Power Supply Sequencing Solution: ADM1087 Simple Sequencer™# ADM1087AKSREEL7 - 3.3V Hot Swap Power Manager Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The ADM1087AKSREEL7 is specifically designed for hot-swap applications in 3.3V systems, providing controlled power-up sequencing and overcurrent protection. Typical implementations include:
- Live Board Insertion/Removal : Enables safe insertion and removal of PCBs from powered backplanes without system disruption
- Inrush Current Limiting : Controls initial current surge during power-up to prevent bus voltage droop
- Fault Protection : Monitors for overcurrent conditions and provides rapid shutdown capability
- Power Sequencing : Manages controlled power-up timing for multi-rail systems
### Industry Applications
Telecommunications Equipment
- Network switches and routers with hot-swappable line cards
- Base station controller cards requiring live maintenance
- Telecom backplane systems with multiple plug-in modules
Data Center Infrastructure
- Server blade systems with hot-swappable compute modules
- Storage area network (SAN) equipment
- RAID controller cards requiring fault protection
Industrial Control Systems
- Programmable logic controller (PLC) I/O modules
- Industrial computer backplanes
- Process control interface cards
### Practical Advantages and Limitations
Advantages:
- Integrated Solution : Combines current sensing, timing control, and fault protection in single package
- Precise Current Limiting : ±10% accuracy over temperature range
- Fast Response Time : <1μs overcurrent detection and shutdown
- Low Component Count : Reduces board space and BOM complexity
- Wide Temperature Range : -40°C to +85°C operation
Limitations:
- Fixed Voltage Operation : Optimized for 3.3V systems only
- Current Limit Range : Limited to preset threshold values
- Package Constraints : SOT-23-6 package may require thermal considerations in high-current applications
- No Voltage Monitoring : Lacks undervoltage/overvoltage monitoring capabilities
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Gate Drive Strength
- Issue : Slow MOSFET turn-on causing excessive power dissipation
- Solution : Ensure external MOSFET has appropriate gate capacitance rating for internal charge pump capability
Pitfall 2: PCB Trace Resistance
- Issue : Excessive trace resistance between sense resistor and IC affecting current limit accuracy
- Solution : Place sense resistor as close as possible to IC, use Kelvin connections
Pitfall 3: Thermal Management
- Issue : Power dissipation in external MOSFET during startup
- Solution : Calculate MOSFET SOA (Safe Operating Area) and implement proper heatsinking
Pitfall 4: Bypass Capacitor Selection
- Issue : Insufficient bypassing causing false triggering
- Solution : Use low-ESR ceramic capacitors close to VCC and GND pins
### Compatibility Issues with Other Components
Power MOSFET Selection
- Requirement : Logic-level N-channel MOSFET with VGS(th) < 2.5V
- Compatibility : Must handle inrush current and have appropriate RDS(on)
- Recommendation : Select MOSFETs with VDS rating ≥ 20V for margin
Sense Resistor Requirements
- Precision : 1% tolerance or better recommended
- Power Rating : Must handle continuous current and fault conditions
- Temperature Coefficient : Low TCR (<100 ppm/°C) for stable current limiting
Power Supply Compatibility
- Input Range : Compatible with 3.0V to 3.6V systems
- Sequencing : May require coordination with other power management ICs
- Noise Immunity : Sensitive to
