Secondary Over-Voltage Protection for 2-4 cell in series Li-Ion/Poly (4.55V) 8-TSSOP -40 to 110# BQ29414PWR Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The BQ29414PWR is a secondary overvoltage protector specifically designed for 2-series to 4-series cell lithium-ion/polymer battery packs . Its primary function is to monitor individual cell voltages and provide protection against overvoltage conditions that could damage batteries or create safety hazards.
Primary applications include:
- Portable electronic devices : Smartphones, tablets, laptops, and portable medical equipment
- Power tools : Cordless drills, saws, and other battery-operated tools
- Electric mobility : E-bikes, e-scooters, and personal transportation devices
- Backup power systems : UPS systems and emergency power supplies
- Consumer electronics : Digital cameras, portable speakers, and gaming devices
### Industry Applications
- Consumer Electronics : Provides critical safety protection for high-density battery packs in compact devices
- Automotive : Used in automotive infotainment systems and auxiliary power systems (not for primary vehicle propulsion)
- Industrial Equipment : Protects battery packs in industrial handheld devices and measurement equipment
- Medical Devices : Ensures safety in portable medical monitoring equipment and diagnostic devices
- Energy Storage : Small-scale residential and commercial energy storage systems
### Practical Advantages
Strengths:
- High accuracy : ±25mV overvoltage detection accuracy across temperature range
- Low power consumption : Typically 18μA operating current, 1μA shutdown current
- Fast response time : Typically 4ms overvoltage detection delay
- Small package : TSSOP-14 package saves board space
- Wide voltage range : Supports 2-4 series cells (6V to 20V operating range)
- Integrated delay timer : Eliminates need for external timing components
Limitations:
- Secondary protection only : Must be used with a primary protection IC
- Limited to 4-series cells : Not suitable for higher voltage battery packs
- No undervoltage protection : Only provides overvoltage monitoring
- Temperature dependency : Performance varies with operating temperature (-40°C to +85°C)
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Incorrect Cell Configuration
- Problem : Miswiring cell connections can cause false triggering or failure to protect
- Solution : Carefully follow the VC1-VC4 pin connections to respective cell nodes
Pitfall 2: Inadequate Bypass Capacitors
- Problem : Voltage transients causing false overvoltage detection
- Solution : Place 100nF ceramic capacitors close to each VCx pin and VSS
Pitfall 3: Poor Layout Affecting Accuracy
- Problem : Noise coupling into sensitive analog inputs
- Solution : Use separate analog and power ground planes with single-point connection
Pitfall 4: Incorrect Delay Timing
- Problem : Protection triggering too early or too late
- Solution : Properly calculate CDLY capacitor value for desired delay time using formula: t_DLY = C_DLY × 1450
### Compatibility Issues
Compatible Components:
- Primary protectors : BQ29700 series, BQ29330 series
- Fuel gauges : BQ34Z100, BQ40Z50 series
- Chargers : BQ24610, BQ24725 series
- MOSFETs : Low RDS(on) N-channel MOSFETs for protection FETs
Potential Conflicts:
- Voltage regulators : Ensure compatible voltage levels with system microcontroller
- Communication interfaces : No I2C/SPI interface; status monitoring through DO pin only
- Power sequencing : Proper startup sequence required to avoid latch-up
