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LM25069 Positive Low Voltage Power Limiting Hot Swap Controller
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July 15, 2009
LM25069
Positive Low Voltage Power Limiting Hot Swap Controller
General Description
The LM25069 positive hot swap controller provides intelligent control of the power supply voltage to the load during insertion and removal of circuit cards from a live system backplane or other "hot" power sources. The LM25069 provides in-rush current control to limit system voltage droop and transients. The current limit and power dissipation in the external series pass N-Channel MOSFET are programmable, ensuring operation within the Safe Operating Area (SOA). The POWER GOOD output indicates when the output voltage is within 1.3V of the input voltage. The input under-voltage and over-voltage lockout levels and hysteresis are programmable, as well as the initial insertion delay time and fault detection time. The LM25069-1 latches off after a fault detection, while the LM25069-2 automatically restarts at a fixed duty cycle. The LM25069 is available in a 10 pin MSOP package.
Features
■ Operating range: +2.9V to +17V ■ In-rush current limit for safe board insertion into live power ■ ■ ■ ■ ■ ■ ■ ■ ■ ■
sources Programmable maximum power dissipation in the external pass device Adjustable current limit Circuit breaker function for severe over-current events Internal high side charge pump and gate driver for external N-channel MOSFET Adjustable under-voltage lockout (UVLO) and hysteresis Adjustable over-voltage lockout (OVLO) and hysteresis Initial insertion timer allows ringing and transients to subside after system connection Programmable fault timer avoids nuisance trips Active high open drain POWER GOOD output Available in latched fault and automatic restart versions
Applications
■ Server Backplane Systems ■ Base Station Power Distribution Systems ■ Solid State Circuit Breaker
Package
■ MSOP-10
Typical Application
30086701
Positive Power Supply Control
© 2009 National Semiconductor Corporation
300867
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LM25069
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Connection Diagram
30086702
Top View 10-Lead MSOP
Ordering Information
Order Number LM25069PMME-1 LM25069PMM-1 LM25069PMMX-1 LM25069PMME-2 LM25069PMM-2 LM25069PMMX-2 Fault Response Latch Off Latch Off Latch Off Auto Restart Auto Restart Auto Restart MSOP-10 MUB10A Package Type NSC Package Drawing Supplied As 250 Units on Tape and Reel 1000 Units on Tape and Reel 3500 Units on Tape and Reel 250 Units on Tape and Reel 1000 Units on Tape and Reel 3500 Units on Tape and Reel
Pin Descriptions
Pin # 1 Name SENSE Description Current sense input Applications Information The voltage across the current sense resistor (RS) is measured from VIN to this pin. If the voltage across RS reaches 50mV the load current is limited and the fault timer activates. A small ceramic bypass capacitor close to this pin is recommended to suppress transients which occur when the load current is switched off. An external resistor divider from the system input voltage sets the under-voltage turn-on threshold. An internal 20 µA current source provides hysteresis. The enable threshold at the pin is 1.17V. This pin can also be used for remote shutdown control. An external resistor divider from the system input voltage sets the over-voltage turn-off threshold. An internal 20 µA current source provides hysteresis. The disable threshold at the pin is 1.16V. An external capacitor connected to this pin sets the insertion time delay and the Fault Timeout Period. The capacitor also sets the restart timing of the LM25069-2. An external resistor connected to this pin, in conjunction with the current sense resistor (RS), sets the maximum power dissipation allowed in the external series pass MOSFET. An open drain output. When the external MOSFET VDS decreases below 1.3V, the PGD indicator is active (high). When the external MOSFET VDS increases above 1.9V the PGD indicator switches low.
2 3
VIN UVLO/EN
Positive supply input Under-voltage lockout
4
OVLO
Over-voltage lockout
5 6 7
GND TIMER PWR
Circuit ground Timing capacitor Power limit set
8
PGD
Power Good indicator
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2
LM25069
Pin # 9
Name OUT
Description Output feedback Gate drive output
Applications Information Connect to the output rail (external MOSFET source). Internally used to determine the MOSFET VDS voltage for power limiting, and to control the PGD indicator. Connect to the external MOSFET’s gate. This pin's voltage is limited at 19.5V above ground.
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10
GATE
3
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LM25069
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Storage Temperature Junction Temperature Lead Temperature (soldering 4 sec)
-65°C to +150°C +150°C +260°C
VIN to GND (Note 5) SENSE, OUT, PGD to GND UVLO to GND OVLO to GND VIN to SENSE ESD Rating (Note 2.