- Consumer applications such as set-top boxes, CPE devices, LCD displays, peripherals and battery chargers
- Industrial and automotive audio power supplies
- 5V, 12V and 24V Distributed Power Systems
Simplified schematic and typical design
The material of the capacitor is not so important in this case, the large capacitor is for energy storage and the small capacitor is for filtering.
This can be seen.
For different models of the same series with different current outputs, check the Io (maximum value) as follows:
TPS54331 package: D package and DDA package, DDA more than one pin9 to realize the
The description doesn't look the same to actually view the DR is the D package:
12V to 5V Circuit
Chip houses provide design simulation software, but don't want to bother.
Step 1: Refer to simplified design drawings
Refer to the simplified design drawings when available:
Look at the diagram of the bottom plate:
After analyzing:
Step 2: Comparison with Application Typical Circuit
The above is a relatively simple circuit, right not, words have a typical circuit, the following is the datasheet application of the typical circuit:
Visualize both, then use the typical circuit:
Just use this circuit and adjust the resistor, inductor and and capacitor to control the output voltage magnitude.
Step 3: Adjust the output voltage
The output voltage of the TPS54331 device can be externally regulated through a resistive voltage divider network.
5V = 0.8V x ( R5/R6 + 1)
R5/R6 + 1 = 5/0.8
R5/R6 = 6.25 - 1
R5/R6 = 5.25
Since the resistance value is chosen to be a high precision 1% resistor and then preferably standardized, it is possible to view theHardware Practical Tips: Resistor Accuracy and Common Resistance Tables", the resistance values R6 are chosen to be 20KΩ and R5 to be 105KΩ.
Capacitors, not adjusted.
Step 4: Adjust the inductor
Lmin = (5V x (12V – 5V) / (12V x 0.3 x 3A x 570kHz)
Lmin = (5V x 7V) / (3.6V x 3A x 570kHz)
Lmin = 35 / (10.8 x 570000)
Lmin = 35 / 6156000
Lmin = 0.00000568551(H)
Lmin = 5.68551(uH)
Just pick a larger 6.8uH.
The following is calculated once using 0.2:
Lmin = (5V x (12V – 5V) / (12V x 0.2 x 3A x 570kHz)
Lmin = (5V x 7V) / (2.4V x 3A x 570kHz)
Lmin = 35 / (7.2 x 570000)
Lmin = 35 / 3384000
Lmin = 0.00001034278(H)
Lmin = 10.34278(uH)
Choosing 0.2 gets you 10.3uH, and choosing larger gets you 12uH. (Note that we use 6.8uH like the rest of the schematic).
Step 5: Control Power Chip Enable
Add a self-locking control switch to control EN enable.
