Overview
The LM3485MM/NOPB, produced by Texas Instruments, is a high-efficiency hysteretic PFET buck controller designed for a wide range of applications. This controller uses a simple and robust hysteretic control architecture, eliminating the need for control-loop compensation. It is ideal for developing small, low-cost switching buck regulators with high efficiency and low component count. The LM3485MM/NOPB supports a wide input voltage range of 4.5V to 35V and can adjust the output voltage from 1.242V to VIN, making it versatile for various power supply needs.
Key Specifications
| Parameter | Min | Max | Unit | |
|---|---|---|---|---|
| Supply Voltage | 4.5 | - | 35 | V |
| Operating Junction Temperature | -40 | - | 125 | °C |
| Feedback Voltage | 1.217 | 1.242 | 1.267 | V |
| Comparator Hysteresis | 10 | 15 | 20 | mV |
| Current Limit Comparator Trip Voltage | 110 | - | 880 | mV |
| Maximum Operating Frequency | - | - | > 1 MHz | - |
| Junction-to-Ambient Thermal Resistance (RθJA) | - | - | 163.3 | °C/W |
Key Features
- Easy-to-Use Control Methodology: No control-loop compensation required, simplifying the design process.
- Wide Input Range: Supports input voltages from 4.5V to 35V.
- Adjustable Output Range: Output voltage can be adjusted from 1.242V to VIN.
- High Efficiency: Achieves up to 93% efficiency.
- 100% Duty Cycle Operation: Allows for ultralow dropout operation.
- Current Limit Protection: Engages to protect against over-current conditions.
- Low Component Count: Reduces the number of external components needed.
- Hysteretic Control Circuit: Uses a comparator-based voltage control loop with 10 mV hysteresis for noise-free operation.
Applications
The LM3485MM/NOPB is suitable for a variety of applications, including but not limited to:
- Power Supplies: For developing small, low-cost switching buck regulators.
- Industrial Control Systems: Where high efficiency and reliability are crucial.
- Consumer Electronics: Such as in power adapters, battery chargers, and other portable devices.
- Automotive Systems: For applications requiring robust and efficient power management.
Q & A
- What is the input voltage range of the LM3485MM/NOPB?
The input voltage range is from 4.5V to 35V. - How is the output voltage adjusted?
The output voltage can be adjusted using two external resistors connected to the FB pin. - What is the typical feedback voltage of the LM3485MM/NOPB?
The typical feedback voltage is 1.242V. - Does the LM3485MM/NOPB require control-loop compensation?
No, it does not require control-loop compensation due to its hysteretic control architecture. - What is the maximum operating frequency of the LM3485MM/NOPB?
The maximum operating frequency is greater than 1 MHz. - How does the current limit protection work?
The current limit protection engages when the inductor current is too high, turning the PFET off for approximately 9 µs. - What is the junction-to-ambient thermal resistance (RθJA) of the LM3485MM/NOPB?
The RθJA is 163.3 °C/W. - In what modes can the LM3485MM/NOPB operate?
The LM3485MM/NOPB can operate in both discontinuous conduction mode at light loads and continuous conduction mode at heavy loads. - What is the purpose of the feed-forward capacitor (Cff) in the LM3485MM/NOPB?
The feed-forward capacitor influences the operating frequency and output ripple voltage by sourcing or sinking current through it. - Is the LM3485MM/NOPB suitable for high-efficiency applications?
Yes, it achieves high efficiency of up to 93%.
