Overview
The LM25069PMM-1/NOPB, produced by Texas Instruments, is a positive low voltage power limiting hot swap controller. This device is designed to provide intelligent control of the power supply voltage during the insertion and removal of circuit cards from live system backplanes or other 'hot' power sources. It ensures safe and controlled in-rush current limiting, preventing voltage sag and transients that could affect other circuits in the system.
The LM25069 features an internal high side charge pump and gate driver for an external N-channel MOSFET, adjustable under-voltage and over-voltage lockout levels, and a programmable fault timer. It also includes a power good output indicator and a circuit breaker function for severe over-current conditions.
Key Specifications
| Parameter | Min. | Typ. | Max. | Units |
|---|---|---|---|---|
| Operating Voltage Range | 2.9 | - | 17 | V |
| Transient Capability | - | - | 20 | V |
| Operating Temperature Range | -40 | - | 85 | °C |
| Power Limit Sense Voltage (PWRLIM-1) | 19 | 25 | 31 | mV |
| Power Good Threshold (Decreasing) | 1.3 | 1.9 | - | V |
| Power Good Hysteresis | - | - | 0.6 | V |
| Output Low Voltage (ISINK = 2 mA) | 15 | 30 | - | mV |
| Off Leakage Current (VPGD = 17V) | - | - | 1 | µA |
Key Features
- Internal high side charge pump and gate driver for external N-channel MOSFET
- Adjustable under-voltage lockout (UVLO) and over-voltage lockout (OVLO)
- Programmable current limit and power dissipation in the external series pass MOSFET
- Initial insertion timer allows ringing and transients to subside after system connection
- Programmable fault timer to avoid nuisance trips
- Active high open drain POWER GOOD output
- Circuit breaker function for severe over-current conditions
- Available in latched fault and automatic restart versions (LM25069-1 and LM25069-2)
Applications
- Server backplane systems
- Base station power distribution systems
- Solid state circuit breaker applications
- In-rush current limiting for safe board insertion into live power sources
Q & A
- What is the operating voltage range of the LM25069?
The operating voltage range of the LM25069 is from +2.9V to +17V, with a transient capability to 20V.
- What is the purpose of the internal high side charge pump and gate driver in the LM25069?
The internal high side charge pump and gate driver are used to control the external N-channel MOSFET, ensuring proper turn-on and turn-off of the MOSFET during power-up and power-down sequences.
- How does the LM25069 handle in-rush current limiting?
The LM25069 limits in-rush current by actively controlling the current delivered to the load during the insertion of a circuit card into a live backplane. It monitors the drain current and power dissipation of the MOSFET and adjusts the gate voltage accordingly.
- What is the function of the POWER GOOD output pin?
The POWER GOOD output pin indicates when the output voltage is within 1.3V of the system input voltage (VSYS), signaling that the system is ready for operation.
- How does the LM25069 handle fault conditions?
The LM25069 has a fault timer and restart mechanism. If a fault condition is detected, the device can either latch off (LM25069-1) or automatically restart (LM25069-2) after a predefined period.
- What are the key differences between the LM25069-1 and LM25069-2 versions?
The LM25069-1 latches off after a fault detection and requires external re-enable, while the LM25069-2 automatically restarts with a defined timing cycle.
- What is the significance of the under-voltage lockout (UVLO) and over-voltage lockout (OVLO) in the LM25069?
The UVLO and OVLO ensure that the series pass MOSFET is enabled only when the input supply voltage is within the desired operating range, preventing operation outside safe voltage thresholds.
- How is the power limiting function implemented in the LM25069?
The power limiting function monitors the drain-source voltage and drain current of the MOSFET and modulates the gate voltage to keep the power dissipation within the Safe Operating Area (SOA) of the MOSFET.
- What is the recommended resistor value for the sense resistor (RS) in the LM25069 application?
The sense resistor (RS) should be no larger than 200 mΩ to ensure stable operation of the current limit control loop.
- In what package is the LM25069 available?
The LM25069 is available in a 10-pin VSSOP (DGS) package.[
