Overview
The LM25085, produced by Texas Instruments, is a high-efficiency PFET buck (step-down) DC-DC controller that utilizes the constant on-time (COT) control principle. This controller is designed to facilitate the development of small, efficient buck regulators for a wide range of applications. It operates over a broad input voltage range of 4.5V to 42V and features an integrated high voltage bias regulator and a PFET gate driver. The LM25085 is particularly suited for applications requiring ultra-fast load transient response and nearly constant operating frequency with line and load variations.
Key Specifications
| Parameter | Test Conditions | MIN | TYP | MAX | UNIT |
|---|---|---|---|---|---|
| VIN to GND | -0.3 | 45 | V | ||
| ISEN to GND | -3 | VIN + 0.3 | V | ||
| ADJ to GND | -0.3 | VIN + 0.3 | V | ||
| RT, FB to GND | -0.3 | 7 | V | ||
| VIN to VCC, VIN to PGATE | -0.3 | 10 | V | ||
| Input Operating Current (IIN) | Non-Switching, FB = 1.4V | 1.25 | 1.75 | mA | |
| Shutdown Current (IQ) | RT = 0V | 175 | 300 | µA | |
| VCC REGULATOR (VCC(reg)) | VIN = 9V, FB = 1.4V, ICC = 0mA | 6.9 | 7.7 | 8.5 | V |
| Soft-Start Time (tSS) | 1.4 | 2.5 | 4.3 | ms | |
| Junction Shutdown Temperature (TSD) | 170 | °C | |||
| Junction Shutdown Hysteresis (THYS) | 20 | °C |
Key Features
- Wide Input Voltage Range: 4.5V to 42V
- Constant On-Time Regulation: No loop compensation required, ultra-fast load transient response
- Adjustable Current Limit: Using RDS(ON) or a current sense resistor
- Programmable Switching Frequency: Up to 1MHz
- Nearly Constant Operating Frequency: With line and load variations
- 100% Duty Cycle Operation: For low dropout voltage
- Adjustable Output Voltage: From 1.25V
- Precision Feedback Reference: ±2% accuracy
- Internal Soft-Start Timer: Reduces startup stresses and current surges
- Thermal Shutdown: Protects against catastrophic failures due to overheating
Applications
- Automotive Infotainment: Suitable for automotive systems requiring high reliability and efficiency
- Battery/Super Capacitor Chargers: Efficient charging solutions for various battery types
- LED Drivers: Ideal for driving LEDs in various lighting applications
Q & A
- What is the input voltage range of the LM25085?
The input voltage range of the LM25085 is 4.5V to 42V.
- What is the constant on-time regulation principle?
The constant on-time regulation principle eliminates the need for loop compensation, simplifying circuit implementation and resulting in ultra-fast load transient response.
- How can the current limit be adjusted in the LM25085?
The current limit can be adjusted using either the RDS(ON) of the PFET or an external current sense resistor.
- What is the maximum switching frequency of the LM25085?
The switching frequency can be programmed up to 1MHz.
- Does the LM25085 support 100% duty cycle operation?
Yes, the LM25085 supports 100% duty cycle operation, which is beneficial for low dropout voltage applications.
- What is the precision of the feedback reference voltage?
The feedback reference voltage has a precision of ±2%.
- How does the internal soft-start timer function?
The internal soft-start timer ramps the feedback reference voltage from 0V to 1.25V during startup, reducing startup stresses and current surges.
- What is the purpose of the thermal shutdown feature?
The thermal shutdown feature protects the device against catastrophic failures by disabling the VCC regulator and gate driver if the junction temperature exceeds 170°C.
- What are some common applications of the LM25085?
The LM25085 is commonly used in automotive infotainment, battery/super capacitor chargers, and LED drivers.
- Is the LM25085 suitable for automotive applications?
Yes, the LM25085-Q1 is AEC-Q100 Grade 1 Qualified, making it suitable for automotive applications with an operating junction temperature range of -40°C to 125°C.
